Validation of a Hypothesis: Colonization of Black Smokers by Hyperthermophilic Microorganisms - Wirth, Reinhard; Luckner, Manja; Wanner, Gerhard (Frontiers in Microbiology, 2018)

Bringing microbial diversity into focus: high-resolution analysis of iron mats from the Lō'ihi Seamount - Scott, Jarrod J; Glazer, Brian T; Emerson, David (ENVIRONMENTAL MICROBIOLOGY, 2017)
Thirty kilometers south of the island of Hawaii lies the Lihi Seamount, an active submarine volcano that hosts a network of low-temperature hydrothermal vents enriched in ferrous iron that supports extensive microbial mats. These mats, which can be a half a meter deep, are composed of ferric iron bound to organic polymers - the metabolic byproduct of iron-oxidizing Zetaproteobacteria. Though the role of Zetaproteobacteria in mat formation is well established, we have a limited understanding of how differences in diversity are related to mat morphology. We used Minimum Entropy Decomposition and ZetaOtu classification to demonstrate cryptic diversity between closely related Zetaproteobacteria while showing habitat and geographic specificity. Veiled mats, common structures at Lihi, exhibit distinct community composition and contain diversity not detected in other mat types, including specific Zetaproteobacteria and an unclassified Gammaproteobacteria. Our analyses also indicate that diversity can change dramatically across small spatial transects from points of active venting, yet we found comparatively few differences between major sampling sites. This study provides a better picture of the microbiome responsible for iron mat production at Lihi and has broad implications for our understanding of these globally distributed communities.
Keywords: AUV Sentry (Autonomous Underwater Vehicle); ROV Jason (Remotely Operated Vehicle)

A decade of volcanic construction and destruction at the summit of NW Rota-1 seamount: 2004-2014 - Schnur, Susan R; Chadwick Jr., William W; Embley, Robert W; Ferrini, Vicki L; de Ronde, Cornel E J; Cashman, Katharine V; Deardorff, Nicholas D; Merle, Susan G; Dziak, Robert P; Haxel, Joe H; Matsumoto, Haru (JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 2017)
Arc volcanoes are important to our understanding of submarine volcanism because at some sites frequent eruptions cause them to grow and collapse on human timescales. This makes it possible to document volcanic processes. Active submarine eruptions have been observed at the summit of NW Rota-1 in the Mariana Arc. We use remotely operated vehicle videography and repeat high-resolution bathymetric surveys to construct geologic maps of the summit of NW Rota-1 in 2009 and 2010 and relate them to the geologic evolution of the summit area over a 10year period (2004-2014). We find that 2009 and 2010 were characterized by different eruptive styles, which affected the type and distribution of eruptive deposits at the summit. Year 2009 was characterized by ultraslow extrusion and autobrecciation of lava at a single eruptive vent, producing a large cone of blocky lava debris. In 2010, higher-energy explosive eruptions occurred at multiple closely spaced vents, producing a thin blanket of pebble-sized tephra overlying lava flow outcrops. A landslide that occurred between 2009 and 2010 had a major effect on lithofacies distribution by removing the debris cone and other unconsolidated deposits, revealing steep massive flow cliffs. This relatively rapid alternation between construction and destruction forms one end of a seamount growth and mass wasting spectrum. Intraplate seamounts, which tend to grow larger than arc volcanoes, experience collapse events that are orders of magnitude larger and much less frequent than those occurring at subduction zone settings. Our results highlight the interrelated cyclicity of eruptive activity and mass wasting at submarine arc volcanoes.
Keywords: ROV Jason (Remotely Operated Vehicle)

Deep-sea coral and hardbottom habitats on the west Florida slope, eastern Gulf of Mexico - Ross, S W; Rhode, M; Brooke, S (Deep Sea Research Part I: Oceanographic Research Papers, 2017)
Until recently, benthic habitats dominated by deep-sea corals (DSC) appeared to be less extensive on the slope of the Gulf of Mexico (GOM) than in the northeast Atlantic Ocean or off the southeastern US. There are relatively few bioherms (i.e., coral-built mounds) in the northern GOM, and most DSCs are attached to existing hard substrata (e.g., authigenically formed carbonate). The primary structure-forming, DSC in the GOM is Lophelia pertusa, but structure is also provided by other living and dead scleractinians, antipatharians (black corals), octocorals (gorgonians, soft corals), hydrocorals and sponges, as well as abundant rocky substrata. The best development of DSCs in the GOM was previously documented within Viosca Knoll oil and gas lease blocks 826 and 862/906 (north-central GOM) and on the Campeche Bank (southern GOM in Mexican waters). This paper documents extensive deep reef ecosystems composed of DSC and rocky hard-bottom recently surveyed on the West Florida Slope (WFS, eastern GOM) during six research cruises (2008–2012). Using multibeam sonar, CTD casts, and video from underwater vehicles, we describe the physical and oceanographic characteristics of these deep reefs and provide size or area estimates of deep coral and hardground habitats. The multibeam sonar analyses revealed hundreds of mounds and ridges, some of which were subsequently surveyed using underwater vehicles. Mounds and ridges in {<}525 m depths were usually capped with living coral colonies, dominated by L. pertusa. An extensive rocky scarp, running roughly north-south for at least 229 km, supported lower abundances of scleractinian corals than the mounds and ridges, despite an abundance of settlement substrata. Areal comparisons suggested that the WFS may exceed other parts of the GOM slope in extent of living deep coral coverage and other deep-reef habitat (dead coral and rock). The complex WFS region warrants additional studies to better understand the influences of oceanography and geology on the occurrence of DSC and associated organisms. Protection measures are being considered to ensure the long-term integrity of this diverse ecosystem.
Keywords: ROV Jason (Remotely Operated Vehicle)

Distributions and habitat associations of deep-water corals in Norfolk and Baltimore Canyons, Mid-Atlantic Bight, USA - Brooke, S D; Watts, M W; Heil, A D; Rhode, M; Mienis, F; Duineveld, G C A; Davies, A J; Ross, S W (Deep Sea Research Part II: Topical Studies in Oceanography, 2017)
A multi-disciplinary study of two major submarine canyons, Baltimore Canyon and Norfolk Canyon, off the US mid-Atlantic coast focused on the ecology and biology of canyon habitats, particularly those supporting deep-sea corals. Historical data on deep-sea corals from these canyons were sparse with less than 750 records for the mid-Atlantic region, with most being soft sediment species. This study substantially increased the number of deep-sea coral records for the target canyons and the region. Large gorgonians were the dominant structure-forming coral taxa on exposed hard substrates, but several species of scleractinians were also documented, including first observations of Lophelia pertusa in the mid-Atlantic Bight region. Coral distribution varied within and between the two canyons, with greater abundance of the octocoral Paragorgia arborea in Baltimore Canyon, and higher occurrence of stony corals in Norfolk Canyon; these observations reflect the differences in environmental conditions, particularly turbidity, between the canyons. Some species have a wide distribution (e.g., P. arborea, Primnoa resedaeformis, Anthothela grandiflora), while others are limited to certain habitat types and/or depth zones (e.g., Paramuricea placomus, L. pertusa, Solenosmilia variabilis). The distribution of a species is driven by a combination of factors, which include availability of appropriate physical structure and environmental conditions. Although the diversity of the structure-forming corals (gorgonians, branching scleractinians and large anemones) was low, many areas of both canyons supported high coral abundance and a diverse coral-associated community. The canyons provide suitable habitat for the development of deep-sea coral communities that is not readily available elsewhere on the sedimented shelf and slope of the Mid-Atlantic Bight.
Keywords: ROV Jason (Remotely Operated Vehicle)

Evidence for microbial mediation of subseafloor nitrogen redox processes at Loihi Seamount, Hawaii - Sylvan, Jason B.; Wankel, Scott D.; LaRowe, Douglas E.; Charoenpong, Chawalit N.; Huber, Julie A.; Moyer, Craig L.; Edwards, Katrina J. (Geochimica et Cosmochimica Acta, 2017)
The role of nitrogen cycling in submarine hydrothermal systems is far less studied than that of other biologically reactive elements such as sulfur and iron. In order to address this knowledge gap, we investigated nitrogen redox processes at Loihi Seamount, Hawaii, using a combination of biogeochemical and isotopic measurements, bioenergetic calculations and analysis of the prokaryotic community composition in venting fluids sampled during four cruises in 2006, 2008, 2009 and 2013. Concentrations of NH4+ were positively correlated to dissolved Si and negatively correlated to NO3− + NO2−, while NO2− was not correlated to NO3− + NO2−, dissolved Si or NH4+. This is indicative of hydrothermal input of NH4+ and biological mediation influencing NO2− concentrations. The stable isotope ratios of NO3− ($δ$15N and $δ$18O) was elevated with respect to background seawater, with $δ$18O values exhibiting larger changes than corresponding $δ$15N values, reflecting the occurrence of both production and reduction of NO3− by an active microbial community. $δ$15N-NH4+ values ranged from 0‰ to +16.7‰, suggesting fractionation during consumption and potentially N-fixation as well. Bioenergetic calculations reveal that several catabolic strategies involving the reduction of NO3− and NO2− coupled to sulfide and iron oxidation could provide energy to microbes in Loihi fluids, while 16S rRNA gene sequencing of Archaea and Bacteria in the fluids reveals groups known to participate in denitrification and N-fixation. Taken together, our data support the hypothesis that microbes are mediating N-based redox processes in venting hydrothermal fluids at Loihi Seamount.
Keywords: ROV Jason (Remotely Operated Vehicle)

Fe isotope fractionation between chalcopyrite and dissolved Fe during hydrothermal recrystallization: An experimental study at 350 °C and 500 bars - Syverson, D D; Luhmann, A J; Tan, C Y; Borrok, D M; Ding, K; Seyfried, W E (Geochimica et Cosmochimica Acta, 2017)
Equilibrium Fe isotope fractionation between chalcopyrite and dissolved Fe was determined in acidic chloride-bearing fluid at 350 °C and 500 bars. The study utilized deformable gold-cell technology, which allowed time-series sampling of solution during chalcopyrite recrystallization and isotope exchange. A key element of the experimental design involved the addition of anomalous dissolved 57Fe to an on-going experiment as a means of determining the degree and rate of isotope exchange. Taking explicit account of imposed chemical and isotopic mass balance constraints of Fe in fluid and mineral (chalcopyrite) reservoirs, these data indicate that no more than 1000 h is required for the isotopically anomalous dissolved Fe reservoir to exchange completely with the coexisting chalcopyrite. The experimental calibration of the rate of Fe isotope exchange for the $δ$57Fe-spiked experiment provides critical insight for the time necessary to achieve Fe isotope exchange in two non-spiked, but otherwise identical experiments. The Fe isotope data indicate that the equilibrium fractionation between chalcopyrite and dissolved Fe, $Δ$56FeCpy-Fe (aq), at 350 °C is small, 0.09 ± 0.17‰ (2$σ$), and is in good agreement with recent theoretical equilibrium predictions. Owing to the apparent rate of Fe isotope exchange at 350 °C, it is likely that chalcopyrite formed at high temperature deep-sea vents (black smoker systems) achieves isotopic equilibrium, and effectively records the Fe isotopic composition of the coexisting end-member hydrothermal fluid. Comparison of the experimental mineral–fluid equilibrium fractionation factors with conjugate chalcopyrite and dissolved Fe pairs sampled from high temperature hydrothermal vent systems at Axial Caldera and Main Endeavour Field (Juan de Fuca Ridge) are in agreement with this inference. The experimental data were further used to determine the mineral–mineral equilibrium Fe isotope fractionation between pyrite-chalcopyrite, $Δ$56FePyr-Cpy, at 350 °C by combining previously determined pyrite-Fe2+(aq) equilibrium fractionation data with chalcopyrite-Fe2+(aq) from this study. The empirically determined $Δ$56FePyr-Cpy value, 0.90 ± 0.34‰ (2$σ$), is consistent with theoretical predictions, and when coupled with mineral–fluid Fe isotope fractionation systematics and experimentally determined exchange rates, helps to delineate processes of sulfide mineralization in hydrothermal systems.
Keywords: HOV Alvin (Human Occupied Vehicle)

Gene flow between Atlantic and Pacific Ocean basins in three lineages of deep-sea clams (Bivalvia: Vesicomyidae: Pliocardiinae) and subsequent limited gene flow within the Atlantic - LaBella, A L; Van Dover, C L; Jollivet, D; Cunningham, C W (Deep Sea Research Part II: Topical Studies in Oceanography, 2017)
Pliocardiin (vesicomyid) clams rely on microbial symbionts for nutrition and are obligate inhabitants of deep-sea chemosynthetic ecosystems. Unlike many other invertebrate hosts of chemosynthetic microbes, pliocardiin clams are found in every ocean in a variety of reducing habitats, including hydrothermal vents, cold seeps, organic falls and deep-sea fans. The global distribution of pliocardiin clams suggests historical gene flow between ocean basins. We focus on 3 pliocardiin genera—‘Pliocardia' I, Calyptogena and Abyssogena—each of which has a pair of sister clades in the Atlantic and Pacific. Our work tests the hypothesis that historical gene flow between the Atlantic and Pacific Oceans within these genera was interrupted by the closure of the Panamanian seaway and tests whether isolation between the ocean basins is the result of vicariance or past colonization. These questions are investigated in the context of fossil evidence, biogeography and phylogenetics. This study revealed a set of substitution rates consistent with other invertebrate studies ($μ$=0.8{%}/My/lineage), and a set consistent with much lower rates often attributed to deep-sea organisms ($μ$=0.3{%}/My/lineage). Among the Pacific/Atlantic sister pairs, ‘Pliocardia' I COI divergence per lineage is intermediate (2.5{%}), Calyptogena is the highest (6.1{%}) and Abyssogena the lowest (0.8{%}). The substitution rates suggest that ‘Pliocardia' I and Calyptogena have histories of at least 2.8 My in the Atlantic, with Calyptogena likely older. The slower rate, however, is inconsistent with both the maximum age of the family and several well studied fossils: leaving the faster rate preferred. With the faster rate, the Abyssogena southwardae clade diverged from its Pacific sister clade around 1 Mya, which likely post-dates the closure of the Isthmus of Panama and the opening of the Bering Strait. In light of this recent divergence, we test the previously proposed hypothesis that there is a high level of ongoing gene flow between Atlantic populations of A. southwardae. A. southwardae has colonized a broad geographic range of seep sites including the West Florida Escarpment, the Barbados Accretionary Prism, the Lobes of Congo, and the Mid-Atlantic Ridge north and south of the Romanche Transform Fault. Coalescent methods detect gene flow between Barbados and the Mid-Atlantic ridge; and between the West Florida Escarpment and the Lobes of Congo. All other comparisons failed to detect gene flow, contrary to prevailing interpretations of connectivity across the entire Atlantic Basin.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Macrofaunal communities associated with chemosynthetic habitats from the U.S. Atlantic margin: A comparison among depth and habitat types - Bourque, J R; Robertson, C M; Brooke, S; Demopoulos, A W J (Deep Sea Research Part II: Topical Studies in Oceanography, 2017)
Hydrocarbon seeps support distinct benthic communities capable of tolerating extreme environmental conditions and utilizing reduced chemical compounds for nutrition. In recent years, several locations of methane seepage have been mapped along the U.S. Atlantic continental slope. In 2012 and 2013, two newly discovered seeps were investigated in this region: a shallow site near Baltimore Canyon (BCS, 366–412 m) and a deep site near Norfolk Canyon (NCS, 1467–1602 m), with both sites containing extensive chemosynthetic mussel bed and microbial mat habitats. Sediment push cores, suction samples, and Ekman box cores were collected to quantify the abundance, diversity, and community structure of benthic macrofauna ({>}300 $μ$m) in mussel beds, mats, and slope habitats at both sites. Community data from the deep site were also assessed in relation to the associated sediment environment (organic carbon and nitrogen, stable carbon and nitrogen isotopes, grain size, and depth). Infaunal assemblages and densities differed both between depths and among habitat types. Macrofaunal densities in microbial mats were four times greater than those present in mussel beds and slope sediments and were dominated by the annelid families Dorvilleidae, Capitellidae, and Tubificidae, while mussel habitats had higher proportions of crustaceans. Diversity was lower in BCS microbial mat habitats, but higher in mussel and slope sediments compared to NCS habitats. Multivariate statistical analysis revealed specific sediment properties as important for distinguishing the macrofaunal communities, including larger grain sizes present within NCS microbial mat habitats and depleted stable carbon isotopes ($δ$13C) in sediments present at mussel beds. These results suggest that habitat differences in the quality and source of organic matter are driving the observed patterns in the infaunal assemblages, including high $β$ diversity and high variability in the macrofaunal community composition. This study is the first investigation of seep infauna along the U.S. Atlantic slope north of the Blake Ridge Diapir and provides a baseline for future regional comparisons to other seep habitats along the Atlantic margin.
Keywords: ROV Jason (Remotely Operated Vehicle)

Magnetic exploration of a low-temperature ultramafic-hosted hydrothermal site (Lost City, 30 degrees N, MAR) - Szitkar, Florent; Tivey, Maurice A; Kelley, Deborah S; Karson, Jeffrey A; Fruh-Green, Gretchen L; Denny, Alden R (EARTH AND PLANETARY SCIENCE LETTERS, 2017)
A 2003 high-resolution magnetic survey conducted by the Autonomous Underwater Vehicle ABE over the low-temperature, ultramafic-hosted hydrothermal field Lost City reveals a weak positive magnetic anomaly. This observation is in direct contrast to recent observations of strong positive magnetic anomalies documented over the high-temperature ultramafic-hosted hydrothermal vents fields Rainbow and Ashadze, which indicates that temperature may control the production of magnetization at these sites. The Lost City survey provides a unique opportunity to study a field that is, to date, one of a kind, and is an end member of ultramafic-hosted hydrothermal systems. Our results highlight the key contribution of temperature on magnetite production resulting from serpentinization reactions. Whereas high temperature promotes significant production and partitioning of iron into magnetite, low temperature favors iron partitioning into various alteration phases, resulting in a magnetite-poor rock. Moreover, the distribution of magnetic anomalies confirms results of a previous geological survey indicating the progressive migration of hydrothermal activity upslope. These discoveries contribute to the results of 25 yrs of magnetic exploration of a wide range of hydrothermal sites, from low- to high temperature and from basalt- to ultramafic-hosted, and thereby validate using high-resolution magnetics as a crucial parameter for locating and characterizing hydrothermal sites hosting unique chemosynthetic-based ecosystems and potentially mineral-rich deposits. (C) 2016 Elsevier B.V. All rights reserved.
Keywords: AUV ABE (Autonomous Benthic Explorer)

Methane fates in the benthos and water column at cold seep sites along the continental margin of Central and North America - Hansman, R L; Thurber, A R; Levin, L A; Aluwihare, L I (Deep Sea Research Part I: Oceanographic Research Papers, 2017)
The potential influence of methane seeps on carbon cycling is a key question for global assessments, but the study of carbon cycling in surface sediments and the water column of cold seep environments is complicated by the high temporal and spatial variability of fluid and gas fluxes at these sites. In this study we directly examined carbon sources supporting benthic and planktonic food webs at venting methane seeps using isotopic and molecular approaches that integrate this variability. At four seep environments located along North and Central America, microorganisms from two size fractions were collected over several days from 2800 to 9050 l of seawater to provide a time-integrated measure of key microbial groups and the carbon sources supporting the overall planktonic microbial community. In addition to water column measurements, the extent of seafloor methane release was estimated at two of the sites by examining the stable carbon isotopic signature ($δ$13C) of benthic metazoan infauna. This signature reveals carbon sources fueling the base of the food chain and thus provides a metric that represents a time-integrated view of the dominant microbial processes within the sediment. The stable carbon isotopic composition of microbial DNA ($δ$13C-DNA), which had values between −17.0 and −19.5‰, indicated that bulk planktonic microbial production was not ultimately linked to methane or other 13C-depleted seep-derived carbon sources. Instead these data support the importance of organic carbon derived from either photo- or chemoautotrophic CO2 fixation to the planktonic food web. Results of qPCR of microbial DNA sequences coding for a subunit of the particulate methane monooxygenase gene (pmoA) showed that only a small percentage of the planktonic microbial community were potential methane oxidizers possessing pmoA ({<}5{%} of 16S rRNA gene copies). There was an overall decrease of 13C-depleted carbon fueling the benthic metazoan community from 3 to 5 cm below the seafloor to the sediment surface, reflecting limited use of isotopically depleted carbon at the sediment surface. Rare methane emission as indicated by limited aerobic methane oxidation acts to corroborate our findings for the planktonic microbial community.
Keywords: HOV Alvin (Human Occupied Vehicle)

Methane seepage effects on biodiversity and biological traits of macrofauna inhabiting authigenic carbonates - Levin, L A; Mendoza, G F; Grupe, B M (Deep Sea Research Part II: Topical Studies in Oceanography, 2017)
Authigenic carbonate rocks at methane seeps are recognized as hosting diverse and abundant invertebrate assemblages, with potential forcing from fluid seepage and hydrography. Mensurative studies of carbonate macrofauna ({>}0.3 mm) at Hydrate Ridge, OR revealed little effect of water depth and overlying oxygenation (at 600 m and 800 m) but a large influence of seepage activity on density, taxonomic composition, diversity, and biological traits (feeding, lifestyle, motility, size and calcification). Rocks exposed to active seepage had 3–4× higher total macrofaunal densities than under inactive conditions. Assemblages exhibited higher species richness and reduced evenness (greater dominance) under active seepage than inactive conditions, but no difference in H′ or rarefaction diversity. Actively seeping sites were characterized by errant (motile), bacterial grazing, small- and medium-sized, heavily calcified species, whereas inactive sites exhibited a greater diversity of feeding modes and more burrowers, sessile, large and lightly calcified species. Active rocks supported more exogonid (Syllidae), ampharetid, and cirratulid polychaetes, provannid snails, pyropeltid limpets, nemerteans, and sponges; whereas inactive rocks supported higher densities of ophiuroids, isopods, gammarid amphipods, hydroids, Typosyllis (Syllidae) and tanaids. Transplant experiments, in which rocks were transferred between active and inactive sites at Hydrate Ridge North (600 m), revealed that assemblages respond within 13 months to increase or cessation of seepage, taking on the feeding, size and calcification characteristics of the background fauna at the new site. Lifestyles and motility patterns shifted more slowly as the sessile, attached species did not track seepage as quickly. Provannid snails and pyropeltid limpets rapidly colonized rocks transplanted to active sites and disappeared when transplanted to inactive sites. Given the known variability of fluid fluxes and rapid community response, a mosaic of communities changing in space and time is hypothesized to generate the relatively high species diversity at methane seeps.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Rapid variations in fluid chemistry constrain hydrothermal phase separation at the Main Endeavour Field - Love, B; Lilley, M; Butterfield, D; Olson, E; Larson, B (Geochemistry, Geophysics, Geosystems, 2017)
Previous work at the Main Endeavour Field (MEF) has shown that chloride concentration in high-temperature vent fluids has not exceeded 510 mmol/kg (94{%} of seawater), which is consistent with brine condensation and loss at depth, followed by upward flow of a vapor phase toward the seafloor. Magmatic and seismic events have been shown to affect fluid temperature and composition and these effects help narrow the possibilities for sub-surface processes. However, chloride-temperature data alone are insufficient to determine details of phase separation in the upflow zone. Here we use variation in chloride and gas content in a set of fluid samples collected over several days from one sulfide chimney structure in the MEF to constrain processes of mixing and phase separation. The combination of gas (primarily magmatic CO2 and seawater-derived Ar) and chloride data, indicate that neither variation in the amount of brine lost, nor mixing of the vapor phase produced at depth with variable quantities of (i) brine or (ii) altered gas rich seawater that has not undergone phase separation, can explain the co-variation of gas and chloride content. The gas-chloride data require additional phase separation of the ascending vapor-like fluid. Mixing and gas partitioning calculations show that near-critical temperature and pressure conditions can produce the fluid compositions observed at Sully vent as a vapor-liquid conjugate pair or as vapor-liquid pair with some remixing, and that the gas partition coefficients implied agree with theoretically predicted values.
Keywords: HOV Alvin (Human Occupied Vehicle)

SyPRID sampler: A large-volume, high-resolution, autonomous, deep-ocean precision plankton sampling system - Billings, A; Kaiser, C; Young, C M; Hiebert, L S; Cole, E; Wagner, J K S; Van Dover, C L (Deep Sea Research Part II: Topical Studies in Oceanography, 2017)
The current standard for large-volume (thousands of cubic meters) zooplankton sampling in the deep sea is the MOCNESS, a system of multiple opening–closing nets, typically lowered to within 50 m of the seabed and towed obliquely to the surface to obtain low-spatial-resolution samples that integrate across 10 s of meters of water depth. The SyPRID (Sentry Precision Robotic Impeller Driven) sampler is an innovative, deep-rated (6000 m) plankton sampler that partners with the Sentry Autonomous Underwater Vehicle (AUV) to obtain paired, large-volume plankton samples at specified depths and survey lines to within 1.5 m of the seabed and with simultaneous collection of sensor data. SyPRID uses a perforated Ultra-High-Molecular-Weight (UHMW) plastic tube to support a fine mesh net within an outer carbon composite tube (tube-within-a-tube design), with an axial flow pump located aft of the capture filter. The pump facilitates flow through the system and reduces or possibly eliminates the bow wave at the mouth opening. The cod end, a hollow truncated cone, is also made of UHMW plastic and includes a collection volume designed to provide an area where zooplankton can collect, out of the high flow region. SyPRID attaches as a saddle-pack to the Sentry vehicle. Sentry itself is configured with a flight control system that enables autonomous survey paths to low altitudes. In its verification deployment at the Blake Ridge Seep (2160 m) on the US Atlantic Margin, SyPRID was operated for 6 h at an altitude of 5 m. It recovered plankton samples, including delicate living larvae, from the near-bottom stratum that is seldom sampled by a typical MOCNESS tow. The prototype SyPRID and its next generations will enable studies of plankton or other particulate distributions associated with localized physico-chemical strata in the water column or above patchy habitats on the seafloor.
Keywords: AUV Sentry (Autonomous Underwater Vehicle)

Telepresence is a potentially transformative tool for field science - Marlow, Jeffrey; Borrelli, Chiara; Jungbluth, Sean P; Hoffman, Colleen; Marlow, Jennifer; Girguis, Peter R; Team, AT-36 (PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 2017)
Keywords: AUV Sentry (Autonomous Underwater Vehicle); HOV Alvin (Human Occupied Vehicle)

Time series video analysis of bubble release processes at natural hydrocarbon seeps in the Northern Gulf of Mexico - Johansen, C; Todd, A C; MacDonald, I R (Marine and Petroleum Geology, 2017)
This research quantifies the rate and volume of oil and gas released from two natural seep sites in the Gulf of Mexico: lease blocks GC600 (1200 m depth) and MC118 (850 m depth). Our objectives were to determine variability in release rates and bubble size at five individual vents and to investigate the effects of tidal fluctuations on bubble release. Observations with autonomous video cameras captured the formation of individual bubbles as they were released through partially exposed deposits of gas hydrate. Image processing techniques determined bubble type (oily, gaseous, and mixed: oily and gaseous), size distribution, release rate, and temporal variations (observation intervals ranged from 3 h to 26 d). A semi-automatic bubble counting algorithm was developed to analyze bubble count and release rates from video data. This method is suitable for discrete vents with small bubble streams commonly seen at seeps and is adaptable to multiple in situ set-ups. Two vents at GC600 (Birthday Candles 1 and Birthday Candles 2) were analyzed. They released oily bubbles with an average diameter of 5.0 mm at a rate of 4.7 bubbles s−1, and 1.3 bubbles s−1, respectively. Approximately 1 km away, within the GC600 seep site, two more vents (Mega Plume 1 and Mega Plume 2) were analyzed. These vents released a mixture of oily and gaseous bubbles with an average diameter of 3.9 mm at a rate of 49 bubbles s−1, and 81 bubbles s−1, respectively. The fifth vent at MC118 (Rudyville) released gaseous bubbles with an average diameter of 3.0 mm at a rate of 127 bubbles s−1. Pressure records at Mega Plume and Rudyville showed a diurnal tidal cycle (24.5 h). Rudyville was the only vent that demonstrated any positive correlation ($ρ$ = 0.60) to the 24.5 h diurnal tidal cycle. However, these observations were not conclusive regarding tidal effects on bubble release.
Keywords: HOV Alvin (Human Occupied Vehicle)

The transfer of bomb radiocarbon and anthropogenic lead to the deep North Atlantic Ocean observed from a deep sea coral - Lee, J M; Eltgroth, S F; Boyle, E A; Adkins, J F (Earth and Planetary Science Letters, 2017)
Deep-ocean, View the MathML source$Δ$C14, Pb concentrations, and Pb isotopes were reconstructed from a deep-sea coral Enallopsammia rostrata from 1410 m depth off of Bermuda. Our high-resolution time series is created from closely spaced radial cross sections, with samples taken from the center of concentric coral growth bands that we show to be the oldest portion of the section. Prebomb radiocarbon ages from the coral demonstrate that the vertical growth rate of the coral is linear, and the age of the coral is estimated to be 560–630 yr old based on the growth rate. Using this age model to reconstruct View the MathML source$Δ$C14 in deep seawater, we first detect bomb radiocarbon at the coral growth site around 1980, and show that View the MathML source$Δ$C14 increased from −80±1‰−80±1‰ (average 1930–1979) to a plateau at −39±3‰−39±3‰ (1999–2001). Pb/Ca of the coral ranges between 1.1–4.5 nmol/mol during the 16th and 17th centuries, and Pb isotope ratios (206Pb/207Pb = 1.21, 208Pb/207Pb = 2.495) in this period agree with pre-anthropogenic values found in the pelagic sediments of the North Atlantic Ocean basin. Coral Pb/Ca is slightly elevated to 6.2±0.9 nmol/mol6.2±0.9 nmol/mol between the 1740s and the 1850s and then increases to 25.1±0.2 nmol/mol25.1±0.2 nmol/mol in the 1990s. The increase in coral Pb/Ca is accompanied by a decrease in coral 206Pb/207Pb and 208Pb/207Pb, indicating that the increase was caused by the infiltration of anthropogenic Pb to the coral growth site. Comparing our data to the surface coral View the MathML source$Δ$C14 and Pb records from Bermuda reveals a time scale of tracer transport from the surface ocean to the coral growth site. Some characteristic features, e.g., the bomb-derived View the MathML source$Δ$C14 increase, appear in the deep ocean approximately 25 yr later than the surface, but the overall increase of View the MathML source$Δ$C14 and Pb in the deep ocean is smaller and slower than the surface, showing the importance of mixing during the transport of these tracers.
Keywords: HOV Alvin (Human Occupied Vehicle)

Arsenic concentrations and species in three hydrothermal vent worms, Ridgeia piscesae, Paralvinella sulficola and Paralvinella palmiformis - Maher, W A; Duncan, E; Dilly, G; Foster, S; Krikowa, F; Lombi, E; Scheckel, K; Girguis, P (Deep Sea Research Part I: Oceanographic Research Papers, 2016)
Hydrothermal vents are surficial expressions of subsurface geological and hydrological processes. Fluids emitting from active vents are chemically distinct from bottom seawater, and are enriched in dissolved metals and metalloids, including arsenic. Vent organisms accumulate arsenic but the arsenic speciation in these non-photosynthetic organisms is largely unknown. Here, arsenic concentrations and chemical species were measured in three deep sea hydrothermal vent worms (Ridgeia piscesae, Paralvinella sulfincola and Paralvinella palmiformis ) from the Juan de Fuca Ridge in the Northwest pacific. R. piscesae has similar arsenic concentrations (3.8–35 µg g−1) to shallow water polychaetes while P. sulfincola and P. palmiformis have significantly higher arsenic concentrations (420–1417 and 125–321 µg g−1 respectively). R. piscesae contains appreciable quantities of inorganic arsenic (36±14{%}), monomethyl arsenic (2±2{%}), dimethyl arsenic (34±21{%}), an unknown methyl arsenical (7±16{%}), OSO3-arsenosugar (5±9{%}), TETRA (4±5{%}), ThioPO4/ThioDMAE (1±2{%}) and an unknown thio-arsenical (12±14{%}). These results suggests that host and symbionts are either involved in the methylation of arsenic, or are bathed in fluids enriched in methylated arsenic as a result of free-living microbial activity. The host carrying out methylation, however, cannot be ruled out. In contrast, 96–97{%} of the arsenic in P. sulfincola and P. palmiformis is inorganic arsenic, likely the result of arsenic precipitation within and upon the mucus they ingest while feeding. While all worms have oxo- and thio arsenosugars (2–30{%}), Paralvinella also have small amounts of arsenobetaine ({<}0.001–0.21{%}). The presence of arsenosugars, arsenobetaine and other minor arsenic species in the absence of photosynthesising algae/bacteria indicates that they may be formed by vent animals in the absence of sunlight, but at this time their formation cannot be explained.
Keywords: HOV Alvin (Human Occupied Vehicle)

Assessing microbial processes in deep-sea hydrothermal systems by incubation at in situ temperature and pressure - McNichol, J; Sylva, S P; Thomas, F; Taylor, C D; Sievert, S M; Seewald, J S (Deep Sea Research Part I: Oceanographic Research Papers, 2016)
At deep-sea hydrothermal vents, a large source of potential chemical energy is created when reducing vent fluid and oxidizing seawater mix. In this environment, chemolithoautotrophic microbes catalyze exergonic redox reactions which in turn provide the energy needed to fuel their growth and the fixation of CO2 into biomass. In addition to producing new organic matter, this process also consumes compounds contained both in vent fluid and entrained seawater (e.g. H2, NO3−). Despite their biogeochemical importance, such reactions have remained difficult to quantify due to methodological limitations. To address this knowledge gap, this study reports a novel application of isobaric gas-tight fluid samplers for conducting incubations of hydrothermal vent fluids at in situ temperature and pressure. Eighteen {\~{}}24 h incubations were carried out, representing seven distinct conditions that examine amendments consisting of different electron donors and acceptors. Microbial activity was observed in all treatments, and time series chemical measurements showed that activity was limited by electron acceptor supply, confirming predictions based on geochemical data. Also consistent with these predictions, the presence of nitrate increased rates of hydrogen consumption and yielded ammonium as a product of nitrate respiration. The stoichiometry of predicted redox reactions was also determined, revealing that the sulfur and nitrogen cycles are incompletely understood at deep-sea vents, and likely involve unknown intermediate redox species. Finally, the measured rates of redox processes were either equal to or far greater than what has been reported in previous studies where in situ conditions were not maintained. In addition to providing insights into deep-sea hydrothermal vent biogeochemistry, the methods described herein also offer a practical approach for the incubation of any deep-sea pelagic sample under in situ conditions.
Keywords: ROV Jason (Remotely Operated Vehicle)

Candidatus Desulfofervidus auxilii, a hydrogenotrophic sulfate-reducing bacterium involved in the thermophilic anaerobic oxidation of methane - Krukenberg, V; Harding, K; Richter, M; Gloeckner, F O; Gruber-Vodicka, H R; Adam, B; Berg, J S; Knittel, K; Tegetmeyer, H E; Boetius, A; Wegener, G (Environmental Microbiology, 2016)
The anaerobic oxidation ofmethane (AOM) ismediated by consortia of anaerobic methane-oxidizing archaea (ANME) and their specific partner bacteria. In thermophilic AOM consortia enriched from Guaymas Basin, members of the ANME-1 clade are associated with bacteria of the HotSeep-1 cluster, which likely perform direct electron exchange via nanowires. The partner bacterium was enriched with hydrogen as sole electron donor and sulfate as electron acceptor. Based on phylogenetic, genomic and metabolic characteristics we propose to name this chemolithoautotrophic sulfate reducer Candidatus Desulfofervidus auxilii. Ca.D. auxilii grows on hydrogen at temperatures between 50 degrees C and 70 degrees C with an activity optimum at 60 degrees C and doubling time of 4-6 days. Its genome draft encodes for canonical sulfate reduction, periplasmic and soluble hydrogenases and autotrophic carbon fixation via the reductive tricarboxylic acid cycle. The presence of genes for pili formation and cytochromes, and their similarity to genes of Geobacter spp., indicate a potential for syntrophic growth via direct interspecies electron transfer when the organism grows in consortia with ANME. This first ANME-free enrichment of an AOM partner bacterium and its characterization opens the perspective for a deeper understanding of syntrophy in anaerobic methane oxidation.
Keywords: HOV Alvin (Human Occupied Vehicle)

Colonization of over a thousand Cibicidoides wuellerstorfi (foraminifera: Schwager, 1866) on artificial substrates in seep and adjacent off-seep locations in dysoxic, deep-sea environments - Burkett, A M; Rathburn, A E; Perez, Elena M; Levin, L A; Martin, J B (Deep Sea Research Part I: Oceanographic Research Papers, 2016)
After {\~{}}1 yr on the seafloor at water depths of {\~{}}700 m on Hydrate Ridge in the Pacific, eight colonization experiments composed primarily of a plastic mesh cube (from here on refered to as SEA3, for Seafloor Epibenthic Attachment Cubes) were colonized by 1076 Cibicidoides wuellerstorfi on {\~{}}1841 cm2 of experimental substrate. This species is typically considered an indicator of well-oxygenated conditions, and recruitment of such large numbers in bottom waters with low dissolved oxygen availability (0.24–0.37 mL/L) indicate that this taxon may not be as limited by oxygen as previously thought. Clues about substrate preferences were evident from the distribution, or lack thereof, of individuals among plastic mesh, coated steel frame, wooden dowels and reflective tape. Abundance, individual size distributions within cage populations and isotopic biogeochemistry of living foraminifera colonizing experimental substrates were compared between active seep and adjacent off-seep experiment locations, revealing potential differences between these environments. Few studies have examined foraminiferal colonization of hard substrates in the deep-sea and to our knowledge no previous study has compared foraminiferal colonization of active seep and off-seep substrates from the same region. This study provides initial results of recruitment, colonization, geochemical and morphological aspects of the paleoceanographically significant species, C. wuellerstorfi, from dynamic deep-sea environments. Further experimental deployments of SEA3s will provide a means to assess relatively unknown ecologic dynamics of important foraminiferal deep-sea species.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Comparative geochemistry of four ferromanganese crusts from the Pacific Ocean and significance for the use of Ni isotopes as paleoceanographic tracers - Gueguen, B; Rouxel, O J; Rouget, M-L; Bollinger, C; Ponzevera, E; Germain, Y; Fouquet, Y (Geochimica et Cosmochimica Acta, 2016)
{Ferromanganese (Fe-Mn) crusts are potential archive of the Ni isotope composition of seawater through time. In this study we aim at (1) understanding Ni isotope fractionation mechanisms and metal enrichment processes in Fe-Mn deposits, (2) addressing global vs. local control of Ni isotope composition of these deposits. Two Fe-Mn crusts from the North Pacific Ocean (Apuupuu Seamount, Hawaii) and two Fe-Mn crusts from the South Pacific Ocean (near Rurutu Island, Austral archipelago of French Polynesia) were characterized for their elemental geochemistry and Ni isotope composition. Geochemical analyses were performed at millimeter intervals in order to provide time-resolved record of Ni isotopes. Chronology and growth rates were determined using cosmogenic 10Be isotope abundances. The results show that, despite different growth rates, textures and geochemical patterns, Fe-Mn crusts from both North and South Pacific Oceans have fairly homogenous Ni isotope compositions over the last ∼17 Ma, yielding average $δ$60/58Ni values of 1.79 ± 0.21‰ (2sd
Keywords: ROV Jason (Remotely Operated Vehicle)

A “core-top” screen for trace element proxies of environmental conditions and growth rates in the calcite skeletons of bamboo corals (Isididae) - Thresher, R E; Fallon, S J; Townsend, A T (Geochimica et Cosmochimica Acta, 2016)
We test for trace element proxies in the high-magnesium calcite fraction of bamboo coral internodes by comparing environmental conditions and growth rates to the specimen-mean compositions of 73 corals that were live-caught at depths ranging from 3 to 3950 m and collected from habitats ranging from tropical coral reefs to the Antarctic slope. Comparisons were done at a large geographic scale (LGS) and for a well sampled area south of Australia, across depths at a single site, in order to help separate the effects of environmental variables that co-vary at one spatial scale, but not the other. Thirty-seven trace elements were measured using solution-based Sector Field ICP-MS, of which seventeen were significantly detected in more than a third of the specimens. Only eight element/calcium ratios correlated significantly with any environmental variable at the large geographic scale, and only four did so at the local level. At the LGS, the highest correlation was between ambient temperature and Mg/Ca, which accounted for 89{%} of the variance across specimens, spanned all four Isidid sub-families and was independently significant in the two best sampled sub-families. The predictive (geometric mean) relationship is View the MathML sourceT(°C)=-23.9(±2.46)+0.34(±0.25)Mg/Ca(mmol/mol) Turn MathJax on spanning a temperature range of −1.9 to 26.8 °C, Mg/Ca ratios from 58.6 to 155.1 mmol/mol, and an uncertainty (RMS) of 2.78 °C. The numbers in parentheses are 95{%} CIs. The slope of the regression does not differ significantly from that of abiotic high-Mg calcites, which suggests that the temperature-dependent incorporation of Mg into the carbonate results from kinetic reactions at the crystal surface. Analysis at the SH scale for the sub-set of specimens for which we had data suggests is also affected by growth rates. There were no obvious trace element correlates at either spatial scale of salinity or oxygen levels that could not be accounted for by covariance between these environmental parameters and, in most cases, temperature. Single and multiple correlation analyses also confirm previous suggestions that Ba/Ca in bamboo coral calcite is a proxy for seawater barium and hence refractory nutrients, suggest that Sr/Ca is influenced by specimen-mean Mg/Ca ratios and water temperature as well as possibly seawater Sr/Ca, and falsify for bamboo corals P/Ca (as well as P/Cd and Cd/Ca) as a proxy for seawater phosphate levels. The predictive relationship between Isidid skeletal-mean Ba/Ca and seawater silicate concentrations appears to be linear, and is given by View the MathML sourcesilicate($μ$molkg-1)=-56.7(±20.8)+9217(±1632)Ba/Ca(mmol/mol) Turn MathJax on spanning a silicate range of 0.5 to 120 $μ$mol kg−1, a Ba/Ca range of 0.0042 to 0.0195 mmol/mol, and with an uncertainty (RMS) of 33.1 $μ$mol kg−1. Mn/Ca differences among specimens and sites are highly significant and appear to reflect seawater Mn, suggesting a proxy for this micronutrient. The compilation of growth rate data across 34 specimens indicates a wide range of growth rates even among con-familial specimens from within a single habitat, and suggests both ambient temperature and food availability underlie at least part of this variability.
Keywords: ROV Jason (Remotely Operated Vehicle)

Cross-hole tracer experiment reveals rapid fluid flow and low effective porosity in the upper oceanic crust - Neira, N M; Clark, J F; Fisher, A T; Wheat, C G; Haymon, R M; Becker, K (Earth and Planetary Science Letters, 2016)
Numerous field, laboratory, and modeling studies have explored the flows of fluid, heat, and solutes during seafloor hydrothermal circulation, but it has been challenging to determine transport rates and flow directions within natural systems. Here we present results from the first cross-hole tracer experiment in the upper oceanic crust, using four subseafloor borehole observatories equipped with autonomous samplers to track the transport of a dissolved tracer (sulfur hexafluoride, SF6) injected into a ridge-flank hydrothermal system. During the first three years after tracer injection, SF6 was transported both north and south through the basaltic aquifer. The observed tracer transport rate of ∼2–3 m/day is orders of magnitude greater than bulk rates of flow inferred from thermal and chemical observations and calculated with coupled fluid-heat flow simulations. Taken together, these results suggest that the effective porosity of the upper volcanic crust through which much tracer was transported is {<}1{%}, with fluid flowing rapidly along a few well-connected channels. This is consistent with the heterogeneous (layered, faulted, and/or fractured) nature of the volcanic upper oceanic crust.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Crustal magnetization and the subseafloor structure of the ASHES vent field, Axial Seamount, Juan de Fuca Ridge: Implications for the investigation of hydrothermal sites - Tontini, F C; Crone, T J; de Ronde, C E J; Fornari, D J; Kinsey, J C; Mittelstaedt, E; Tivey, M K (Geophysical Research Letters, 2016)
High-resolution geophysical data have been collected using the Autonomous Underwater Vehicle (AUV) Sentry over the ASHES (Axial Seamount Hydrothermal Emission Study) high-temperature ({\~{}}348°C) vent field at Axial Seamount, on the Juan de Fuca Ridge. Multiple surveys were performed on a 3-D grid at different altitudes above the seafloor, providing an unprecedented view of magnetic data resolution as a function of altitude above the seafloor. Magnetic data derived near the seafloor show that the ASHES field is characterized by a zone of low magnetization, which can be explained by hydrothermal alteration of the host volcanic rocks. Surface manifestations of hydrothermal activity at the ASHES vent field are likely controlled by a combination of local faults and fractures and different lava morphologies near the seafloor. Three-dimensional inversion of the magnetic data provides evidence of a vertical, pipe-like upflow zone of the hydrothermal fluids with a vertical extent of {\~{}}100 m.
Keywords: AUV Sentry (Autonomous Underwater Vehicle)

Deep-sea coral $δ$13C: A tool to reconstruct the difference between seawater pH and $δ$11B-derived calcifying fluid pH - Martin, P; Goodkin, N F; Stewart, J A; Foster, G L; Sikes, E L; White, H K; Hennige, S; Roberts, J M (Geophysical Research Letters, 2016)
{The boron isotopic composition ($δ$11B) of coral skeleton is a proxy for seawater pH. However, $δ$11B-based pH estimates must account for the pH difference between seawater and the coral calcifying fluid, $Δ$pH. We report that skeletal $δ$11B and $Δ$pH are related to the skeletal carbon isotopic composition ($δ$13C) in four genera of deep-sea corals collected across a natural pH range of 7.89–8.09, with $Δ$pH related to $δ$13C by $Δ$pH = 0.029 × $δ$13C + 0.929
Keywords: HOV Alvin (Human Occupied Vehicle)

Development and Application of a New Mobile pH Calibrator for Real-Time Monitoring of pH in Diffuse Flow Hydrothermal Vent Fluids - Tan, C Y; Ding, K; Seyfried, W E (Marine Technology Society Journal, 2016)
In situ measurement of pH in diffuse flow hydrothermal vent fluids is necessary to investigate the feedback between geochemical and biochemical processes. Accurate pH determination has been unusually challenging owing to temperature and pressure effects that place severe constraints on the performance of a wide variety of pH sensor systems. In this paper, we describe a newly developed mobile pH calibrator (MpHC), which makes use of In situ calibration protocols that enhance the accuracy of pH measurement and monitoring on the ocean floor at deep-sea hydrothermal vents. The MpHC combines the physically robust and highly sensitive iridium solid-state pH electrode with a flow control system to perform 2-point calibration with on-board pH buffer solutions. The small size and novel design of the sensor probe allow more effective access to seafloor hydrothermal vent fluids and their associated sulfide structures and biological communities. The MpHC is capable of In situ deployment by submersible via ICL (inductively couple link) communication around hydrothermal vents at pressures and temperatures up to 45 MPa and 100 degrees C, respectively. In this paper, we also present results of In situ calibration methods used to correct the standard potential and slope (mV/pH) of the solid-state electrode for temperature effects. The MpHC has been deployed most recently using the submersible Alvin during cruise AT26-17 to Axial Seamount and Main Endeavour Field, Juan De Fuca Ridge in the NE Pacific. With In situ calibration functionality, the MpHC offers the prospect of more successful longer-term measurements in keeping with power availability provided by cabled seafloor observatories coming online in the NE Pacific.
Keywords: HOV Alvin (Human Occupied Vehicle)

Diffuse venting at the ASHES hydrothermal field: Heat flux and tidally modulated flow variability derived from in situ time-series measurements - Mittelstaedt, E; Fornari, D J; Crone, T J; Kinsey, J C; Kelley, D S; Elend, M J (Geochemistry, Geophysics, Geosystems, 2016)
Time-series measurements of diffuse exit-fluid temperature and velocity collected with a new, deep-sea camera, and temperature measurement system, the Diffuse Effluent Measurement System (DEMS), were examined from a fracture network within the ASHES hydrothermal field located in the caldera of Axial Seamount, Juan de Fuca Ridge. The DEMS was installed using the HOV Alvin above a fracture near the Phoenix vent. The system collected 20 s of 20 Hz video imagery and 24 s of 1 Hz temperature measurements each hour between 22 July and 2 August 2014. Fluid velocities were calculated using the Diffuse Fluid Velocimetry (DFV) technique. Over the similar to 12 day deployment, median upwelling rates and mean fluid temperature anomalies ranged from 0.5 to 6 cm/s and 0 degrees C to similar to 6.5 degrees C above ambient, yielding a heat flux of 0.29 +/- 0.22 MW M-2 and heat output of 3.1 +/- 2.5 kW. Using a photo mosaic to measure fracture dimensions, the total diffuse heat output from cracks across ASHES field is estimated to be 2.05 +/- 1.95 MW. Variability in temperatures and velocities are strongest at semidiurnal periods and show significant coherence with tidal height variations. These data indicate that periodic variability near Phoenix vent is modulated both by tidally controlled bottom currents and seafloor pressure, with seafloor pressures being the dominant influence. These results emphasize the importance of local permeability on diffuse hydrothermal venting at mid-ocean ridges and the need to better quantify heat flux associated with young oceanic crust.
Keywords: AUV Sentry (Autonomous Underwater Vehicle); HOV Alvin (Human Occupied Vehicle)

A distinct and active bacterial community in cold oxygenated fluids circulating beneath the western flank of the Mid-Atlantic ridge - Meyer, Julie L; Jaekel, Ulrike; Tully, Benjamin J; Glazer, Brian T; Wheat, C Geoffrey; Lin, Huei-Ting; Hsieh, Chih-Chiang; Cowen, James P; Hulme, Samuel M; Girguis, Peter R; Huber, Julie A (SCIENTIFIC REPORTS, 2016)
The rock-hosted, oceanic crustal aquifer is one of the largest ecosystems on Earth, yet little is known about its indigenous microorganisms. Here we provide the first phylogenetic and functional description of an active microbial community residing in the cold oxic crustal aquifer. Using subseafloor observatories, we recovered crustal fluids and found that the geochemical composition is similar to bottom seawater, as are cell abundances. However, based on relative abundances and functional potential of key bacterial groups, the crustal fluid microbial community is heterogeneous and markedly distinct from seawater. Potential rates of autotrophy and heterotrophy in the crust exceeded those of seawater, especially at elevated temperatures (25 degrees C) and deeper in the crust. Together, these results reveal an active, distinct, and diverse bacterial community engaged in both heterotrophy and autotrophy in the oxygenated crustal aquifer, providing key insight into the role of microbial communities in the ubiquitous cold dark subseafloor biosphere.
Keywords: ROV Jason (Remotely Operated Vehicle)

Examining the diversity of microbes in a deep-sea coral community impacted by the Deepwater Horizon oil spill - Simister, R L; Antzis, E W; White, H K (Deep Sea Research Part II: Topical Studies in Oceanography, 2016)
Deep-sea surface sediments and flocculent material (floc) associated with corals containing oil originating from the Deepwater Horizon (DWH) oil spill were examined to determine the diversity of microbes and the presence of functional genes involved in oil degradation. For all samples, 16S rRNA clone libraries were constructed to obtain full-length sequences and Illumina amplicon sequencing was used to further probe the diversity of the microbial community. The 16S rRNA gene data obtained by Illumina amplicon sequencing revealed Proteobacteria (55–64{%}) as the dominant bacteria in both sediment and floc samples. The floc samples were comprised of mostly aerobic or facultative aerobic phylotypes including Rhizobiales, Rhodobacterales, Sphingomonadales, Rickettsiales, Alteromonadales, Pseudomonadales, whereas mixtures of the aforementioned aerobic species and anaerobic phylotypes such as Desulfobacterales, Desulfuromonadales and Desulfarculales were present in the sediment samples. Genera affiliated with oil-degrading bacteria were identified in both sediment and floc samples. To evaluate the potential of the microbial community to degrade oil, clone libraries were constructed for the alkB gene (one of the structural genes of alkane hydroxylase involved in the aerobic degradation of n-alkanes of chain length {>}C5–C16) and the alkylsuccinate synthase/benzylsuccinate synthases (assA/bssA) gene (involved in the anaerobic degradation of n-alkanes [via assA] and polycyclic aromatic hydrocarbons [PAHs; via bssA]). The alkB gene was present in all samples with the majority of sequences clustering to members of the Proteobacteria closely aligned to environmental sequences from hydrocarbon seep environments. The assA/bssA genes were only detected in sediment samples and were closely affiliated with $δ$-Proteobacteria previously detected in oil-contaminated sediments and oil-enrichment cultures. These data provide insight into the differences between environments impacted by the DWH oil spill and highlight the functional diversity of oil-degrading microbes associated with a deep-sea coral community.
Keywords: HOV Alvin (Human Occupied Vehicle)

Experimental evidence for selective settlement of meiofauna from two distinct environments after sediment suspension - Mevenkamp, L; Van Campenhout, J; Vanreusel, A (Journal of Experimental Marine Biology and Ecology, 2016)
The cosmopolitan distribution of many meiofaunal organisms raises questions about their dispersal. The small size and the lack of a planktonic life stage of most meiofauna taxa including free-living nematodes suggest that passive dispersal is a main factor determining their distribution. This study investigates the settling behaviour of meiofauna in a water column under no-flow conditions. Two ex situ settling experiments were conducted with (1) macrophyte associated meiofauna from an intertidal salt marsh and (2) meiofauna of sulphidic sediments associated with bacterial mats from the deep-sea Håkon Mosby mud volcano. Cilyndrical containers filled with sieved seawater were used as settling chambers and five different substrates, placed on the bottom of the containers, were offered to the descending meiofaunal assemblage. The substrates used in experiment 1 were agar with bacteria, agar with Fucus spiralis, sulphidic agar medium, bare agar and an empty Petri dish. For experiment 2 azoic sediment with algae, azoic sediment with bacteria, a sulphidic medium, bare azoic sediment and an empty Petri dish were used. The intertidal experiment revealed that nematodes and nauplius larvae showed four- to tenfold higher densities in the Fucus treatment compared with the controls whereas deep-sea nematode and harpacticoid copepod densities in the sulphide treatment were more than three times higher compared with all other treatments. In both experiments nematode composition did not differ from the reference samples whereas proportions of harpacticoid copepods were increased in the treatments of the deep-sea experiment compared with the reference sample suggesting a better ability to select settlement sites than nematodes. In both experiments meiofauna abundance was highest in substrates with similar characteristics as their original habitat. These findings indicate that some meiofaunal organisms can selectively settle once they are suspended in the water column in the absence of water flow and therefore actively contribute to their dispersal at small spatial scales.
Keywords: AUV Sentry (Autonomous Underwater Vehicle)

Gene expression profiling of microbial activities and interactions in sediments under haloclines of E. Mediterranean deep hypersaline anoxic basins - Edgcomb, V P; Pachiadaki, M; Mara, P; Kormas, K; Leadbetter, E R; Bernhard, J M (ISME Journal, 2016)
Deep-sea hypersaline anoxic basins (DHABs) in the Eastern Mediterranean Sea are considered some of the most polyextreme habitats on Earth. In comparison to microbial activities occurring within the haloclines and brines of these unusual water column habitats near the Mediterranean seafloor, relatively little is known about microbial metabolic activities in the underlying sediments. In addition, it is not known whether activities are shaped by the unique chemistries of the different DHAB brines and whether evidence exists for active microbial eukaryotes in those sediments. Metatranscriptome analysis was applied to sediment samples collected using ROV Jason from underneath the haloclines of Urania, Discovery and L'Atalante DHABs and a control site. We report on expression of genes associated with sulfur and nitrogen cycling, putative osmolyte biosynthetic pathways and ion transporters, trace metal detoxification, selected eukaryotic activities (particularly of fungi), microbemicrobe interactions, and motility in sediments underlying the haloclines of three DHABs. Relative to our control sediment sample collected outside of Urania Basin, microbial communities (including eukaryotes) in the Urania and Discovery DHAB sediments showed upregulation of expressed genes associated with nitrogen transformations, osmolyte biosynthesis, heavy metals resistance and metabolism, eukaryotic organelle functions, and cell-cell interactions. Sediments underlying DHAB haloclines that have cumulative physico-chemical stressors within the limits of tolerance for microoorganisms can therefore be hotspots of activity in the deep Mediterranean Sea.
Keywords: ROV Jason (Remotely Operated Vehicle)

Geochemistry and iron isotope systematics of hydrothermal plume fall-out at East Pacific Rise 9°50′N - Rouxel, O J; Toner, B M; Manganini, S J; German, C R (Chemical Geology, 2016)
While gross hydrothermal fluxes entering the ocean are known to be significant, much remains unknown about the fate of this material as it disperses through the oceans, and its impact upon ocean biogeochemistry. Mineral precipitation within hydrothermal plumes removes hydrothermally-sourced metals from solution and also acts to scavenge trace elements from the surrounding water column. Here, we investigate the fate of particulate Fe released from high-temperature hydrothermal venting at EPR 9°50′N and its potential impact on local deep-ocean Fe-isotopic and geochemical budgets. We measured the geochemical composition, mineralogy and Fe isotope systematics of hydrothermal plume products in order to determine whether mineral precipitation imposes characteristic Fe-isotope “fingerprints” for hydrothermally sourced Fe in the deep ocean. Our sampling includes sediment trap deployments after the eruptive event of Jan. 2006, allowing the examination of temporal changes of hydrothermal fluxes over a 160 day period. Results show that Fe isotope composition in the high-temperature vent fluids is rather constant over the sampling period 2004–2008, and that secular variations of $δ$56Fe values of plume particles from − 0.03 to − 0.91‰ (relative to IRMM-14 standard) could be explained by local processes leading to variable mixing extents of hydrothermal, biogenic and lithogenic particles. Through geochemical modeling, we have calculated the relative abundances of hydrothermal plume components such as sulfides, Fe oxyhydroxides, organic matter, biogenic and lithogenic phases. We demonstrate that Fe isotope fractionation in the hydrothermal plume occurs during the formation and rapid settling of Fe-sulfides that are characterized by $δ$56Fe values ranging from − 0.73 ± 0.13‰ to − 0.86 ± 0.13‰, which is systematically lower than the end-member hydrothermal fluids ($δ$56Fe = − 0.4‰). This study suggests that both the initial Fe isotope composition of the high-temperature vent fluids and its initial Fe/H2S ratio (i.e. Fe-sulfide precipitation versus Fe-oxyhydroxide precipitation) should impose characteristic Fe isotope “fingerprints” for hydrothermally derived Fe in the deep ocean.
Keywords: HOV Alvin (Human Occupied Vehicle)

Growth rates and ages of deep-sea corals impacted by the Deepwater Horizon oil spill - Prouty, N G; Fisher, C R; Demopoulos, A W J; Druffel, E R M (Deep Sea Research Part II: Topical Studies in Oceanography, 2016)
The impact of the April 2010 Deepwater Horizon (DWH) spill on deep-sea coral communities in the Gulf of Mexico (GoM) is still under investigation, as is the potential for these communities to recover. Impacts from the spill include observation of corals covered with flocculent material, with bare skeleton, excessive mucous production, sloughing tissue, and subsequent colonization of damaged areas by hydrozoans. Information on growth rates and life spans of deep-sea corals is important for understanding the vulnerability of these ecosystems to both natural and anthropogenic perturbations, as well as the likely duration of any observed adverse impacts. We report radiocarbon ages and radial and linear growth rates based on octocorals (Paramuricea spp. and Chrysogorgia sp.) collected in 2010 and 2011 from areas of the DWH impact. The oldest coral radiocarbon ages were measured on specimens collected 11 km to the SW of the oil spill from the Mississippi Canyon (MC) 344 site: 599 and 55 cal yr BP, suggesting continuous life spans of over 600 years for Paramuricea biscaya, the dominant coral species in the region. Calculated radial growth rates, between 0.34 $μ$m yr−1 and 14.20 $μ$m yr−1, are consistent with previously reported proteinaceous corals from the GoM. Anomalously low radiocarbon ($Δ$14C) values for soft tissue from some corals indicate that these corals were feeding on particulate organic carbon derived from an admixture of modern surface carbon and a low 14C carbon source. Results from this work indicate fossil carbon could contribute 5–10{%} to the coral soft tissue $Δ$14C signal within the area of the spill impact. The influence of a low 14C carbon source (e.g., petro-carbon) on the particulate organic carbon pool was observed at all sites within 30 km of the spill site, with the exception of MC118, which may have been outside of the dominant northeast–southwest zone of impact. The quantitatively assessed extreme longevity and slow growth rates documented here highlight the vulnerability of these long-lived deep sea coral species to disturbance.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

The Guaymas Basin Hiking Guide to Hydrothermal Mounds, Chimneys, and Microbial Mats: Complex Seafloor Expressions of Subsurface Hydrothermal Circulation - Teske, A P; de Beer, D; McKay, L J; Tivey, M K; Biddle, J F; Hoer, D R; Lloyd, K G; Lever, M A; Roy, H; Albert, D B; Mendlovitz, H P; MacGregor, B J (Frontiers in Microbiology, 2016)
The hydrothermal mats, mounds, and chimneys of the southern Guaymas Basin are the surface expression of complex subsurface hydrothermal circulation patterns. In this overview, we document the most frequently visited features of this hydrothermal area with photographs, temperature measurements, and selected geochemical data; many of these distinct habitats await characterization of their microbial communities and activities. Microprofiler deployments on microbial mats and hydrothermal sediments show their steep geochemical and thermal gradients at millimeter-scale vertical resolution. Mapping these hydrothermal features and sampling locations within the southern Guaymas Basin suggest linkages to underlying shallow sills and heat flow gradients. Recognizing the inherent spatial limitations of much current Guaymas Basin sampling calls for comprehensive surveys of the wider spreading region.
Keywords: HOV Alvin (Human Occupied Vehicle)

How Clonal Is Clonal? Genome Plasticity across Multicellular Segments of a "Candidatus Marithrix sp." Filament from Sulfidic, Briny Seafloor Sediments in the Gulf of Mexico - Salman-Carvalho, V; Fadeev, E; Joye, S B; Teske, A P (Frontiers in Microbiology, 2016)
"Candidatus Marithrix" is a recently described lineage within the group of large sulfur bacteria (Beggiatoaceae, Gammaproteobacteria). This genus of bacteria comprises vacuolated, attached-living filaments that inhabit the sediment surface around vent and seep sites in the marine environment. A single filament is ca. 100 mu m in diameter, several millimeters long, and consists of hundreds of clonal cells, which are considered highly polyploid. Based on these characteristics, "Candidatus Marithrix" was used as a model organism for the assessment of genomic plasticity along segments of a single filament using next generation sequencing to possibly identify hotspots of microevolution. Using six consecutive segments of a single filament sampled from a mud volcano in the Gulf of Mexico, we recovered ca. 90{%} of the "Candidatus Marithrix" genome in each segment. There was a high level of genome conservation along the filament with average nucleotide identities between 99.98 and 100{%}. Different approaches to assemble all reads into a complete consensus genome could not fill the gaps. Each of the six segment datasets encoded merely a few hundred unique nucleotides and 5 or less unique genes the residual content was redundant in all datasets. Besides the overall high genomic identity, we identified a similar number of single nucleotide polymorphisms (SNPs) between the clonal segments, which are comparable to numbers reported for other clonal organisms. An increase of SNPs with greater distance of filament segments was not observed. The polyploidy of the cells was apparent when analyzing the heterogeneity of reads within a segment. Here, a strong increase in single nucleotide variants, or "intrasegmental sequence heterogeneity" (ISH) events, was observed. These sites may represent hotspots for genome plasticity, and possibly microevolution, since two thirds of these variants were not co-localized across the genome copies of the multicellular filament.
Keywords: HOV Alvin (Human Occupied Vehicle)

Hydrogen and thiosulfate limits for growth of a thermophilic, autotrophic Desulfurobacterium species from a deep-sea hydrothermal vent - Stewart, Lucy C; Llewellyn, James G; Butterfield, David A; Lilley, Marvin D; Holden, James F (ENVIRONMENTAL MICROBIOLOGY REPORTS, 2016)
Hydrothermal fluids (341 degrees C and 19 degrees C) were collected {<}1m apart from a black smoker chimney and a tubeworm mound on the Boardwalk edifice at the Endeavour Segment in the northeastern Pacific Ocean to study anaerobic microbial growth in hydrothermal mineral deposits. Geochemical modelling of mixed vent fluid and seawater suggests the mixture was anoxic above 55 degrees C and that low H-2 concentrations (79molkg(-1) in end-member hydrothermal fluid) limit anaerobic hydrogenotrophic growth above this temperature. A thermophilic, hydrogenotrophic sulfur reducer, Desulfurobacterium strain HR11, was isolated from the 19 degrees C fluid raising questions about its H-2-dependent growth kinetics. Strain HR11 grew at 40-77 degrees C (T-opt 72-75 degrees C), pH 5-8.5 (pH(opt) 6-7) and 1-5{%} (wt vol(-1)) NaCl (NaClopt 3-4{%}). The highest growth rates occurred when S2O32- and S degrees were reduced to H2S. Modest growth occurred by NO3- reduction. Monod constants for its growth were K-s of 30M for H-2 and K-s of 20M for S2O32- with a (max) of 2.0h(-1). The minimum H-2 and S2O32- concentrations for growth were 3M and 5M respectively. Possible sources of S2O32- and S degrees are from abiotic dissolved sulfide and pyrite oxidation by O-2.
Keywords: ROV Jason (Remotely Operated Vehicle)

Impact of protists on a hydrocarbon-degrading bacterial community from deep-sea Gulf of Mexico sediments: A microcosm study - Beaudoin, D J; Carmichael, C A; Nelson, R K; Reddy, C M; Teske, A P; Edgcomb, V P (Deep-Sea Research. Part II: Topical Studies in Oceanography, 2016)
In spite of significant advancements towards understanding the dynamics of petroleum hydrocarbon degrading microbial consortia, the impacts (direct or indirect via grazing activities) of bacterivorous protists remain largely unknown. Microcosm experiments were used to examine whether protistan grazing affects the petroleum hydrocarbon degradation capacity of a deep-sea sediment microbial community from an active Gulf of Mexico cold seep. Differences in n-alkane content between native sediment microcosms and those treated with inhibitors of eukaryotes were assessed by comprehensive two-dimensional gas chromatography following 30–90 day incubations and analysis of shifts in microbial community composition using small subunit ribosomal RNA gene clone libraries. More biodegradation was observed in microcosms supplemented with eukaryotic inhibitors. SSU rRNA gene clone libraries from oil-amended treatments revealed an increase in the number of proteobacterial clones (particularly $γ$-proteobacteria) after spiking sediments with diesel oil. Bacterial community composition shifted, and degradation rates increased, in treatments where protists were inhibited, suggesting protists affect the hydrocarbon degrading capacity of microbial communities in sediments collected at this Gulf of Mexico site.
Keywords: HOV Alvin (Human Occupied Vehicle)

Inflation-predictable behavior and co-eruption deformation at Axial Seamount - Nooner, Scott L; Chadwick Jr., William W (SCIENCE, 2016)
Deformation of the ground surface at active volcanoes provides information about magma movements at depth. Improved seafloor deformation measurements between 2011 and 2015 documented a fourfold increase in magma supply and confirmed that Axial Seamount's eruptive behavior is inflation-predictable, probably triggered by a critical level of magmatic pressure. A 2015 eruption was successfully forecast on the basis of this deformation pattern and marked the first time that deflation and tilt were captured in real time by a new seafloor cabled observatory, revealing the timing, location, and volume of eruption-related magma movements. Improved modeling of the deformation suggests a steeply dipping prolate-spheroid pressure source beneath the eastern caldera that is consistent with the location of the zone of highest melt within the subcaldera magma reservoir determined from multichannel seismic results.
Keywords: AUV Sentry (Autonomous Underwater Vehicle); ROV Jason (Remotely Operated Vehicle)

Insights into methane dynamics from analysis of authigenic carbonates and chemosynthetic mussels at newly-discovered Atlantic Margin seeps - Prouty, N G; Sahy, D; Ruppel, C D; Roark, E B; Condon, D; Brooke, S; Ross, S W; Demopoulos, A W J (Earth and Planetary Science Letters, 2016)
The recent discovery of active methane venting along the US northern and mid-Atlantic margin represents a new source of global methane not previously accounted for in carbon budgets from this region. However, uncertainty remains as to the origin and history of methane seepage along this tectonically inactive passive margin. Here we present the first isotopic analyses of authigenic carbonates and methanotrophic deep-sea mussels, Bathymodiolus sp., and the first direct constraints on the timing of past methane emission, based on samples collected at the upper slope Baltimore Canyon (∼385 m water depth) and deepwater Norfolk (∼1600 m) seep fields within the area of newly-discovered venting. The authigenic carbonates at both sites were dominated by aragonite, with an average View the MathML source$δ$C13 signature of −47‰−47‰, a value consistent with microbially driven anaerobic oxidation of methane-rich fluids occurring at or near the sediment–water interface. Authigenic carbonate U and Sr isotope data further support the inference of carbonate precipitation from seawater-derived fluids rather than from formation fluids from deep aquifers. Carbonate stable and radiocarbon (View the MathML source$δ$C13 and View the MathML source$Δ$C13) isotope values from living Bathymodiolus sp. specimens are lighter than those of seawater dissolved inorganic carbon, highlighting the influence of fossil carbon from methane on carbonate precipitation. U–Th dates on authigenic carbonates suggest seepage at Baltimore Canyon between 14.7±0.6 ka14.7±0.6 ka to 15.7±1.6 ka15.7±1.6 ka, and at the Norfolk seep field between 1.0±0.7 ka1.0±0.7 ka to 3.3±1.3 ka3.3±1.3 ka, providing constraint on the longevity of methane efflux at these sites. The age of the brecciated authigenic carbonates and the occurrence of pockmarks at the Baltimore Canyon upper slope could suggest a link between sediment delivery during Pleistocene sea-level lowstand, accumulation of pore fluid overpressure from sediment compaction, and release of overpressure through subsequent venting. Calculations show that the Baltimore Canyon site probably has not been within the gas hydrate stability zone (GHSZ) in the past 20 ka, meaning that in-situ release of methane from dissociating gas hydrate cannot be sustaining the seep. We cannot rule out updip migration of methane from dissociation of gas hydrate that occurs farther down the slope as a source of the venting at Baltimore Canyon, but consider that the history of rapid sediment accumulation and overpressure may play a more important role in methane emissions at this site.
Keywords: ROV Jason (Remotely Operated Vehicle)

Linkages between mineralogy, fluid chemistry, and microbial communities within hydrothermal chimneys from the Endeavour Segment, Juan de Fuca Ridge - Lin, T J; Ver Eecke, H C; Breves, E A; Dyar, M D; Jamieson, J W; Hannington, M D; Dahle, H; Bishop, J L; Lane, M D; Butterfield, D A; Kelley, D S; Lilley, M D; et al. (Geochemistry, Geophysics, Geosystems, 2016)
Rock and fluid samples were collected from three hydrothermal chimneys at the Endeavour Segment, Juan de Fuca Ridge to evaluate linkages among mineralogy, fluid chemistry, and microbial community composition within the chimneys. Mössbauer, midinfrared thermal emission, and visible-near infrared spectroscopies were utilized for the first time to characterize vent mineralogy, in addition to thin-section petrography, X-ray diffraction, and elemental analyses. A 282°C venting chimney from the Bastille edifice was composed primarily of sulfide minerals such as chalcopyrite, marcasite, and sphalerite. In contrast, samples from a 300°C venting chimney from the Dante edifice and a 321°C venting chimney from the Hot Harold edifice contained a high abundance of the sulfate mineral anhydrite. Geochemical modeling of mixed vent fluids suggested the oxic-anoxic transition zone was above 100°C at all three vents, and that the thermodynamic energy available for autotrophic microbial redox reactions favored aerobic sulfide and methane oxidation. As predicted, microbes within the Dante and Hot Harold chimneys were most closely related to mesophilic and thermophilic aerobes of the Betaproteobacteria and Gammaproteobacteria and sulfide-oxidizing autotrophic Epsilonproteobacteria. However, most of the microbes within the Bastille chimney were most closely related to mesophilic and thermophilic anaerobes of the Deltaproteobacteria, especially sulfate reducers, and anaerobic hyperthermophilic archaea. The predominance of anaerobes in the Bastille chimney indicated that other environmental factors promote anoxic conditions. Possibilities include the maturity or fluid flow characteristics of the chimney, abiotic Fe2+ and S2− oxidation in the vent fluids, or O2 depletion by aerobic respiration on the chimney outer wall.
Keywords: HOV Alvin (Human Occupied Vehicle)

Mesoscale biogeophysical characterization of Woolsey Mound (northern Gulf of Mexico), a new attribute of natural marine hydrocarbon seeps architecture - Macelloni, L; Lutken, C B; Ingrassia, M; D' Emidio, M; Pizzi, M (Marine Geology, 2016)
Located on the continental slope in 900 m of water, Woolsey Mound dominates seafloor morphology at Mississippi Canyon 118. The carbonate-hydrate mound is the site of the Gulf of Mexico Hydrates Research Consortium's seafloor observatory to investigate and monitor hydrographic, geophysical, geological, geochemical and biological processes of the hydrocarbon system, northern Gulf of Mexico. Innovative survey and monitoring systems, sensors, and tools have been developed to extract samples and data to unravel the history, character and composition of the site. Many hours of visual data have been collected to investigate benthic communities thriving at the cold seep site associated with the mound. These communities' habitats are described here, for the first time, in terms of faunal assemblage, substrate nature, and presence/absence of chemosynthetic species. Based on these factors, we grouped them into four benthic meso-habitats. We speculate that the spatial distribution of these meso-habitats is large enough to make this characteristic comparable to the geophysical response of the seismo-acoustic systems. We have tested this hypothesis carefully analyzing the relationship between benthic habitats zonation and the geophysical response of Side Scan Sonar, Chirp Subbottom, Surface Source Deep Receiver (SSDR) vertical incidence profiler and 3-D oil industry multichannel data. We observe that the geophysical response is not unique, a single habitat may correlate with many geophysical attributes, or a single geophysical attribute may span many habitats. However, we find that geophysical data can predict seep locations. They can also convey some information concerning community composition and complexity that function as proxies for seep duration/age while specific community components are believed to reflect composition of seep fluids. Although preliminary, this approach represents a novel classification/characterization for seafloor hydrocarbon seeps, one that reflects a historical component.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Metagenomic resolution of microbial functions in deep-sea hydrothermal plumes across the Eastern Lau Spreading Center - Anantharaman, Karthik; Breier, John A; Dick, Gregory J (ISME JOURNAL, 2016)
Microbial processes within deep-sea hydrothermal plumes affect ocean biogeochemistry on global scales. In rising hydrothermal plumes, a combination of microbial metabolism and particle formation processes initiate the transformation of reduced chemicals like hydrogen sulfide, hydrogen, methane, iron, manganese and ammonia that are abundant in hydrothermal vent fluids. Despite the biogeochemical importance of this rising portion of plumes, it is understudied in comparison to neutrally buoyant plumes. Here we use metagenomics and bioenergetic modeling to describe the abundance and genetic potential of microorganisms in relation to available electron donors in five different hydrothermal plumes and three associated background deep-sea waters from the Eastern Lau Spreading Center located in the Western Pacific Ocean. Three hundred and thirty one distinct genomic `bins' were identified, comprising an estimated 951 genomes of archaea, bacteria, eukarya and viruses. A significant proportion of these genomes is from novel microorganisms and thus reveals insights into the energy metabolism of heretofore unknown microbial groups. Community-wide analyses of genes encoding enzymes that oxidize inorganic energy sources showed that sulfur oxidation was the most abundant and diverse chemolithotrophic microbial metabolism in the community. Genes for sulfur oxidation were commonly present in genomic bins that also contained genes for oxidation of hydrogen and methane, suggesting metabolic versatility in these microbial groups. The relative diversity and abundance of genes encoding hydrogen oxidation was moderate, whereas that of genes for methane and ammonia oxidation was low in comparison to sulfur oxidation. Bioenergetic-thermodynamic modeling supports the metagenomic analyses, showing that oxidation of elemental sulfur with oxygen is the most dominant catabolic reaction in the hydrothermal plumes. We conclude that the energy metabolism of microbial communities inhabiting rising hydrothermal plumes is dictated by the underlying plume chemistry, with a dominant role for sulfur-based chemolithoautotrophy.
Keywords: ROV Jason (Remotely Operated Vehicle)

Metatranscriptomic insights into polyphosphate metabolism in marine sediments - Jones, Daniel S; Flood, Beverly E; Bailey, Jake V (ISME JOURNAL, 2016)
Microorganisms can influence inorganic phosphate (P-i) in pore waters, and thus the saturation state of phosphatic minerals, by accumulating and hydrolyzing intracellular polyphosphate (poly-P). Here we used comparative metatranscriptomics to explore microbial poly-P utilization in marine sediments. Sulfidic marine sediments from methane seeps near Barbados and from the Santa Barbara Basin (SBB) oxygen minimum zone were incubated under oxic and anoxic sulfidic conditions. Pi was sequestered under oxic conditions and liberated under anoxic conditions. Transcripts homologous to poly-P kinase type 2 (ppk2) were 6-22 x more abundant in metatranscriptomes from the anoxic incubations, suggesting that reversible poly-P degradation by Ppk2 may be an important metabolic response to anoxia by marine microorganisms. Overall, diverse taxa differentially expressed homologues of genes for poly-P degradation (ppk2 and exopolyphosphatase) under different incubation conditions. Sulfur-oxidizing microorganisms appeared to preferentially express genes for poly-P degradation under anoxic conditions, which may impact phosphorus cycling in a wide range of oxygen-depleted marine settings.
Keywords: ROV Jason (Remotely Operated Vehicle)

Microbial Communities in Methane- and Short Chain Alkane-Rich Hydrothermal Sediments of Guaymas Basin - Dowell, Frederick; Cardman, Zena; Dasarathy, Srishti; Kellermann, Matthias Y; Lipp, Julius S; Ruff, S Emil; Biddle, Jennifer F; McKay, Luke J; MacGregor, Barbara J; Lloyd, Karen G; Albert, Daniel B; Mendlovitz, Howard; et al. (FRONTIERS IN MICROBIOLOGY, 2016)
The hydrothermal sediments of Guaymas Basin, an active spreading center in the Gulf of California (Mexico), are rich in porewater methane, short-chain alkanes, sulfate and sulfide, and provide a model system to explore habitat preferences of microorganisms, including sulfate-dependent, methane- and short chain alkane-oxidizing microbial communities. In this study, hot sediments (above 60 degrees C) covered with sulfur-oxidizing microbial mats surrounding a hydrothermal mound (termed ``Mat Mound{\{}''{\}}) were characterized by porewater geochemistry of methane, C-2-C-6 short-chain alkanes, sulfate, sulfide, sulfate reduction rate measurements, in situ temperature gradients, bacterial and archaeal 16S rRNA gene clone libraries and V6 tag pyrosequencing. The most abundantly detected groups in the Mat mound sediments include anaerobic methane-oxidizing archaea of the ANME-1 lineage and its sister Glade ANME-1Guaymas, the uncultured bacterial groups SEEP-SRB2 within the Deltaproteobacteria and the separately branching HotSeep-1 Group; these uncultured bacteria are candidates for sulfate-reducing alkane oxidation and for sulfate-reducing syntrophy with ANME archaea. The archaeal dataset indicates distinct habitat preferences for ANME-1, ANME-1-Guaymas, and ANME-2 archaea in Guaymas Basin hydrothermal sediments. The bacterial groups SEEP-SRB2 and HotSeep-1 co-occur with ANME-1 and ANME-1Guaymas in hydrothermally active sediments underneath microbial mats in Guaymas Basin. We propose the working hypothesis that this mixed bacterial and archaeal community catalyzes the oxidation of both methane and short-chain alkanes, and constitutes a microbial community signature that is characteristic for hydrothermal and/or cold seep sediments containing both substrates.
Keywords: HOV Alvin (Human Occupied Vehicle)

Mid-water current aided localization for autonomous underwater vehicles - Medagoda, L; Williams, S B; Pizarro, O; Kinsey, J C; Jakuba, M V (Autonomous Robots, 2016)
Survey-class autonomous underwater vehicles (AUVs) typically rely on Doppler Velocity Logs (DVL) for precision localization near the seafloor. In cases where the seafloor depth is greater than the DVL bottom-lock range, localizing between the surface and the seafloor presents a localization problem since both GPS and DVL observations are unavailable in the mid-water column. This work proposes a solution to this problem that exploits the fact that current profile layers of the water column are near constant over short time scales (in the scale of minutes). Using observations of these currents obtained with the Acoustic Doppler Current Profiler mode of the DVL during descent, along with data from other sensors, the method discussed herein constrains position error. The method is validated using field data from the Sirius AUV coupled with view-based Simultaneous Localization and Mapping (SLAM) and on descents up to 3km deep with the Sentry AUV.
Keywords: AUV Sentry (Autonomous Underwater Vehicle)

Nanocalorimetric Characterization of Microbial Activity in Deep Subsurface Oceanic Crustal Fluids - Robador, Alberto; LaRowe, Douglas E; Jungbluth, Sean P; Lin, Huei-Ting; Rappe, Michael S; Nealson, Kenneth H; Amend, Jan P (FRONTIERS IN MICROBIOLOGY, 2016)
Although fluids within the upper oceanic basaltic crust harbor a substantial fraction of the total prokaryotic cells on Earth, the energy needs of this microbial population are unknown. In this study, a nanocalorimeter (sensitivity down to 1.2 nW ml(-1)) was used to measure the enthalpy of microbially catalyzed reactions as a function of temperature in samples from two distinct crustal fluid aquifers. Microorganisms in unamended, warm (63 degrees C) and geochemically altered anoxic fluids taken from 292 meters sub-basement (msb) near the Juan de Fuca Ridge produced 267.3 mJ of heat over the course of 97 h during a step-wise isothermal scan from 35.5 to 85.0 degrees C. Most of this heat signal likely stems from the germination of thermophilic endospores (6.66 x 10(4) cells ml(-1) FLUID) and their subsequent metabolic activity at temperatures greater than 50 degrees C. The average cellular energy consumption (5.68 pW cell(-1)) reveals the high metabolic potential of a dormant community transported by fluids circulating through the ocean crust. By contrast, samples taken from 293 msb from cooler (3.8 degrees C), relatively unaltered oxic fluids, produced 12.8 mJ of heat over the course of 14 h as temperature ramped from 34.8 to 43.0 degrees C. Corresponding cell-specific energy turnover rates (0.18 pW cell(-1)) were converted to oxygen uptake rates of 24.5 nmol O-2 ml(-1) FLUID d(-1), validating previous model predictions of microbial activity in this environment. Given that the investigated fluids are characteristic of expansive areas of the upper oceanic crust, the measured metabolic heat rates can be used to constrain boundaries of habitability and microbial activity in the oceanic crust.
Keywords: ROV Jason (Remotely Operated Vehicle)

New records of the deep-sea anemone Phelliactis callicyclus Riemann-Zurneck, 1973 (Cnidaria, Actiniaria, Hormathiidae) from the Gulf of California, Mexico - Hendrickx, M E; Hinojosa-Corona, A; Ayon-Parente, M (Zootaxa, 2016)
Specimens of a deep-sea anemone were observed in photographs and video footage taken with the Remotely Operated Vehicle JASON (WHOI Deep Submergence Laboratory) in the Gulf of California, Mexico, in May 2008. Comparison of our material with photographs and description of this species available in literature indicate that the sea anemones filmed during the JASON survey are most likely to represent Phelliactis callicyclus Riemann-Zurneck, 1973. This species has previously been reported from a locality in the Gulf of California near the present record. During the JASON survey, 28 specimens of P. callicyclus were spotted in 27 locations during six dives. The specimens occurred on angular rock outcrops along the escarpments of the transform faults of the Gulf of California, between depths of 993-2543 m and at temperatures ranging from 2.3 to 4.5 degrees C. Based on these new records, Phelliactis callicyclus appears to be widely spread in the Gulf of California.
Keywords: ROV Jason (Remotely Operated Vehicle)

Newly upgraded ROV Jason: Bigger and better (Ocean News {&} Technology, 2016)
A major, {\$}2.4 million upgrade funded by the National Science Foundation has made the ROV Jason more capable than ever. This 12-month-long project, conducted by engineers at WHOI, which designed and built the vehicle, has increased the vehicle payload and range of activities and streamlined the vehicle operation. This is Jason's first upgrade of this magnitude since its second-generation launch in 2002; the original Jason was launched in 1988. The ROV is operated by WHOI for the nation's ocean scientists as part of the National Deep Submergence Facility. The upgrade has other added benefits as well. The heavy lift capability will be used at seafloor sites where several-hundred-meters-long sensor strings are routinely deployed into and recovered from seafloor bore holes.
Keywords: ROV Jason (Remotely Operated Vehicle)

Novel microbial assemblages inhabiting crustal fluids within mid-ocean ridge flank subsurface basalt - Jungbluth, S P; Bowers, R M; Lin, H-T; Cowen, J P; Rappe, M S (ISME Journal, 2016)
Although little is known regarding microbial life within our planet's rock-hosted deep subseafloor biosphere, boreholes drilled through deep ocean sediment and into the underlying basaltic crust provide invaluable windows of access that have been used previously to document the presence of microorganisms within fluids percolating through the deep ocean crust. In this study, the analysis of 1.7 million small subunit ribosomal RNA genes amplified and sequenced from marine sediment, bottom seawater and basalt-hosted deep subseafloor fluids that span multiple years and locations on the Juan de Fuca Ridge flank was used to quantitatively delineate a subseafloor microbiome comprised of distinct bacteria and archaea. Hot, anoxic crustal fluids tapped by newly installed seafloor sampling observatories at boreholes U1362A and U1362B contained abundant bacterial lineages of phylogenetically unique Nitrospirae, Aminicenantes, Calescamantes and Chloroflexi. Although less abundant, the domain Archaea was dominated by unique, uncultivated lineages of marine benthic group E, the Terrestrial Hot Spring Crenarchaeotic Group, the Bathyarchaeota and relatives of cultivated, sulfate-reducing Archaeoglobi. Consistent with recent geochemical measurements and bioenergetic predictions, the potential importance of methane cycling and sulfate reduction were imprinted within the basalt-hosted deep subseafloor crustal fluid microbial community. This unique window of access to the deep ocean subsurface basement reveals a microbial landscape that exhibits previously undetected spatial heterogeneity.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Oceanographic patterns and carbonate chemistry in the vicinity of cold-water coral reefs in the Gulf of Mexico: Implications for resilience in a changing ocean - Georgian, Samuel E; DeLeo, Danielle; Durkin, Alanna; Gomez, Carlos E; Kurman, Melissa; Lunden, Jay J; Cordes, Erik E (LIMNOLOGY AND OCEANOGRAPHY, 2016)
To accurately assess the threat that global climate change poses to marine systems, a detailed baseline of the current carbonate chemistry and other oceanographic conditions is required. Despite the heightened vulnerability of deep-sea communities to ocean acidification, there have been relatively few studies investigating the carbonate chemistry immediately above cold-water coral reefs. Here, we present data collected during five cruises from 2010 to 2014 in the northern Gulf of Mexico and quantify the carbonate system and other oceanographic parameters in offshore surface-waters, the water column, and at deep benthic sites. Benthic sites containing the scleractinian cold-water coral L. pertusa occurred in waters with a relatively wide temperature range (6.8-13.6 degrees C), low potential density (sigma(theta)=26.9 +/- 0.3 kg m(-3)), low dissolved oxygen concentration (111.3 +/- 2.0 mu mol kg(-1)), low pH(T) (7.87 +/- 0.04), low Omega(ARAG) (1.31 +/- 0.14), and a low availability of carbonate ions (94.4 +/- 9.2 mu mol kg(-1)) compared with L. pertusa habitats in other regions. Based on previous modelling and experimental results, these values place L. pertusa at the edge of its viable niche in the deep Gulf of Mexico. However, significantly elevated total alkalinity (+139-44 mu mol kg(-1)) was detected above large L. pertusa mounds, suggesting that carbonate dissolution within the mounds may be partially ameliorating the direct effects of ocean acidification. Together, these results provide an important baseline for assessing future oceanographic changes in the Gulf of Mexico and for predicting the resilience of cold-water coral reefs to global climate and ocean change.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Patterns and variability in geochemical signatures and microbial activity within and between diverse cold seep habitats along the lower continental slope, Northern Gulf of Mexico - Bowles, Marshall; Hunter, Kimberley S; Samarkin, Vladimir; Joye, Samantha (DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY, 2016)
We collected 69 sediment cores from distinct ecological and geological settings along the deep slope in the Northern Gulf of Mexico to evaluate whether specific geochemical- or habitat-related factors correlated with rates of microbial processes and geochemical signatures. By collecting replicate cores from distinct habitats across multiple sites, we illustrate and quantify the heterogeneity of cold seep geochemistry and microbial activity. These data also document the factors driving unique aspects of the geochemistry of deep slope gas, oil and brine seeps. Surprisingly little variation was observed between replicate (n=2-5) cores within sites for most analytes (except methane), implying that the common practice of collecting one core for geochemical analysis can capture the signature of a habitat in most cases. Depth-integrated concentrations of methane, dissolved inorganic carbon (DIC), and calcium were the predominant geochemical factors that correlated with a site's ecological or geological settings. Pore fluid methane concentration was related to the phosphate and DIC concentration, as well as to rates of sulfate reduction. While distinctions between seep habitats were identified from geochemical signatures, habitat specific geochemistry varied little across sites. The relative concentration of dissolved inorganic nitrogen versus phosphorus suggests that phosphorus availability limits biomass production at cold seeps. Correlations between calcium, chloride, and phosphate concentrations were indicative of brine-associated phosphate transport, suggesting that in addition to the co-migration of methane, dissolved organic carbon, and ammonium with brine, phosphate delivery is also associated with brine advection. (C) 2016 Published by Elsevier Ltd.
Keywords: ROV Jason (Remotely Operated Vehicle)

Petrology and geochronology of lavas from Ka‘ula Volcano: Implications for rejuvenated volcanism of the Hawaiian mantle plume - Garcia, M O; Weis, D; Jicha, B R; Ito, G; Hanano, D (Geochimica et Cosmochimica Acta, 2016)
Marine surveying and submersible sampling of Ka‘ula Volcano, located 100 km off the axis of the Hawaiian chain, revealed widespread areas of young volcanism. New 40Ar/39Ar and geochemical analyses of the olivine-phyric submarine and subaerial volcanic rocks show that Ka‘ula is shrouded with 1.9–0.5 Ma alkalic basalts. The ages and chemistry of these rocks overlap with rejuvenated lavas on nearby, northern Hawaiian Island shields (Ni‘ihau, Kaua‘i and South Kaua‘i Swell). Collectively, these rejuvenated lavas cover a vast area (∼7000 km2), much more extensive than any other area of rejuvenated volcanism worldwide. Ka‘ula rejuvenated lavas range widely in alkalinity and incompatible element abundances (e.g., up to 10× P2O5 at a given MgO value) and ratios indicating variable degrees of melting of a heterogeneous source. Heavy REE elements in Ka‘ula lavas are pinned at a mantle normalized Yb value of 10 ± 1, reflecting the presence of garnet in the source. Trace element ratios indicate the source also contained phlogopite and an Fe–Ti oxide. The new Ka‘ula ages show that rejuvenated volcanism was nearly coeval from ∼0.3 to 0.6 Ma along a 450 km segment of the Hawaiian Islands (from West Maui to north of Ka‘ula). The ages and volumes for rejuvenated volcanism are inconsistent with all but one geodynamic melting model proposed to date. This model advocates a significant contribution of pyroxenite to rejuvenated magmas. Analyses of olivine phenocryst compositions suggest a major (33–69{%}) pyroxenite component in Ka‘ula rejuvenated lavas, which correlates positively with radiogenic Pb isotope ratios for Ka‘ula. This correlation is also observed in lavas from nearby South Kaua‘i lavas, as was reported for Atlantic oceanic islands. The presence of pyroxenite in the source may have extended the duration and volume of Hawaiian rejuvenated volcanism.
Keywords: ROV Jason (Remotely Operated Vehicle)

Productivity, metabolism and physiology of free-living chemoautotrophic Epsilonproteobacteria - McNichol, J (2016)
Chemoautotrophic ecosystems at deep-sea hydrothermal vents were discovered in 1977, but not until 1995 were free-living autotrophic Epsilonproteobacteria identified as important microbial community members. Because the deep-sea is food-starved, the autotrophic metabolism of hydrothermal vent Epsilonproteobacteria may be very important for deep-sea consumers. However, quantifying their metabolic activities in situ has remained difficult, and biochemical mechanisms underlying their autotrophic physiology are poorly described. To gain insight into environmental processes, an approach was developed for incubations of microbes at in situ pressure and temperature (25 MPa, 24°C) with various combinations of electron donors/acceptors (H2, O2 and NO3 and 13HCO3) as a tracer to track carbon fixation. During short (18-24 h) incubations of low-temperature vent fluids from Crab Spa (9°N East Pacific Rise), the concentration of electron donors/acceptors and cell numbers were monitored to quantify microbial processes. Measured rates were generally higher than previous studies, and the stoichiometry of microbially-catalyzed redox reactions revealed new insights into sulfur and nitrogen cycling. Single-cell, taxonomically-resolved tracer incorporation showed Epsilonproteobacteria dominated carbon fixation, and their growth efficiency was calculated based on electron acceptor consumption. Using these data, in situ primary productivity, microbial standing stock, and average biomass residence time of the deep-sea vent subseafloor biosphere were estimated. Finally, the population structures of the most abundant genera Sulfurimonas and Thioreductor were shown to be strongly influenced by pO2 and temperature respectively, providing a mechanism for niche differentiation in situ. To gain insights into the core biochemical reactions underlying autotrophy in Epsilonprotebacteria, a theoretical metabolic model of Sulfurimonas denitrificans was developed. Validated iteratively by comparing in silico yields with data from chemostat experiments, the model generated hypotheses explaining critical, yet so far unresolved reactions supporting chemoautotrophy in Epsilonproteobacteria. For example, it provides insight into how energy is conserved during sulfur oxidation coupled to denitrification, how reverse electron transport produces ferredoxin for carbon fixation, and why aerobic growth yields are only slightly higher compared to denitrification. As a whole, this thesis provides important contributions towards understanding core mechanisms of chemoautrophy, as well as the in situ productivity, physiology and ecology of autotrophic Epsilonproteobacteria.
Keywords: ROV Jason (Remotely Operated Vehicle)

Sedimentary pyrite $δ$34S differs from porewater sulfide in Santa Barbara Basin: Proposed role of organic sulfur - Raven, M R; Sessions, A L; Fischer, W W; Adkins, J F (Geochimica et Cosmochimica Acta, 2016)
Santa Barbara Basin sediments host a complex network of abiotic and metabolic chemical reactions that knit together the carbon, sulfur, and iron cycles. From a 2.1-m sediment core collected in the center of the basin, we present high-resolution profiles of the concentrations and isotopic compositions of all the major species in this system: sulfate, sulfide (∑H2S), elemental sulfur (S0), pyrite, extractable organic sulfur (OS), proto-kerogen S, total organic and dissolved inorganic carbon, and total and reducible iron. Below 10 cm depth, the core is characterized by low apparent sulfate reduction rates ({<}0.01 mM/yr) except near the sulfate-methane transition zone. Surprisingly, pyrite forming in shallow sediments is ∼30‰ more 34S-depleted than coexisting ∑H2S in porewater. S0 has the same strongly 34S-depleted composition as pyrite where it forms near the sediment–water interface, though not at depth. This pattern is not easily explained by conventional hypotheses in which sedimentary pyrite derives from abiotic reactions with porewater ∑H2S or from the products of S0 disproportionation. Instead, we propose that pyrite formation in this environment occurs within sulfate reducing microbial aggregates or biofilms, where it reflects the isotopic composition of the immediate products of bacterial sulfate reduction. Porewater ∑H2S in Santa Barbara Basin may be more 34S-enriched than pyrite due to equilibration with relatively 34S-enriched OS. The difference between OS and pyrite $δ$34S values would then reflect the balance between microbial sulfide formation and the abundance of exchangeable OS. Both OS and pyrite $δ$34S records thus have the potential to provide valuable information about biogeochemical cycles and redox structure in sedimentary paleoenvironments.
Keywords: ROV Jason (Remotely Operated Vehicle)

Subaqueous cryptodome eruption, hydrothermal activity and related seafloor morphologies on the andesitic North Su volcano - Thal, J; Tivey, M A; Yoerger, D R; Bach, W (Journal of Volcanology and Geothermal Research, 2016)
North Su is a double-peaked active andesite submarine volcano located in the eastern Manus Basin of the Bismarck Sea that reaches a depth of 1154 m. It hosts a vigorous and varied hydrothermal system with black and white smoker vents along with several areas of diffuse venting and deposits of native sulfur. Geologic mapping based on ROV observations from 2006 and 2011 combined with morphologic features identified from repeated bathymetric surveys in 2002 and 2011 documents the emplacement of a volcanic cryptodome between 2006 and 2011. We use our observations and rock analyses to interpret an eruption scenario where highly viscous, crystal-rich andesitic magma erupted slowly into the water-saturated, gravel-dominated slope of North Su. An intense fragmentation process produced abundant blocky clasts of a heterogeneous magma (olivine crystals within a rhyolitic groundmass) that only rarely breached through the clastic cover onto the seafloor. Phreatic and phreatomagmatic explosions beneath the seafloor cause mixing of juvenile and pre-existing lithic clasts and produce a volcaniclastic deposit. This volcaniclastic deposit consists of blocky, non-altered clasts next, variably (1–100{%}) altered clasts, hydrothermal precipitates and crystal fragments. The usually applied parameters to identify juvenile subaqueous lava fragments, i.e. fluidal shape or chilled margin, were not applicable to distinguish between pre-existing non-altered clasts and juvenile clasts. This deposit is updomed during further injection of magma and mechanical disruption. Gas-propelled turbulent clast-recycling causes clasts to develop variably rounded shapes. An abundance of blocky clasts and the lack of clasts typical for the contact of liquid lava with water is interpreted to be the result of a cooled, high-viscosity, crystal-rich magma that failed as a brittle solid upon stress. The high viscosity allows the lava to form blocky and short lobes. The pervasive volcaniclastic cover on North Su is partly cemented by hydrothermal precipitates. These hydrothermally-cemented breccias, crusts and single pillars show that hydrothermal circulation through a thick layer of volcaniclastic deposits can temporarily increase slope stability through precipitation and cementation.
Keywords: AUV ABE (Autonomous Benthic Explorer); ROV Jason (Remotely Operated Vehicle)

Subseafloor microbial communities in hydrogen-rich vent fluids from hydrothermal systems along the Mid-Cayman Rise - Reveillaud, Julie; Reddington, Emily; McDermott, Jill; Algar, Christopher; Meyer, Julie L; Sylva, Sean; Seewald, Jeffrey; German, Christopher R; Huber, Julie A (ENVIRONMENTAL MICROBIOLOGY, 2016)
Warm fluids emanating from hydrothermal vents can be used as windows into the rocky subseafloor habitat and its resident microbial community. Two new vent systems on the Mid-Cayman Rise each exhibits novel geologic settings and distinctively hydrogen-rich vent fluid compositions. We have determined and compared the chemistry, potential energy yielding reactions, abundance, community composition, diversity, and function of microbes in venting fluids from both sites: Piccard, the world's deepest vent site, hosted in mafic rocks; and Von Damm, an adjacent, ultramafic-influenced system. Von Damm hosted a wider diversity of lineages and metabolisms in comparison to Piccard, consistent with thermodynamic models that predict more numerous energy sources at ultramafic systems. There was little overlap in the phylotypes found at each site, although similar and dominant hydrogen-utilizing genera were present at both. Despite the differences in community structure, depth, geology, and fluid chemistry, energetic modelling and metagenomic analysis indicate near functional equivalence between Von Damm and Piccard, likely driven by the high hydrogen concentrations and elevated temperatures at both sites. Results are compared with hydrothermal sites worldwide to provide a global perspective on the distinctiveness of these newly discovered sites and the interplay among rocks, fluid composition and life in the subseafloor.
Keywords: ROV Jason (Remotely Operated Vehicle)

Sustained in situ measurements of dissolved oxygen, methane and water transport processes in the benthic boundary layer at MC118, northern Gulf of Mexico - Martens, Christopher S; Mendlovitz, Howard P; Seim, Harvey; Lapham, Laura; D'Emidio, Marco (DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY, 2016)
Within months of the BP Macondo Wellhead blowout, elevated methane concentrations within the water column revealed a significant retention of light hydrocarbons in deep waters plus corresponding dissolved oxygen (DO) deficits. However, chemical plume tracking efforts were hindered by a lack of in situ monitoring capabilities. Here, we describe results from in situ time-series, lander-based investigations of physical and biogeochemical processes controlling dissolved oxygen, and methane at Mississippi Canyon lease block 118 (similar to 18 km from the oil spill) conducted shortly after the blowout through April 2012. Multiple sensor arrays plus open-cylinder flux chambers ({\{}''{\}}chimneys{\{}''{\}}) deployed from a benthic lander collected oxygen, methane, pressure, and current speed and direction data within one meter of the seafloor. The ROVARD lander system was deployed for an initial 21-day test experiment (9/13/2010-10/04/2010) at 882 m depth before a longer 160-day deployment (10/24/2011-4/01/2012) at 884 m depth. Temporal variability in current directions and velocities and water temperatures revealed strong influences of bathymetrically steered currents and overlying along-shelf flows on local and regional water transport processes. DO concentrations and temperature were inversely correlated as a result of water mass mixing processes. Flux chamber measurements during the 160-day deployment revealed total oxygen utilization (TOU) averaging 11.6 mmol/m(2) day. Chimney DO concentrations measured during the 21-day deployment exhibited quasi-daily variations apparently resulting from an interaction between near inertial waves and the steep topography of an elevated scarp immediately adjacent to the 21-day deployment site that modulated currents at the top of the chimney. Variability in dissolved methane concentrations suggested significant temporal variability in gas release from nearby hydrocarbon seeps and/or delivery by local water transport processes. Free-vehicle (lander) monitoring over time scales of months to years utilizing in situ sensors can provide an understanding of processes controlling water transport, respiration and the fate and impacts of accidental and natural gas and oil releases. (C) 2015 Elsevier Ltd. All rights reserved.
Keywords: ROV Jason (Remotely Operated Vehicle)

Temperature and Redox Effect on Mineral Colonization in Juan de Fuca Ridge Flank Subsurface Crustal Fluids - Baquiran, Jean-Paul M; Ramirez, Gustavo A; Haddad, Amanda G; Toner, Brandy M; Hulme, Samuel; Wheat, Charles G; Edwards, Katrina J; Orcutt, Beth N (FRONTIERS IN MICROBIOLOGY, 2016)
To examine microbe-mineral interactions in subsurface oceanic crust, we evaluated microbial colonization on crustal minerals that were incubated in borehole fluids for 1 year at the seafloor wellhead of a crustal borehole observatory (IODP Hole U1301A, Juan de Fuca Ridge flank) as compared to an experiment that was not exposed to subsurface crustal fluids (at nearby IODP Hole U1301B). In comparison to previous studies at these same sites, this approach allowed assessment of the effects of temperature, fluid chemistry, and/or mineralogy on colonization patterns of different mineral substrates, and an opportunity to verify the approach of deploying colonization experiments at an observatory wellhead at the seafloor instead of within the borehole. The Hole U1301B deployment did not have biofilm growth, based on microscopy and DNA extraction, thereby confirming the integrity of the colonization design against bottom seawater intrusion. In contrast, the Hole U1301A deployment supported biofilms dominated by Epsilonproteobacteria (43.5{%} of 370 16S rRNA gene clone sequences) and Gammaproteobacteria (29.3{%}). Sequence analysis revealed overlap in microbial communities between different minerals incubated at the Hole U1301A wellhead, indicating that mineralogy did not separate biofilm structure within the 1-year colonization experiment. Differences in the Hole U1301A wellhead biofilm community composition relative to previous studies from within the borehole using similar mineral substrates suggest that temperature and the diffusion of dissolved oxygen through plastic components influenced the mineral colonization experiments positioned at the wellhead. This highlights the capacity of low abundance crustal fluid taxa to rapidly establish communities on diverse mineral substrates under changing environmental conditions such as from temperature and oxygen.
Keywords: ROV Jason (Remotely Operated Vehicle)

Thermal and geochemical influences on microbial biogeography in the hydrothermal sediments of Guaymas Basin, Gulf of California - McKay, Luke; Klokman, Vincent W; Mendlovitz, Howard P; LaRowe, Douglas E; Hoer, Daniel R; Albert, Daniel; Amend, Jan P; Teske, Andreas (ENVIRONMENTAL MICROBIOLOGY REPORTS, 2016)
Extreme thermal gradients and compressed metabolic zones limit the depth range of microbial colonization in hydrothermally active sediments at Guaymas Basin. We investigated the physicochemical characteristics of this ecosystem and their influence on microbial community structure. Temperature-related trends of C-13 values of methane and dissolved inorganic carbon from 36 sediment cores suggest in situ thermal limits for microbial anaerobic methane oxidation and organic carbon re-mineralization near 80 degrees C and 100 degrees C respectively. Temperature logging probes deposited in hydrothermal sediments for 8 days demonstrate substantial thermal fluctuations of up to 25 degrees C. Putative anaerobic methanotroph (ANME) populations dominate the archaeal community, transitioning from ANME-1 archaea in warm surficial sediments towards ANME-1 Guaymas archaea as temperatures increase downcore. Since ANME archaea performing anaerobic oxidation of methane double on longer time scales (months) compared with relatively rapid in situ temperature fluctuations (hours to days), we conclude that ANME archaea possess a high tolerance for short-term shifts in the thermal regime.
Keywords: HOV Alvin (Human Occupied Vehicle)

Tracing the production and fate of individual archaeal intact polar lipids using stable isotope probing - Kellermann, Matthias Y; Yoshinaga, Marcos Y; Wegener, Gunter; Krukenberg, Viola; Hinrichs, Kai-Uwe (ORGANIC GEOCHEMISTRY, 2016)
Analysis of cellular membrane lipids has been widely applied to describe the microbial community composition in natural systems. When combined with stable isotope probing (SIP) experiments, deuterium label (D2O) uptake into lipids enables assessment of microbial biomass production. We performed SIP on methane-rich, hydrothermally-heated sediments to examine the de novo production of individual archaeal intact polar lipids (IPLs) by mesophilic anaerobic methane oxidizing group-1 archaea (ANME-1). The greatest extent of label uptake was by phosphatidyl glycerol archaeol (PG-AR), reaching 50{%} of the medium's label concentration in only 10 days. This indicates PG-AR as an important cell membrane lipid during the active growth phase of mesophilic ANME-1. Much less label uptake was into intact polar glycerol dibiphytanyl glycerol tetraethers (GDGTs), especially for those bound to diglycosidic head groups. The low production of these GDGTs contrasts with their predominance in ANME-1-dominated natural samples. We attribute the differential label uptake among individual IPLs to the ANME-1 tetraether biosynthetic pathway. This mechanism likely involves head-to-head condensation of two molecules of PG-AR and progressive substitution of PG by glycosidic head groups. The observation that ANME-1 invest in the synthesis of diethers during optimum growth suggests intact ARs and/or phosphate-bearing tetraethers as important biomarkers for actively growing populations in natural environments, while the diglycosidic GDGTs appear to signal stationary ANME-1 communities. (C) 2016 Elsevier Ltd. All rights reserved.
Keywords: HOV Alvin (Human Occupied Vehicle)

Transcription, Signaling Receptor Activity, Oxidative Phosphorylation, and Fatty Acid Metabolism Mediate the Presence of Closely Related Species in Distinct Intertidal and Cold-Seep Habitats - Van Campenhout, Jelle; Vanreusel, Ann; Van Belleghem, Steven; Derycke, Sofie (GENOME BIOLOGY AND EVOLUTION, 2016)
Bathyal cold seeps are isolated extreme deep-sea environments characterized by low species diversity while biomass can be high. The Hakon Mosby mud volcano (Barents Sea, 1,280 m) is a rather stable chemosynthetic driven habitat characterized by prominent surface bacterial mats with high sulfide concentrations and low oxygen levels. Here, the nematode Halomonhystera hermesithrives in high abundances (11,000 individuals 10 cm(-2)). Halomonhystera hermesi is a member of the intertidal Halomonhystera disjuncta species complex that includes five cryptic species (GD 1-5). GD1-5's common habitat is characterized by strong environmental fluctuations. Here, we compared the transcriptomes of H. hermesi and GD1, H. hermesi's closest relative. Genes encoding proteins involved in oxidative phosphorylation are more strongly expressed in H. hermesi than in GD1, and many genes were only observed in H. hermesi while being completely absent in GD1. Both observations could in part be attributed to high sulfide concentrations and low oxygen levels. Additionally, fatty acid elongation was also prominent in H. hermesi confirming the importance of highly unsaturated fatty acids in this species. Significant higher amounts of transcription factors and genes involved in signaling receptor activity were observed in GD1 (many of which were completely absent in H. hermesi), allowing fast signaling and transcriptional reprogramming which can mediate survival in dynamic intertidal environments. GC content was approximately 8{%} higher in H. hermesi coding unigenes resulting in differential codon usage between both species and a higher proportion of amino acids with GC-rich codons in H. hermesi. In general our results showed that most pathways were active in both environments and that only three genes are under natural selection. This indicates that also plasticity should be taken in consideration in the evolutionary history of Halomonhystera species. Such plasticity, as well as possible preadaptation to low oxygen and high sulfide levels might have played an important role in the establishment of a cold-seep Halomonhystera population.
Keywords: AUV Sentry (Autonomous Underwater Vehicle)

Transience and persistence of natural hydrocarbon seepage in Mississippi Canyon, Gulf of Mexico - Garcia-Pineda, O; MacDonald, I; Silva, M; Shedd, W; Daneshgar Asl, S; Schumaker, B (Deep Sea Research Part II: Topical Studies in Oceanography, 2016)
Analysis of the magnitude of oil discharged from natural hydrocarbon seeps can improve understanding of the carbon cycle and the Gulf of Mexico (GOM) ecosystem. With use of a large archive of remote sensing data, in combination with geophysical and multibeam data, we identified, mapped, and characterized natural hydrocarbon seeps in the Macondo prospect region near the wreck site of the drill-rig Deepwater Horizon (DWH). Satellite image processing and the cluster analysis revealed locations of previously undetected seep zones. Including duplicate detections, a total of 562 individual gas plumes were also observed in multibeam surveys. In total, SAR imagery confirmed 52 oil-producing seep zones in the study area. In almost all cases gas plumes were associated with oil-producing seep zones. The cluster of seeps in the vicinity of lease block MC302 appeared to host the most persistent and prolific oil vents. Oil slicks and gas plumes observed over the DWH site were consistent with discharges of residual oil from the wreckage. In contrast with highly persistent oil seeps observed in the Green Canyon and Garden Banks lease areas, the seeps in the vicinity of Macondo Prospect were intermittent. The difference in the number of seeps and the quantity of surface oil detected in Green Canyon was almost two orders of magnitude greater than in Mississippi Canyon.
Keywords: HOV Alvin (Human Occupied Vehicle)

Trophosome of the Deep-Sea Tubeworm Riftia pachyptila Inhibits Bacterial Growth - Klose, Julia; Aistleitner, Karin; Horn, Matthias; Krenn, Liselotte; Dirsch, Verena; Zehl, Martin; Bright, Monika (PLOS ONE, 2016)
The giant tubeworm Riftia pachyptila lives in symbiosis with the chemoautotrophic gamma-proteobacterium Cand. Endoriftia persephone. Symbionts are released back into the environment upon host death in high-pressure experiments, while microbial fouling is not involved in trophosome degradation. Therefore, we examined the antimicrobial effect of the tubeworm's trophosome and skin. The growth of all four tested Gram-positive, but only of one of the tested Gram-negative bacterial strains was inhibited by freshly fixed and degrading trophosome (incubated up to ten days at either warm or cold temperature), while no effect on Saccharomyces cerevisiae was observed. The skin did not show antimicrobial effects. A liquid chromatography-mass spectrometric analysis of the ethanol supernatant of fixed trophosomes lead to the tentative identification of the phospholipids 1-palmitoleyl-2-lyso- phosphatidylethanolamine, 2-palmitoleyl-1-lyso-phosphatidylethanolamine and the free fatty acids palmitoleic, palmitic and oleic acid, which are known to have an antimicrobial effect. As a result of tissue autolysis, the abundance of the free fatty acids increased with longer incubation time of trophosome samples. This correlated with an increasing growth inhibition of Bacillus subtilis and Listeria welshimeri, but not of the other bacterial strains. Therefore, the free fatty acids produced upon host degradation could be the cause of inhibition of at least these two bacterial strains.
Keywords: ROV Jason (Remotely Operated Vehicle)

Vertical water mass structure in the North Atlantic influences the bathymetric distribution of species in the deep-sea coral genus Paramuricea - Radice, V Z; Quattrini, A M; Wareham, V E; Edinger, E N; Cordes, E E (Deep Sea Research Part I: Oceanographic Research Papers, 2016)
Deep-sea corals are the structural foundation of their ecosystems along continental margins worldwide, yet the factors driving their broad distribution are poorly understood. Environmental factors, especially depth-related variables including water mass properties, are thought to considerably affect the realized distribution of deep-sea corals. These factors are governed by local and regional oceanographic conditions that directly influence the dispersal of larvae, and therefore affect the ultimate distribution of adult corals. We used molecular barcoding of mitochondrial and nuclear sequences to identify species of octocorals in the genus Paramuricea collected from the Labrador Sea to the Grand Banks of Newfoundland, Canada at depths of 150–1500 m. The results of this study revealed overlapping bathymetric distributions of the Paramuricea species present off the eastern Canadian coast, including the presence of a few cryptic species previously designated as Paramuricea placomus. The distribution of Paramuricea species in the western North Atlantic differs from the Gulf of Mexico, where five Paramuricea species exhibit strong segregation by depth. The different patterns of Paramuricea species in these contrasting biogeographic regions provide insight into how water mass structure may shape species distribution. Investigating Paramuricea prevalence and distribution in conjunction with oceanographic conditions can help demonstrate the factors that generate and maintain deep-sea biodiversity.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Voluminous eruption from a zoned magma body after an increase in supply rate at Axial Seamount - Chadwick, W W; Paduan, J B; Clague, D A; Dreyer, B M; Merle, S G; Bobbitt, A M; Caress, D W; Philip, B T; Kelley, D S; Nooner, S L (Geophysical Research Letters, 2016)
Axial Seamount is the best monitored submarine volcano in the world, providing an exceptional window into the dynamic interactions between magma storage, transport, and eruption processes in a mid-ocean ridge setting. An eruption in April 2015 produced the largest volume of erupted lava since monitoring and mapping began in the mid-1980s after the shortest repose time, due to a recent increase in magma supply. The higher rate of magma replenishment since 2011 resulted in the eruption of the most mafic lava in the last 500–600 years. Eruptive fissures at the volcano summit produced pyroclastic ash that was deposited over an area of at least 8 km2. A systematic spatial distribution of compositions is consistent with a single dike tapping different parts of a thermally and chemically zoned magma reservoir that can be directly related to previous multichannel seismic-imaging results.
Keywords: AUV Sentry (Autonomous Underwater Vehicle); ROV Jason (Remotely Operated Vehicle)

Activity and phylogenetic diversity of sulfate-reducing microorganisms in low-temperature subsurface fluids within the upper oceanic crust - Robador, Alberto; Jungbluth, Sean P; LaRowe, Douglas E; Bowers, Robert M; Rappe, Michael S; Amend, Jan P; Cowen, James P (FRONTIERS IN MICROBIOLOGY, 2015)
The basaltic ocean crust is the largest aquifer system on Earth, yet the rates of biological activity in this environment are unknown. Low-temperature ({<}100 degrees C) fluid samples were investigated from two borehole observatories in the Juan de Fuca Ridge (JFR) flank, representing a range of upper oceanic basement thermal and geochemical properties. Microbial sulfate reduction rates (SRR) were measured in laboratory incubations with S-35-sulfate over a range of temperatures and the identity of the corresponding sulfate-reducing microorganisms (SRM) was studied by analyzing the sequence diversity of the functional marker dissimilatory (bi)sulfite reductase (dsrAB) gene. We found that microbial sulfate reduction was limited by the decreasing availability of organic electron donors in higher temperature, more altered fluids. Thermodynamic calculations indicate energetic constraints for metabolism, which together with relatively higher cell-specific SRR reveal increased maintenance requirements, consistent with novel species-level dsrAB phylotypes of thermophilic SRM. Our estimates suggest that microbially-mediated sulfate reduction may account for the removal of organic matter in fluids within the upper oceanic crust and underscore the potential quantitative impact of microbial processes in deep subsurface marine crustal fluids on marine and global biogeochemical carbon cycling.
Keywords: ROV Jason (Remotely Operated Vehicle)

Advances in In Situ Alignment Calibration of Doppler and High/Low-end Attitude Sensors for Underwater Vehicle Navigation: Theory and Experimental Evaluation - Troni, Giancarlo; Whitcomb, Louis L (JOURNAL OF FIELD ROBOTICS, 2015)
This paper reports the development and comparative performance evaluation, using laboratory and at-sea field data, of new methods for the problem of in situ calibration of the alignment rotation matrix between Doppler sonar velocity sensors and attitude sensors arising in the navigation of underwater vehicles. Most previously reported solutions to this alignment calibration problem require the use of absolute navigation fixes of the underwater vehicle, thus requiring additional navigation sensors and/or beacons to be located externally and apart from the underwater vehicle. We report four novel alignment calibration methods employing only internal vehicle navigation sensors for velocity, acceleration, attitude, and depth. We report the results of comparative analysis of the performance of these new methods and a previously reported method with a navigation laboratory and at-sea field data. Laboratory data were obtained with the Johns Hopkins University JHU remotely operated underwater vehicle in the JHU Hydrodynamic Test Facility. At-sea field data were obtained from deep-water survey missions of the Sentry autonomous underwater vehicle conducted in March, 2011 in the Kermadec Arc in the Southern Pacific Ocean. In addition, we report a comparative experimental evaluation of several recently reported calibration methods when employing low-cost microelectromechanical system attitude sensors. In all these cases, the results reveal consistent differences in performance of the various methods when analyzed on navigation data from several different vehicle dives.
Keywords: AUV Sentry (Autonomous Underwater Vehicle)

Bacterial diversity and successional patterns during biofilm formation on freshly exposed basalt surfaces at diffuse-flow deep-sea vents - Gulmann, L K; Beaulieu, S E; Shank, T M; Ding, K; Seyfried, W E; Sievert, S M (Frontiers in Microbiology, 2015)
Many deep-sea hydrothermal vent systems are regularly impacted by volcanic eruptions, leaving fresh basalt where abundant animal and microbial communities once thrived. After an eruption, microbial biofilms are often the first visible evidence of biotic re-colonization. The present study is the first to investigate microbial colonization of newly exposed basalt surfaces in the context of vent fluid chemistry over an extended period of time (4–293 days) by deploying basalt blocks within an established diffuse-flow vent at the 9°50′ N vent field on the East Pacific Rise. Additionally, samples obtained after a recent eruption at the same vent field allowed for comparison between experimental results and those from natural microbial re-colonization. Over 9 months, the community changed from being composed almost exclusively of Epsilonproteobacteria to a more diverse assemblage, corresponding with a potential expansion of metabolic capabilities. The process of biofilm formation appears to generate similar surface-associated communities within and across sites by selecting for a subset of fluid-associated microbes, via species sorting. Furthermore, the high incidence of shared operational taxonomic units over time and across different vent sites suggests that the microbial communities colonizing new surfaces at diffuse-flow vent sites might follow a predictable successional pattern.
Keywords: HOV Alvin (Human Occupied Vehicle)

Bathymodiolus growth dynamics in relation to environmental fluctuations in vent habitats - Nedoncelle, K; Lartaud, F; Pereira, L Contreira; Yuecel, M; Thurnherr, A M; Mullineaux, L; Le Bris, N (DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS, 2015)
The deep-sea mussel Bathymodiolus thermophilus is a dominant species in the East Pacific Rise (EPR) hydrothermal vent fields. On the EPR volcanically unstable area, this late colonizer reaches high biomass within 4-5 years on new habitats created. by lava flows. The environmental conditions and growth rates characterizing the reestablishment of B. thermophilus populations are however largely unknown, leaving unconstrained the role of this foundation species in the ecosystem dynamics. A typical example from the vent field at 9 degrees 50'N that was affected by the last massive eruption was the Bio-9 hydrothermal vent site. Here, six years later, a large mussel population had reestablished. The von Bertalanffy growth model estimates the oldest B. thermophilus specimens to be 1.3 year-old in March 2012, consistent with the observation of scarce juveniles among tubeworms in 2010. Younger cohorts were also observed in 2012 but the low number of individuals, relatively to older cohorts, suggests limited survival or growth of new recruits at this site, that could reflect unsuitable habitat conditions. To further explore this asumption, we investigated the relationships between mussel growth dynamics and habitat properties. The approach combined sclerochronology analyses of daily shell growth with continuous habitat monitoring for two mussel assemblages; one from the Bio-9 new settlement and a second from the V-vent site unreached by the lava flow. At both vent sites, semi-diurnal fluctuations of abiotic conditions were recorded using sensors deployed in the mussel bed over 5 to 10 days. These data depict steep transitions from well oxygenated to oxygen-depleted conditions and from alkaline to acidic pH, combined with intermittent sulfide exposure. These semi-diurnal fluctuations exhibited marked changes in amplitude over time, exposing mussels to distinct regimes of abiotic constraints. The V-vent samples allowed growth patterns to be examined at the scale of individual life and compared to long-term records of habitat temperature and oceanographic mooring data in the years following the eruption. Both shell growth and habitat temperature at V-vent varied over the spring-neap tidal cycle and over longer periods of c.a. 60 days. The correlation of growth rate with temperature and, for some individuals, with current velocities supports the idea that tidal forcing impacts growth. Its influence on habitat conditions includes the spring-neap cycle, which is not reflected in current velocities but influences the venting rate. Additionally, it is expected that mesoscale eddies periodically passing across the ridge imprint shell growth through the influence of bottom current on the decimeter-thick mixing interface where mussels thrive. We conclude that diurnal-semidiurnal tidal fluctuations exert major abiotic constraints on B. thermophilus mussels and that low-frequency fluctuations act as significant determinants on growth. Finally, we postulate that the modulation of tidal fluctuations by large-scale hydrodynamic forcing ultimately constrains the capacity of this mussel species to form high biomass aggregations. This study indeed shows that the absence of these strong hydrodynamic drivers would limit the alternance of oxic and sulfidic conditions and significantly affect the growth rate of this species over time. (C) 2015 Elsevier Ltd. All rights reserved.
Keywords: HOV Alvin (Human Occupied Vehicle)

Carbon fixation by basalt-hosted microbial communities - Orcutt, Beth N; Sylvan, Jason B; Rogers, Daniel R; Delaney, Jennifer; Lee, Raymond W; Girguis, Peter R (FRONTIERS IN MICROBIOLOGY, 2015)
Oceanic crust is a massive potential habitat for microbial life on Earth, yet our understanding of this ecosystem is limited due to difficulty in access. In particular, measurements of rates of microbial activity are sparse. We used stable carbon isotope incubations of crustal samples, coupled with functional gene analyses, to examine the potential for carbon fixation on oceanic crust. Both seafloor-exposed and subseafloor basalts were recovered from different mid-ocean ridge and hot spot environments (i.e., the Juan de Fuca Ridge, the Mid-Atlantic Ridge, and the Loihi Seamount) and incubated with C-13-labeled bicarbonate. Seafloor-exposed basalts revealed incorporation of C-13-label into organic matter over time, though the degree of incorporation was heterogeneous. The incorporation of C-13 into biomass was inconclusive in subseafloor basalts. Translating these measurements into potential rates of carbon fixation indicated that 0.1-10 nmol C g(-1) rock d(-1) could be fixed by seafloor-exposed rocks. When scaled to the global production of oceanic crust, this suggests carbon fixation rates of 10(9)-10(12) g C year(-1), which matches earlier predictions based on thermodynamic calculations. Functional gene analyses indicate that the Calvin cycle is likely the dominant biochemical mechanism for carbon fixation in basalt-hosted biofilms, although the reductive acetyl-CoA pathway and reverse TCA cycle likely play some role in net carbon fixation. These results provide empirical evidence for autotrophy in oceanic crust, suggesting that basalt-hosted autotrophy could be a significant contributor of organic matter in this remote and vast environment.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Centuries-old shipwreck discovered off North Carolina (Ocean News {&} Technology, 2015)
Scanning sonar from a scientific expedition has revealed the remains of a previously unknown shipwreck more than a mile deep off the North Carolina coast. Artifacts on the wreck indicate it might date to the American Revolution. Marine scientists from Duke University, North Carolina State University and the University of Oregon discovered the wreck on 12 July during a research expedition aboard the Woods Hole Oceanographic Institution (WHOI) research ship Atlantis. They spotted the wreck while using WHOI's AUV Sentry and the manned submersible Alvin. The team had been searching for a mooring that was deployed on a previous research trip in the area in 2012.
Keywords: AUV Sentry (Autonomous Underwater Vehicle)

Cetia pacifica gen. nov., sp nov., a chemolithoautotrophic, thermophilic, nitrate-ammonifying bacterium from a deep-sea hydrothermal vent - Grosche, Ashley; Sekaran, Hema; Perez-Rodriguez, Ileana; Starovoytov, Valentin; Vetriani, Costantino (INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY, 2015)
A thermophilic, anaerobic, chemolithoautotrophic bacterium, strain TB-6(T), was isolated from a deep-sea hydrothermal vent located on the East Pacific Rise at 9 degrees N. The cells were Gram-staining-negative and rod-shaped with one or more polar flagella. Cell size was approximately 1-1.5 mu m in length and 0.5 mu m in width. Strain TB-6(T) grew between 45 and 70 degrees C (optimum 55-60 degrees C), 0 and 35 g NaCl l(-1) (optimum 20-30 gl(-1)) and pH 4.5 and 7.5 (optimum pH 5.5-6.0). Generation time under optimal conditions was 2 h. Growth of strain TB-6(T) occurred with H-2 as the energy source, CO2 as the carbon source and nitrate or sulfur as electron acceptors, with formation of ammonium or hydrogen sulfide, respectively. Acetate, (+)-n-glucose, Casamino acids, sucrose and yeast extract were not used as carbon and energy sources. Inhibition of growth occurred in the presence of lactate, peptone and tryptone under a H-2/CO2 (80 :20; 200 kPa) gas phase. Thiosulfate, sulfite, arsenate, selenate and oxygen were not used as electron acceptors. The G +C content of the genomic DNA was 36.8 molo/o. Phylogenetic analysis of the 16S rRNA gene of strain TB-6(T) showed that this organism branched separately from the three most closely related genera, Caminibacter, Nautilia and Lebetimonas, within the family Nautiliaceae. Strain TB-6(T) contained several unique fatty acids in comparison with other members of the family Nautiliaceae. Based on experimental evidence, it is proposed that the organism represents a novel species and genus within the family Nautiliaceae, Cetia pacifica, gen. nov., sp. nov. The type strain is TB-6(T) (=DSM 27783T=JCM 19563(T)).
Keywords: HOV Alvin (Human Occupied Vehicle)

Characterization of a novel thermostable patatin-like protein from a Guaymas basin metagenomic library - Fu, Ling; He, Ying; Xu, Fangdi; Ma, Qun; Wang, Fengping; Xu, Jun (EXTREMOPHILES, 2015)
Deep-sea hydrothermal vents are a natural habitat for thermophiles, in which contain plenty of enzymes that can function at high temperatures. In this work, we constructed a fosmid library in Escherichia coli using metagenomic DNA isolated from a chimney sample collected in the hydrothermal vents in Guaymas Basin. The library was screened for lipolytic activity and positive clones were subjected to subcloning. A novel patatin-like protein (PLP) that exhibited less than 45 {%} identity in amino acid sequence to known enzymes was obtained. Common features of the patatin-like proteins, such as four conserved blocks, were detected. Interestingly, there was an Ala at site 42 in PLP instead of the first Gly-residue in the consensus sequence Gly-X-Ser-X-Gly found in other PLP homologs. The active sites of PLP were Ser44 and Asp160. Spectrophotometric assays with different p-nitrophenyl esters demonstrated a preference for p-nitrophenyl butyrate (C4) and p-nitrophenyl decanoate (C10). Moreover, PLP demonstrated optimal activity at 70 A degrees C and at pH 9.0 (Tris-HCl). The activation energy from the linear Arrhenius plot was found to be 38.3 +/- A 0.9 kJ/mol. The K (m) and V (max) of PLP for C4 were 304 +/- A 38 mu M and 14 +/- A 0.38 mu mol min(-1) mg(-1), respectively. Gene-mining of the metagenome dataset that was generated by pyrosequencing the same chimney sample resulted in identification of 20 PLP homolog gene fragments, which could represent promising examples of this category of thermostable proteins.
Keywords: HOV Alvin (Human Occupied Vehicle)

Characterization of vent fauna at the Mid-Cayman Spreading Center - Plouviez, Sophie; Jacobson, Alixandra; Wu, Mengyou; Van Dover, Cindy L (DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS, 2015)
Hydrothermal vents in the deep sea have a global distribution on mid-ocean ridges and comprise at least six biogeographic provinces. A geographically isolated vent system was recently discovered on the Mid-Cayman Spreading Center (MCSC). Here, we describe the faunal assemblages associated with this system and their relationship to known biogeographic provinces. Taxa from MCSC vents were sorted based on morphology and barcoded using the cytochrome oxidase I (COI) and 16S ribosomal RNA (16S) genes for identification. Distinct faunal assemblages were recognized around vent chimneys at two hydrothermal vent fields (Von Damm and Beebe) separated by a distance of similar to 13 km and {>} 2.5-km depth along the Mid-Cayman Spreading Center. These results suggest that depth and/or local conditions structure faunal assemblages in this region. COI and microsatellite markers were then used to explore the genetic structure of the shrimp Rimicaris hybisae, the only abundant species shared between the shallow Von Damm and the deep Beebe vent fields. R. hybisae was not genetically differentiated between the Von Damm Spire and Beebe chimneys, suggesting this species is better adapted for bathymetric dispersal and the differences in local conditions than other MCSC species. In addition, a third faunal assemblage dominated by two species of tubeworms was identified at Von Damm in association with weakly diffuse flow sites (including the site known as ``Marker X18{\{}''{\}}). The Marker X18 assemblage shares species with seeps in the region. Fauna shared with both vents and seeps at the MCSC reinforces the need for a global biogeographic study of deep-sea chemosynthetic fauna that is not focused on specific habitats. (C) 2014 Elsevier Ltd. All rights reserved.
Keywords: ROV Jason (Remotely Operated Vehicle)

Comparison of Archaeal and Bacterial Diversity in Methane Seep Carbonate Nodules and Host Sediments, Eel River Basin and Hydrate Ridge, USA - Mason, Olivia U; Case, David H; Naehr, Thomas H; Lee, Raymond W; Thomas, Randal B; Bailey, Jake V; Orphan, Victoria J (MICROBIAL ECOLOGY, 2015)
Anaerobic oxidation of methane (AOM) impacts carbon cycling by acting as a methane sink and by sequestering inorganic carbon via AOM-induced carbonate precipitation. These precipitates commonly take the form of carbonate nodules that form within methane seep sediments. The timing and sequence of nodule formation within methane seep sediments are not well understood. Further, the microbial diversity associated with sediment-hosted nodules has not been well characterized and the degree to which nodules reflect the microbial assemblage in surrounding sediments is unknown. Here, we conducted a comparative study of microbial assemblages in methane-derived authigenic carbonate nodules and their host sediments using molecular, mineralogical, and geochemical methods. Analysis of 16S rRNA gene diversity from paired carbonate nodules and sediments revealed that both sample types contained methanotrophic archaea (ANME-1 and ANME-2) and syntrophic sulfate-reducing bacteria (Desulfobacteraceae and Desulfobulbaceae), as well as other microbial community members. The combination of geochemical and molecular data from Eel River Basin and Hydrate Ridge suggested that some nodules formed in situ and captured the local sediment-hosted microbial community, while other nodules may have been translocated or may represent a record of conditions prior to the contemporary environment. Taken together, this comparative analysis offers clues to the formation regimes and mechanisms of sediment-hosted carbonate nodules.
Keywords: HOV Alvin (Human Occupied Vehicle)

Constraints from melt inclusions on depths of magma residence at intermediate magma supply along the Galapagos Spreading Center - Colman, Alice; Sinton, John M; Wanless, V Dorsey (EARTH AND PLANETARY SCIENCE LETTERS, 2015)
Shallow, seismically imaged melt lenses are a ubiquitous feature of mid-ocean ridges with high magma supply; melt lenses deepen and become less continuous along axis as the rate of magma supply decreases. Despite compelling petrologic evidence for evolution of magma within the crust prior to eruption at lower magma supply, melt lenses are rarely detected along ridge segments with rates of magma supply less than 0.3 x 10(6) m(3)/yr/km, and the depths of sub-axial magma reservoirs are therefore poorly known. We use ion microprobe measurements of H2O and CO2 concentrations of olivine-hosted melt inclusions to calculate vapor saturation pressures that constrain crystallization depths at two locations along the Galapagos Spreading Center (94.2 degrees W and 95 degrees W). These sites were chosen to examine crystallization pressures in the presence (94.2 degrees W) and absence (95 degrees W) of a seismically imaged melt lens. At 95 degrees W, where magma supply is too low to sustain a seismically resolvable melt lens, samples were selected from each of the three most recent eruptive units, allowing us to document temporal variations in vapor saturation pressures and the depth of magma residence at this location. Clusters in melt inclusion entrapment depths for these eruptions range from 3.0 to 3.4 km below the seafloor, indicating that magmas at 95 degrees W resided at a narrow range of mid-crustal depths prior to eruption, generally consistent with the global trend of increasing melt lens depth with decreasing rate of magma supply. A discrepancy between seismic data and the peak in melt inclusion entrapment depths at 94.2 degrees W may reflect temporal variability of magmatic systems at this location. This study demonstrates the potential for using measurements of the concentrations of H2O and CO2 in olivine-hosted melt inclusions to determine the depths of crustal magmatic systems that feed mid-ocean ridge eruptions, even in locations where seismic studies have not detected melt lenses. (C) 2014 Elsevier B.V. All rights reserved.
Keywords: HOV Alvin (Human Occupied Vehicle)

Coupled Ge/Si and Ge isotope ratios as geochemical tracers of seafloor hydrothermal systems: Case studies at Loihi Seamount and East Pacific Rise 9°50′N - Escoube, R; Rouxel, O J; Edwards, K J; Glazer, B; Donard, O F X (Geochimica et Cosmochimica Acta, 2015)
Germanium (Ge) and Silicon (Si) exhibit similar geochemical behavior in marine environments but are variably enriched in seafloor hydrothermal fluids relative to seawater. In this study, Ge isotope and Ge/Si ratio systematics were investigated in low temperature hydrothermal vents from Loihi Seamount (Pacific Ocean, 18°54′N, 155°15′W) and results were compared to high-temperature vents from the East Pacific Rise (EPR) at 9°50′N. Loihi offers the opportunity to understand contrasting Ge and Si behavior in low temperature seafloor hydrothermal systems characterized by abundant Fe oxyhydroxide deposition at the seafloor. The results show that both Ge/Si and $δ$74/70Ge in hydrothermal fluids are fractionated relative to the basaltic host rocks. The enrichment in Ge vs. Si relative to fresh basalts, together with Ge isotope fractionation ($Δ$74/70Gefluid-basalt up to 1.15‰ at EPR 9°50′N and 1.64‰ at Loihi) are best explained by the precipitation of minerals (e.g. quartz and Fe-sulfides) during higher temperature seawater–rock reactions in the subsurface. The study of Fe-rich hydrothermal deposits at Loihi, largely composed of Fe-oxyhydroxides, shows that Ge isotopes are also fractionated upon mineral precipitation at the seafloor. We obtained an average Ge isotope fractionation factor between Fe-oxyhydroxide (ferrihydrite) and dissolved Ge in the fluid of −2.0 ± 0.6‰ (2sd), and a maximum value of −3.6 ± 0.6‰ (2sd), which is consistent with recent theoretical and experimental studies. The study of a hydrothermal chimney at Bio 9 vent at EPR 9°50′N also demonstrates that Ge isotopes are fractionated by approximately −5.6 ± 0.6‰ (2sd) during precipitation of metal sulfides under hydrothermal conditions. Using combined Ge/Si and estimated Ge isotope signatures of Ge sinks and sources in seawater, we propose a preliminary oceanic budget of Ge which reveals that an important sink, referred as the “missing Ge sink”, may correspond to Ge sequestration into authigenic Fe-oxyhydroxides in marine sediments. This study shows that combining Ge/Si and $δ$74/70Ge systematics provides a useful tool to trace hydrothermal Ge and Si sources in marine environments and to understand formation processes of seafloor hydrothermal deposits.
Keywords: ROV Jason (Remotely Operated Vehicle)

A deep-sea community, including Lophelia pertusa, at unusually shallow depths in the western North Atlantic Ocean off northeastern Florida - Ross, Steve W; Brooke, Sandra; Quattrini, Andrea M; Rhode, Mike; Watterson, J Carter (MARINE BIOLOGY, 2015)
Living colonies of the cold-water scleractinian coral Lophelia pertusa and other typically deep-water organisms were discovered in unusually shallow depths (180-250 m) off northeastern Florida. Observations of L. pertusa on rocky substrata and coral-built mounds represent the shallowest records of large colonies of this coral in the western Atlantic Ocean. Bioherms up to 30 m tall, extensive areas of eroded L. pertusa rubble, and a well-developed cold-water community indicated that these sites are long-term features, rather than short-term opportunistic responses to temporary shifts in environmental conditions. Species that are commonly observed on deeper reefs off the southeastern USA were abundant at the shallow sites. The most abundant fishes on reef habitats were Helicolenus dactylopterus, Laemonema barbatulum, Dysommina rugosa, and Anthias spp. In addition to L. pertusa, the most common macroinvertebrates on hard substrata were Eumunida picta, Chaceon fenneri, octocorals, cup corals, and glass sponges. Bottom and near-bottom temperatures (7-10 A degrees C) and nutrient concentrations at the shallow sites were similar to those normally encountered at 500-600 m in this region. The shallow reef sites occur in an area known for frequent Gulf Stream-driven upwelling of deep, nutrient-rich water. However, the upwelling must be persistent or permanent in order to maintain deep-sea communities at such shallow depths. Based on these data, this area is under final review by the US Department of Commerce for inclusion in one of the regional Coral Habitat Areas of Particular Concern.
Keywords: ROV Jason (Remotely Operated Vehicle)

Differences in recovery between deep-sea hydrothermal vent and vent-proximate communities after a volcanic eruption - Gollner, Sabine; Govenar, Breea; Arbizu, Pedro Martinez; Mills, Susan; Le Bris, Nadine; Weinbauer, Markus; Shank, Timothy M; Bright, Monika (DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS, 2015)
Deep-sea hydrothermal vents and the surrounding basalt seafloor are subject to major natural disturbance events such as volcanic eruptions. In the near future, anthropogenic disturbance in the form of deep-sea mining could also significantly affect the faunal communities of hydrothermal vents. In this study, we monitor and compare the recovery of insular, highly productive vent communities and vent-proximate basalt communities following a volcanic eruption that destroyed almost all existing communities at the East Pacific Rise, 9 degrees 50'N in 2006. To study the recovery patterns of the benthic communities, we placed settlement substrates at vent sites and their proximate basalt areas and measured the prokaryotic abundance and compared the meio- and macrofaunal species richness and composition at one, two and four years after the eruption. In addition, we collected samples from the overlying water column with a pelagic pump, at one and two years after the volcanic eruption, to determine the abundance of potential meiofauna colonisers. One year after eruption, mean meio- and macrofaunal abundances were not significantly different from pre-eruption values in vent habitats (meio: 8-1838 ind. 64 cm(-2) in 2006; 3-6246 ind. 64 cm(-2) in 2001/02; macro: 95-1600 ind. 64 cm(-2) in 2006; 205-4577 ind. 64 cm(-2) in 2001/02) and on non-vent basalt habitats (meio: 10-1922 ind. 64 cm(-2) in 2006; 8328 ind. 64 cm(-2) in 2003/04; macro: 14-3351 ind. 64 cm(-2) in 2006; 2-63 ind. 64 cm(-2) in 2003/04), but species recovery patterns differed between the two habitat types. In the vent habitat, the initial community recovery was relatively quick but incomplete four years after eruption, which may be due to the good dispersal capabilities of vent endemic macrofauna and vent endemic dirivultid copepods. At vents, 42{%} of the pre-eruption meio- and 39{%} of macrofaunal species had returned. In addition, some new species not evident prior to the eruption were found. At the tubeworm site Tica, a total of 26 meio- and 19 macrofaunal species were found in 2009, which contrasts with the 24 meio- and 29 macrofauna species detected at the site in 2001/01 In the basalt habitat, community recovery of meiofauna was slower with only 28{%} of the original 64 species present four years after eruption. The more limited dispersal capabilities of meiofauna basalt specialists such as nematodes or harpacticoid copepods probably caused this pattern. In contrast, 67{%} of the original 27 macrofaunal species had recolonized the basalt by 2009. Our results suggest that not only vent communities, but also species-rich communities of vent-proximate habitats require attention in conservation efforts. (C) 2015 Elsevier Ltd. All rights reserved.
Keywords: HOV Alvin (Human Occupied Vehicle)

Dissolved amino acids in oceanic basaltic basement fluids - Lin, H-T; Amend, J P; LaRowe, D E; Bingham, J-P; Cowen, J P (Geochimica et Cosmochimica Acta, 2015)
The oceanic basaltic basement contains the largest aquifer on Earth and potentially plays an important role in the global carbon cycle as a net sink for dissolved organic carbon (DOC). However, few details of the organic matter cycling in the subsurface are known because great water depths and thick sediments typically hinder direct access to this environment. In an effort to examine the role of water–rock–microorganism interaction on organic matter cycling in the oceanic basaltic crust, basement fluid samples collected from three borehole observatories installed on the eastern flank of the Juan de Fuca Ridge were analyzed for dissolved amino acids. Our data show that dissolved free amino acids (1–13 nM) and dissolved hydrolyzable amino acids (43–89 nM) are present in the basement. The amino acid concentrations in the ridge-flank basement fluids are at the low end of all submarine hydrothermal fluids reported in the literature and are similar to those in deep seawater. Amino acids in recharging deep seawater, in situ amino acid production, and diffusional input from overlying sediments are potential sources of amino acids in the basement fluids. Thermodynamic modeling shows that amino acid synthesis in the basement can be sustained by energy supplied from inorganic substrates via chemolithotrophic metabolisms. Furthermore, an analysis of amino acid concentrations and compositions in basement fluids support the notion that heterotrophic activity is ongoing. Similarly, the enrichment of acidic amino acids and depletion of hydrophobic ones relative to sedimentary particulate organic matter suggests that surface sorption and desorption also alters amino acids in the basaltic basement. In summary, although the oceanic basement aquifer is a net sink for deep seawater DOC, similar amino acid concentrations in basement aquifer and deep seawater suggest that DOC is preferentially removed in the basement over dissolved amino acids. Our data also suggest that organic carbon cycling occurs in the oceanic basaltic basement, where an active subsurface biosphere is likely responsible for amino acid synthesis and degradation.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Diversity and composition of the copepod communities associated with megafauna around a cold seep in the Gulf of Mexico with remarks on species biogeography - Plum, Christoph; Gollner, Sabine; Martinez-Arbizu, Pedro; Bright, Monika (MARINE BIODIVERSITY, 2015)
In order to characterize the copepod communities associated with tubeworm and mussel aggregations around a hydrocarbon seep in the Green Canyon of the Gulf of Mexico, diversity, abundance, and community composition were analyzed. Also analyzed were species biogeography and the potential connectivity to other chemosynthesis-based habitats. Copepod abundance and biomass were very low among tubeworms and mussels, with 0.22 to 6.08 individuals per 10 cm(2) sampled area and 9.02 to 42.43 mu g wet weight 10 cm(2) sampled area, respectively; but, abundance was significantly higher among the mussels. Fifty-five copepod species were identified, of which most were newly discovered and primarily belonging to the Harpacticoida order. Four copepod species were previously recorded from other food-rich and hard-substrata environments, such as hydrothermal vents or wood falls. Another four species showed close morphological proximity to species described from cold seeps, hydrothermal vents, and wood falls. Copepod diversity and community composition showed no significant differences between the foundation species. However, differences in the relative abundance and dominance of single species indicate a rather homogeneous community in mussel beds and a more heterogeneous community among tubeworms, indicating that foundation species may shape the abundance and community composition of associated copepods at cold seeps.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

A Dwarf Male Reversal in Bone-Eating Worms - Rouse, Greg W; Wilson, Nerida G; Worsaae, Katrine; Vrijenhoek, Robert C (CURRENT BIOLOGY, 2015)
Darwin {\{}[{\}}1] hypothesized that sexes in a species should be similar unless sexual selection, fecundity selection, or resource partitioning has driven them apart. Male dwarfism has evolved multiple times in a range of animals, raising questions about factors that drive such extreme size dimorphism {\{}[{\}}2-4]. Ghiselin {\{}[{\}}5] noted that dwarf males are more common among smaller marine animals, and especially among sedentary and sessile species living at low densities, where mates are difficult to find, or in deep-sea environments with limited energy sources. These benefits of male dwarfism apply well to Osedax (Annelida: Siboglinidae), bone-eating marine worms {\{}[{\}}6]. Osedax males, notable for extreme sexual size dimorphism (SSD), are developmentally arrested larvae that produce sperm from yolk reserves. Harems of dwarf males reside in the lumen of the tube surrounding a female. Herein, we describe Osedax priapus n. sp., a species that deviates remarkably by producing males that anchor into, and feed on, bone via symbiont-containing ``roots,{\{}''{\}} just like female Osedax. Phylogenetic analyses revealed O. priapus n. sp. as a derived species, and the absence of dwarf males represents a character reversal for this genus. Some dwarf male features are retained due to functional and morphological constraints. Since O. priapus n. sp. males are anchored in bone, they possess an extensible trunk that allows them to roam across the bone to contact and inseminate females. Evolutionary and ecological implications of a loss of male dwarfism are discussed.
Keywords: ROV Jason (Remotely Operated Vehicle)

Effect of depth and vent fluid composition on the carbon sources at two neighboring deep-sea hydrothermal vent fields (Mid-Cayman Rise) - Bennett, S A; Van Dover, C L; Breier, J A; Coleman, M L (Deep-Sea Research Part I: Oceanographic Research Papers, 2015)
In this study, we have used stable isotopes of megafauna, microbial mats and particulate organic matter to examine the effect of depth and vent fluid composition on the carbon sources at two proximal, chemically distinct hydrothermal vent fields along the Mid-Cayman Rise. The basalt hosted Piccard vent field (4980 m) is twice as deep as the ultramafic hosted Von Damm vent field (2300 m) and has very different faunal assemblages. Of particular note is the presence of seep-associated fauna, Escarpia and Lamellibrachia tubeworms, at the Von Damm vent field. We identify a greater range of carbon sources and a suggestion of increased photosynthetic inputs to the Von Damm vent field compared to Piccard vent field. Rimicaris hybisae shrimp are the only abundant species shared between the two vent fields with $δ$13C values ranging between −22.7 and −10.1‰. Higher concentrations of hydrogen sulfide in the vent fluids at Piccard is proposed to be responsible for varying the relative contributions of the carbon fixation cycles used by their epibionts. Seep-associated fauna at Von Damm rely on elevated, thermogenic hydrocarbon content of the vent fluids for their carbon source ($δ$13C values ranging from −21.3 to 11.6‰). They also derive energy from hydrogen sulfide formed by the microbial reduction of sulfide ($δ$34S values ranging from −10.2 to −6.9‰). The tubeworms have very short roots (buried at most a centimeter into rubble), suggesting that microbial sulfate reduction must be occurring either in the shallow subsurface and/or in the anterior part of the tube. Overall, megafauna at Von Damm vent field appear to have a smaller food chain length (smaller $δ$15N range) but a greater breadth of trophic resources compared to the megafauna at the Piccard vent field.
Keywords: ROV Jason (Remotely Operated Vehicle)

Estimations of heat transfer from Grotto's North Tower: A NEPTUNE Observatory case study - Rona, Peter A; Bemis, Karen G; Xu, Guangyu; Mitsuzawa, Kyohiko (DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY, 2015)
The overall heat transfer through an active hydrothermal sulfide edifice, in particular the North Tower of Grotto, has been estimated at 80 MW or greater based on the following in situ measurements and assumptions: (1) The heat transfer by diffuse flow is estimated at 33-380 MW based on extrapolating the acoustically mapped area to all sides of the North Tower ({\{}''{\}}visible{\{}''{\}} area=30 m(2); extrapolated area= 100 m(2)) and using the range of available spot measurements of temperature (6-23 degrees C) and vertical velocity (0.07-0.28 m/s). The lower number (33 MW) is more likely, but there is insufficient knowledge of the temporal and spatial variability of diffuse flow to be certain. (2) The heat transfer by focused flow is estimated at 30-70 MW based on summing the estimated individual rates of heat transfer for 4 out of 7 documented black smokers and flanges. (3) Conductive heat transfer out of the mound is unknown, but is likely to be much less than the advective heat transfer. Additionally, the plume transport of heat is estimated at 20-40 MW based on the direct measurement of temperature within the plume (at 5-25 m above the top of the edifice). Despite uncertainties, the lower estimate of plume versus smoker heat transfer suggests that heat transfer is dominantly by diffuse flow. Furthermore, not all plumes from individual smokers may merge even for so small an area as the North Tower of Grotto. (C) 2015 Elsevier Ltd. All rights reserved.
Keywords: ROV Jason (Remotely Operated Vehicle)

``Fingerprinting\''\} tectono-magmatic provenance using trace elements in igneous zircon} - Grimes, C B; Wooden, J L; Cheadle, M J; John, B E (CONTRIBUTIONS TO MINERALOGY AND PETROLOGY, 2015)
Over 5300 recent SHRIMP-RG analyses of trace elements (TE) in igneous zircon have been compiled and classified based on their original tectono-magmatic setting to empirically evaluate ``geochemical fingerprints{\{}''{\}} unique to those settings. Immobile element geochemical fingerprints used for lavas are applied with the same rational to zircon, including consideration of mineral competition on zircon TE ratios, and new criteria for distinguishing mid-ocean ridge (MOR), magmatic arc, and ocean island (and other plume-influenced) settings are proposed. The elemental ratios in zircon effective for fingerprinting tectono-magmatic provenance are systematically related to lava composition from equivalent settings. Existing discrimination diagrams using zircon U/Yb versus Hf or Y do not distinguish TE-enriched ocean island settings (i.e., Iceland, Hawaii) from magmatic arc settings. However, bivariate diagrams with combined cation ratios involving U-Nb-Sc-Yb-Gd-Ce provide a more complete distinction of zircon from these settings. On diagrams of U/Yb versus Nb/Yb, most MOR, ocean island, and kimberlite zircon define a broad ``mantle-zircon array{\{}''{\}}; arc zircon defines a parallel array offset to higher U/Yb. Distinctly low U/Yb ratios of MOR zircon (typically {<}0.1) mirror their parental magmas and long-term incompatible element depletion of the MORB mantle. Plume-influenced sources are distinguished from MOR by higher U/Yb, U/Nb, Nb/Yb, and Nb/Sc. For zircon with U/Yb {>}0.1, high Sc/Yb separates arc settings from low-Sc/Yb plume-influenced sources. The slope of scandium enrichment trends in zircon differ between MOR and continental arc settings, likely reflecting the involvement of amphibole during melt differentiation. Scandium is thus also critical for discriminating provenance, but its behavior in zircon probably reflects contrasting melt fractionation trends between tholeiitic and calc-alkaline systems more than compositional differences in primitive magmas sourced at each tectono-magmatic source.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

From deep-sea volcanoes to human pathogens: a conserved quorum-sensing signal in Epsilonproteobacteria - Perez-Rodriguez, Ileana; Bolognini, Marie; Ricci, Jessica; Bini, Elisabetta; Vetriani, Costantino (ISME Journal, 2015)
Chemosynthetic Epsilonproteobacteria from deep-sea hydrothermal vents colonize substrates exposed to steep thermal and redox gradients. In many bacteria, substrate attachment, biofilm formation, expression of virulence genes and host colonization are partly controlled via a cell density-dependent mechanism involving signal molecules, known as quorum sensing. Within the Epsilonproteobacteria, quorum sensing has been investigated only in human pathogens that use the luxS/autoinducer-2 (AI-2) mechanism to control the expression of some of these functions. In this study we showed that luxS is conserved in Epsilonproteobacteria and that pathogenic and mesophilic members of this class inherited this gene from a thermophilic ancestor. Furthermore, we provide evidence that the luxS gene is expressed-and a quorum-sensing signal is produced-during growth of Sulfurovum lithotrophicum and Caminibacter mediatlanticus, two Epsilonproteobacteria from deep-sea hydrothermal vents. Finally, we detected luxS transcripts in Epsilonproteobacteria-dominated biofilm communities collected from deep-sea hydrothermal vents. Taken together, our findings indicate that the epsiloproteobacterial lineage of the LuxS enzyme originated in high-temperature geothermal environments and that, in vent Epsilonproteobacteria, luxS expression is linked to the production of AI-2 signals, which are likely produced in situ at deep-sea vents. We conclude that the luxS gene is part of the ancestral epsilonproteobacterial genome and represents an evolutionary link that connects thermophiles to human pathogens.
Keywords: HOV Alvin (Human Occupied Vehicle)

Genomic and transcriptomic evidence for scavenging of diverse organic compounds by widespread deep-sea archaea - Li, M; Baker, B J; Anantharaman, K; Jain, S; Breier, J A; Dick, G J (Nature Communications, 2015)
Microbial activity is one of the most important processes to mediate the flux of organic carbon from the ocean surface to the seafloor. However, little is known about the microorganisms that underpin this key step of the global carbon cycle in the deep oceans. Here we present genomic and transcriptomic evidence that five ubiquitous archaeal groups actively use proteins, carbohydrates, fatty acids and lipids as sources of carbon and energy at depths ranging from 800 to 4,950 m in hydrothermal vent plumes and pelagic background seawater across three different ocean basins. Genome-enabled metabolic reconstructions and gene expression patterns show that these marine archaea are motile heterotrophs with extensive mechanisms for scavenging organic matter. Our results shed light on the ecological and physiological properties of ubiquitous marine archaea and highlight their versatile metabolic strategies in deep oceans that might play a critical role in global carbon cycling.
Keywords: ROV Jason (Remotely Operated Vehicle)

Genomic insights into the uncultivated marine Zetaproteobacteria at Loihi Seamount - Field, Erin K; Sczyrba, Alexander; Lyman, Audrey E; Harris, Christopher C; Woyke, Tanja; Stepanauskas, Ramunas; Emerson, David (ISME JOURNAL, 2015)
The Zetaproteobacteria are a candidate class of marine iron-oxidizing bacteria that are typically found in high iron environments such as hydrothermal vent sites. As much remains unknown about these organisms due to difficulties in cultivation, single-cell genomics was used to learn more about this elusive group at Loihi Seamount. Comparative genomics of 23 phylogenetically diverse single amplified genomes (SAGs) and two isolates indicate niche specialization among the Zetaproteobacteria may be largely due to oxygen tolerance and nitrogen transformation capabilities. Only Form II ribulose 1,5-bisphosphate carboxylase (RubisCO) genes were found in the SAGs, suggesting that some of the uncultivated Zetaproteobacteria may be adapted to low oxygen and/or high carbon dioxide concentrations. There is also genomic evidence of oxygen-tolerant cytochrome c oxidases and oxidative stress-related genes, indicating that others may be exposed to higher oxygen conditions. The Zetaproteobacteria also have the genomic potential for acquiring nitrogen from numerous sources including ammonium, nitrate, organic compounds, and nitrogen gas. Two types of molybdopterin oxidoreductase genes were found in the SAGs, indicating that those found in the isolates, thought to be involved in iron oxidation, are not consistent among all the Zetaproteobacteria. However, a novel cluster of redox-related genes was found to be conserved in 10 SAGs as well as in the isolates warranting further investigation. These results were used to isolate a novel iron-oxidizing Zetaproteobacteria. Physiological studies and genomic analysis of this isolate were able to support many of the findings from SAG analyses demonstrating the value of these data for designing future enrichment strategies.
Keywords: ROV Jason (Remotely Operated Vehicle)

Geologic implications of seafloor character and carbonate lithification imaged on the domal core of Atlantis Massif - Greene, J A; Tominaga, M; Blackman, D K (Deep-Sea Research Part II: Topical Studies in Oceanography, 2015)
We document the seafloor character on Atlantis Massif, an ocean core complex located at 30°N on the Mid-Atlantic Ridge, with an emphasis on the distribution of carbonate features. Seafloor imagery, near-bottom backscatter, and bathymetry were analyzed on the Central Dome and the Western Shoulder of the exposed footwall to the detachment, and on the Eastern Block, a hanging wall to the fault. We merged Argo II still images to produce photo-mosaics and evaluated these together with video imagery, acoustic reflectivity, and basic rock composition. The seafloor was classified as unconsolidated sediment, lithified carbonate crust, consolidated carbonate cap, exposed basement, or rubble, and the spatial distribution of each type was assessed. Unconsolidated sediment, exposed basement, and rubble were documented in all three regions studied. Lithified carbonate crust was also present on the Western Shoulder and eastern Central Dome. Consolidated carbonate cap was found on the Eastern Block. The formation of the carbonate rock is interpreted to reflect precipitation and/or sediment cementation via fluids derived from serpentinization. Both processes occur at the nearby Lost City Hydrothermal Field. The newly documented locations of seafloor carbonate lithification therefore mark pathways of past, possibly recent, fluid flux from subsurface water-rock reaction zones and represent an additional constituent of the carbon cycling hosted by oceanic lithosphere.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV DSL-120 (Remotely Operated Vehicle)

Identification of sulfur sources and isotopic equilibria in submarine hot-springs using multiple sulfur isotopes - McDermott, J M; Ono, S; Tivey, M K; Seewald, J S; Shanks, W C (Geochimica et Cosmochimica Acta, 2015)
Multiple sulfur isotopes were measured in metal sulfide deposits, elemental sulfur, and aqueous hydrogen sulfide to constrain sulfur sources and the isotopic systematics of precipitation in seafloor hydrothermal vents. Areas studied include the Eastern Manus Basin and Lau Basin back-arc spreading centers and the unsedimented basalt-hosted Southern East Pacific Rise (SEPR) and sediment-hosted Guaymas Basin mid-ocean ridge spreading centers. Chalcopyrite and dissolved hydrogen sulfide (H2S) $δ$34S values range from −5.5‰ to +5.6‰ in Manus Basin samples, +2.4‰ to +6.1‰ in Lau Basin samples, and +3.7‰ to +5.7‰ in SEPR samples. Values of $δ$34S for cubic cubanite and H2S range from −1.4‰ to +4.7‰ in Guaymas Basin samples. Multiple sulfur isotope systematics in fluid-mineral pairs from the SEPR and Lau Basin show that crustal host rock and thermochemical reduction of seawater-derived dissolved sulfate (SO4) are the primary sources of sulfur in mid-ocean ridge and some back-arc systems. At PACMANUS and SuSu Knolls hydrothermal systems in the Eastern Manus Basin, a significant contribution of sulfur is derived from disproportionation of magmatic sulfur dioxide (SO2), while the remaining sulfur is derived from crustal host rocks and SO4 reduction. At the sedimented Guaymas Basin hydrothermal system, sulfur sources include crustal host rock, reduced seawater SO4, and biogenic sulfide. Vent fluid flow through fresher, less-mature sediment supplies an increased quantity of reactant organic compounds that may reduce 34S-enriched SO4, while fluid interaction with more highly-altered sediments results in H2S characterized by a small, but isotopically-significant input of 34S-depleted biogenic sulfides. Near-zero $Δ$33S values in all samples implicate the abiotic processes of SO4 reduction and leaching of host rock as the major contributors to sulfur content at a high temperature unsedimented mid-ocean ridge and at a back-arc system. $Δ$33S values indicate that SO2 disproportionation is an additional process that contributes sulfur to a different back-arc system and to acid spring-type hydrothermal fluid circulation. At the sedimented Guaymus Basin, near-zero $Δ$33S values are also observed, despite negative $δ$34S values that indicate inputs of biogenic pyrite for some samples. In contrast with previous studies reporting isotope disequilibrium between H2S and chalcopyrite, the $δ$34S values of chalcopyrite sampled from the inner 1–2 mm of a chimney wall are within ±1‰ of $δ$34S values for H2S in the paired vent fluid, suggesting equilibrium fluid-mineral sulfur isotope exchange at 300–400 °C. Isotopic equilibrium between hydrothermal fluid H2S and precipitating chalcopyrite implies that sulfur isotopes in the chalcopyrite lining across a chimney wall may accurately record past hydrothermal activity.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Inter-comparison of the potentially active prokaryotic communities in the halocline sediments of Mediterranean deep-sea hypersaline basins - Kormas, K; Pachiadaki, M; Karayanni, H; Leadbetter, E R; Bernhard, J M; Edgcomb, V P (Extremophiles, 2015)
The sediment microbiota of the Mediterranean deep-sea anoxic hypersaline basins (DHABs) are understudied relative to communities in the brines and halocline waters. In this study, the active fraction of the prokaryotic community in the halocline sediments of L' Atalante, Urania, and Discovery DHABs was investigated based on extracted total RNA and 454 pyrosequencing of the 16S rRNA gene. Bacterial and archaeal communities were different in the sediments underlying the halocline waters of the three habitats, reflecting the unique chemical settings of each basin. The relative abundance of unique operational taxonomic units (OTUs) was also different between deep-sea control sediments and sediments underlying DHAB haloclines, suggesting adaptation to the steep DHAB chemical gradients. Only a few OTUs were affiliated to known bacterial halophilic and/or anaerobic groups. Many OTUs, including some of the dominant ones, were related to aerobic taxa. Archaea were detected only in few halocline samples, with lower OTU richness relative to Bacteria, and were dominated by taxa associated with methane cycling. This study suggests that, while metabolically active prokaryotic communities appear to be present in sediments underlying the three DHABs investigated, their diversity and activity are likely to be more reduced in sediments underlying the brines.
Keywords: ROV Jason (Remotely Operated Vehicle)

Intergradation between discrete lineages of Tevnia jerichonana, a deep-sea hydrothermal vent tubeworm - Zhang, H; Johnson, S B; Flores, V R; Vrijenhoek, R C (Deep-Sea Research Part II: Topical Studies in Oceanography, 2015)
We describe a broad zone of intergradation between genetically differentiated, northern and southern lineages of the hydrothermal vent tubeworm, Tevnia jerichonana. DNA sequences from four genes, nuclear HSP and ATPs$α$ and mitochondrial COI and Cytb were examined in samples from eastern Pacific vent localities between 13°N and 38°S latitude. Allelic frequencies at these loci exhibited concordant latitudinal clines, and genetic differentiation (pairwise $Φ$ST's) increased with geographical distances between sample localities. Though this pattern of differentiation suggested isolation-by-distance (IBD), it appeared to result from hierarchical population structure. Genotypic assignment tests identified two population clusters comprised of samples from the northern East Pacific Rise (NEPR: 9–13°N) and an extension of the Pacific-Antarctic Ridge (PAR: 31–32°S) with a zone of intergradation along the southern East Pacific Rise (SEPR: 7–17°S). The overall degrees of DNA sequence divergence between the NEPR and PAR populations were slight and not indicative of lengthy isolation. Bayesian assignment methods suggested that the SEPR populations constitute intergrades that connect the NEPR and PAR populations. Though it typically is difficult to distinguish between primary and secondary intergradation, our results were consistent with parallel studies of vent-restricted species that suggest a high degree of demographic instability along the superfast-spreading SEPR axis. Frequent local extinctions and immigration from NEPR and PAR refugia probably shaped the observed pattern of intergradation.
Keywords: HOV Alvin (Human Occupied Vehicle)

Investigation of extractable organic compounds in deep-sea hydrothermal vent fluids along the Mid-Atlantic Ridge - McCollom, Thomas M; Seewald, Jeffrey S; German, Christopher R (GEOCHIMICA ET COSMOCHIMICA ACTA, 2015)
The possibility that deep-sea hydrothermal vents may contain organic compounds produced by abiotic synthesis or by microbial communities living deep beneath the surface has led to numerous studies of the organic composition of vent fluids. Most of these studies have focused on methane and other light hydrocarbons, while the possible occurrence of more complex organic compounds in the fluids has remained largely unstudied. To address this issue, the presence of higher molecular weight organic compounds in deep-sea hydrothermal fluids was assessed at three sites along the Mid-Atlantic Ridge that span a range of temperatures (51 to {>}360 degrees C), fluid compositions, and host-rock lithologies (mafic to ultramafic). Samples were obtained at several sites within the Lucky Strike, Rainbow, and Lost City hydrothermal fields. Three methods were employed to extract organic compounds for analysis, including liquid: liquid extraction, cold trapping on the walls of a coil of titanium tubing, and pumping fluids through cartridges filled with solid phase extraction (SPE) sorbents. The only samples to consistently yield high amounts of extractable organic compounds were the warm (51-91 degrees C), highly alkaline fluids from Lost City, which contained elevated concentrations of C-8, C-10, and C-12 n-alkanoic acids and, in some cases, trithiolane, hexadecanol, squalene, and cholesterol. Collectively, the C-8-C-12 acids can account for about 15{%} of the total dissolved organic carbon in the Lost City fluids. The even-carbon-number predominance of the alkanoic acids indicates a biological origin, but it is unclear whether these compounds are derived from microbial activity occurring within the hydrothermal chimney proximal to the site of fluid discharge or are transported from deeper within the system. Hydrothermal fluids from the Lucky Strike and Rainbow fields were characterized by an overall scarcity of extractable dissolved organic compounds. Trace amounts of aromatic hydrocarbons including phenanthrenes and benzothiophene were the only compounds that could be identified as indigenous components of these fluids. Although hydrocarbons and fatty acids were observed in some samples, those compounds were likely derived from particulate matter or biomass entrained during fluid collection. In addition, extracts of some fluid samples from the Rainbow field were found to contain an unresolved complex mixture (UCM) of organic compounds. This UCM shared some characteristics with organic matter extracted from bottom seawater, suggesting that the organic matter observed in these samples might represent seawater-derived compounds that had persisted, albeit with partial alteration, during circulation through the hydrothermal system. While there is considerable evidence that Rainbow and Lost City vent fluids contain methane and other light hydrocarbons produced through abiotic reduction of inorganic carbon, we found no evidence for more complex organic compounds with an abiotic origin in the same fluids. (C) 2015 Elsevier Ltd. All rights reserved.
Keywords: ROV Jason (Remotely Operated Vehicle)

Long-term explosive degassing and debris flow activity at West Mata submarine volcano - Dziak, R P; Bohnenstiehl, D R; Baker, E T; Matsumoto, H; Caplan-Auerbach, J; Embley, R W; Merle, S G; Walker, S L; Lau, T-K.; Chadwick Jr., W W (GEOPHYSICAL RESEARCH LETTERS, 2015)
West Mata is a 1200m deep submarine volcano where explosive boninite eruptions were observed in 2009. The acoustic signatures from the volcano's summit eruptive vents Hades and Prometheus were recorded with an in situ (similar to 25m range) hydrophone during ROV dives in May 2009 and with local (similar to 5km range) moored hydrophones between December 2009 and August 2011. The sensors recorded low frequency (1-40Hz), short duration explosions consistent with magma bubble bursts from Hades, and broadband, 1-5min duration signals associated with episodes of fragmentation degassing from Prometheus. Long-term eruptive degassing signals, recorded through May 2010, preceded a several month period of declining activity. Degassing episodes were not recorded acoustically after early 2011, although quieter effusive eruption activity may have continued. Synchronous optical measurements of turbidity made between December 2009 and April 2010 indicate that turbidity maxima resulted from occasional south flank slope failures triggered by the collapse of accumulated debris during eruption intervals.
Keywords: ROV Jason (Remotely Operated Vehicle)

The Lost City hydrothermal system: Constraints imposed by vent fluid chemistry and reaction path models on subseafloor heat and mass transfer processes - Seyfried, W E; Pester, N J; Tutolo, B M; Ding, K (Geochimica et Cosmochimica Acta, 2015)
Since the first reported discovery of the Lost City hydrothermal system in 2001, it was recognized that seawater alteration of ultramafic rocks plays a key role in the composition of the coexisting vent fluids. The unusually high pH and high concentrations of H2 and CH4 provide compelling evidence for this. Here we report the chemistry of hydrothermal fluids sampled from two vent structures (Beehive: ∼90–116 °C, and M6: ∼75 °C) at Lost City in 2008 during cruise KNOX18RR using ROV Jason 2 and R/V Revelle assets. The vent fluid chemistry at both sites reveals considerable overlap in concentrations of dissolved gases (H2, CH4), trace elements (Cs, Rb, Li, B and Sr), and major elements (SO4, Ca, K, Na, Cl), including a surprising decrease in dissolved Cl, suggesting a common source fluid is feeding both sites. The absence of Mg and relatively high concentrations of Ca and sulfate suggest solubility control by serpentine–diopside–anhydrite, while trace alkali concentrations, especially Rb and Cs, are high, assuming a depleted mantle protolith. In both cases, but especially for Beehive vent fluid, the silica concentrations are well in excess of those expected for peridotite alteration and the coexistence of serpentine–brucite at all reasonable temperatures. However, both the measured pH and silica values are in better agreement with serpentine–diopside–tremolite-equilibria. Geochemical modeling demonstrates that reaction of plagioclase with serpentinized peridotite can shift the chemical system away from brucite and into the tremolite stability field. This is consistent with the complex intermingling of peridotite and gabbroic bodies commonly observed within the Atlantis Massif. We speculate the existence of such plagioclase bearing peridotite may also account for the highly enriched trace alkali (Cs, Rb) concentrations in the Lost City vent fluids. Additionally, reactive transport modeling taking explicit account of temperature dependent rates of mineral dissolution and precipitation clarifies the feedback between permeability, heat loss, and changes in the dissolved Si of the vent fluids. Assuming both the Beehive and M6 vent fluids were sourced at similar subseafloor conditions (tremolite buffered at 200 °C), model results indicate loss of approximately 30{%} Si upon cooling to ∼150 °C during upflow. However, Si concentrations remained largely conservative with continued cooling to lower temperatures owing to unfavorable reaction kinetics. While consistent with the Beehive endmember composition, these results fail to explain the relative Si depletion in the lower temperature M6 fluids. Thus, it may be that more robust kinetic models for silicates are needed to accurately account for the mechanism and rate of silica removal in the unusually high pH of the Lost City vent fluids.
Keywords: HOV Alvin (Human Occupied Vehicle)

Measuring fluid flow and heat output in seafloor hydrothermal environments - Germanovich, L N; Hurt, R S; Smith, J E; Genc, G; Lowell, R P (Journal of Geophysical Research: Solid Earth, 2015)
We review techniques for measuring fluid flow and advective heat output from seafloor hydrothermal systems and describe new anemometer and turbine flowmeter devices we have designed, built, calibrated, and tested. These devices allow measuring fluid velocity at high-and low-temperature focused and diffuse discharge sites at oceanic spreading centers. The devices perform at ocean floor depths and black smoker temperatures and can be used to measure flow rates ranging over 2 orders of magnitude. Flow velocity is determined from the rotation rate of the rotor blades or paddle assembly. These devices have an open bearing design that eliminates clogging by particles or chemical precipitates as the fluid passes by the rotors. The devices are compact and lightweight enough for deployment from either an occupied or remotely operated submersible. The measured flow rates can be used in conjunction with vent temperature or geochemical measurements to obtain heat outputs or geochemical fluxes from both vent chimneys and diffuse flow regions. The devices have been tested on 30 Alvin dives on the Juan de Fuca Ridge and 3 Jason dives on the East Pacific Rise (EPR). We measured an anomalously low entrainment coefficient (0.064) and report 104 new measurements over a wide range of discharge temperatures (5 degrees-363 degrees C), velocities (2-199 cm/s), and depths (1517-2511 m). These include the first advective heat output measurements at the High Rise vent field and the first direct fluid flow measurement at Middle Valley. Our data suggest that black smoker heat output at the Main Endeavour vent field may have declined since 1994 and that after the 2005-2006 eruption, the high-temperature advective flow at the EPR 9 degrees 50'N field may have become more channelized, predominately discharging through the Bio 9 structure. We also report 16 measurements on 10 Alvin dives and 2 Jason dives with flow meters that predate devices described in this work and were used in the process of their development. This includes the first advective measurements in the Lau Basin and at the EPR 9 degrees 39.5'N. We discuss potential error sources and how they may affect the accuracy of measurements by our devices and other devices. In particular, we use the turbulent plume theory to evaluate the effect of entrainment of ambient seawater.
Keywords: ROV Jason (Remotely Operated Vehicle)

Metazoans of redoxcline sediments in Mediterranean deep-sea hypersaline anoxic basins - Bernhard, Joan M; Morrison, Colin R; Pape, Ellen; Beaudoin, David J; Todaro, M Antonio; Pachiadaki, Maria G; Kormas, Konstantinos Ar; Edgcomb, Virginia P (BMC BIOLOGY, 2015)
Background: The deep-sea hypersaline anoxic basins (DHABs) of the Mediterranean (water depth similar to 3500 m) are some of the most extreme oceanic habitats known. Brines of DHABs are nearly saturated with salt, leading many to suspect they are uninhabitable for eukaryotes. While diverse bacterial and protistan communities are reported from some DHAB haloclines and brines, loriciferans are the only metazoan reported to inhabit the anoxic DHAB brines. Our goal was to further investigate metazoan communities in DHAB haloclines and brines. Results: We report observations from sediments of three DHAB (Urania, Discovery, L'Atalante) haloclines, comparing these to observations from sediments underlying normoxic waters of typical Mediterranean salinity. Due to technical difficulties, sampling of the brines was not possible. Morphotype analysis indicates nematodes are the most abundant taxon; crustaceans, loriciferans and bryozoans were also noted. Among nematodes, Daptonema was the most abundant genus; three morphotypes were noted with a degree of endemicity. The majority of rRNA sequences were from planktonic taxa, suggesting that at least some individual metazoans were preserved and inactive. Nematode abundance data, in some cases determined from direct counts of sediments incubated in situ with CellTracker (TM) Green, was patchy but generally indicates the highest abundances in either normoxic control samples or in upper halocline samples; nematodes were absent or very rare in lower halocline samples. Ultrastructural analysis indicates the nematodes in L'Atalante normoxic control sediments were fit, while specimens from L'Atalante upper halocline were healthy or had only recently died and those from the lower halocline had no identifiable organelles. Loriciferans, which were only rarely encountered, were found in both normoxic control samples as well as in Discovery and L'Atalante haloclines. It is not clear how a metazoan taxon could remain viable under this wide range of conditions. Conclusions: We document a community of living nematodes in normoxic, normal saline deep-sea Mediterranean sediments and in the upper halocline portions of the DHABs. Occurrences of nematodes in mid-halocline and lower halocline samples did not provide compelling evidence of a living community in those zones. The possibility of a viable metazoan community in brines of DHABs is not supported by our data at this time.
Keywords: ROV Jason (Remotely Operated Vehicle)

Microbial biofilms associated with fluid chemistry and megafaunal colonization at post-eruptive deep-sea hydrothermal vents - O'Brien, C E; Giovannelli, D; Govenar, B W; Luther, G W; Lutz, R A; Shank, T M; Vetriani, C (Deep-Sea Research Part II: Topical Studies in Oceanography, 2015)
At deep-sea hydrothermal vents, reduced, super-heated hydrothermal fluids mix with cold, oxygenated seawater. This creates temperature and chemical gradients that support chemosynthetic primary production and a biomass-rich community of invertebrates. In late 2005/early 2006 an eruption occurred on the East Pacific Rise at 9°50′N, 104°17′W. Direct observations of the post-eruptive diffuse-flow vents indicated that the earliest colonizers were microbial biofilms. Two cruises in 2006 and 2007 allowed us to monitor and sample the early steps of ecosystem recovery. The main objective of this work was to characterize the composition of microbial biofilms in relation to the temperature and chemistry of the hydrothermal fluids and the observed patterns of megafaunal colonization. The area selected for this study had local seafloor habitats of active diffuse flow (in-flow) interrupted by adjacent habitats with no apparent expulsion of hydrothermal fluids (no-flow). The in-flow habitats were characterized by higher temperatures (1.6–25.2 °C) and H2S concentrations (up to 67.3 µM) than the no-flow habitats, and the microbial biofilms were dominated by chemosynthetic Epsilonproteobacteria. The no-flow habitats had much lower temperatures (1.2–5.2 °C) and H2S concentrations (0.3–2.9 µM), and Gammaproteobacteria dominated the biofilms. Siboglinid tubeworms colonized only in-flow habitats, while they were absent at the no-flow areas, suggesting a correlation between siboglinid tubeworm colonization, active hydrothermal flow, and the composition of chemosynthetic microbial biofilms.
Keywords: HOV Alvin (Human Occupied Vehicle)

Microbial Communities on Seafloor Basalts at Dorado Outcrop Reflect Level of Alteration and Highlight Global Lithic Clades - Lee, Michael D; Walworth, Nathan G; Sylvan, Jason B; Edwards, Katrina J; Orcutt, Beth N (FRONTIERS IN MICROBIOLOGY, 2015)
Areas of exposed basalt along mid-ocean ridges and at seafloor outcrops serve as conduits of fluid flux into and out of a subsurface ocean, and microbe-mineral interactions can influence alteration reactions at the rock-water interface. Located on the eastern flank of the East Pacific Rise, Dorado Outcrop is a site of low temperature ({<} 20 degrees C) hydrothermal venting and represents a new end-member in the current survey of seafloor basalt biomes. Consistent with prior studies, a survey of 16S rRNA gene sequence diversity using universal primers targeting the V4 hypervariable region revealed much greater richness and diversity on the seafloor rocks than in surrounding seawater. Overall, Gamma-, Alpha-, and Deltaproteobacteria, and Thaumarchaeota dominated the sequenced communities, together making up over half of the observed diversity, though bacterial sequences were more abundant than archaeal in all samples. The most abundant bacterial reads were closely related to the obligate chemolithoautotrophic, sulfur-oxidizing Thioprofundum lifl-lotrophicum, suggesting carbon and sulfur cycling as dominant metabolic pathways in this system. Representatives of Thaumarchaeota were detected in relatively high abundance on the basalts in comparison to bottom water, possibly indicating ammonia oxidation. In comparison to other sequence datasets from globally distributed seafloor basalts, this study reveals many overlapping and cosmopolitan phylogenetic groups and also suggests that substrate age correlates with community structure.
Keywords: AUV Sentry (Autonomous Underwater Vehicle); ROV Jason (Remotely Operated Vehicle)

Microbial Iron Mats at the Mid-Atlantic Ridge and Evidence that Zetaproteobacteria May Be Restricted to Iron-Oxidizing Marine Systems - Scott, J J; Breier, J A; Luther, G W; Emerson, D (PLoS ONE, 2015)
Chemolithoautotrophic iron-oxidizing bacteria play an essential role in the global iron cycle. Thus far, the majority of marine iron-oxidizing bacteria have been identified as Zetaproteobacteria, a novel class within the phylum Proteobacteria. Marine iron-oxidizing microbial communities have been found associated with volcanically active seamounts, crustal spreading centers, and coastal waters. However, little is known about the presence and diversity of iron-oxidizing communities at hydrothermal systems along the slow crustal spreading center of the Mid-Atlantic Ridge. From October to November 2012, samples were collected from rust-colored mats at three well-known hydrothermal vent systems on the Mid-Atlantic Ridge (Rainbow, Trans-Atlantic Geotraverse, and Snake Pit) using the ROV Jason II. The goal of these efforts was to determine if iron-oxidizing Zetaproteobacteria were present at sites proximal to black smoker vent fields. Small, diffuse flow venting areas with high iron(II) concentrations and rust-colored microbial mats were observed at all three sites proximal to black smoker chimneys. A novel, syringe-based precision sampler was used to collect discrete microbial iron mat samples at the three sites. The presence of Zetaproteobacteria was confirmed using a combination of 16S rRNA pyrosequencing and single-cell sorting, while light micros-copy revealed a variety of iron-oxyhydroxide structures, indicating that active iron-oxidizing communities exist along the Mid-Atlantic Ridge. Sequencing analysis suggests that these iron mats contain cosmopolitan representatives of Zetaproteobacteria, but also exhibit diversity that may be uncommon at other iron-rich marine sites studied to date. A meta-analysis of publically available data encompassing a variety of aquatic habitats indicates that Zetaproteobacteria are rare if an iron source is not readily available. This work adds to the growing understanding of Zetaproteobacteria ecology and suggests that this organism is likely locally restricted to iron-rich marine environments but may exhibit wide-scale geographic distribution, further underscoring the importance of Zetaproteobacteria in global iron cycling.
Keywords: ROV Jason (Remotely Operated Vehicle)

Molecular study of bacterial diversity within the trophosome of the vestimentiferan tubeworm Ridgeia piscesae - Forget, Nathalie L; Perez, Maeva; Juniper, S Kim (MARINE ECOLOGY-AN EVOLUTIONARY PERSPECTIVE, 2015)
A large proportion of the faunal biomass in hydrothermal vent ecosystems relies on symbiotic relationships, with bacteria as a source of nutrition. Whereas multiple symbioses have been observed in diverse vent hosts, siboglinid tubeworms have been thought to harbour a single endosymbiont phylotype affiliated to the Gammaproteobacteria. In the case of the Northeast Pacific vestimentiferan Ridgeia piscesae, two previous studies suggested the presence of more than one symbiont. The possibility of multiple, and possibly habitat-specific, symbionts in R. piscesae provided a potential explanation for the tube-worm's broad ecological niche, compared with other hydrothermal vent siboglinids. This study further explored the diversity of trophosome bacteria in R. piscesae using two methodological approaches not yet applied to this symbiosis. We carried out 454-pyrosequencing on trophosome samples from 46 individual worms and used catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH) to verify the presence of the major groups detected in the pyrotag data. Both methods yielded inconsistent and sometimes contradictory results between sampling sites, and neither provided irrefutable evidence for the presence of symbionts other than the expected Gammaproteobacteria. We therefore conclude that the other adaptive mechanisms must be considered to explain the broad physico-chemical niche occupied by the different growth forms of R. piscesae.
Keywords: HOV Alvin (Human Occupied Vehicle)

Molten sulfur lakes of intraoceanic arc volcanoes - de Ronde, C E J; Chadwick, W W; Ditchburn, R G; Embley, R W; Tunnicliffe, V; Baker, E T; Walker, S L; Ferrini, V L; Merle, S M (Volcanic Lakes, 2015)

Near conductive cooling rates in the upper-plutonic section of crust formed at the East Pacific Rise - Faak, K; Coogan, L A; Chakraborty, S (Earth and Planetary Science Letters, 2015)
A new geospeedometer, based on diffusion modeling of Mg in plagioclase, is used to determine cooling rates of the upper section of the lower oceanic crust formed at fast-spreading mid-ocean ridges. The investigated natural sample suites include gabbroic rocks formed at three different locations along the fast-spreading East Pacific Rise. These samples cover a depth interval of 0–840 m below the sheeted dike/gabbro boundary and therefore allow the variation of cooling rate as a function of depth within the upper plutonic sequence to be determined. We demonstrate that the cooling rates we obtained are robust (reproducible and consistent across different vertical sections at fast spreading ridges) and decrease significantly with increasing sample depth (covering almost 4 orders of magnitude, ranging from ∼1 °C y−1 for the shallowest samples to 0.0003 °C y−1 for the deepest samples). Both the absolute cooling rates, and the rate of decrease of cooling rate with depth, are consistent with conductive thermal models. In contrast, the absolute cooling rates determined from the deeper samples ({>}300 m below DGB), and the large decrease in cooling rate with depth are inconsistent with thermal models that include substantial cooling by off-axis hydrothermal circulation within the upper plutonic section of the crust.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Observation windows of the deep submersible Alvin - Mavor, J W (Marine Technology Society Journal, 2015)
The basis of the design of ALVIN plexiglas windows is presented. Results of several tests of plexiglas windows are presented and discussed. It is concluded that the lapping of windows into their seats is unnecessary and that a close fit is not required. ALVIN windows are conservative in design for the operating depth of 6000 feet. The use of a test window seat which does not simulate the hull strains is satisfactory for window test. It is recommended that the conical window seat be extended inward beyond the window to allow for normal elastic extrusion. Plexiglas windows are susceptible to collision damage due to brittleness and low strength of the material. An external rubber gasket is required to prevent low pressure leakage.
Keywords: HOV Alvin (Human Occupied Vehicle)

The path to COVIS: A review of acoustic imaging of hydrothermal flow regimes - Bemis, K G; Silver, D; Xu, G; Light, R; Jackson, D R; Jones, C D; Ozer, S; Liu, L (Deep-Sea Research Part II: Topical Studies in Oceanography, 2015)
Acoustic imaging of hydrothermal flow regimes started with the incidental recognition of a plume on a routine sonar scan for obstacles in the path of the human-occupied submersible ALVIN. Developments in sonar engineering, acoustic data processing and scientific visualization have been combined to develop technology which can effectively capture the behavior of focused and diffuse hydrothermal discharge. This paper traces the development of these acoustic imaging techniques for hydrothermal flow regimes from their conception through to the development of the Cabled Observatory Vent Imaging Sonar (COVIS). COVIS has monitored such flow eight times a day for several years. Successful acoustic techniques for estimating plume entrainment, bending, vertical rise, volume flux, and heat flux are presented as is the state-of-the-art in diffuse flow detection.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Pathways for abiotic organic synthesis at submarine hydrothermal fields - McDermott, Jill M; Seewald, Jeffrey S; German, Christopher R; Sylva, Sean P (PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 2015)
Arguments for an abiotic origin of low-molecular weight organic compounds in deep-sea hot springs are compelling owing to implications for the sustenance of deep biosphere microbial communities and their potential role in the origin of life. Theory predicts that warm H-2-rich fluids, like those emanating from serpentinizing hydrothermal systems, create a favorable thermodynamic drive for the abiotic generation of organic compounds from inorganic precursors. Here, we constrain two distinct reaction pathways for abiotic organic synthesis in the natural environment at the Von Damm hydrothermal field and delineate spatially where inorganic carbon is converted into bioavailable reduced carbon. We reveal that carbon transformation reactions in a single system can progress over hours, days, and up to thousands of years. Previous studies have suggested that CH4 and higher hydrocarbons in ultramafic hydrothermal systems were dependent on H-2 generation during active serpentinization. Rather, our results indicate that CH4 found in vent fluids is formed in H-2-rich fluid inclusions, and higher n-alkanes may likely be derived from the same source. This finding implies that, in contrast with current paradigms, these compounds may form independently of actively circulating serpentinizing fluids in ultramafic-influenced systems. Conversely, widespread production of formate by SCO2 reduction at Von Damm occurs rapidly during shallow subsurface mixing of the same fluids, which may support anaerobic methanogenesis. Our finding of abiogenic formate in deep-sea hot springs has significant implications for microbial life strategies in the present- day deep biosphere as well as early life on Earth and beyond.
Keywords: ROV Jason (Remotely Operated Vehicle)

Phylogenetic placement of Cibicidoides wuellerstorfi (Schwager, 1866) from methane seeps and non-seep habitats on the Pacific margin - Burkett, A M; Rathburn, A E; Perez, M E; Levin, L A; Cha, H; Rouse, G W (GEOBIOLOGY, 2015)
Benthic foraminifera are among the most abundant groups found in deep-sea habitats, including methane seep environments. Unlike many groups, no endemic foraminiferal species have been reported from methane seeps, and to our knowledge, genetic data are currently sparse for Pacific deep-sea foraminifera. In an effort to understand the relationships between seep and non-seep populations of the deep-sea foraminifera Cibicidoides wuellerstorfi, a common paleo-indicator species, specimens from methane seeps in the Pacific were analyzed and compared to one another for genetic similarities of small subunit rDNA (SSU rDNA) sequences. Pacific Ocean C. wuellerstorfi were also compared to those collected from other localities around the world (based on 18S gene available on Genbank, e.g., Schweizer et al., 2009). Results from this study revealed that C. wuellerstorfi living in seeps near Costa Rica and Hydrate Ridge are genetically similar to one another at the species level. Individuals collected from the same location that display opposite coiling directions (dextral and sinstral) had no species level genetic differences. Comparisons of specimens with genetic information available from Genbank (SSU rDNA) showed that Pacific individuals, collected for this study, are genetically similar to those previously analyzed from the North Atlantic and Antarctic. These observations provide strong evidence for the true cosmopolitan nature of C. wuellerstorfi and highlight the importance of understanding how these microscopic organisms are able to maintain sufficient genetic exchange to remain within the same species between seep and non-seep habitats and over global distances.
Keywords: ROV Jason (Remotely Operated Vehicle)

Predicting the response of the deep-ocean microbiome to geochemical perturbations by hydrothermal vents - Reed, Daniel C; Breier, John A; Jiang, Houshuo; Anantharaman, Karthik; Klausmeier, Christopher A; Toner, Brandy M; Hancock, Cathrine; Speer, Kevin; Thurnherr, Andreas M; Dick, Gregory J (ISME JOURNAL, 2015)
Submarine hydrothermal vents perturb the deep-ocean microbiome by injecting reduced chemical species into the water column that act as an energy source for chemosynthetic organisms. These systems thus provide excellent natural laboratories for studying the response of microbial communities to shifts in marine geochemistry. The present study explores the processes that regulate coupled microbial-geochemical dynamics in hydrothermal plumes by means of a novel mathematical model, which combines thermodynamics, growth and reaction kinetics, and transport processes derived from a fluid dynamics model. Simulations of a plume located in the ABE vent field of the Lau basin were able to reproduce metagenomic observations well and demonstrated that the magnitude of primary production and rate of autotrophic growth are largely regulated by the energetics of metabolisms and the availability of electron donors, as opposed to kinetic parameters. Ambient seawater was the dominant source of microbes to the plume and sulphur oxidisers constituted almost 90{%} of the modelled community in the neutrally-buoyant plume. Data from drifters deployed in the region allowed the different time scales of metabolisms to be cast in a spatial context, which demonstrated spatial succession in the microbial community. While growth was shown to occur over distances of tens of kilometers, microbes persisted over hundreds of kilometers. Given that high-temperature hydrothermal systems are found less than 100 km apart on average, plumes may act as important vectors between different vent fields and other environments that are hospitable to similar organisms, such as oil spills and oxygen minimum zones.
Keywords: ROV Jason (Remotely Operated Vehicle)

Rapid assessment of fish communities on submerged oil and gas platform reefs using remotely operated vehicles - Ajemian, Matthew J; Wetz, Jennifer Jarrell; Shipley-Lozano, Brooke; Stunz, Gregory W (FISHERIES RESEARCH, 2015)
Remotely operated vehicles (ROVs) provide a non-extractive approach to characterizing fish communities in complex habitats. Despite the demonstrated effectiveness of ROVs in studying reef fishes over natural hard-bottom and small artificial reefs, there has been little application of this technology to larger artificial structures (10s of m tall and wide), We explored the utility of ROVs in rapidly characterizing an assemblage of fishes associated with an artificial reef complex in the western Gulf of Mexico (26.9-28.2 degrees N; 95.5-97.0 degrees W) dominated by partially removed and toppled oil and gas platforms. This study reports on an efficient method to sample these structures, where we integrated depth-interval transect (DIT) and continuous roving transect (CRT) protocols to document fish distribution and community structure on 14 artificial reef sites. Consistent with previous hydroacoustic studies, south Texas artificial reefs exhibited a vertically heterogeneous distribution of fishes that varied with structure orientation. These reefs were dominated by economically important lutjanids and carangids, both of which presented sampling challenges due to their patchy distribution around these vast structures. The non-uniform distribution and mobility of these dominant taxa highlight the utility of adopting roving approaches to assess fish communities on these complex structures. We conclude our study with a discussion of important logistical challenges associated with micro-ROV surveys in deepwater habitats, and potential complementary approaches to assist documentation of demersal fishes inhabiting a persistently turbid bottom layer. (C) 2015 Elsevier B.V. All rights reserved.
Keywords: ROV Jason (Remotely Operated Vehicle)

Size matters at deep-sea hydrothermal vents: different diversity and habitat fidelity patterns of meio- and macrofauna - Gollner, Sabine; Govenar, Breea; Fisher, Charles R; Bright, Monika (MARINE ECOLOGY PROGRESS SERIES, 2015)
Species with markedly different sizes interact when sharing the same habitat. Unravelling mechanisms that control diversity thus requires consideration of a range of size classes. We compared patterns of diversity and community structure for meio-and macrofaunal communities sampled along a gradient of environmental stress at deep-sea hydrothermal vents on the East Pacific Rise (9 degrees 50' N) and neighboring basalt habitats. Both meio-and macrofaunal species richnesses were lowest in the high-stress vent habitat, but macrofaunal richness was highest among intermediate-stress vent habitats. Meiofaunal species richness was negatively correlated with stress, and highest on the basalt. In these deep-sea basalt habitats surrounding hydrothermal vents, meiofaunal species richness was consistently higher than that of macrofauna. Consideration of the physiological capabilities and life history traits of different-sized animals suggests that different patterns of diversity may be caused by different capabilities to deal with environmental stress in the 2 size classes. In contrast to meiofauna, adaptations of macrofauna may have evolved to allow them to maintain their physiological homeostasis in a variety of hydrothermal vent habitats and exploit this food-rich deep-sea environment in high abundances. The habitat fidelity patterns also differed: macrofaunal species occurred primarily at vents and were generally restricted to this habitat, but meiofaunal species were distributed more evenly across proximate and distant basalt habitats and were thus not restricted to vent habitats. Over evolutionary time scales these contrasting patterns are likely driven by distinct reproduction strategies and food demands inherent to fauna of different sizes.
Keywords: HOV Alvin (Human Occupied Vehicle)

Sources of organic carbon for Rimicaris hybisae: Tracing individual fatty acids at two hydrothermal vent fields in the Mid-Cayman rise - Streit, Kathrin; Bennett, Sarah A; Van Dover, Cindy L; Coleman, Max (DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS, 2015)
Hydrothermal vents harbor ecosystems mostly decoupled from organic carbon synthesized with the energy of sunlight (photosynthetic carbon source) but fueled instead by oxidation of reduced compounds to generate a chemosynthetic carbon source. Our study aimed to disentangle photosynthetic and chemosynthetic organic carbon sources for the shrimp species Rimicaris hybisae, a primary consumer presumed to obtain its organic carbon mainly from ectosymbiotic chemoautotrophic bacteria living on its gill cover membrane. To provide ectosymbionts with ideal conditions for chemosynthesis, these shrimp live in dense clusters around vent chimneys; they are, however, also found sparsely distributed adjacent to diffuse vent flows, where they might depend on alternative food sources. Densely and sparsely distributed shrimp were sampled and dissected into abdominal tissue and gill cover membrane, covered with ectosymbiotic bacteria, at two hydrothermal vent fields in the Mid-Cayman rise that differ in vent chemistry. Fatty acids (FA) were extracted from shrimp tissues and their carbon isotopic compositions assessed. The FA data indicate that adult R. hybisae predominantly rely on bacteria for their organic carbon needs. Their FA composition is dominated by common bacterial FA of the n7 family (similar to 41{%}). Bacterial FA of the n4 FA family are also abundant and found to constitute good biomarkers for gill ectosymbionts. Sparsely distributed shrimp contain fractions of n4 FA in gill cover membranes similar to 4{%} lower than densely packed ones (similar to 18{%}) and much higher fractions of photosynthetic FA in abdominal tissues, similar to 4{%} more (compared with 1.6{%}), suggesting replacement of ectosymbionts along with exoskeletons (molt), while they take up alternative diets of partly photosynthetic organic carbon. Abdominal tissues also contain photosynthetic FA from a second source taken up presumably during an early dispersal phase and still present to c. 3{%} in adult shrimp. The contribution of photosynthetic carbon to the FA pool of adult R. hybisae is, however, overall small (max. 8{%}). Significant differences in carbon isotopic values of chemosynthetically derived FA between vent fields suggest that different dominant C fixation pathways are being used. (C) 2015 Published by Elsevier Ltd.
Keywords: ROV Jason (Remotely Operated Vehicle)

Stealth export of hydrogen and methane from a low temperature serpentinization system - Larson, B I; Lang, S Q; Lilley, M D; Olson, E J; Lupton, J E; Nakamura, K; Buck, N J (Deep-Sea Research Part II: Topical Studies in Oceanography, 2015)
Chemical input to the deep sea from hydrothermal systems is a globally distributed phenomenon. Hydrothermal discharge is one of the primary mechanisms by which the Earth's interior processes manifest themselves at the Earth's surface, and it provides a source of energy for autotrophic processes by microbes that are too deep to capitalize on sunlight. Much is known about the water-column signature of this discharge from high-temperature mid-ocean Ridge (MOR) environments and their neighboring low-temperature counterparts. Hydrothermal discharge farther away from the ridge, however, has garnered less attention, owing in part to the difficulty in finding this style of venting, which eludes methods of detection that work well for high-temperature ‘black smoker'-type venting. Here we present a case study of the plume from one such ‘invisible' off-axis environment, The Lost City, with an emphasis on the dissolved volatile content of the hydrothermal plume. Serpentinization and abiotic organic synthesis generate significant concentrations of H2 and CH4 in vent fluid, but these species are unevenly transported to the overlying plume, which itself appears to be a composite of two different sources. A concentrated vent cluster on the talus slope channels fluid through at least eight chimneys, producing a water-column plume with the highest observed concentrations of CH4 in the field. In contrast, a saddle in the topography leading up to a carbonate cap hosts broadly distributed, nearly invisible venting apparent only in its water-column signals of redox potential and dissolved gas content, including the highest observed plume H2. After normalizing H2 and CH4 to the 3He background-corrected anomaly (3He$Δ$) to account for mixing and relative amount of mantle input, it appears that, while a minimum of 60{%} of CH4 is transported out of the system, greater than 90{%} of the H2 is consumed in the subsurface prior to venting. The exception to this pattern occurs in the plume originating from the area dubbed Chaff Beach, in which somewhat more than 10{%} of the original H2 remains, indicating that this otherwise unremarkable plume, and others like it, may represent a significant source of H2 to the deep sea.
Keywords: AUV ABE (Autonomous Benthic Explorer); HOV Alvin (Human Occupied Vehicle)

Temporal and spatial variation in temperature experienced by macrofauna at Main Endeavour hydrothermal vent field - Lee, R W; Robert, K; Matabos, M; Bates, A E; Juniper, S K (Deep-Sea Research Part I: Oceanographic Research Papers, 2015)
A significant focus of hydrothermal vent ecological studies has been to understand how species cope with various stressors through physiological tolerance and biochemical resistance. Yet, the environmental conditions experienced by vent species have not been well characterized. This objective requires continuous observations over time intervals that can capture environmental variability at scales that are relevant to animals. We used autonomous temperature logger arrays (four roughly parallel linear arrays of 12 loggers spaced every 10–12 cm) to study spatial and temporal variations in the thermal regime experienced by hydrothermal vent macrofauna at a diffuse flow vent. Hourly temperatures were recorded over eight months from 2010 to 2011 at Grotto vent in the Main Endeavour vent field on the Juan de Fuca Ridge, a focus area of the Ocean Networks Canada cabled observatory. The conspicuous animal assemblages in video footage contained Ridgeia piscesae tubeworms, gastropods (primarily Lepetodrilus fucensis), and polychaetes (polynoid scaleworms and the palm worm Paralvinella palmiformis). Two dimensional spatial gradients in temperature were generally stable over the deployment period. The average temperature recorded by all arrays, and in some individual loggers, revealed distinctive fluctuations in temperature that often corresponded with the tidal cycle. We postulate that this may be related to changes in bottom currents or fluctuations in vent discharge. A marked transient temperature increase lasting over a period of days was observed in April 2011. While the distributions and behavior of Juan de Fuca Ridge vent invertebrates may be partially constrained by environmental temperature and temperature tolerance, except for the one transient high-temperature event, observed fluid temperatures were generally similar to the thermal preferences for some species, and typically well below lethal temperatures for all species. Average temperatures of the four arrays ranged from 4.1 to 11.0 °C during the deployment, indicating that on an hourly timescale the temperature conditions in this tubeworm community were fairly moderate and stable. The generality of these findings and behavioral responses of vent organisms to predictable
Keywords: ROV Jason (Remotely Operated Vehicle)

Testing the depth-differentiation hypothesis in a deepwater octocoral - Quattrini, A M; Baums, I B; Shank, T M; Morrison, C; Cordes, E E (Proceedings of the Royal Society B: Biological Sciences, 2015)
The depth-differentiation hypothesis proposes that the bathyal region is a source of genetic diversity and an area where there is a high rate of species formation. Genetic differentiation should thus occur over relatively small vertical distances, particularly along the upper continental slope (200-1000 m) where oceanography varies greatly over small differences in depth. To test whether genetic differentiation within deepwater octocorals is greater over vertical rather than geographical distances, Callogorgia delta was targeted. This species commonly occurs throughout the northern Gulf of Mexico at depths ranging from 400 to 900 m. We found significant genetic differentiation (FST = 0.042) across seven sites spanning 400 km of distance and 400 m of depth. A pattern of isolation by depth emerged, but geographical distance between sites may further limit gene flow. Water mass boundaries may serve to isolate populations across depth; however, adaptive divergence with depth is also a possible scenario. Microsatellite markers also revealed significant genetic differentiation (FST = 0.434) between C. delta and a closely related species, Callogorgia americana, demonstrating the utility of microsatellites in species delimitation of octocorals. Results provided support for the depth-differentiation hypothesis, strengthening the notion that factors covarying with depth serve as isolation mechanisms in deep-sea populations.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Trace metal concentration and partitioning in the first 1.5 m of hydrothermal vent plumes along the Mid-Atlantic Ridge: TAG, Snakepit, and Rainbow - Findlay, A J; Gartman, A; Shaw, T J; Luther, G W (Chemical Geology, 2015)
To determine the significance of metal fluxes from hydrothermal vents, understanding the speciation, reactivity, and possible transformations of metals and metal sulfides within the hydrothermal plume is critical. In this study, we measure the concentration and partitioning of trace metals (Fe, Mn, Cu, Cd, Co, Pb, Ni) and sulfide phases within the first 1.5 m of the rising plume at three vent fields (TAG, Snakepit, and Rainbow) along the Mid-Atlantic Ridge. A HCl/HNO3 leaching method was used to differentiate metals present in metal mono-sulfides from those in pyrite and chalcopyrite. At all three vent sites, Mn and Fe are primarily in the {<} 0.2 $μ$m (filtered) portion, whereas Cu, Co, Cd, and Pb are mainly in the unfiltered fraction. Significant concentrations of HNO3-extractable metals were found in the {<} 0.2 $μ$m fraction at all three vent sites, indicating that they likely exist in a recalcitrant nanoparticulate phase such as pyrite or chalcopyrite. At TAG and Snakepit, Cu is correlated with Co, as Co enters into chalcopyrite and other CuFeS phases and Zn is correlated with Cd and Pb as they form discrete metal sulfide phases. At Rainbow, Zn, Cd, and Pb are correlated, but Cu and Co are not correlated. The Rainbow data are consistent with the higher metal to sulfide ratio found at Rainbow. These speciation differences are significant as both mineral type and size will affect the amount of metal transported from the vent site and its availability for biogeochemical processes.
Keywords: ROV Jason (Remotely Operated Vehicle)

Variation in the diets of hydrothermal vent gastropods - Govenar, B W; Fisher, C R; Shank, T M (Deep-Sea Research Part II: Topical Studies in Oceanography, 2015)
A prevailing paradigm of hydrothermal vent ecology is that primary consumers feed on chemoautotrophic bacteria. However, for the purposes of reconstructing vent food webs and for tracking energy flow from the generation of rock and fluid chemistry through primary/ secondary productivity and consumption to the overlying water column, it remains unclear which consumers feed on which bacteria. In paired analyses of carbon and nitrogen tissue stable isotope values with unique 16S rRNA sequences from the stomach contents, we determined that two species of gastropod grazers appear to feed on epsilon-proteobacteria, while two other species have more diverse diets, including one species that consumes alpha-proteobacteria, planctomycetes, and non-green sulfur bacteria. Different carbon fixation pathways used by epsilon- and alpha-proteobacteria may account for the variation in the carbon stable isotope values among the consumers. Furthermore, our results indicate that trophic specialization and niche partitioning may contribute to the distribution and abundance of vent-endemic gastropods and support the hypothesis that consumers in the warmer habitats commonly feed on epsilon-proteobacteria that use the rTCA cycle, while in the cooler habitats they feed on additional bacteria that use the CBB cycle. These results suggest that the phylogenetic and metabolic diversity of free-living bacteria may play an important and previously overlooked role in facilitating species coexistence among primary consumers at hydrothermal vents and other chemosynthesis-based ecosystems.
Keywords: HOV Alvin (Human Occupied Vehicle)

Age and growth of the cold-water scleractinian Solenosmilia variabilis and its reef on SW Pacific seamounts - Fallon, S J; Thresher, R E; Adkins, J (CORAL REEFS, 2014)
Little is known about growth rates of deep-water reef-forming corals or the rates at which these reefs accumulate. Such information is critical for determining the resilience of the reefs to anthropogenic impacts such as trawling and climate change. We radiocarbon date live-caught and sub-fossil samples of the bioherm-forming coral Solenosmilia variabilis collected from precisely known depths and locations by means of a remotely operated vehicle on seamounts south of Tasmania, Australia. The growth rate of colonies live-caught between 958 and 1,454 m, which spans most of the depth range of the species locally, ranged from 0.84 to 1.25 mm linear extension yr(-1) and tended to be higher in the deeper-caught material. Analysis of skeletal microstructure suggests annual deposition of growth increments near the growing tips, but not closer to the base, as the skeleton is extended and thickened. Dating of sub-fossil material indicates S. variabilis has been present on Tasmanian seamounts for at least the last 47,000 yrs and a reef accumulation rate of 0.27 mm yr(-1).
Keywords: ROV Jason (Remotely Operated Vehicle)

Alvin Cleared to Return to Service (Ocean News {&} Technology, 2014)
After a 3-year overhaul and major upgrade, the US' deepest-diving research submersible, Alvin, has been cleared to return to work exploring the ocean's depths. The sub has been out of service since December 2010, undergoing a major upgrade that included the replacement of its personnel sphere with a newly fabricated, larger, more capable hull. The Woods Hole Oceanographic Institution operates the Navy-owned sub for the National Deep Submergence Facility on behalf of a consortium of universities and research organizations conducting deep ocean research. The Navy certified Alvin using its Deep Submergence Scope of Certification process, reviewing the design, construction, and materials used to ensure the vehicle performs as expected.
Keywords: HOV Alvin (Human Occupied Vehicle)

Alvin: Ocean Research Submarine - Walsh, Joseph B.; Rainnie, William D. (Mechanical Engineering, 2014)
Keywords: HOV Alvin (Human Occupied Vehicle)

Alvin takes first science dive since overhaul (Ocean News {&} Technology, 2014)
Alvin, the nation's only deep-sea research submarine, took its first scientific dive Mar 15, 2014 after a 39- month hiatus and a major overhaul that dramatically upgraded the sub. Because the first dive site was only 320 m deep, the sub was on the bottom about 12 mm later, and Woods Hole Oceanographic Institution scientist Susan Humphris, Alvin pilot Bob Waters, and pilot-in-training Nathan Brown spent the next 5 hrs doing the undersea equivalent of a road test. Humphris described the tests of the Alvin's new command-and-control features that automatically maintain the sub's position, attitude, or heading.
Keywords: HOV Alvin (Human Occupied Vehicle)

Alvin's animals: scientists in the sub have discovered hundreds of previously unknown species - Madin, K (Oceanus, 2014)
Keywords: HOV Alvin (Human Occupied Vehicle)

The Anatomy of a Buried Submarine Hydrothermal System, Clark Volcano, Kermadec Arc, New Zealand - de Ronde, C E J; Walker, S L; Ditchburn, R G; Tontini, F Caratori; Hannington, M D; Merle, S G; Timm, C; Handler, M R; Wysoczanski, R J; Dekov, V M; Kamenov, G D; Baker, E T; et al. (ECONOMIC GEOLOGY, 2014)
Clark volcano of the Kermadec arc, northeast of New Zealand, is a large stratovolcano comprised of two coalescing volcanic cones; an apparently younger, more coherent, twin-peaked edifice to the northwest and a relatively older, more degraded and tectonized cone to the southeast. High-resolution water column surveys show an active hydrothermal system at the summit of the NW cone largely along a ridge spur connecting the two peaks, with activity also noted at the head of scarps related to sector collapse. Clark is the only known cone volcano along the Kermadec arc to host sulfide mineralization. Volcano-scale gravity and magnetic surveys over Clark show that it is highly magnetized, and that a strong gravity gradient exists between the two edifices. Modeling suggests that a crustal-scale fault lies between these two edifices, with thinner crust beneath the NW cone. Locations of regional earthquake epicenters show a southwest-northeast trend bisecting the two Clark cones, striking northeastward into Tangaroa volcano. Detailed mapping of magnetics above the NW cone summit shows a highly magnetized ring structure 350 m below the summit that is not apparent in the bathymetry; we believe this structure represents the top of a caldera. Oblate zones of low (weak) magnetization caused by hydrothermal fluid upflow, here termed burn holes, form a pattern in the regional magnetization resembling Swiss cheese. Presumably older burn holes occupy the inner margin of the ring structure and show no signs of hydrothermal activity, while younger burn holes are coincident with active venting on the summit. A combination of mineralogy, geochemistry, and seafloor mapping of the NW cone shows that hydrothermal activity today is largely manifest by widespread diffuse venting, with temperatures ranging between 56 degrees and 106 degrees C. Numerous, small ({<}= 30 cm high) chimneys populate the summit area, with one site host to the similar to 7-m-tall ``Twin Towers{\{}''{\}} chimneys with maximum vent fluid temperatures of 221 degrees C (pH 4.9), consistent with delta S-34(anhydrite-pyrite) values indicating formation temperatures of similar to 228 degrees to 249 degrees C. Mineralization is dominated by pyrite-marcasite-barite-anhydrite. Radiometric dating using the Ra-228/Ra-226 and Ra-226/Ba methods shows active chimneys to be {<}20 with most {<}2 years old. However, the chimneys at Clark show evidence for mixing with, and remobilizing of, barite as old as 19,000 years. This is consistent with Nd and Sr isotope compositions of Clark chimney and sulfate crust samples that indicate mixing of similar to 40{%} seawater with a vent fluid derived from low K lavas. Similarly, REE data show the hydrothermal fluids have interacted with a plagioclase-rich source rock. A holistic approach to the study of the Clark hydrothermal system has revealed a two-stage process whereby a caldera-forming volcanic event preceded a later cone-building event. This ensured a protracted (at least 20 ka yrs) history of hydrothermal activity and associated mineral deposition. If we assume at least 200-m-high walls for the postulated (buried) caldera, then hydrothermal fluids would have exited the seafloor 20 ka years ago at least 550 m deeper than they do today, with fluid discharge temperatures potentially much hotter (similar to 350 degrees C). Subsequent to caldera infilling, relatively porous volcaniclastic and other units making up the cone acted as largescale filters, enabling ascending hydrothermal fluids to boil and mix with seawater subseafloor, effectively removing the metals (including remobilized Cu) in solution before they reached the seafloor. This has implications for estimates for the metal inventory of seafloor hydrothermal systems pertaining to arc hydrothermal systems.
Keywords: AUV ABE (Autonomous Benthic Explorer); AUV Sentry (Autonomous Underwater Vehicle)

Benthic protists and fungi of Mediterranean deep hypsersaline anoxic basin redoxcline sediments - Bernhard, J M; Kormas, K; Pachiadaki, M; Rocke, E; Beaudoin, D J; Morrison, C; Visscher, P T; Cobban, A; Starczak, V R; Edgcomb, V P (Frontiers in Microbiology, 2014)
Some of the most extreme marine habitats known are the Mediterranean deep hypersaline anoxic basins (DHABs; water depth ∼3500 m). Brines of DHABs are nearly saturated with salt, leading many to suspect they are uninhabitable for eukaryotes. While diverse bacterial and protistan communities are reported from some DHAB water-column haloclines and brines, the existence and activity of benthic DHAB protists have rarely been explored. Here, we report findings regarding protists and fungi recovered from sediments of three DHAB (Discovery, Urania, L' Atalante) haloclines, and compare these to communities from sediments underlying normoxic waters of typical Mediterranean salinity. Halocline sediments, where the redoxcline impinges the seafloor, were studied from all three DHABs. Microscopic cell counts suggested that halocline sediments supported denser protist populations than those in adjacent control sediments. Pyrosequencing analysis based on ribosomal RNA detected eukaryotic ribotypes in the halocline sediments from each of the three DHABs, most of which were fungi. Sequences affiliated with Ustilaginomycotina Basidiomycota were the most abundant eukaryotic signatures detected. Benthic communities in these DHABs appeared to differ, as expected, due to differing brine chemistries. Microscopy indicated that only a low proportion of protists appeared to bear associated putative symbionts. In a considerable number of cases, when prokaryotes were associated with a protist, DAPI staining did not reveal presence of any nuclei, suggesting that at least some protists were carcasses inhabited by prokaryotic scavengers.
Keywords: ROV Jason (Remotely Operated Vehicle)

Biodiversity and community composition of sediment macrofauna associated with deep-sea Lophelia pertusa habitats in the Gulf of Mexico - Demopoulos, A W J; Bourque, J R; Frometa, J (Deep-Sea Research. Part I: Oceanographic Research Papers, 2014)
Scleractinian corals create three-dimensional reefs that provide sheltered refuges, facilitate sediment accumulation, and enhance colonization of encrusting fauna. While heterogeneous coral habitats can harbor high levels of biodiversity, their effect on the community composition within nearby sediments remains unclear, particularly in the deep sea. Sediment macrofauna from deep-sea coral habitats (Lophelia pertusa) and non-coral, background sediments were examined at three sites in the northern Gulf of Mexico (VK826, VK906, MC751, 350–500 m depth) to determine whether macrofaunal abundance, diversity, and community composition near corals differed from background soft-sediments. Macrofaunal densities ranged from 26 to 125 individuals 32 cm−2 and were significantly greater near coral versus background sediments only at VK826. Of the 86 benthic invertebrate taxa identified, 16 were exclusive to near-coral habitats, while 14 were found only in background sediments. Diversity (Fisher's $α$) and evenness were significantly higher within near-coral sediments only at MC751 while taxon richness was similar among all habitats. Community composition was significantly different both between near-coral and background sediments and among the three primary sites. Polychaetes numerically dominated all samples, accounting for up to 70{%} of the total individuals near coral, whereas peracarid crustaceans were proportionally more abundant in background sediments (18{%}) than in those near coral (10{%}). The reef effect differed among sites, with community patterns potentially influenced by the size of reef habitat. Taxon turnover occurred with distance from the reef, suggesting that reef extent may represent an important factor in structuring sediment communities near L. pertusa. Polychaete communities in both habitats differed from other Gulf of Mexico (GOM) soft sediments based on data from previous studies, and we hypothesize that local environmental conditions found near L. pertusa may influence the macrofaunal community structure beyond the edges of the reef. This study represents the first assessment of L. pertusa-associated sediment communities in the GOM and provides baseline data that can help define the role of transition zones, from deep reefs to soft sediments, in shaping macrofaunal community structure and maintaining biodiversity; this information can help guide future conservation and management activities.
Keywords: ROV Jason (Remotely Operated Vehicle)

Bringing Alvin back on board: 'swimmers' are key links between sub and ship - Winner, C; Lippsett, L (Oceanus, 2014)
Keywords: HOV Alvin (Human Occupied Vehicle)

THE CASCADIA INITIATIVE A Sea Change In Seismological Studies of Subduction Zones - Toomey, Douglas R; Allen, Richard M; Barclay, Andrew H; Bell, Samuel W; Bromirski, Peter D; Carlson, Richard L; Chen, Xiaowei; Collins, John A; Dziak, Robert P; Evers, Brent; Forsyth, Donald W; Gerstoft, Peter; et al. (OCEANOGRAPHY, 2014)
Increasing public awareness that the Cascadia subduction zone in the Pacific Northwest is capable of great earthquakes (magnitude 9 and greater) motivates the Cascadia Initiative, an ambitious onshore/offshore seismic and geodetic experiment that takes advantage of an amphibious array to study questions ranging from megathrust earthquakes, to volcanic arc structure, to the formation, deformation and hydration of the Juan De Fuca and Gorda Plates. Here, we provide an overview of the Cascadia Initiative, including its primary science objectives, its experimental design and implementation, and a preview of how the resulting data are being used by a diverse and growing scientific community. The Cascadia Initiative also exemplifies how new technology and community-based experiments are opening up frontiers for marine science. The new technology shielded ocean bottom seismometers is allowing more routine investigation of the source zone of megathrust earthquakes, which almost exclusively lies offshore and in shallow water. The Cascadia Initiative offers opportunities and accompanying challenges to a rapidly expanding community of those who use ocean bottom seismic data.
Keywords: ROV Jason (Remotely Operated Vehicle)

Ciliates along Oxyclines of Permanently Stratified Marine Water Columns - Edgcomb, V P; Pachiadaki, M (Journal of Eukaryotic Microbiology, 2014)
Studies of microbial communities in areas of the world where permanent marine water column oxyclines exist suggest they are "hotspots" of microbial activity, and that these water features and the anoxic waters below them are inhabited by diverse protist taxa, including ciliates. These communities have minimal taxonomic overlap with those in overlying oxic water columns. Some ciliate taxa have been detected in multiple locations where these stable water column oxyclines exist; however, differences in such factors as hydrochemistry in the habitats that have been studied suggest local selection for distinct communities. We compare published data on ciliate communities from studies of deep marine water column oxyclines in Caricao Basin, Venezuela, and the Black Sea, with data from coastal, shallower oxycline waters in Framvaren and Mariager fjords, and from several deep-sea hypersaline anoxic basins in the Eastern Mediterranean Sea. Putative symbioses between Bacteria, Archaea, and ciliates observed along these oxyclines suggests a strategy of cooperative metabolism for survival that includes chemosynthetic autotrophy and exchanges of metabolic intermediates or end products between hosts and their prokaryotic partners.
Keywords: ROV Jason (Remotely Operated Vehicle)

Close association of active nitrifiers with Beggiatoa mats covering deep-sea hydrothermal sediments - Winkel, Matthias; de Beer, Dirk; Lavik, Gaute; Peplies, Joerg; Mussmann, Marc I (ENVIRONMENTAL MICROBIOLOGY, 2014)
Hydrothermal sediments in the Guaymas Basin are covered by microbial mats that are dominated by nitrate-respiring and sulphide-oxidizing Beggiatoa. The presence of these mats strongly correlates with sulphide- and ammonium-rich fluids venting from the subsurface. Because ammonium and oxygen form opposed gradients at the sediment surface, we hypothesized that nitrification is an active process in these Beggiatoa mats. Using biogeochemical and molecular methods, we measured nitrification and determined the diversity and abundance of nitrifiers. Nitrification rates ranged from 74 to 605molNl-1matday-1, which exceeded those previously measured in hydrothermal plumes and other deep-sea habitats. Diversity and abundance analyses of archaeal and bacterial ammonia monooxygenase subunit A genes, archaeal 16S ribosomal RNA pyrotags and fluorescence in situ hybridization confirmed that ammonia- and nitrite-oxidizing microorganisms were associated with Beggiatoa mats. Intriguingly, we observed cells of bacterial and potential thaumarchaeotal ammonia oxidizers attached to narrow, Beggiatoa-like filaments. Such a close spatial coupling of nitrification and nitrate respiration in mats of large sulphur bacteria is novel and may facilitate mat-internal cycling of nitrogen, thereby reducing loss of bioavailable nitrogen in deep-sea sediments.
Keywords: HOV Alvin (Human Occupied Vehicle)

The Cobb hot spot: HIMU-DMM mixing and melting controlled by a progressively thinning lithospheric lid - Chadwick, John; Keller, Randall; Kamenov, George; Yogodzinski, Gene; Lupton, John (GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 2014)
The Cobb Seamount Chain in the northeast Pacific basin records the composition of the Cobb hot spot for the past 33 Myr, as the migrating Juan de Fuca Ridge approached and ultimately overran it ca. 0.5 Myr ago. In this first comprehensive geochemical study of the Cobb chain, major and trace element compositions and Sr, Nd, Pb, and Hf isotopic ratios were measured for whole-rock samples from throughout the chain, and He isotopes were acquired for olivine phenocrysts from one seamount. Trace element modeling indicates increased melting along the chain over time, with progressively more depleted lavas as the ridge approached the hot spot. The isotopic data reveal the first evidence of the high mu (mu=U-238/Pb-204) (HIMU) mantle component in the north Pacific basin and are consistent with a progressively decreasing mixing proportion of HIMU melts relative to those from depleted mid-ocean ridge basalt mantle (DMM) in the chain over time. Decreasing lithospheric thickness over the Cobb hot spot due to the approach of the migrating Juan de Fuca ridge allowed adiabatic melting to continue to shallower depths, leading to increased melt fractions of the refractory DMM component in the hot spot and more depleted and MORB-like lavas in the younger Cobb seamounts.
Keywords: HOV Alvin (Human Occupied Vehicle)

Complete mitochondrial genomes elucidate phylogenetic relationships of the deep-sea octocoral families Coralliidae and Paragorgiidae - Figueroa, D F; Baco, A R (Biology and Geology of Deep-Sea Coral Ecosystems: Proceedings of the Fifth International Symposium on Deep Sea Corals, 2014)
In the past decade, molecular phylogenetic analyses of octocorals have shown that the current morphological taxonomic classification of these organisms needs to be revised. The latest phylogenetic analyses show that most octocorals can be divided into three main clades. One of these clades contains the families Coralliidae and Paragorgiidae. These families share several taxonomically important characters and it has been suggested that they may not be monophyletic; with the possibility of the Coralliidae being a derived branch of the Paragorgiidae. Uncertainty exists not only in the relationship of these two families, but also in the classification of the two genera that make up the Coralliidae, Corallium and Paracorallium. Molecular analyses suggest that the genus Corallium is paraphyletic, and it can be divided into two main clades, with the Paracorallium as members of one of these clades. In this study we sequenced the whole mitochondrial genome of five species of Paragorgia and of five species of Corallium to use in a phylogenetic analysis to achieve two main objectives; the first to elucidate the phylogenetic relationship between the Paragorgiidae and Coralliidae and the second to determine whether the genera Corallium and Paracorallium are monophyletic. Our results show that other members of the Coralliidae share the two novel mitochondrial gene arrangements found in a previous study in Corallium konojoi and Paracorallium japonicum; and that the Corallium konojoi arrangement is also found in the Paragorgiidae. Our phylogenetic reconstruction based on all the protein coding genes and ribosomal RNAs of the mitochondrial genome suggest that the Coralliidae are not a derived branch of the Paragorgiidae, but rather a monophyletic sister branch to the Paragorgiidae. While our manuscript was in review a study was published using morphological data and several fragments from mitochondrial genes to redefine the taxonomy of the Coralliidae. Paracorallium was subsumed into Corallium and the genus Hemicorallium was resurrected. This left two disjunct clades as Corallium, making that genus paraphyletic. One of the clades includes the type specimens of Corallium, indicating that clade should remain Corallium. For the other clade, we support the resurrection of the genus Pleurocorallium to fix the paraphyly of Corallium. Based on congruent phylogenies in both studies, the genus Pleurocorallium includes the species C. secundum, C. kishinouyei, C. konojoi, C. elatius, and C. niveum.
Keywords: HOV Alvin (Human Occupied Vehicle)

Deep-sea hydrothermal vent Epsilonproteobacteria encode a conserved and widespread nitrate reduction pathway (Nap) - Vetriani, Costantino; Voordeckers, James W; Crespo-Medina, Melitza; O'Brien, Charles E; Giovannelli, Donato; Lutz, Richard A (ISME JOURNAL, 2014)
Despite the frequent isolation of nitrate-respiring Epsilonproteobacteria from deep-sea hydrothermal vents, the genes coding for the nitrate reduction pathway in these organisms have not been investigated in depth. In this study we have shown that the gene cluster coding for the periplasmic nitrate reductase complex (nap) is highly conserved in chemolithoautotrophic, nitrate-reducing Epsilonproteobacteria from deep-sea hydrothermal vents. Furthermore, we have shown that the napA gene is expressed in pure cultures of vent Epsilonproteobacteria and it is highly conserved in microbial communities collected from deep-sea vents characterized by different temperature and redox regimes. The diversity of nitrate-reducing Epsilonproteobacteria was found to be higher in moderate temperature, diffuse flow vents than in high temperature black smokers or in low temperatures, substrate-associated communities. As NapA has a high affinity for nitrate compared with the membrane-bound enzyme, its occurrence in vent Epsilonproteobacteria may represent an adaptation of these organisms to the low nitrate concentrations typically found in vent fluids. Taken together, our findings indicate that nitrate reduction is widespread in vent Epsilonproteobacteria and provide insight on alternative energy metabolism in vent microorganisms. The occurrence of the nap cluster in vent, commensal and pathogenic Epsilonproteobacteria suggests that the ability of these bacteria to respire nitrate is important in habitats as different as the deep-sea vents and the human body.
Keywords: HOV Alvin (Human Occupied Vehicle)

Depth-dependent gene flow in Gulf of Mexico cold seep Lamellibrachia tubeworms (Annelida, Siboglinidae) - Cowart, Dominique A; Halanych, Kenneth M; Schaeffer, Stephen W; Fisher, Charles R (HYDROBIOLOGIA, 2014)
Lamellibrachia vestimentiferan tubeworms form aggregations at hydrocarbon cold seeps in the deep Gulf of Mexico (GoM), creating structures that provide living space for other fauna. In the GoM, three Lamellibrachia taxa vary in morphology and depth ranges: Lamellibrachia luymesi (300-950 m), Lamellibrachia sp. 1 (950-2,604 m), and Lamellibrachia sp. 2 (1,175-3,304 m). While Lamellibrachia sp. 2 is consistently identified as a separate species, L. luymesi and sp. 1 cannot be discriminated using barcoding markers cytochrome oxidase subunit 1 (COI) and large ribosomal subunit rDNA (16S). To determine if limited gene flow was a factor in the formation of these taxa, we employed more quickly evolving markers, including mitochondrial cytochrome B (CYTB), hemoglobin subunit B2 intron (HbB2i), and six polymorphic microsatellites; microsatellites were amplified across 45 L. luymesi and sp. 1 individuals. Additionally, we used microsatellites to ask whether populations of Lamellibrachia sp. 1 and sp. 2 show evidence of significant structure. Despite a lack of resolution seen with CYTB and HbB2i, L. luymesi and sp. 1 form genetically differentiated clusters at the cross-amplified microsatellites. Furthermore, we find no evidence for population structure for either Lamellibrachia sp. 1 or sp. 2 across the GoM.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Development and evolution of detachment faulting along 50 km of the Mid-Atlantic Ridge near 16.5°N - Smith, D K; Schouten, H; Dick, H J B; Cann, J R; Salters, V; Marschall, H R; Ji, F; Yoerger, D R; Sanfilippo, A; Parnell-Turner, R; Palmiotto, C; Zheleznov, A; et al. (Geochemistry, Geophysics, Geosystems, 2014)
A multifaceted study of the slow spreading Mid-Atlantic Ridge (MAR) at 16.5°N provides new insights into detachment faulting and its evolution through time. The survey included regional multibeam bathymetry mapping, high-resolution mapping using AUV Sentry, seafloor imaging using the TowCam system, and an extensive rock-dredging program. At different times, detachment faulting was active along ∼50 km of the western flank of the study area, and may have dominated spreading on that flank for the last 5 Ma. Detachment morphologies vary and include a classic corrugated massif, noncorrugated massifs, and back-tilted ridges marking detachment breakaways. High-resolution Sentry data reveal a new detachment morphology; a low-angle, irregular surface in the regional bathymetry is shown to be a finely corrugated detachment surface (corrugation wavelength of only tens of meters and relief of just a few meters). Multiscale corrugations are observed 2–3 km from the detachment breakaway suggesting that they formed in the brittle layer, perhaps by anastomosing faults. The thin wedge of hanging wall lavas that covers a low-angle (6°) detachment footwall near its termination are intensely faulted and fissured; this deformation may be enhanced by the low angle of the emerging footwall. Active detachment faulting currently is limited to the western side of the rift valley. Nonetheless, detachment fault morphologies also are present over a large portion of the eastern flank on crust {>}2 Ma, indicating that within the last 5 Ma parts of the ridge axis have experienced periods of two-sided detachment faulting.
Keywords: AUV Sentry (Autonomous Underwater Vehicle)

Dissolved hydrogen and methane in the oceanic basaltic biosphere - Lin, Huei-Ting; Cowen, James P; Olson, Eric J; Lilley, Marvin D; Jungbluth, Sean P; Wilson, Samuel T; Rappe, Michael S (EARTH AND PLANETARY SCIENCE LETTERS, 2014)
The oceanic basaltic crust is the largest aquifer on Earth and has the potential to harbor substantial subsurface microbial ecosystems, which hitherto remains largely uncharacterized and is analogous to extraterrestrial subsurface habitats. Within the sediment-buried 3.5 Myr old basaltic crust of the eastern Juan de Fuca Ridge flank, the circulating basement fluids have moderate temperature (similar to 65 degrees C) and low to undetectable dissolved oxygen and nitrate concentrations. Sulfate, present in high concentrations, is therefore expected to serve as the major electron acceptor in this subsurface environment. This study focused on the availability and potential sources of two important electron donors, methane (CH4) and hydrogen (H-2), for the subseafloor biosphere. High integrity basement fluids were collected via fluid delivery lines associated with Integrated Ocean Drilling Program (IODP) Circulation Obviation Retrofit Kits (CORKs) that extend from basement depths to outlet ports at the seafloor. Two new CORKs installed during IODP 327 in 2010, 1362A and 1362B, were sampled in 2011 and 2013. The two CORKs are superior than earlier style CORKs in that they are equipped with coated casing and polytetrafluoroethylene fluid delivery lines, reducing the interaction between casing materials with the environment. Additional samples were collected from an earlier style CORK at Borehole 1301A. The basement fluids are enriched in H-2 (0.05-1.8 mu mol/kg), suggesting that the ocean basaltic aquifer can support H-2-driven metabolism. The basement fluids also contain significant amount of CH4 (5-32 mu mol/kg), revealing CH4 as an available substrate for subseafloor basaltic habitats. The delta C-13 values of CH4 from the three boreholes ranged from -22.5 to -58 parts per thousand, while the delta H-2 values ranged from 316 to 57 parts per thousand. The isotopic compositions of CH4 and the molecular compositions of hydrocarbons suggest that CH4 in the basement fluids is of both biogenic and abiotic origins, varying among sites and sampling times. The delta H-2 values of CH4 in CORK 1301A fluid samples are much more positive than found in all other marine environments investigated to date and are best explained by the partial microbial oxidation of biogenic CH4. In conclusion, our study shows that CH4 and H-2 are persistently available to fuel the deep biosphere and that CH4 is both produced and potentially consumed by microorganisms in the oceanic basement. (C) 2014 Elsevier B.V. All rights reserved.
Keywords: ROV Jason (Remotely Operated Vehicle)

Distribution and size fractionation of elemental sulfur in aqueous environments: The Chesapeake Bay and Mid-Atlantic Ridge - Findlay, Alyssa J; Gartman, Amy; MacDonald, Daniel J; Hanson, Thomas E; Shaw, Timothy J; Luther III, George W (GEOCHIMICA ET COSMOCHIMICA ACTA, 2014)
Elemental sulfur is an important intermediate of sulfide oxidation and may be produced via abiotic and biotic pathways. In this study the concentration and size fractionation of elemental sulfur were measured in two different sulfidic marine environments: the Chesapeake Bay and buoyant hydrothermal vent plumes along the Mid-Atlantic Ridge. Nanoparticulate sulfur ({<}0.2 mu m) was found to comprise up to 90{%} of the total elemental sulfur in anoxic deep waters of the Chesapeake Bay. These data were compared with previous studies of elemental sulfur, and represent one of the few reports of nanoparticulate elemental sulfur in the environment. Additionally, a strain of phototrophic sulfide oxidizing bacteria isolated from the Chesapeake Bay was shown to produce elemental sulfur as a product of sulfide oxidation. Elemental sulfur concentrations are also presented from buoyant hydrothermal vent plumes located along the Mid-Atlantic Ridge. In the Mid-Atlantic Ridge plume, S-0 concentrations up to 33 mu M were measured in the first meter of rising plumes at three different vent sites, and nanoparticulate S-0 was up to 44{%} of total elemental sulfur present. (C) 2014 Elsevier Ltd. All rights reserved.
Keywords: ROV Jason (Remotely Operated Vehicle)

Diverse magma flow directions during construction of sheeted dike complexes at fast- to superfast-spreading centers - Horst, A J; Varga, R J; Gee, J S; Karson, J A (EARTH AND PLANETARY SCIENCE LETTERS, 2014)
Dike intrusion is a fundamental process during upper oceanic crustal accretion at fast- to superfast-spreading ridges. Based on the distribution of magma along fast-spreading centers inferred from marine geophysical data, models predict systematic steep flow at magmatically robust segment centers and shallow magma flow toward distal segment ends. Anisotropy of magnetic susceptibility (AMS) fabrics from 48 fully-oriented block samples of dikes from upper oceanic crust exposed at Hess Deep Rift and Pito Deep Rift reveal a wide range of magma flow directions that are not consistent with such simple magma supply models. The AMS is interpreted to arise from distribution anisotropy of titanomagnetite crystals based on weak shape-preferred orientation of opaque oxide and plagioclase crystals generally parallel to AMS maximum eigenvectors. Most dike samples show normal AMS fabrics with maximum eigenvector directions ranging from subvertical to subhorizontal. The distributions of inferred magma flow lineations from maximum eigenvectors show no preferred flow pattern, even after structural correction. We use a Kolmogorov Smirnov test (KS-test) to show that the distribution of bootstrapped flow lineation rakes from Pito Deep are not statistically distinct from Hess Deep, and neither are distinguishable from Oman and Troodos Ophiolite AMS data. Magma flow directions in sheeted dikes from these two seafloor escarpments also do not correlate with available geochemistry in any systematic way as previously predicted. These results indicate distinct compositional sources feed melt that is injected into dikes at fast- to superfast-spreading ridges with no preference for subhorizontal or subvertical magma flow. Collectively, results imply ephemeral melt lenses at different along-axis locations within the continuous axial magma chamber and either direct injection or intermingling of melt from other deeper ridge-centered or off-axis sources. (C) 2014 Elsevier B.V. All rights reserved.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Diversity and abundance of Bacteria and nirS-encoding denitrifiers associated with the Juan de Fuca Ridge hydrothermal system - Bourbonnais, Annie; Juniper, S Kim; Butterfield, David A; Anderson, Rika E; Lehmann, Moritz F (ANNALS OF MICROBIOLOGY, 2014)
Denitrification, which results in the loss of bioavailable nitrogen-an essential macronutrient for all living organisms-may potentially affect chemosynthetic primary production in hydrothermal vent ecosystems where sub-oxic conditions favorable to denitrification are common. Here we describe the diversity and abundance of denitrifying bacteria in the subsurface biosphere at Axial Volcano and the Endeavour Segment on the Juan de Fuca Ridge using a combination of quantitative polymerase chain reaction assays, and small subunit ribosomal RNA (SSU or 16S rRNA) pyrotag and nitrite reductase (nirS) clone library sequencing methods. Bacterial communities were diverse and dominated by members of the epsilon- and gamma-proteobacteria, including taxonomic groups containing known denitrifiers. Assemblages of denitrifiers that could be evaluated by nirS gene sequence comparisons showed low diversity. The single nirS sequence shared by the two locations, affiliated with a gamma-proteobacteria isolated from estuarine sediments (Pseudomonas sp. BA2), represented more than half of all sequences recovered when clustered at 97 {%} identity. All other nirS sequences clustered into different taxonomic groups, indicating important differences in denitrifier community membership between the two sites. Total nirS gene abundance was at least two orders of magnitude lower than 16S rRNA abundance. Overall, our results demonstrate that the diversity and abundance of the nirS gene-containing bacterial community are rather low, as might be expected under the extreme conditions encountered in the subsurface biosphere of hydrothermal vent systems, and do not correlate clearly with any environmental variables investigated (i.e., pH, temperature, and H2S, NO3-, NH4+ concentrations).
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Eruption of a deep-sea mud volcano triggers rapid sediment movement - Feseker, T; Boetius, A; Wenzhöfer, F; Blandin, J; Olu, K; Yoerger, D R; Camilli, R; German, C R; de Beer, D (Nature Communications, 2014)
Submarine mud volcanoes are important sources of methane to the water column. However, the temporal variability of their mud and methane emissions is unknown. Methane emissions were previously proposed to result from a dynamic equilibrium between upward migration and consumption at the seabed by methane-consuming microbes. Here we show non-steady-state situations of vigorous mud movement that are revealed through variations in fluid flow, seabed temperature and seafloor bathymetry. Time series data for pressure, temperature, pH and seafloor photography were collected over 431 days using a benthic observatory at the active Håkon Mosby Mud Volcano. We documented 25 pulses of hot subsurface fluids, accompanied by eruptions that changed the landscape of the mud volcano. Four major events triggered rapid sediment uplift of more than a metre in height, substantial lateral flow of muds at average velocities of 0.4 m per day, and significant emissions of methane and CO2 from the seafloor.
Keywords: AUV Sentry (Autonomous Underwater Vehicle)

Eruptive and tectonic history of the Endeavour Segment, Juan de Fuca Ridge, based on AUV mapping data and lava flow ages - Clague, D A; Dreyer, B M; Paduan, J B; Martin, J F; Caress, D W; Gill, J B; Kelley, D S; Thomas, H; Portner, R A; Delaney, J R; Guilderson, T P; McGann, M L (Geochemistry, Geophysics, Geosystems, 2014)
High-resolution bathymetric surveys from autonomous underwater vehicles ABE and D. Allan B. were merged to create a coregistered map of 71.7 km(2) of the Endeavour Segment of the Juan de Fuca Ridge. Radiocarbon dating of foraminifera in cores from three dives of remotely operated vehicle Doc Ricketts provide minimum eruption ages for 40 lava flows that are combined with the bathymetric data to outline the eruptive and tectonic history. The ages range from Modern to 10,700 marine-calibrated years before present (yr BP). During a robust magmatic phase from {>}10,700 yr BP to approximate to 4300 yr BP, flows erupted from an axial high and many flowed {>}5 km down the flanks; some partly buried adjacent valleys. Axial magma chambers (AMCs) may have been wider than today to supply dike intrusions over a 2 km wide axial zone. Summit Seamount formed by approximate to 4770 yr BP and was subsequently dismembered during a period of extension with little volcanism starting approximate to 4300 yr BP. This tectonic phase with only rare volcanic eruptions lasted until approximate to 2300 yr BP and may have resulted in near-solidification of the AMCs. The axial graben formed by crustal extension during this period of low magmatic activity. Infrequent eruptions occurred on the flanks between 2620-1760 yr BP and within the axial graben since approximate to 1750 yr BP. This most recent phase of limited volcanic and intense hydrothermal activity that began approximate to 2300 yr BP defines a hydrothermal phase of ridge development that coincides with the present-day 1 km wide AMCs and overlying hydrothermal vent fields.
Keywords: AUV ABE (Autonomous Benthic Explorer)

Eruptive modes and hiatus of volcanism at West Mata seamount, NE Lau basin: 1996–2012 - Embley, R W; Merle, S G; Baker, E T; Rubin, K H; Lupton, J E; Resing, J A; Dziak, R P; Lilley, M D; Chadwick, W W; Shank, T M; Greene, R; Walker, S L; et al. (Geochemistry, Geophysics, Geosystems, 2014)
We present multiple lines of evidence for years to decade-long changes in the location and character of volcanic activity at West Mata seamount in the NE Lau basin over a 16 year period, and a hiatus in summit eruptions from early 2011 to at least September 2012. Boninite lava and pyroclasts were observed erupting from its summit in 2009, and hydroacoustic data from a succession of hydrophones moored nearby show near-continuous eruptive activity from January 2009 to early 2011. Successive differencing of seven multibeam bathymetric surveys of the volcano made in the 1996–2012 period reveals a pattern of extended constructional volcanism on the summit and northwest flank punctuated by eruptions along the volcano's WSW rift zone (WSWRZ). Away from the summit, the volumetrically largest eruption during the observational period occurred between May 2010 and November 2011 at ∼2920 m depth near the base of the WSWRZ. The (nearly) equally long ENE rift zone did not experience any volcanic activity during the 1996–2012 period. The cessation of summit volcanism recorded on the moored hydrophone was accompanied or followed by the formation of a small summit crater and a landslide on the eastern flank. Water column sensors, analysis of gas samples in the overlying hydrothermal plume and dives with a remotely operated vehicle in September 2012 confirmed that the summit eruption had ceased. Based on the historical eruption rates calculated using the bathymetric differencing technique, the volcano could be as young as several thousand years.
Keywords: ROV Jason (Remotely Operated Vehicle)

Eruptive timing and 200 year episodicity at 92 degrees W on the hot spot-influenced Galapagos Spreading Center derived from geomagnetic paleointensity - Bowles, Julie A; Colman, Alice; McClinton, J Timothy; Sinton, John M; White, Scott M; Rubin, Kenneth H (GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 2014)
Eruptive timing in mid-ocean ridge systems is relatively poorly constrained, despite being an important variable in our understanding of many mid-ocean ridge processes, including volcanic construction; magma recharge, flux, and storage; and the stability of hydrothermal systems and biological communities. Only a handful of absolute eruption chronologies exist, yet they are essential in understanding how eruptive timing varies with important controlling variables. To construct an eruptive history at one location on the Galapagos Spreading Center, we present age determinations derived from geomagnetic paleointensity. To aid interpretation of the paleointensity data, we also present results from on-bottom magnetic anomaly measurements and forward modeling of topographic-induced magnetic anomalies. Anomalies may lead to a 1-2 mu T bias in flow-mean paleointensities, which does not significantly affect the overall interpretation. Paleointensity results for the three youngest sampled units are indistinguishable, consistent with the flows being emplaced in relatively rapid succession. Comparisons with models of geomagnetic field behavior suggest these flows were erupted sometime in the past 100-200 years. The fourth sampled unit has a significantly higher paleointensity, consistent with an age of roughly 400 years. The possible bias in paleointensity data allows for ages as young as similar to 50 years for the youngest three flows and 200-400 years for the oldest flow. This age distribution demonstrates an episodicity in the emplacement of the largest flows at this location, with a 200-300 year period of relative quiescence between emplacement of the oldest unit and the three youngest units.
Keywords: HOV Alvin (Human Occupied Vehicle)

First observations of the cold-water coral Lophelia pertusa in mid-Atlantic canyons of the USA - Brooke, S; Ross, S W (Deep-Sea Research. Part II: Topical Studies in Oceanography, 2014)
The structure-forming, cold-water coral Lophelia pertusa is widely distributed throughout the North Atlantic Ocean and also occurs in the South Atlantic, North Pacific and Indian oceans. This species has formed extensive reefs, chiefly in deep water, along the continental margins of Europe and the United States, particularly off the southeastern U.S. coastline and in the Gulf of Mexico. There were, however, no records of L. pertusa between the continental slope off Cape Lookout, North Carolina (NC) (∼34°N, 76°W), and the rocky Lydonia and Oceanographer canyons off Cape Cod, Massachusetts (MA) (∼40°N, 68°W). During a research cruise in September 2012, L. pertusa colonies were observed on steep walls in both Baltimore and Norfolk canyons. These colonies were all approximately 2 m or less in diameter, usually hemispherical in shape and consisted entirely of live polyps. The colonies were found between 381 m and 434 m with environmental observations of: temperature 6.4–8.6 °C; salinity 35.0–35.6; and dissolved oxygen 2.06–4.41 ml L−1, all of which fall within the range of known L. pertusa distributions. All colonies were observed on vertical walls or underneath overhangs in areas of high current, which differs from observations further south, where L. pertusa colonizes rocky ledges and outcroppings, often forming large bioherms. We discuss observations from Baltimore and Norfolk canyons in the context of the known distribution of this species in the North Atlantic.
Keywords: ROV Jason (Remotely Operated Vehicle)

Forever competent: deep-sea bivalves are colonized by their chemosynthetic symbionts throughout their lifetime - Wentrup, Cecilia; Wendeberg, Annelie; Schimak, Mario; Borowski, Christian; Dubilier, Nicole (ENVIRONMENTAL MICROBIOLOGY, 2014)
Symbiotic bivalves at hydrothermal vents and cold seeps host chemosynthetic bacteria intracellularly in gill cells. In bivalves, the gills grow continuously throughout their lifetime by forming new filaments. We examined how newly developed gill tissues are colonized in bivalves with horizontal and vertical symbiont transmission (Bathymodiolus mussels versus a vesicoymid clam) using fluorescence in situ hybridization and transmission electron microscopy. Symbiont colonization was similar in mussels and clams and was independent of the transmission modes. Symbionts were absent in the growth zones of the gills, indicating that symbionts colonize newly formed gill filaments de novo after they are formed and that gill colonization is a continuous process throughout the host's lifetime. Symbiont abundance and distribution suggested that colonization is shaped by the developmental stage of host cells. Self-infection, in which new gill cells are colonized by symbionts from ontogenetically older gill tissues, may also play a role. In mussels, symbiont infection led to changes in gill cell structure similar to those described from other epithelial cells infected by intracellular pathogens, such as the loss of microvilli. A better understanding of the factors that affect symbiont colonization of bivalve gills could provide new insights into interactions between intracellular bacteria and epithelial tissues.
Keywords: HOV Alvin (Human Occupied Vehicle)

Geologic setting of PACManus hydrothermal area - High resolution mapping and in situ observations - Thal, Janis; Tivey, Maurice; Yoerger, Dana; Joens, Niels; Bach, Wolfgang (Marine Geology, 2014)
This study presents a systematic analysis and interpretation of autonomous underwater vehicle-based microbathymetry combined with remotely operated vehicle (ROV) video recordings, rock analyses and temperature measurements within the PACManus hydrothermal area located on Pual Ridge in the Bismarck Sea of eastern Manus Basin. The data obtained during research cruise Magellan-06 and So-216 provides a framework for understanding the relationship between the volcanism, tectonism and hydrothermal activity. PACManus is a submarine felsic vocanically-hosted hydrothermal area that hosts multiple vent fields located within several hundred meters of one another but with different fluid chemistries, vent temperatures and morphologies. The total area of hydrothermal activity is estimated to be 20,279 m(2). The microbathymetry maps combined with the ROV video observations allow for precise high-resolution mapping estimates of the areal extents of hydrothermal activity. We find the distribution of hydrothermal fields in the PACManus area is primarily controlled by volcanic features that include lava domes, thick and massive blocky lava flows, breccias and feeder dykes. Spatial variation in the permeability of local volcanic facies appears to control the distribution of venting within a field. We define a three-stage chronological sequence for the volcanic evolution of the PACManus based on lava flow morphology, sediment cover and lava SiO2 concentration. In Stage-1, sparsely to moderately porphyritic dacite lavas (68-69.8 wt.{%} SiO2) erupted to form domes or cryptodomes. In Stage-2, aphyric lava with slightly lower SiO2 concentrations (67.2-67.9 wt.{%} SiO2) formed jumbled and pillowed lava flows. In the most recent phase Stage-3, massive blocky lavas with 69 to 72.5 wt{%} SiO2 were erupted through multiple vents constructing a volcanic ridge identified as the PACManus neovolcanic zone. The transition between these stages may be gradual and related to progressive heating of a silicic magma following a recharge event of hot, mantle-derived melts.
Keywords: AUV ABE (Autonomous Benthic Explorer); ROV Jason (Remotely Operated Vehicle)

Greenhouse gases generated from the anaerobic biodegradation of natural offshore asphalt seepages in southern California - Lorenson, Thomas D; Wong, Florence L; Dartnell, Peter; Sliter, Ray W (GEO-MARINE LETTERS, 2014)
Significant offshore asphaltic deposits with active seepage occur in the Santa Barbara Channel offshore southern California. The composition and isotopic signatures of gases sampled from the oil and gas seeps reveal that the coexisting oil in the shallow subsurface is anaerobically biodegraded, generating CO2 with secondary CH4 production. Biomineralization can result in the consumption of as much as 60{%} by weight of the original oil, with C-13 enrichment of CO2. Analyses of gas emitted from asphaltic accumulations or seeps on the seafloor indicate up to 11{%} CO2 with C-13 enrichment reaching +24.8aEuro degrees. Methane concentrations range from less than 30{%} up to 98{%} with isotopic compositions of -34.9 to -66.1aEuro degrees. Higher molecular weight hydrocarbon gases are present in strongly varying concentrations reflecting both oil-associated gas and biodegradation; propane is preferentially biodegraded, resulting in an enriched C-13 isotopic composition as enriched as -19.5aEuro degrees. Assuming the 132 million barrels of asphaltic residues on the seafloor represent similar to 40{%} of the original oil volume and mass, the estimated gas generated is 5.0x10(10) kg (similar to 76x10(9) m(3)) CH4 and/or 1.4x10(11) kg CO2 over the lifetime of seepage needed to produce the volume of these deposits. Geologic relationships and oil weathering inferences suggest the deposits are of early Holocene age or even younger. Assuming an age of similar to 1,000 years, annual fluxes are on the order of 5.0x10(7) kg (similar to 76x10(6) m(3)) and/or 1.4x10(8) kg for CH4 and CO2, respectively. The daily volumetric emission rate (2.1x10(5) m(3)) is comparable to current CH4 emission from Coal Oil Point seeps (1.5x10(5) m(3)/day), and may be a significant source of both CH4 and CO2 to the atmosphere provided that the gas can be transported through the water column.
Keywords: ROV Jason (Remotely Operated Vehicle)

High-resolution ecological niche modelling of the cold-water coral Lophelia pertusa in the Gulf of Mexico - Georgian, Samuel E; Shedd, William; Cordes, Erik E (MARINE ECOLOGY PROGRESS SERIES, 2014)
The niche of many deep-sea species remains poorly resolved despite decades of seafloor exploration. Without better information on the distribution and habitat preference of key species, a complete understanding of the ecology of deep-sea communities will remain unattainable. It is increasingly apparent that cold-water corals are among the dominant foundation species in the deep sea, providing both structurally complex habitat and significant ecosystem services. In this study, the niche and distribution of the cold-water coral Lophelia pertusa in the Gulf of Mexico was evaluated using the maximum entropy (Maxent) approach. Ecological niche models were constructed for a broad region of the northern Gulf of Mexico using data gridded at a spatial resolution of 25 m, including bathymetry, substrate type, export productivity, and aragonite saturation state at depth. Fine-scale models were constructed at a resolution of 5 m using only remotely sensed bathymetric and surface reflectivity data. The broad-scale model performed well, with an area under the curve (AUC) of 0.981. All fine-scale models performed well when verified using training data (average AUC of 0.963) and when validated using independent occurrence data from a new geographic region (average AUC of 0.937). The distribution of L. pertusa in the Gulf of Mexico was found to be controlled primarily by depth, local topography, and availability of hard substrate. While these factors have long been associated with the success of cold-water corals, their relative importance has never been quantified in the Gulf of Mexico, making it historically difficult to precisely delineate L. pertusa's niche and predict its distribution in unexplored regions. Given these results, we suggest that future expeditions combine remotely sensed data with niche modelling techniques to increase the efficiency of deep-sea exploration.
Keywords: AUV Sentry (Autonomous Underwater Vehicle); ROV Jason (Remotely Operated Vehicle)

High-resolution near-bottom vector magnetic anomalies over Raven Hydrothermal Field, Endeavour Segment, Juan de Fuca Ridge - Tivey, M A; Johnson, H P; Salmi, M S; Hutnak, M (Journal of Geophysical Research: Solid Earth, 2014)
High-resolution, near-bottom vector magnetic data were collected by remotely operated vehicle Jason over the Raven hydrothermal vent field (47°57.3′N 129°5.75′W) located north of Main Endeavour vent field on the Endeavour segment of the Juan de Fuca Ridge. The survey was part of a comprehensive heat flow study of the Raven site using innovative thermal blanket technology to map the heat flux and crustal fluid pathways around a solitary hydrothermal vent field. Raven hydrothermal activity is presently located along the western axial valley wall, while additional inactive hydrothermal deposits are found to the NW on the upper rift valley wall. Magnetic inversion results show discrete areas of reduced magnetization associated with both active and inactive hydrothermal vent deposits that also show high conductive heat flow. Higher spatial variability in the heat flow patterns compared to the magnetization is consistent with the heat flow reflecting the currently active but ephemeral thermal environment of fluid flow, while crustal magnetization is representative of the static time-averaged effect of hydrothermal alteration. A general NW to SE trend in reduced magnetization across the Raven area correlates closely with the distribution of hydrothermal deposits and heat flux patterns and suggests that the fluid circulation system at depth is likely controlled by local crustal structure and magma chamber geometry. Magnetic gradient tensor components computed from vector magnetic data improve the resolution of the magnetic anomaly source and indicate that the hydrothermally altered zone directly beneath the Raven site is approximately 15 × 106 m3 in volume.
Keywords: ROV Jason (Remotely Operated Vehicle)

Hydrothermal sulfide accumulation along the Endeavour Segment, Juan de Fuca Ridge - Jamieson, J W; Clague, D A; Hannington, M D (Earth and Planetary Science Letters, 2014)
Hydrothermal sulfide deposits that form on the seafloor are often located by the detection of hydrothermal plumes in the water column, followed by exploration with deep-towed cameras, side-scan sonar imaging, and finally by visual surveys using remotely-operated vehicle or occupied submersible. Hydrothermal plume detection, however, is ineffective for finding hydrothermally-inactive sulfide deposits, which may represent a significant amount of the total sulfide accumulation on the seafloor, even in hydrothermally active settings. Here, we present results from recent high-resolution, autonomous underwater vehicle-based mapping of the hydrothermally-active Endeavour Segment of the Juan de Fuca Ridge, in the Northeast Pacific Ocean. Analysis of the ridge bathymetry resulted in the location of 581 individual sulfide deposits along 24 km of ridge length. Hydrothermal deposits were distinguished from volcanic and tectonic features based on the characteristics of their surface morphology, such as shape and slope angles. Volume calculations for each deposit results in a total volume of 372,500 m3 of hydrothermal sulfide–sulfate–silica material, for an equivalent mass of ∼1.2 Mt of hydrothermal material on the seafloor within the ridge's axial valley, assuming a density of 3.1 g/cm3. Much of this total volume is from previously undocumented inactive deposits outside the main active vent fields. Based on minimum ages of sulfide deposition, the deposits accumulated at a maximum rate of ∼400 t/yr, with a depositional efficiency (proportion of hydrothermal material that accumulates on the seafloor to the total amount hydrothermally mobilized and transported to the seafloor) of ∼5{%}. The calculated sulfide tonnage represents a four-fold increase over previous sulfide estimates for the Endeavour Segment that were based largely on accumulations from within the active fields. These results suggest that recent global seafloor sulfide resource estimates, which were based mostly on the sizes and distribution of hydrothermally-active deposits, may be similarly underestimating the amount of sulfide along the global submarine neovolcanic zones.
Keywords: AUV ABE (Autonomous Benthic Explorer); HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Imaging of CO2 bubble plumes above an erupting submarine volcano, NW Rota-1, Mariana Arc - Chadwick Jr., William W; Merle, Susan G; Buck, Nathaniel J; Lavelle, J William; Resing, Joseph A; Ferrini, Vicki (GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 2014)
NW Rota-1 is a submarine volcano in the Mariana volcanic arc located similar to 100 km north of Guam. Underwater explosive eruptions driven by magmatic gases were first witnessed there in 2004 and continued until at least 2010. During a March 2010 expedition, visual observations documented continuous but variable eruptive activity at multiple vents at similar to 560 m depth. Some vents released CO2 bubbles passively and continuously, while others released CO2 during stronger but intermittent explosive bursts. Plumes of CO2 bubbles in the water column over the volcano were imaged by an EM122 (12 kHz) multibeam sonar system. Throughout the 2010 expedition numerous passes were made over the eruptive vents with the ship to document the temporal variability of the bubble plumes and relate them to the eruptive activity on the seafloor, as recorded by an in situ hydrophone and visual observations. Analysis of the EM122 midwater data set shows: (1) bubble plumes were present on every pass over the summit and they rose 200-400 m above the vents but dissolved before they reached the ocean surface, (2) bubble plume deflection direction and distance correlate well with ocean current direction and velocity determined from the ship's acoustic doppler current profiler, (3) bubble plume heights and volumes were variable over time and correlate with eruptive intensity as measured by the in situ hydrophone. This study shows that midwater multibeam sonar data can be used to characterize the level of eruptive activity and its temporal variability at a shallow submarine volcano with robust CO2 output.
Keywords: ROV Jason (Remotely Operated Vehicle)

Insights into the population dynamics of the deep-sea coral genus Paramuricea in the Gulf of Mexico - Doughty, C L; Quattrini, A M; Cordes, E E (Biology and Geology of Deep-Sea Coral Ecosystems: Proceedings of the Fifth International Symposium on Deep Sea Corals, 2014)
Species in the genus Paramuricea are among the most common corals in deep waters ({>}200 m) of the Gulf of Mexico. Paramuricea spp. increase habitat heterogeneity and provide substrate for numerous faunal associates, including ophiuroids that occur on the majority of coral colonies. In light of the Deepwater Horizon oil spill in the Gulf of Mexico, it has become apparent that there is a critical need for data on population dynamics within this genus. To date, at least one species of Paramuricea (P. biscaya) is known to be negatively impacted by the spill. Using remotely operated vehicles from 2009 to 2011, we documented the density and size frequency distributions of Paramuricea across 21 sites at depths of 250–2500 m. Molecular barcoding (mtCOI+igr+MutS) was used to delineate species boundaries among the specimens collected. Results suggested that seven haplotypes are present in the Gulf, and appear to be partially segregated by depth [(type H: was used to delineate species boundaries among the specimens collected. Results suggested that seven haplotypes are present in the Gulf, and appear to be partially segregated by depth [(type H: Paramuricea spp. determined by ROV surveys were mapped onto high-resolution bathymetric data, which confirmed the corals' preference for topographic highs composed of hard substrata. At any one site, densities ranged from 0.043±0.01 (VK906, 380 m) to 1.18±0.81 colonies/m2 (GC852, 1410 m). Mortality and recruitment rates were estimated from size-frequency data combined with estimated growth rates. Mortality rate decreased with size, from approximately 20{%} and 70{%} in new recruits of Paramuricea B3 and P. biscaya respectively, to less than 10{%} in colonies over 40 cm in both species. Recruitment rates were estimated from less than one to over 30 individuals per year per site, but patterns in size-frequency histograms suggest that this process is highly variable at the different sites and at different times. These data illustrate that populations of the slow-growing Paramuricea species are sparsely distributed and exhibit low recruitment rates, making them highly susceptible to anthropogenic threats.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Intracellular Oceanospirillales inhabit the gills of the hydrothermal vent snail Alviniconcha with chemosynthetic, gamma-Proteobacterial symbionts - Beinart, R A; Nyholm, S V; Dubilier, N; Girguis, P R (ENVIRONMENTAL MICROBIOLOGY REPORTS, 2014)
Associations between bacteria from the -Proteobacterial order Oceanospirillales and marine invertebrates are quite common. Members of the Oceanospirillales exhibit a diversity of interactions with their various hosts, ranging from the catabolism of complex compounds that benefit host growth to attacking and bursting host nuclei. Here, we describe the association between a novel Oceanospirillales phylotype and the hydrothermal vent snail Alviniconcha. Alviniconcha typically harbour chemoautotrophic - or epsilon-Proteobacterial symbionts inside their gill cells. Via fluorescence in situ hybridization and transmission electron microscopy, we observed an Oceanospirillales phylotype (named AOP for AlviniconchaOceanospirillales phylotype') in membrane-bound vacuoles that were separate from the known - or epsilon-Proteobacterial symbionts. Using quantitative polymerase chain reaction, we surveyed 181 Alviniconcha hosting -Proteobacterial symbionts and 102 hosting epsilon-Proteobacterial symbionts, and found that the population size of AOP was always minor relative to the canonical symbionts (median 0.53{%} of the total quantified 16S rRNA genes). Additionally, we detected AOP more frequently in Alviniconcha hosting -Proteobacterial symbionts than in those hosting epsilon-Proteobacterial symbionts (96{%} and 5{%} of individuals respectively). The high incidence of AOP in -Proteobacteria hosting Alviniconcha implies that it could play a significant ecological role either as a host parasite or as an additional symbiont with unknown physiological capacities.
Keywords: ROV Jason (Remotely Operated Vehicle)

A large volume particulate and water multi-sampler with in situ preservation for microbial and biogeochemical studies - Breier, J A; Sheik, C S; Gomez-Ibanez, D; Sayre-McCord, R T; Sanger, R; Rauch, C; Coleman, M; Bennett, S A; Cron, B R; Li, M; German, C R; Toner, B M; et al. (DEEP-SEA RESEARCH PART I-OCEANOGRAPHIC RESEARCH PAPERS, 2014)
A new tool was developed for large volume sampling to facilitate marine microbiology and biogeochemical studies. It was developed for remotely operated vehicle and hydrocast deployments, and allows for rapid collection of multiple sample types from the water column and dynamic, variable environments such as rising hydrothermal plumes. It was used successfully during a cruise to the hydrothermal vent systems of the Mid-Cayman Rise. The Suspended Particulate Rosette V2 large volume multi-sampling system allows for the collection of 14 sample sets per deployment. Each sample set can include filtered material, whole (unfiltered) water, and filtrate. Suspended particulate can be collected on filters up to 142 mm in diameter and pore sizes down to 0.2 mu m. Filtration is typically at flowrates of 2 L min(-1) For particulate material, filtered volume is constrained only by sampling time and filter capacity, with all sample volumes recorded by digital flowmeter. The suspended particulate filter holders can be filled with preservative and sealed immediately after sample collection. Up to 2 L of whole water, filtrate, or a combination of the two, can be collected as part of each sample set. The system is constructed of plastics with titanium fasteners and nickel alloy spring loaded seals. There are no ferrous alloys in the sampling system. Individual sample lines are prefilled with filtered, deionized water prior to deployment and remain sealed unless a sample is actively being collected. This system is intended to facilitate studies concerning the relationship between marine microbiology and ocean biogeochemistry. (C) 2014 Elsevier Ltd. All rights reserved.
Keywords: ROV Jason (Remotely Operated Vehicle)

Late Holocene Foraminifera of Blake Ridge Diapir: Assemblage Variation and Stable-Isotope Record in gas-hydrate bearing sediments - Panieri, G; Aharon, Paul; Sen Gupta, B K; Camerlenghi, A; Ferrer, F P; Cacho, I (Marine Geology, 2014)
The presence of gas hydrates on the Blake Ridge diapir, northeastern Atlantic Ocean, offers an opportunity to study the impact of methane seepage on the ecology and geochemistry of benthic foraminifera in the late Holocene. Three push cores, covering a time span of {\~{}} 1000 yrs, were retrieved from three distinct microhabitats at the top of the diapir at a water depth of {\~{}} 2150 m: (i) sediments away from seepage (control core), (ii) sediments overlain by clusters of methanotrophic and thiotrophic bivalves, and (iii) chemoautotrophic microbial mats. The foraminiferal assemblages at the two seep sites are marked by a reduction in benthic foraminiferal species diversity, coupled with a near-absence of agglutinated species. However, an opportunistic population rise in CH4- or H2S-tolerant calcareous species (e.g., Globocassidulina subglobosa and Cassidulina laevigata) that utilize the abundant trophic resources at the seeps has led to an increase in the overall assemblage density there. The $δ$18O and $δ$13C values of three species of benthic foraminifera - Gyroidinoides laevigatus, Globocassidulina subglobosa, and Uvigerina peregrina - and the planktonic species Globorotalia menardii were acquired from all three cores. The benthic species from methane seeps yield $δ$13C values of 0.1 to –4.2 (‰VPDB), that are distinctly more 13C-depleted relative to the $δ$13C of 0.4 to –1.0 (‰VPDB) at the control (off seep) site. The species from a mussel-bed site exhibit more negative $δ$13C values than those from microbial mats, possibly reflecting different food sources and higher rate of anaerobic oxidation of methane. The positive $δ$13C values in the paired planktonic species suggest that authigenic carbonate precipitation did not overprint the observed 13C depletions. Hence the probable cause of negative $δ$13C of benthic foraminifera is primary calcification from Dissolved Inorganic Carbon (DIC) containing mixed carbon fractions from (a) highly 13C-depleted, microbially-oxidized methane and (b) a seawater source.
Keywords: HOV Alvin (Human Occupied Vehicle)

Metal concentrations in the tissues of the hydrothermal vent mussel Bathymodiolus: Reflection of different metal sources - Koschinsky, A; Kausch, M; Borowski, C (Marine Environmental Research, 2014)
Hydrothermal vent mussels of the genus Bathymodiolus are ideally positioned for the use of recording hydrothermal fluxes at the hydrothermal vent sites they inhabit. Barium, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Pb, Sr, and U concentrations in tissue sections of Bathymodiolus mussels from several hydrothermal fields between 15°N and 9°S at the Mid-Atlantic Ridge were determined and compared to the surrounding fluids and solid substrates in the habitats. Elements generally enriched in hydrothermal fluids, such as Fe, Cu, Zn, Pb and Cd, were significantly enriched in the gills and digestive glands of the hydrothermal mussels. The rather small variability of Zn (and Mn) and positive correlation with K and earth alkaline metals may indicate a biological regulation of accumulation. Enrichments of Mo and U in many tissue samples indicate that particulate matter such as hydrothermal mineral particles from the plumes can play a more important role as a metal source than dissolved metals. Highest enrichments of Cu in mussels from the Golden Valley site indicate a relation to the ≥400 °C hot heavy-metal rich fluids emanating in the vicinity. In contrast, mussels from the low-temperature Lilliput field are affected by the Fe oxyhydroxide sediment of their habitat. In a comparison of two different sites within the Logatchev field metal distributions in the tissues reflected small-scale local variations in the metal content of the fluids and the particulate material.
Keywords: ROV Jason (Remotely Operated Vehicle)

Microbial consumption of zero-valence sulfur in marine benthic habitats - Pjevac, Petra; Kamyshny Jr., Alexey; Dyksma, Stefan; Mussmann, Marc (ENVIRONMENTAL MICROBIOLOGY, 2014)
Zero-valence sulfur (S-0) is a central intermediate in the marine sulfur cycle and forms conspicuous accumulations at sediment surfaces, hydrothermal vents and in oxygen minimum zones. Diverse microorganisms can utilize S-0, but those consuming S-0 in the environment are largely unknown. We identified possible key players in S-0 turnover on native or introduced S-0 in benthic coastal and deep-sea habitats using the 16S ribosomal RNA approach, (in situ) growth experiments and activity measurements. In all habitats, the epsilonproteobacterial Sulfurimonas/Sulfurovum group accounted for a substantial fraction of the microbial community. Deltaproteobacterial Desulfobulbaceae and Desulfuromonadales were also frequently detected, indicating S-0 disproportionation and S-0 respiration under anoxic conditions. Sulfate production from S-0 particles colonized in situ with Sulfurimonas/Sulfurovum suggested that this group oxidized S-0. We also show that the type strain Sulfurimonas denitrificans is able to access cyclooctasulfur (S-8), a metabolic feature not yet demonstrated for sulfur oxidizers. The ability to oxidize S-0, in particular S-8, likely facilitates niche partitioning among sulfur oxidizers in habitats with intense microbial sulfur cycling such as sulfidic sediment surfaces. Our results underscore the previously overlooked but central role of Sulfurimonas/Sulfurovum group for conversion of free S-0 at the seafloor surface.
Keywords: HOV Alvin (Human Occupied Vehicle)

Microbial distribution in different spatial positions within the walls of a black sulfide hydrothermal chimney - Li, Jiangtao; Zhou, Huaiyang; Fang, Jiasong; Sun, Yannan; Dasgupta, Shamik (MARINE ECOLOGY PROGRESS SERIES, 2014)
Deep-sea hydrothermal chimneys encompass diverse niches for different microbial communities with steep environmental gradients. An active sulfide hydrothermal structure was recovered from the Dudley site of the Main Endeavour Field in the Juan de Fuca Ridge. Subsamples were taken from different spatial positions within the chimney wall and analyzed for mineral composition and microbial biomass and community structure to illustrate the characteristics of microbial distribution and environmental constraints. Mineral analysis showed that the chimney was mainly composed of various Fe-, Zn-, and Cu-rich sulfides, with mineral composition and abundance varying with spatial position. Microbial populations in the chimney predominantly consisted of archaeal members affiliated with the deep-sea hydrothermal vent Euryarchaeota group, Thermococcales, and Desulfurococcales, as well as bacterial members of the Gamma-, Epsilon-, and Deltaproteobacteria. Microbial biomass and composition shifted dramatically and formed different microbial zones within the chimney walls, from predominantly mesophilic, sulfur-oxidizing bacterial communities at the outer surfaces to thermophilic or hyperthermophilic, archaeal sulfur-reducers in the inner layers of the chimney. Based on microbial physiological characteristics and their distribution profiles, we inferred that temperature, fluid geochemistry, and organic compounds probably play an important role in selecting for and sustaining microbial communities. Furthermore, in situ temperature regimes within the chimney walls were roughly estimated based on the temperatures supporting the growth of the dominant microbial groups.
Keywords: HOV Alvin (Human Occupied Vehicle)

Microsporidia-nematode associations in methane seeps reveal basal fungal parasitism in the deep sea - Sapir, Amir; Dillman, Adler R; Connon, Stephanie A; Grupe, Benjamin M; Ingels, Jeroen; Mundo-Ocampo, Manuel; Levin, Lisa A; Baldwin, James G; Orphan, Victoria J; Sternberg, Paul W (FRONTIERS IN MICROBIOLOGY, 2014)
The deep sea is Earth's largest habitat but little is known about the nature of deep-sea parasitism. In contrast to a few characterized cases of bacterial and protistan parasites, the existence and biological significance of deep-sea parasitic fungi is yet to be understood. Here we report the discovery of a fungus-related parasitic microsporidium, Nematocenator marisprofundi n. gen. n. sp. that infects benthic nematodes at methane seeps on the Pacific Ocean floor. This infection is species-specific and has been temporally and spatially stable over 2 years of sampling, indicating an ecologically consistent host-parasite interaction. A high distribution of spores in the reproductive tracts of infected males and females and their absence from host nematodes' intestines suggests a sexual transmission strategy in contrast to the fecal-oral transmission of most microsporidia. N. mansprofundi targets the host's body wall muscles causing cell lysis, and in severe infection even muscle filament degradation. Phylogenetic analyses placed N. marisprofundi in a novel and basal clade not closely related to any described microsporidia clade, suggesting either that microsporidia-nematode parasitism occurred early in microsporidia evolution or that host specialization occurred late in an ancient deep-sea microsporidian lineage. Our findings reveal that methane seeps support complex ecosystems involving interkingdom interactions between bacteria, nematodes, and parasitic fungi and that microsporidia parasitism exists also in the deep-sea biosphere.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Molluscan species diversity at North Pacific hydrothermal vents: What we know and what it may mean - Voight, Janet R (AMERICAN MALACOLOGICAL BULLETIN, 2014)
Hydrothermal vents in the deep sea are harsh, temporally unpredictable habitats with what appears to be a distinct fauna. Decades of subsea research with crewed and remote vehicles have generated a list of known species; is the species list complete? Evidence derived from mollusks sampled at hydrothermal vents on the East Pacific Rise (EPR), and Gorda and Juan de Fuca ridges suggests that the answer is yes. A 2006 compilation of hydrothermal vent species based on decades of research is updated and compared to specimens from these three active ridges in collections of the Field Museum of Natural History (FMNH) that resulted from limited collecting activity. Only three dives at each of the two Gorda Ridge vents collected all named species; 90{%} of the 20 species known from Juan de Fuca Ridge were collected in nine cruises. At the EPR, only 81{%} of the 43 known species were collected, but differences among the ridges were not significant. The limited FMNH collections increased the known ranges of six species from Juan de Fuca to Gorda Ridge and of nine species on the EPR. In addition, the EPR appears to host more rare species, potentially due to the frequent temporal changes at these vents. Mollusks currently known from each ridge, with their expanded ranges, are listed; the implications of these results for recent discoveries of slow-spreading vent fields are discussed.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Nanoparticulate pyrite and other nanoparticles are a widespread component of hydrothermal vent black smoker emissions - Gartman, A; Findlay, A J; Luther, G W (Chemical Geology, 2014)
The presence of nanoparticulate pyrite is reported in hydrothermal emissions from Rainbow, TAG and Snakepit on the Mid-Atlantic Ridge (MAR). When coupled with previously collected data from East Pacific Rise 9°N (EPR) and Lau Basin, these data demonstrate that pyrite nanoparticles are a widespread component of black smoker emissions from hydrothermal vents and are found in significant concentrations at a fast spreading mid-ocean Ridge (EPR), a back-arc basin (Lau Basin), and a slow spreading mid-ocean Ridge (MAR). The maximum percentage of filtered iron emitted as nanoparticulate pyrite was found to be as high as 25{%}, 10{%}, and 5{%}, respectively. As a widespread component of hydrothermal vent emissions, these nanoparticles may be an important source of iron to the world's oceans. Metals such as Cu and Zn are detected in pyrite-containing aggregates at all sites, and chalcopyrite was a component of nanoparticle aggregates at MAR. Iron containing silicate nanoparticles are also identified, and indicate that nanoparticles other than sulfides should also be considered when determining transport implications of hydrothermal vent emissions. The varied morphologies and the presence of different minerals within these nanoparticles provide insight into their formation and stability.
Keywords: ROV Jason (Remotely Operated Vehicle)

New insights into cerium anomalies and mechanisms of trace metal enrichment in authigenic carbonate from hydrocarbon seeps - Hu, Y; Feng, D; Peckmann, J; Roberts, H H; Chen, D (Chemical Geology, 2014)
Authigenic carbonates that form at marine hydrocarbon seeps provide a unique geological archive of past local environmental conditions and pore fluid geochemistry. Recent work on such carbonates revealed variable cerium (Ce) anomalies and anomalous enrichments of certain trace metals. However, the mechanisms accounting for such anomalies remain poorly constrained. Here, we characterize the rare earth element (REE) patterns of carbonate phases and the trace metal patterns of bulk carbonate rocks sampled at three hydrocarbon seeps located at Congo Fan pockmarks (CF) and the Gulf of Mexico sites AC645 and GB425. The analyzed CF, GB425, and AC645 carbonates yielded different REE patterns, displaying positive, no, as well as negative Ce anomalies. The covariation of molybdenum (Mo) with uranium (U), including authigenic Mo (Moauth) and U (Uauth) enrichments as well as (Mo/U)auth ratios proved useful to obtain new insight into the applicability of Ce anomalies to constrain past redox conditions. Trace element patterns suggest that (1) CF carbonates formed in a restricted sulfidic environment, while (2) the AC645 site experienced intermittent oxygenation causing negative Ce anomalies, and (3) environmental conditions were variable at the GB425 mud volcano site. Interestingly, GB425 carbonates show significant Mo, arsenic (As), and antimony (Sb) enrichments with the enrichment factor of As (AsEF) correlating well with the authigenic Fe fraction. These results suggest that iron oxyhydroxides played an important role in the adsorption of Mo, As, and Sb in the water column and their transfer to the sediment. The combination of trace metal and REE geochemistry of authigenic carbonates used here is a promising tool to better assess past variability of redox conditions and biogeochemical processes at marine hydrocarbon seeps.
Keywords: HOV Alvin (Human Occupied Vehicle)

Nitrate-based niche differentiation by distinct sulfate-reducing bacteria involved in the anaerobic oxidation of methane - Green-Saxena, A; Dekas, A E; Dalleska, N F; Orphan, V J (ISME JOURNAL, 2014)
Diverse associations between methanotrophic archaea (ANME) and sulfate-reducing bacterial groups (SRB) often co-occur in marine methane seeps; however, the ecophysiology of these different symbiotic associations has not been examined. Here, we applied a combination of molecular, geochemical and Fluorescence in situ hybridization (FISH) coupled to nanoscale secondary ion mass spectrometry (FISH-NanoSIMS) analyses of in situ seep sediments and methane-amended sediment incubations from diverse locations (Eel River Basin, Hydrate Ridge and Costa Rican Margin seeps) to investigate the distribution and physiology of a newly identified subgroup of the Desulfobulbaceae (seepDBB) found in consortia with ANME-2c archaea, and compared these with the more commonly observed associations between the same ANME partner and the Desulfobacteraceae (DSS). FISH analyses revealed aggregates of seepDBB cells in association with ANME-2 from both environmental samples and laboratory incubations that are distinct in their structure relative to co-occurring ANME/DSS consortia. ANME/seepDBB aggregates were most abundant in shallow sediment depths below sulfide-oxidizing microbial mats. Depth profiles of ANME/seepDBB aggregate abundance revealed a positive correlation with elevated porewater nitrate relative to ANME/DSS aggregates in all seep sites examined. This relationship with nitrate was supported by sediment microcosm experiments, in which the abundance of ANME/seepDBB was greater in nitrate-amended incubations relative to the unamended control. FISH-NanoSIMS additionally revealed significantly higher N-15-nitrate incorporation levels in individual aggregates of ANME/seepDBB relative to ANME/DSS aggregates from the same incubation. These combined results suggest that nitrate is a geochemical effector of ANME/seepDBB aggregate distribution, and provides a unique niche for these consortia through their utilization of a greater range of nitrogen substrates than the ANME/DSS.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

The origin of methanethiol in midocean ridge hydrothermal fluids - Reeves, Eoghan P; McDermott, Jill M; Seewald, Jeffrey S (PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 2014)
Simple alkyl thiols such as methanethiol (CH3SH) are widely speculated to form in seafloor hot spring fluids. Putative CH3SH synthesis by abiotic (nonbiological) reduction of inorganic carbon (CO2 or CO) has been invoked as an initiation reaction for the emergence of protometabolism and microbial life in primordial hydrothermal settings. Thiols are also presumptive ligands for hydrothermal trace metals and potential fuels for associated microbial communities. In an effort to constrain sources and sinks of CH3SH in seafloor hydrothermal systems, we determined for the first time its abundance in diverse hydrothermal fluids emanating from ultramafic, mafic, and sediment-covered midocean ridge settings. Our data demonstrate that the distribution of CH3SH is inconsistent with meta-stable equilibrium with inorganic carbon, indicating that production by abiotic carbon reduction is more limited than previously proposed. CH3SH concentrations are uniformly low (similar to 10(-8) M) in high-temperature fluids ({>}200 degrees C) from all unsedimented systems and, in many cases, suggestive of meta-stable equilibrium with CH4 instead. Associated low-temperature fluids ({<}200 degrees C) formed by admixing of seawater, however, are invariably enriched in CH3SH (up to similar to 10-6 M) along with NH4+ and low-molecular-weight hydrocarbons relative to high-temperature source fluids, resembling our observations from a sediment-hosted system. This strongly implicates thermogenic interactions between upwelling fluids and microbial biomass or associated dissolved organic matter during subsurface mixing in crustal aquifers. Widespread thermal degradation of subsurface organic matter may be an important source of organic production in unsedimented hydrothermal systems and may influence microbial metabolic strategies in cooler near-sea-floor and plume habitats.
Keywords: ROV Jason (Remotely Operated Vehicle)

Oxygen and carbon isotope fractionation in calcitic deep-sea corals: Implications for paleotemperature reconstruction - Kimball, J B; Dunbar, R B; Guilderson, T P (Chemical Geology, 2014)
Inhabiting areas of the ocean where paleoenvironmental records are sparse, deep-sea corals represent valuable yet largely untapped Holocene records of intermediate and deep ocean variability. $δ$18O and $δ$13C were analyzed in nine live-collected deep-sea gorgonian corals (Isididae and Coralliidae) in order to further develop the “lines” paleotemperature method. Least squares linear regression analysis for full lifespan $δ$18O vs. $δ$13C (corrected for $δ$18Owater and $δ$13CDIC) was utilized to yield equations of the form y = mx + b. $δ$18O and intercept values were found to be a function of temperature, and to approximate calcite $δ$18O equilibrium. The corals in this study extend the previously reported calibration (Hill et al., 2011) over a broader range of temperatures from 5 °C to 11.2 °C. When combined with the data from Hill et al. (2011), a new expression for the relationship between the $δ$18Ointercept value and temperature is proposed: T (°C) = -4.12 ± 0.38 ($δ$18Ointercept) + 12.32 ± 0.75(R2 = 0.90, p value {<} 0.0001) Error estimates are ± 0.7 °C for corals living at cold temperatures (2 °C), ± 1.4 °C in warmer waters (11 °C), and ± 0.5 °C at the mean water temperature of the data set (4.6 °C). The first multi-specimen verification of the “lines” method was performed on three co-located bamboo (Isididae) corals and found to give nearly coincident $δ$18O intercepts. Detailed intraspecimen sampling reveals $δ$18O and $δ$13C isotopic variability within coeval portions of the skeleton. In one specimen, “lines” method analysis was utilized on multiple samples taken from the same temporal increment of the skeleton, yielding multiple $δ$18O intercepts. Calculated temperatures using the calibration proposed here describe a temperature range of 7.9 to 10.3 °C, which approaches the temperature range of 11.1 ± 0.7 °C at the coral collection location.
Keywords: HOV Alvin (Human Occupied Vehicle)

A phylogenetic approach to octocoral community structure in the deep Gulf of Mexico - Quattrini, A M; Etnoyer, P J; Doughty, C; English, Lisa; Falco, R; Remon, N; Rittinghouse, M; Cordes, E E (Biology and Geology of Deep-Sea Coral Ecosystems: Proceedings of the Fifth International Symposium on Deep Sea Corals, 2014)
{Deep-sea communities are becoming increasingly vulnerable to anthropogenic disturbances, as fishing, hydrocarbon exploration and extraction, and mining activities extend into deeper water. Negative impacts from such activities were recently documented in the Gulf of Mexico (GoM), where the Deepwater Horizon oil spill caused substantial damage to a deep-water octocoral community. Although a faunal checklist and numerous museum records are currently available for the entire GoM, local-scale diversity and assemblage structure of octocoral communities remains unknown, particularly in deep water. On a series of recent cruises (2008–2011) using remotely operated vehicles, 435 octocorals were collected from 33 deep-water sites (250–2500 m) in the northern GoM. To elucidate species boundaries, the extended mitochondrial barcode (COI+igr1+msh) was successfully amplified and sequenced for 422 of these specimens, yielding a total of 64 haplotypes representing at least 52 species. Further, at least 29{%} of the species collected were either previously not known to occur in the GoM (12 species) or represent new species (at least three species). Overall, species richness at each site was fairly low (1–12 spp.). The greatest species richness occurred at the shallowest () was successfully amplified and sequenced for 422 of these specimens, yielding a total of 64 haplotypes representing at least 52 species. Further, at least 29{%} of the species collected were either previously not known to occur in the GoM (12 species) or represent new species (at least three species). Overall, species richness at each site was fairly low (1–12 spp.). The greatest species richness occurred at the shallowest (n=8 spp.) and the deepest (2100–2500 m: DC673
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Post Eruption inflation of the East Pacific Rise at 9 degrees 50 ' N - Nooner, S L; Webb, S C; Buck, W R; Cormier, M H (Geochemistry, Geophysics, Geosystems, 2014)
In June 2008, we installed a geodetic network at 9 degrees 50' N on the East Pacific Rise to track the long-term movement of magma following the 2005/6 eruption. This network consists of 10 concrete benchmarks stretching from the ridge to 9 km off-axis. During three campaign-style surveys, measurements of vertical seafloor motions were made at each of these benchmarks by precisely recording ambient seawater pressure as a proxy for seafloor depth with a mobile pressure recorder (MPR). The MPR was deployed using the manned submersible Alvin in 2008 and 2009 and the remotely operated vehicle Jason in 2011. The MPR observations are supplemented with data from a multiyear deployment of continuously recording bottom pressure recorders (BPRs) extending along this segment of the ridge that can record rapid changes in seafloor depth from seafloor eruptions and/or dike intrusions. These measurements show no diking events and up to 12 cm of volcanic inflation that occurred from December 2009 to October 2011 in the area of the 2005/6 eruption. These observations are fit with an inflating point source at a depth of 2.7 km and volume change of 2.3 x 10(6) m(3)/yr located on the ridge axis at approximately 9 degrees 51.166' N, 407 m from our northernmost benchmark, suggesting that the magma chamber underlying this segment of the ridge is being recharged from a deeper source at a rate that is about half the long-term inflation rate observed at Axial Seamount on the Juan de Fuca Ridge. These data represent the second location that active volcanic uplift has been measured on a mid-ocean ridge segment, and the first on a nonhotspot influenced segment.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Primitive melt replenishment and crystal-mush disaggregation in the weeks preceding the 2005–2006 eruption 9°50′N9°50′N, EPR - Moore, A; Coogan, L A; Costa, F; Perfit, M R (Earth and Planetary Science Letters, 2014)
The 2005–2006 eruption at ∼9°50′N, East Pacific Rise provides an exceptional opportunity to investigate the magma plumbing system beneath a well-studied ridge system. The eruption was preceded by two years of increasingly intense seismicity and occurred from the same location as a previous and well-characterized eruption in 1991–1992. Here we use the crystal cargo of samples from this eruption to investigate magma reservoir processes in the lead-up to the eruption, as well as their temporal relationship to the seismicity that preceded it. Compositional zoning in some plagioclase crystals indicates primitive melt replenishment occurred roughly six weeks or less before the eruption. This replenishing event is seen only in the crystals from the central region of the eruption (9°50′–9°52′N). This is also the area where the most primitive lava compositions are observed and together these observations support models of replenishment being spatially focused. The short time between the input of a more primitive melt and eruption onto the seafloor suggests replenishment likely contributed to triggering the eruption. Rare resorbed plagioclase crystals, and glomerocrysts of plagioclase and olivine, some of which have rims far from equilibrium with their host melt, suggest that disaggregation of a crystal mush occurred within a few days prior to eruption. Interstitial melt from within this mush zone must have been mixed back into the erupted lava—a form of in situ crystallization. Thus, the erupted magmas evolved in a replenished-tapped magma reservoir in which at least a part of the crystallization occurred in situ.
Keywords: HOV Alvin (Human Occupied Vehicle)

Quantitative estimate of heat flow from a mid-ocean ridge axial valley, Raven field, Juan de Fuca Ridge: Observations and inferences - Salmi, M S; Johnson, H P; Tivey, M A; Hutnak, M (Journal of Geophysical Research: Solid Earth, 2014)
A systematic heat flow survey using thermal blankets within the Endeavour segment of the Juan de Fuca Ridge axial valley provides quantitative estimates of the magnitude and distribution of conductive heat flow at a mid-ocean ridge, with the goal of testing current models of hydrothermal circulation present within newly formed oceanic crust. Thermal blankets were deployed covering an area of 700 by 450 m in the Raven Hydrothermal vent field area located 400 m north of the Main Endeavour hydrothermal field. A total of 176 successful blanket deployment sites measured heat flow values that ranged from 0 to 31 W m−2. Approximately 53{%} of the sites recorded values lower than 100 mW m−2, suggesting large areas of seawater recharge and advective extraction of lithospheric heat. High heat flow values were concentrated around relatively small “hot spots.” Integration of heat flow values over the Raven survey area gives an estimate of conductive heat output of 0.3 MW, an average of 0.95 W m−2, over the survey area. Fluid circulation cell dimensions and scaling equations allow calculation of a Rayleigh number of approximately 700 in Layer 2A. The close proximity of high and low heat flow areas, coupled with previous estimates of surficial seafloor permeability, argues for the presence of small-scale hydrothermal fluid circulation cells within the high-porosity uppermost crustal layer of the axial seafloor.
Keywords: ROV Jason (Remotely Operated Vehicle)

Sedimentation rates test models of oceanic detachment faulting - Parnell-Turner, R; Cann, J R; Smith, D K; Schouten, H; Yoerger, D R; Palmiotto, C; Zheleznov, A; Bai, H (Geophysical Research Letters, 2014)
Long-lived detachment faults play an important role in the construction of new oceanic crust at slow-spreading mid-oceanic ridges. Although the corrugated surfaces of exposed low-angle faults demonstrate past slip, it is difficult to determine whether a given fault is currently active. If inactive, it is unclear when slip ceased. This judgment is crucial for tectonic reconstructions where detachment faults are present, and for models of plate spreading. We quantify variation in sediment thickness over two corrugated surfaces near 16.5°N at the Mid-Atlantic Ridge using near-bottom Compressed High Intensity Radar Pulse (CHIRP) data. We show that the distribution of sediment and tectonic features at one detachment fault is consistent with slip occurring today. In contrast, another corrugated surface 20 km to the south shows a sediment distribution suggesting that slip ceased {\~{}}150,000 years ago. Data presented here provide new evidence for active detachment faulting, and suggest along-axis variations in fault activity occur over tens of kilometers.
Keywords: AUV Sentry (Autonomous Underwater Vehicle)

Seven-year enrichment: macrofaunal succession in deep-sea sediments around a 30 tonne whale fall in the Northeast Pacific - Smith, Craig R; Bernardino, Angelo F; Baco, Amy; Hannides, Angelos; Altamira, Iris (MARINE ECOLOGY PROGRESS SERIES, 2014)
Whale falls cause massive organic and sulfide enrichment of underlying sediments, yielding energy-rich conditions in oligotrophic deep-sea ecosystems. While the fauna colonizing whale skeletons has received substantial study, sediment macrofaunal community response to the geochemical impacts of deep-sea whale falls remains poorly evaluated. We present a 7 yr case study of geochemical impacts, macrofaunal community succession, and chemoautotrophic community persistence in sediments around a 30 t gray-whale carcass implanted at 1675 m in the well-oxygenated Santa Cruz Basin on the California margin. The whale fall yielded intense, patchy organic-carbon enrichment ({>}15{%} organic carbon) and pore-water sulfide enhancement ({>}5 mM) in nearby sediments for 6 to 7 yr, supporting a dense assemblage of enrichment opportunists and chemosymbiotic vesicomyid clams. Faunal succession in the whale-fall sediments resembled the scavenger-opportunist-sulfophile sequence previously described for epifaunal communities on sunken whale skeletons. The intense response of enrichment opportunists functionally resembles responses to organic loading in shallow-water ecosystems, such as at sewer outfalls and fish farms. Of 100 macrofaunal species in the whale-fall sediments, 10 abundant species were unique to whale falls; 6 species were shared with cold seeps, 5 with hydrothermal vents, and 12 with nearby kelp and wood falls. Thus, whale-fall sediments may provide dispersal stepping stones for some generalized reducing-habitat species but also support distinct macrofaunal assemblages and contribute significantly to beta diversity in deep-sea ecosystems.
Keywords: HOV Alvin (Human Occupied Vehicle)

Spatial patterns of Aquificales in deep-sea vents along the Eastern Lau Spreading Center (SW Pacific) - Ferrera, Isabel; Banta, Amy B; Reysenbach, Anna-Louise (SYSTEMATIC AND APPLIED MICROBIOLOGY, 2014)
The microbial diversity associated with actively venting deep-sea hydrothermal deposits is tightly connected to the geochemistry of the hydrothermal fluids. Although the dominant members of these deposits drive the structure of the microbial communities, it is less well understood whether the lower abundance groups are as closely connected to the geochemical milieu, or driven perhaps by biotic factors such as microbial community interactions. We used the natural geochemical gradients that exist in the back-arc basin, Eastern Lau Spreading Center and Valu-Fa Ridge (ELSC/VFR) in the Southwestern Pacific, to explore whether the chemolithotrophic Aquificales are influenced by geographical location, host-rock of the vent field or deposit type. Using a combination of cloning, DNA fingerprinting (DGGE) and enrichment culturing approaches, all genera of this order previously described at marine vents were detected, i.e., Desulfurobacterium, Thermovibrio,Aquilex, Hydrogenivirga, Persephonella and Hydrogenothermus. The comparison between clone libraries and DGGE showed similar patterns of distribution of different Aquificales whereas results differed for the enrichment cultures that were retrieved. However, the use of cultivation-based and -independent methods did provide complementary phylogenetic diversity overview of the Aquificales in these systems. Together, this survey revealed that the ELSC/VFR contains some of the largest diversity of Aquificales ever reported at a deep-sea vent area, that the diversity patterns are tied to the geography and geochemistry of the system, and that this geochemical diverse back-arc basin may harbor new members of the Aquificales. (C) 2014 Elsevier GmbH. All rights reserved.
Keywords: ROV Jason (Remotely Operated Vehicle)

Spatial patterns of tissue stable isotope contents give insight into the nutritional sources for seep communities on the Gulf of Mexico lower slope - Becker, Erin L; Cordes, Erik E; Macko, Stephen A; Lee, Raymond W; Fisher, Charles R (MARINE ECOLOGY PROGRESS SERIES, 2014)
In this study, we present the first thorough trophic characterization of cold seep macrofaunal communities on the Gulf of Mexico lower continental slope ({>} 1000 m depth). We analyzed tissue delta C-13, delta N-15, and delta S-34 of vestimentiferan tubeworms, bathymodiolin mussels, vesicomyid clams, and their associated macrofaunal communities from discrete collections made across the entire lower slope. Over half of macrofauna associated with mussels and about half associated with vestimentiferans had delta C-13 values below -45{%}. We also observed high spatial variability in the delta C-13 values of entire local communities, and the delta C-13 of associated fauna were significantly correlated with the delta C-13 compositions of the symbiotic species from the same location. These data indicate widespread incorporation of methane-derived carbon in mussel and vestimentiferan communities. This finding was particularly surprising in communities associated with older vestimentiferans, given the low rates of seepage observed in similar communities on the upper slope. On average, delta N-13 values in mussels and their associates were significantly more depleted and more variable than vestimentiferans, clams, and their associates, and there was a significant linear relationship between tissue delta N-15 values of mussels and their associated communities. The tissue delta S-34 values in macrofauna associated with vestimentiferans were more variable and significantly more depleted than mussel associates (delta S-34 = -16.8 to + 19.1{%} for vestimentiferan associates and delta S-34 = -3.1 to + 20.8{%} for mussel associates), consistent with higher isotopic fractionation during sulfate reduction in vestimentiferan habitats and a potentially higher nutritional contribution of sulfide-derived organic sulfur in vestimentiferan communities.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Strain-level genomic variation in natural populations of Lebetimonas from an erupting deep-sea volcano - Meyer, Julie L; Huber, Julie A (ISME JOURNAL, 2014)
Chemolithoautotrophic Epsilonproteobacteria are ubiquitous in sulfidic, oxygen-poor habitats, including hydrothermal vents, marine oxygen minimum zones, marine sediments and sulfidic caves and have a significant role in cycling carbon, hydrogen, nitrogen and sulfur in these environments. The isolation of diverse strains of Epsilonproteobacteria and the sequencing of their genomes have revealed that this group has the metabolic potential to occupy a wide range of niches, particularly at dynamic deep-sea hydrothermal vents. We expand on this body of work by examining the population genomics of six strains of Lebetimonas, a vent-endemic, thermophilic, hydrogen-oxidizing Epsilonproteobacterium, from a single seamount in the Mariana Arc. Using Lebetimonas as a model for anaerobic, moderately thermophilic organisms in the warm, anoxic subseafloor environment, we show that genomic content is highly conserved and that recombination is limited between closely related strains. The Lebetimonas genomes are shaped by mobile genetic elements and gene loss as well as the acquisition of novel functional genes by horizontal gene transfer, which provide the potential for adaptation and microbial speciation in the deep sea. In addition, these Lebetimonas genomes contain two operons of nitrogenase genes with different evolutionary origins. Lebetimonas expressed nifH during growth with nitrogen gas as the sole nitrogen source, thus providing the first evidence of nitrogen fixation in any Epsilonproteobacteria from deep-sea hydrothermal vents. In this study, we provide a comparative overview of the genomic potential within the Nautiliaceae as well as among more distantly related hydrothermal vent Epsilonproteobacteria to broaden our understanding of microbial adaptation and diversity in the deep sea.
Keywords: ROV Jason (Remotely Operated Vehicle)

Strong Depth-Related Zonation of Megabenthos on a Rocky Continental Margin ( similar to 700-4000 m) off Southern Tasmania, Australia: e85872 - Thresher, R; Althaus, F; Adkins, J; Gowlett-Holmes, K; Alderslade, Phil; Dowdney, Jo; Cho, W; Gagnon, A; Staples, D; McEnnulty, F (PLoS ONE, 2014)
Assemblages of megabenthos are structured in seven depth-related zones between {\~{}}700 and 4000 m on the rocky and topographically complex continental margin south of Tasmania, southeastern Australia. These patterns emerge from analysis of imagery and specimen collections taken from a suite of surveys using photographic and in situ sampling by epibenthic sleds, towed video cameras, an autonomous underwater vehicle and a remotely operated vehicle (ROV). Seamount peaks in shallow zones had relatively low biomass and low diversity assemblages, which may be in part natural and in part due to effects of bottom trawl fishing. Species richness was highest at intermediate depths (1000-1300 m) as a result of an extensive coral reef community based on the bioherm-forming scleractinian Solenosmilia variabilis. However, megabenthos abundance peaked in a deeper, low diversity assemblage at 2000-2500 m. The S. variabilis reef and the deep biomass zone were separated by an extensive dead, sub-fossil S. variabilis reef and a relatively low biomass stratum on volcanic rock roughly coincident with the oxygen minimum layer. Below 2400 m, megabenthos was increasingly sparse, though punctuated by occasional small pockets of relatively high diversity and biomass. Nonetheless, megabenthic organisms were observed in the vast majority of photographs on all seabed habitats and to the maximum depths observed - a sandy plain below 3950 m. Taxonomic studies in progress suggest that the observed depth zonation is based in part on changing species mixes with depth, but also an underlying commonality to much of the seamount and rocky substrate biota across all depths. Although the mechanisms supporting the extraordinarily high biomass in 2000-2500 m depths remains obscure, plausible explanations include equatorwards lateral transport of polar production and/or a response to depth-stratified oxygen availability.
Keywords: AUV ABE (Autonomous Benthic Explorer); ROV Jason (Remotely Operated Vehicle)

Symbiont-driven sulfur crystal formation in a thiotrophic symbiosis from deep-sea hydrocarbon seeps - Eichinger, Irmgard; Schmitz-Esser, Stephan; Schmid, Markus; Fisher, Charles R; Bright, Monika (ENVIRONMENTAL MICROBIOLOGY REPORTS, 2014)
The siboglinid tubeworm Sclerolinum contortum symbiosis inhabits sulfidic sediments at deep-sea hydrocarbon seeps in the Gulf of Mexico. A single symbiont phylotype in the symbiont-housing organ is inferred from phylogenetic analyses of the 16S ribosomal ribonucleic acid (16S rRNA) gene and fluorescent in situ hybridization. The phylotype we studied here, and a previous study from an arctic hydrocarbon seep population, reveal identical 16S rRNA symbiont gene sequences. While sulfide is apparently the energy source for the symbionts (and ultimately the gutless host), both partners also have to cope with its toxicity. This study demonstrates abundant large sulfur crystals restricted to the trophosome area. Based on Raman microspectroscopy and energy dispersive X-ray analysis, these crystals have the same S8 sulfur configuration as the recently described small sulfur vesicles formed in the symbionts. The crystals reside adjacent to the symbionts in the trophosome. This suggests that their formation is either extra-or intracellular in symbionts. We propose that formation of these crystals provides both energy-storage compounds for the symbionts and serves the symbiosis by removing excess toxic sulfide from host tissues. This symbiont-mediated sulfide detoxification may have been crucial for the establishment of thiotrophic symbiosis and continues to remain an important function of the symbionts.
Keywords: ROV Jason (Remotely Operated Vehicle)

Time integrated variation of sources of fluids and seepage dynamics archived in authigenic carbonates from Gulf of Mexico Gas Hydrate Seafloor Observatory - Feng, D; Birgel, D; Peckmann, J; Roberts, H H; Joye, S B; Sassen, R; Liu, X-L; Hinrichs, K -U; Chen, D (Chemical Geology, 2014)
Authigenic carbonate rocks recovered from the Gulf of Mexico Gas Hydrate Seafloor Observatory in Mississippi Canyon block 118 (MC118) at approximately 900 m water depth were studied using mineralogical, bulk geochemical, and lipid biomarker analyses. Carbonate rocks occurred as fractured blocks and nodular masses incorporated in carbonate breccias. The carbonates were comprised mainly of high-Mg-calcite and aragonite. The stable carbon isotope composition ($δ$13C) of authigenic carbonate varied from − 29.8‰ to − 18.1‰ vs. V-PDB, suggesting a complex mixture of various carbon sources, including dissolved marine inorganic carbon (DIC), oil, as well as methane. Oxygen isotopes ($δ$18O) varied from + 3.4‰ to + 5.8‰. The observed 18O-enrichment in relation to calculated equilibrium values in the carbonates probably reflects decomposition of gas hydrates. The most abundant lipid biomarkers in the carbonates were isoprenoidal glycerol dibiphytanyl glycerol tetraethers (GDGTs), predominated by GDGT-2 and GDGT-3, which are typically indicators of anaerobic methane oxidizing archaea (ANMEs). Mono- and bicyclic biphytanes (derived after ether cleavage of GDGT-2 and GDGT-3) showed strong 13C-depletion, which is characteristic for ANMEs. Interestingly, large differences between the $δ$13C values of the archaeal diether archaeol and acyclic biphytane on the one hand and monocyclic biphytane on the other hand suggest the presence of archaea other than ANMEs. Archaeol and GDGT-0 (containing two acyclic biphytane moieties) are commonly assigned to various methanogenic archaea. Where methane seepage activity is intermediate or low within acoustic wipeout zones at the MC118 gas hydrate site nowadays, microbial communities must have coped with changing conditions as well as longer-term fluctuations in oil and gas seepage or the temporary cessation of hydrocarbon flux in the past. The change from methane seepage to oil seepage or vice versa in addition to flux variability apparently favors the establishment of complex prokaryotic communities dominated by archaea. In addition to anaerobic oxidation of methane, local production of methane is apparently prominent at the study site based on the occurrence of biomarkers of methanogens in the authigenic carbonate. This finding adds to the ongoing multidisciplinary effort to better constrain the environment at the MC118 observatory site and to determine the locally dominant biogeochemical processes.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Understanding a submarine eruption through time series hydrothermal plume sampling of dissolved and particulate constituents: West Mata, 2008-2012 - Baumberger, T; Lilley, M D; Resing, J A; Lupton, J E; Baker, E T; Butterfield, D A; Olson, E J; Fruh-Green, G L (Geochemistry, Geophysics, Geosystems, 2014)
Four cruises between 2008 and 2012 monitored the continuing eruption of West Mata volcano in the NE Lau Basin as it produced plumes of chemically altered water above its summit. Although large enrichments in He-3, CO2, Fe, and Mn were observed in the plumes, the most notable enrichment was that of H-2, which reached concentrations as high as 14,843 nM. Strongly enriched H-2 concentrations in the water column result from reactions between seawater or magmatic water and extremely hot rocks. In 2008, the observation of elevated H-2 concentrations in the water column above West Mata pointed to vigorous ongoing eruptions at the volcano's summit. The eruption was confirmed by visual observations made by the ROV Jason 2 in 2009 and demonstrated that H-2 measurements are a vital instrument to detect ongoing volcanic eruptions at the seafloor. Elevated H-2 in 2010 showed that the eruption was ongoing, although at a reduced level given a maximum H-2 concentration of 4410 nM. In 2012, H-2 levels in the water column declined significantly, to a maximum of only 7 nM, consistent with visual observations from the Quest-4000 ROV that found no evidence of an ongoing volcanic eruption. Methane behaved independently of other measured gases and its concentrations in the hydrothermal plume were very low. We attribute its minimal enrichments to a mixture of mantle carbon reduced to CH4 and biological CH4 from diffuse flow sites. This study demonstrates that ongoing submarine volcanic eruptions are characterized by high dissolved H-2 concentrations present in the overlying water column.
Keywords: ROV Jason (Remotely Operated Vehicle)

Active positioning of vent larvae at a mid-ocean ridge - Mullineaux, L S; McGillicuddy Jr., D J; Mills, S W; Kosnyrev, V K; Thurnherr, A M; Ledwell, J R; Lavelle, J W (DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY, 2013)
The vertical position of larvae of vent species above a mid-ocean ridge potentially has a strong effect on their dispersal. Larvae may be advected upward in the buoyant vent plume, or move as a consequence of their buoyancy or by active swimming. Alternatively, they may be retained near the bottom by the topography of the axial trough, or by downward swimming. At vents near 9 degrees 50'N on the axis of the East Pacific Rise, evidence for active larval positioning was detected in a comparison between field observations of larvae in the plankton in 2006 and 2007 and distributions of non-swimming larvae in a two-dimensional bio-physical model. In the field, few vent larvae were collected at the level of the neutrally buoyant plume (similar to 75 m above the bottom); their relative abundances at that height were much lower than those of simulated larvae from a near-bottom release in the model. This discrepancy was observed for many vent species, particularly gastropods, suggesting that they may actively remain near the bottom by sinking or swimming downward. Near the seafloor, larval abundance decreased from the ridge axis to 1000 m off axis much more strongly in the observations than in the simulations, again pointing to behavior as a potential regulator of larval transport. We suspect that transport off axis was reduced by downward-moving behavior, which positioned larvae into locations where they were isolated from cross-ridge currents by seafloor topography, such as the walls of the axial valley which are not resolved in the model. Cross-ridge gradients in larval abundance varied between gastropods and polychaetes, indicating that behavior may vary between taxonomic groups, and possibly between species. These results suggest that behaviorally mediated retention of vent larvae may be common, even for species that have a long planktonic larval duration and are capable of long-distance dispersal. (C) 2013 Elsevier Ltd. All rights reserved.
Keywords: HOV Alvin (Human Occupied Vehicle)

Activity and positioning of eurythermal hydrothermal vent sulphide worms in a variable thermal environment - Bates, Amanda E; Bird, Tomas J; Robert, Katleen; Onthank, Kirt L; Quinn, Gerry P; Juniper, S Kim; Lee, Raymond W (JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY, 2013)
Here we investigate behavioral responses to fine-scale spatial and temporal temperature gradients in a heat tolerant hydrothermal vent worm (Paralvinella sulfincola). While this species has been a model organism for understanding physiological adaptations to extreme environments, lacking are corroborative in situ experiments and characterization of temperature-related behaviors representing the lower thermal tolerance range of this species. To address this knowledge gap, we first quantified the upper thermal limit for this species using a rapid heating protocol executed remotely on the seafloor. Second, we used a combination of in situ observations and shipboard experiments to test for temperature-dependent patterns in activity and behavior. We confirm that P. sulfincola is remarkably eurythermal and demonstrates a thermal niche breadth exceeding 45 degrees C. We further show that the activity and positioning of worms relate to temperatures within its lower preferred range (i.e., between 4 and 20 degrees C). Worms tended to remain closer to their tube openings and held their branchial crown in a consistent location when fluids were relatively warm. By contrast, when fluids were cooler, both the distance worms were observed from their tubes and positioning of their branchial crown were more variable. A Bayesian hidden Markov model classified each worm at each time interval as being in a high or low activity state according to the magnitude of change in their orientation and how far they moved between successive time lapse images. We found that the transition between active and inactive states at any time period is related to fluid temperature. Our observations indicate that the behavior of the worms is temperature-dependent, which may in turn reflect temperature-related variables such as the delivery of food particles, dissolved oxygen concentration, or relative environmental variability. Our findings demonstrate that this species can respond behaviorally to very fine-scale environmental variability in a manner not simply predicted by models of increasing activity with temperature. (C) 2013 Elsevier B.V. All rights reserved.
Keywords: HOV Alvin (Human Occupied Vehicle)

Anaerobic oxidation of short-chain alkanes in hydrothermal sediments: potential influences on sulfur cycling and microbial diversity - Adams, Melissa M; Hoarfrost, Adrienne L; Bose, Arpita; Joye, Samantha B; Girguis, Peter R (FRONTIERS IN MICROBIOLOGY, 2013)
Short-chain alkanes play a substantial role in carbon and sulfur cycling at hydrocarbon-rich environments globally, yet few studies have examined the metabolism of ethane (C-2), propane (C-3), and butane (C-4) in anoxic sediments in contrast to methane (C-1). In hydrothermal vent systems, short-chain alkanes are formed over relatively short geological time scales via thermogenic processes and often exist at high concentrations. The sediment-covered hydrothermal vent systems at Middle Valley (MV Juan de Fuca Ridge) are an ideal site for investigating the anaerobic oxidation of C-1-C-4 alkanes, given the elevated temperatures and dissolved hydrocarbon species characteristic of these metalliferous sediments. We examined whether MV microbial communities oxidized C-1-C-4 alkanes under mesophilic to thermophilic sulfate-reducing conditions. Here we present data from discrete temperature (25, 55, and 75 degrees C) anaerobic batch reactor incubations of MV sediments supplemented with individual alkanes. Co-registered alkane consumption and sulfate reduction (SR) measurements provide clear evidence for C-1-C-4 alkane oxidation linked to SR over time and across temperatures. In these anaerobic batch reactor sediments, 16S ribosomal RNA pyrosequencing revealed that Deltaproteobacteria, particularly a novel sulfate-reducing lineage, were the likely phylotypes mediating the oxidation of C-2-C-4 alkanes. Maximum C-1-C-4 alkane oxidation rates occurred at 55 degrees C, which reflects the mid-core sediment temperature profile and corroborates previous studies of rate maxima for the anaerobic oxidation of methane (AOM). Of the alkanes investigated, C-3 was oxidized at the highest rate over time, then C-4, C-2, and C-1, respectively. The implications of these results are discussed with respect to the potential competition between the anaerobic oxidation of C-2-C(4)alkanes with AOM for available oxidants and the influence on the fate of C-1 derived from these hydrothermal systems.
Keywords: HOV Alvin (Human Occupied Vehicle)

Archaeal and bacterial glycerol dialkyl glycerol tetraether lipids in chimneys of the Lost City Hydrothermal Field - Lincoln, Sara A; Bradley, Alexander S; Newman, Sharon A; Summons, Roger E (ORGANIC GEOCHEMISTRY, 2013)
We detected archaeal and bacterial glycerol dialkyl glycerol tetraether (GDGT) lipids in carbonate chimneys of the Lost City Hydrothermal Field, an alkaline system near the mid-Atlantic Ridge. Isoprenoidal, archaeal tetraethers from this site include ``H-shaped'' GDGTs, crenarchaeol and GDGTs with 0-3 cyclopentane moieties (here referred to as GDGTs 0-3). Concentrations of GDGT-3 do not track those of GDGTs 0-2 across the sample set, suggesting that its biosynthesis may be subject to different controls. Two branched, bacterial GDGTs (brGDGTs) common in terrigenous environments were also detected. Consulting previously published surveys of microbial diversity at Lost City and literature on known precursor-product relationships, we investigated the provenance of these GDGTs. The principal source of GDGTs 0-3 is likely ANME-1 archaea, abundant at Lost City. H-shaped GDGTs are likely derived from thermophilic Methanobacteria and Thermoprotei. Marine Group I Thaumarchaea detected in Lost City chimneys are a potential source of crenarchaeol, but it is unclear whether they are autotrophic nitrifiers or representatives of a hydrothermal ecotype with different physiology. The detection of branched GDGTs, possibly synthesized by Acidobacteria at Lost City, adds to a growing body of evidence that the capacity for their biosynthesis is not restricted to acidophilic soil bacteria and that they cannot strictly be considered indicators of terrigenous contributions to marine sediments. Input of hydrothermally derived lipids has the potential to complicate paleoproxy applications based on GDGTs. We propose that H-GDGTs be viewed as indicators of hydrothermal input and that their detection in sediments warrants caution in proxy application when a hydrothermal origin for co-occurring isoprenoidal and brGDGTs cannot be excluded. (C) 2013 Elsevier Ltd. All rights reserved.
Keywords: HOV Alvin (Human Occupied Vehicle)

Cemented mounds and hydrothermal sediments on the detachment surface at Kane Megamullion: A new manifestation of hydrothermal venting - Tucholke, B E; Humphris, S E; Dick, H J B (Geochemistry, Geophysics, Geosystems, 2013)
Long-lived detachment faults are now known to be important in tectonic evolution of slow-spreading mid-ocean ridges, and there is increasing evidence that fluid flow plays a critical role in development of detachment systems. Here we document a new manifestation of low-temperature hydrothermal venting associated with the detachment fault that formed Kane Megamullion ∼3.3–2.1 m.y. ago in the western rift-valley wall of the Mid-Atlantic Ridge. Hydrothermal effects on the detachment surface include (1) cemented mounds of igneous rock and chalk debris containing hydrothermal Mn oxides and Fe oxyhydroxides, and (2) layered deposits of similar Fe-Mn minerals ± interbedded chalks. Mounds are roughly conical, ∼1–10 m high, and contain primarily basalts with lesser gabbro, serpentinite, and polymict breccia. The layered Fe-Mn-rich sediments are flat-bedded to contorted and locally are buckled into low-relief linear or polygonal ridges. We propose that the mounds formed where hydrothermal fluids discharged through the detachment hanging wall near the active fault trace. Hydrothermal precipitates cemented hanging-wall debris and welded it to the footwall, and this debris persisted as mounds as the footwall was exhumed and surrounding unconsolidated material sloughed off the sloping detachment surface. Some of the layered Fe-Mn-rich deposits may have precipitated from fluids discharging from the hanging-wall vents, but they also precipitated from low-temperature fluids venting from the exposed footwall through overlying chalks. Observed natural disturbance and abnormally thin hydrogenous Fe-Mn crusts on some contorted, hydrothermal Fe-Mn-rich chalks on ∼2.7 Ma crust suggest diffuse venting that is geologically recent. Results of this study imply that there are significant fluid pathways through all parts of detachment systems and that low-temperature venting through fractured detachment footwalls may continue for several million years off-axis.
Keywords: AUV ABE (Autonomous Benthic Explorer); ROV Jason (Remotely Operated Vehicle)

Characterization of 13 polymorphic microsatellite loci in Rimicaris hybisae, a shrimp from deep-sea hydrothermal vents - Jacobson, A; Plouviez, S; Thaler, A D; Van Dover, C L (Conservation Genetics Resources, 2013)
Rimicaris hybisae is a deep-sea alvinocaridid shrimp found at hydrothermal vents along the Mid-Cayman Spreading Center. Eleven selectively neutral and unlinked polymorphic microsatellite loci were developed for this species and two additional loci were found to cross-amplify from a related species. Nine loci conformed to Hardy-Weinberg expectations. Seven loci cross-amplified with Chorocaris sp. 2, an alvinocaridid shrimp found at vents in the Southwestern Pacific. Microsatellite loci developed for R. hybisae are being deployed to study connectivity and genetic variability of populations along the Mid-Cayman Spreading Center.
Keywords: ROV Jason (Remotely Operated Vehicle)

Characterization of 9 polymorphic microsatellite loci in Lamellibrachia sp 2, a tubeworm found at deep-sea hydrothermal vents and cold seeps - Jacobson, A; Plouviez, S; Thaler, A D; Van Dover, C L (Conservation Genetics Resources, 2013)
Lamellibrachia sp. 2 is a deep-sea vestimentiferan tubeworm found at hydrothermal vents on the Mid-Cayman Spreading Center and at hydrocarbon seeps in the Gulf of Mexico and off the coast of Barbados. Nine selectively neutral and unlinked polymorphic microsatellite loci were developed for this species. Eight of these loci conformed to Hardy-Weinberg expectations. Average observed heterozygosity ranged from 0.14 to 0.92. Microsatellites developed for Lamellibrachia sp. 2 are being deployed to study connectivity and gene flow among populations of this species.
Keywords: ROV Jason (Remotely Operated Vehicle)

Characterizing the distribution and rates of microbial sulfate reduction at Middle Valley hydrothermal vents - Frank, Kiana L; Rogers, Daniel R; Olins, Heather C; Vidoudez, Charles; Girguis, Peter R (ISME JOURNAL, 2013)
Few studies have directly measured sulfate reduction at hydrothermal vents, and relatively little is known about how environmental or ecological factors influence rates of sulfate reduction in vent environments. A better understanding of microbially mediated sulfate reduction in hydrothermal vent ecosystems may be achieved by integrating ecological and geochemical data with metabolic rate measurements. Here we present rates of microbially mediated sulfate reduction from three distinct hydrothermal vents in the Middle Valley vent field along the Juan de Fuca Ridge, as well as assessments of bacterial and archaeal diversity, estimates of total biomass and the abundance of functional genes related to sulfate reduction, and in situ geochemistry. Maximum rates of sulfate reduction occurred at 90 degrees C in all three deposits. Pyrosequencing and functional gene abundance data revealed differences in both biomass and community composition among sites, including differences in the abundance of known sulfate-reducing bacteria. The abundance of sequences for Thermodesulfovibro-like organisms and higher sulfate reduction rates at elevated temperatures suggests that Thermodesulfovibro-like organisms may have a role in sulfate reduction in warmer environments. The rates of sulfate reduction presented here suggest that-within anaerobic niches of hydrothermal deposits-heterotrophic sulfate reduction may be quite common and might contribute substantially to secondary productivity, underscoring the potential role of this process in both sulfur and carbon cycling at vents.
Keywords: HOV Alvin (Human Occupied Vehicle)

Cold-seep habitat mapping: High-resolution spatial characterization of the Blake Ridge Diapir seep field - Wagner, J K S; McEntee, M H; Brothers, L L; German, C R; Kaiser, C L; Yoerger, D R; Van Dover, C L (Deep-Sea Research. Part II: Topical Studies in Oceanography, 2013)
Relationships among seep community biomass, diversity, and physiographic controls such as underlying geology are not well understood. Previous efforts to constrain these relationships at the Blake Ridge Diapir were limited to observations from piloted deep-submergence vehicles. In August 2012, the autonomous underwater vehicle (AUV) Sentry collected geophysical and photographic data over a 0.131 km2 area at the Blake Ridge Diapir seeps. A nested survey approach was used that began with a regional or reconnaissance-style survey using sub-bottom mapping systems to locate and identify seeps and underlying conduits. This survey was followed by AUV-mounted sidescan sonar and multibeam echosounder systems mapping on a mesoscale to characterize the seabed physiography. At the most detailed survey level, digital photographic imaging was used to resolve sub-meter characteristics of the biology. Four pockmarks (25–70 m diameter) were documented, each supporting chemosynthetic communities. Concentric zonation of mussels and clams suggests the influence of chemical gradients on megafaunal distribution. Data collection and analytical techniques used here yield high-resolution habitat maps that can serve as baselines to constrain temporal evolution of seafloor seeps, and to inform ecological niche modeling and resource management.
Keywords: AUV Sentry (Autonomous Underwater Vehicle)

A comparative study of authigenic carbonates from mussel and tubeworm environments: Implications for discriminating the effects of tubeworms - Feng, D; Cordes, E E; Roberts, H H; Fisher, C R (Deep-Sea Research. Part I: Oceanographic Research Papers, 2013)
The Gulf of Mexico hydrocarbon seeps are often populated by dense mussel beds and tubeworm aggregations, as well as exposed authigenic carbonate outcrops. Previous studies suggest the activity of mussels and tubeworms could influence the sediment geochemistry of their habitats, resulting in variations in the stable carbon isotopes of the associated carbonates. However, this conclusion was based on the analyses of samples from a single site. To better understand whether there are consistent differences in the geochemical environments of mussels and tubeworms, mineralogical and stable isotopic compositions of authigenic carbonates from mussel and tubeworm environments from four seep sites were analyzed. The studied sites span a depth range of 1200 m to 2800 m on the northern Gulf of Mexico continental slope. We found that carbonate samples from tubeworm environments were more prone to contain aragonite whereas carbonates from mussel environments were more likely to have calcite. This finding supports the hypothesis that vestimentiferans release sulfate across their roots into the pore waters of the surrounding sediments, a process that could generate a locally sulfate-enriched environment that favors the precipitation of aragonite instead of calcite. Moreover, the $δ$13C values of tubeworm carbonates are generally lighter than that of mussel carbonates from the same site, which is consistent with the fact that tubeworms are fueling extra subsurface methane oxidation through the release of sulfate into the sediment. Such a process, consequently, enriches the subsurface dissolved inorganic carbon pool with light carbon derived from the seeping hydrocarbons. Taken together, our data suggest that tubeworms could produce a carbon isotope shift that is sufficient to influence the sediment geochemistry of their immediate area, and that this impact is reflected in the associated authigenic carbonates.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Detection and phylogenetic analysis of the membrane-bound nitrate reductase (Nar) in pure cultures and microbial communities from deep-sea hydrothermal vents - Perez-Rodriguez, Ileana; Bohnert, Kenneth A; Cuebas, Mariola; Keddis, Ramaydalis; Vetriani, Costantino (FEMS MICROBIOLOGY ECOLOGY, 2013)
Over the past few years the relevance of nitrate respiration in microorganisms from deep-sea hydrothermal vents has become evident. In this study, we surveyed the membrane-bound nitrate reductase (Nar) encoding gene in three different deep-sea vent microbial communities from the East Pacific Rise and the Mid-Atlantic Ridge. Additionally, we tested pure cultures of vent strains for their ability to reduce nitrate and for the presence of the NarG-encoding gene in their genomes. By using the narG gene as a diagnostic marker for nitrate-reducing bacteria, we showed that nitrate reductases related to Gammaproteobacteria of the genus Marinobacter were numerically prevalent in the clone libraries derived from a black smoker and a diffuse flow vent. In contrast, NarG sequences retrieved from a community of filamentous bacteria located about 50cm above a diffuse flow vent revealed the presence of a yet to be identified group of enzymes. 16S rRNA gene-inferred community compositions, in accordance with previous studies, showed a shift from Alpha- and Gammaproteobacteria to Epsilonproteobacteria as the vent fluids become warmer and more reducing. Based on these findings, we argue that Nar-catalyzed nitrate reduction is likely relevant in temperate and less reducing environments where Alpha- and Gammaproteobacteria are more abundant and where nitrate concentrations reflect that of background deep seawater.
Keywords: HOV Alvin (Human Occupied Vehicle)

Diffuse flow environments within basalt- and sediment-based hydrothermal vent ecosystems harbor specialized microbial communities - Campbell, Barbara J; Polson, Shawn W; Allen, Lisa Zeigler; Williamson, Shannon J; Lee, Charles K; Wommack, K Eric; Cary, S Craig (FRONTIERS IN MICROBIOLOGY, 2013)
Hydrothermal vents differ both in surface input and subsurface geochemistry. The effects of these differences on their microbial communities are not clear. Here, we investigated both alpha and beta diversity of diffuse flow-associated microbial communities emanating from vents at a basalt-based hydrothermal system along the East Pacific Rise (EPR) and a sediment-based hydrothermal system, Guaymas Basin. Both Bacteria and Archaea were targeted using high throughput 16S rRNA gene pyrosequencing analyses. A unique aspect of this study was the use of a universal set of 16S rRNA gene primers to characterize total and diffuse flow-specific microbial communities from varied deep-sea hydrothermal environments. Both surrounding seawater and diffuse flow water samples contained large numbers of Marine Group I (MGI) Thaumarchaea and Gammaproteobacteria taxa previously observed in deep-sea systems. However, these taxa were geographically distinct and segregated according to type of spreading center. Diffuse flow microbial community profiles were highly differentiated. In particular, EPR dominant diffuse flow taxa were most closely associated with chemolithoautotrophs, and off axis water was dominated by heterotrophic-related taxa, whereas the opposite was true for Guaymas Basin. The diversity and richness of diffuse flow-specific microbial communities were strongly correlated to the relative abundance of Epsilonproteobacteria, proximity to macrofauna, and hydrothermal system type. Archaeal diversity was higher than or equivalent to bacterial diversity in about one third of the samples. Most diffuse flow-specific communities were dominated by OTUs associated with Epsilonproteobacteria, but many of the Guaymas Basin diffuse flow samples were dominated by either OTUs within the Planctomycetes or hyperthermophilic Archaea. This study emphasizes the unique microbial communities associated with geochemically and geographically distinct hydrothermal diffuse flow environments.
Keywords: HOV Alvin (Human Occupied Vehicle)

Distribution of mega fauna on sulfide edifices on the Eastern Lau Spreading Center and Valu Fa Ridge - Sen, A; Becker, E L; Podowski, E L; Wickes, L N; Ma, S; Mullaugh, K M; Hourdez, S; Luther, G W; Fisher, C R (Deep-Sea Research. Part I: Oceanographic Research Papers, 2013)
Hydrothermal vent sulfide edifices contain some of the most extreme thermal and chemical conditions in which animals are able to live. As a result, sulfide edifices in the East Pacific Rise, Juan de Fuca Ridge, and Mid Atlantic Ridge vent systems often contain distinct faunal assemblages. In this study, we used high-resolution imagery and in-situ physico-chemical measurements within the context of a Geographic Information System (GIS) to examine community structure and niche differentiation of dominant fauna on sulfide edifices in the Eastern Lau Spreading Center (ELSC) and Valu Fa Ridge (VFR) in the Western Pacific Ocean. Our results show that ELSC and VFR sulfide edifices host two distinct types of communities. One type, that covers the majority of sulfide edifice faces, is overall very similar to nearby lava communities and biomass is dominated by the same chemoautotrophic symbiont-containing molluscs that dominate lava communities, namely the provannid gastropods Alviniconcha spp. and Ifremeria nautilei and the mytilid bivalve Bathymodiolus brevior. The spatial distribution of the dominant molluscs is often a variation of the pattern of concentric rings observed on lavas, with Alviniconcha spp. at the tops of edifices where exposure to vent flow is the highest, and I. nautilei and B. brevior below. Our physico-chemical measurements indicate that because of rapid dispersion of vent fluid, habitable area for symbiont-containing fauna is quite limited on sulfide edifices, and the realized niches of the mollusc groups are narrower on sulfide edifices than on lavas. We suggest that competition plays an important role in determining the realized distributions of the mollusc groups on edifices. The other habitat, present in small patches of presumably hot, new anhydrite, is avoided by the dominant symbiont-containing molluscs and inhabited by crabs, shrimp and polynoids that are likely more heat tolerant. The ratio of sulfide concentration to temperature anomaly of vent fluids was significantly different between sulfide edifice sites and lava sites in the southern vent fields but not in the northern vent fields. We suggest that this is due to increased sulfide consumption by a large microbial consortium associated with the more friable andesitic lava substrates in the south.
Keywords: ROV Jason (Remotely Operated Vehicle)

Diversity and Distributional Patterns of Ciliates in Guaymas Basin Hydrothermal Vent Sediments - Coyne, Kathryn J; Countway, Peter D; Pilditch, Conrad A; Lee, Charles K; Caron, David A; Cary, Stephen C (JOURNAL OF EUKARYOTIC MICROBIOLOGY, 2013)
Little is known about protists at deep-sea hydrothermal vents. The vent sites at Guaymas Basin in the Gulf of California are characterized by dense mats of filamentous pigmented or nonpigmented Beggiatoa that serve as markers of subsurface thermochemical gradients. We constructed 18S rRNA libraries to investigate ciliate assemblages in Beggiatoa mats and from bare sediments at the Guaymas vent site. Results indicated a high diversity of ciliates, with 156 operational taxonomic units identified in 548 sequences. Comparison between mat environments demonstrated that ciliate and bacterial assemblages from pigmented mats, nonpigmented mats, and bare sediments were significantly different and highly correlated with bacterial assemblages. Neither bacterial nor ciliate assemblages were correlated with environmental factors. The most abundant ciliates at Guaymas were more likely to be represented in clone libraries from other hydrothermal, deep-sea, and/or anoxic or microaerophilic environments, supporting the hypothesis that these ciliate species are broadly distributed. The orange mat environment included a higher proportion of ciliate sequences that were more similar to those from other environmental studies than to cultured ciliate species, whereas clone libraries from bare sediments included sequences that were the most highly divergent from all other sequences and may represent species that are endemic to Guaymas.
Keywords: HOV Alvin (Human Occupied Vehicle)

Ecological release and niche partitioning under stress:lessons from dorvilleid polychaetes in sulfidic sediments at methane seeps - Levin, L A; Ziebis, W; Mendoza, G; Bertics, V J; Washington, T; Gonzalez, J; Thurber, A R; Ebbe, B; Lee, R W (Deep-Sea Research. Part II: Topical Studies in Oceanography, 2013)
Organisms inhabiting methane seep sediments are exposed to stress in the form of high levels of hydrogen sulfide, which result mainly from sulfate reduction coupled to anaerobic methane oxidation. Dorvilleidae (Polychaeta) have successfully invaded this ecosystem, and multiple species in divergent genetic clades co-occur at high densities. At methane seeps in the NE Pacific off California and Oregon, the genera Ophryotrocha, Parougia and Exallopus are especially well represented. To test the hypothesis that dorvilleid coexistence is facilitated by niche partitioning through sulfide tolerance and trophic patterns, we examined dorvilleid species-specific patterns of occurrence and nutrition at methane seeps off Eel R. [ER] on the Californian continental slope and at Hydrate Ridge [HR] on the Oregon continental slope, and in two habitats (clam bed and microbial mat) characterized by lower and higher hydrogen sulfide levels, respectively. Microelectrode measurements of hydrogen sulfide enabled characterization of environmental sulfide levels for species sampled in background sediment cores and in colonization trays. Dorvilleids tolerated H2S levels from 10 $μ$M to over 2.6 mM, with the majority of species inhabiting sediments with similar environmental H2S concentrations (median 85–100 $μ$M). Dorvilleid species richness was greater at HR than ER, but did not differ between clam bed and microbial mat habitats. Species distribution patterns reflected preferences for ER clam bed (lower sulfide levels), ER mat and HR clam bed (moderate sulfide levels), or HR mat (very high sulfide levels). Nutritional patterns, including trophic diversity and functional similarity, were examined using community stable isotope metrics based on $δ$15N and $δ$13C. Within each region, dorvilleid species exhibited multiple trophic strategies. Co-existing congeners typically exhibited distinct isotope signatures, suggesting trophic partitioning. Trophic diversity and $δ$15N range for whole assemblages (measured by Total Hull Area and Standard Elliptical Area using species averages) and functional redundancy or species packing (measured as distance to nearest neighbor) among species and individuals were generally higher at ER, where sulfide levels were lower than at HR. In contrast, average trophic diversity among individuals within a species was greater at HR than ER. In colonization experiments involving agar-based manipulations of sulfide in tray sediments that mimicked clam bed and mat conditions, dorvilleids comprised 68{%} and 48{%} of colonists at ER and HR, respectively. Dorvilleid species richness was higher in trays that were initially more sulfidic. However, habitat exerted stronger influence on the composition of colonizing dorvilleids than did sulfide additions. In the NE Pacific, regional, habitat and vertical (down-core) variation in hydrogen sulfide creates complex environmental heterogeneity at methane seeps, promoting high diversity of stress-tolerant taxa such as dorvilleid polychaetes.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Evidence for extensive methane venting on the southeastern U.S. Atlantic margin - Brothers, L L; Van Dover, C L; German, C R; Kaiser, C L; Yoerger, D R; Ruppel, C D; Lobecker, E; Skarke, A D; Wagner, J K S (Geology, 2013)
We present the first evidence for widespread seabed methane venting along the southeastern United States Atlantic margin beyond the well-known Blake Ridge diapir seep. Recent ship- and autonomous underwater vehicle (AUV)-collected data resolve multiple water-column anomalies ({>}1000 m height) and extensive new chemosynthetic seep communities at the Blake Ridge and Cape Fear diapirs. These results indicate that multiple, highly localized fluid conduits punctuate the areally extensive Blake Ridge gas hydrate province, and enable the delivery of significant amounts of methane to the water column. Thus, there appears to be an abundance of seabed fluid flux not previously ascribed to the Atlantic margin of the United States.
Keywords: AUV Sentry (Autonomous Underwater Vehicle)

Geomicrobiological linkages between short-chain alkane consumption and sulfate reduction rates in seep sediments - Bose, Arpita; Rogers, Daniel R; Adams, Melissa M; Joye, Samantha B; Girguis, Peter R (FRONTIERS IN MICROBIOLOGY, 2013)
Marine hydrocarbon seeps are ecosystems that are rich in methane, and, in some cases, short-chain (C-2-C-5) and longer alkanes. C-2-C-4 alkanes such as ethane, propane, and butane can be significant components of seeping fluids. Some sulfate-reducing microbes oxidize short-chain alkanes anaerobically, and may play an important role in both the competition for sulfate and the local carbon budget. To better understand the anaerobic oxidation of short-chain n-alkanes coupled with sulfate-reduction, hydrocarbon-rich sediments from the Gulf of Mexico (GoM) were amended with artificial, sulfate-replete seawater and one of four n-alkanes (C-1-C-4) then incubated under strict anaerobic conditions. Measured rates of alkane oxidation and sulfate reduction closely follow stoichiometric predictions that assume the complete oxidation of alkanes to CO2 (though other sinks for alkane carbon likely exist). Changes in the delta C-13 of all the alkanes in the reactors show enrichment over the course of the incubation, with the C-3 and C-4 incubations showing the greatest enrichment (4.4 and 4.5 parts per thousand, respectively). The concurrent depletion in the delta C-13 of dissolved inorganic carbon (DIC) implies a transfer of carbon from the alkane to the DIC pool (-3.5 and -6.7 parts per thousand for C-3 and C-4 incubations, respectively). Microbial community analyses reveal that certain members of the class Deltaproteobacteria are selectively enriched as the incubations degrade C-1-C-4 alkanes. Phylogenetic analyses indicate that distinct phylotypes are enriched in the ethane reactors, while phylotypes in the propane and butane reactors align with previously identified C-3-C-4 alkane-oxidizing sulfate-reducers. These data further constrain the potential influence of alkane oxidation on sulfate reduction rates (SRRs) in cold hydrocarbon-rich sediments, provide insight into their contribution to local carbon cycling, and illustrate the extent to which short-chain alkanes can serve as electron donors and govern microbial community composition and density.
Keywords: HOV Alvin (Human Occupied Vehicle)

Geophysical modeling of collapse-prone zones at Rumble III seamount, southern Pacific Ocean, New Zealand - Tontini, F C; de Ronde, C E J; Kinsey, J C; Soule, A; Yoerger, D; Cocchi, L (Geochemistry, Geophysics, Geosystems, 2013)
Catastrophic collapses of submarine volcanoes have the potential to generate major tsunami, threatening many coastal populations. Recognizing the difficulties surrounding anticipations of these events, quantitative assessment of collapse-prone regions based on detailed morphological, geological, and geophysical mapping can still provide important information about the hazards associated with these collapses. Rumble III is one of the shallowest, and largest, submarine volcanoes found along the Kermadec arc, and is both volcanically and hydrothermally active. Previous surveys have delineated major collapse features at Rumble III; based on time-lapse bathymetry, dramatic changes in the volcano morphology have been shown to have occurred over the interval 2007–2009. Furthermore, this volcano is located just ∼300 km from the east coast of the North Island of New Zealand. Here, we present a geophysical model for Rumble III that provides the locations and sizes of potential weak regions of this volcano. Shipborne and near-seafloor geological and geophysical data collected by the AUV Sentry are used to determine the subsurface distribution of weak and unstable volcanic rocks. The resulting model provides evidence for potentially unstable areas located in the Southeastern flank of this volcano which should be included in future hazard predictions.
Keywords: AUV Sentry (Autonomous Underwater Vehicle)

Growth kinetics and energetics of a deep-sea hyperthermophilic methanogen under varying environmental conditions - Eecke, Helene C Ver; Akerman, Nancy H; Huber, Julie A; Butterfield, David A; Holden, James F (ENVIRONMENTAL MICROBIOLOGY REPORTS, 2013)
{A hyperthermophilic deep-sea methanogen, Methanocaldococcus strain JH146, was isolated from 26 degrees C hydrothermal fluid at Axial Volcano to model high temperature methanogenesis in the subseafloor. Emphasis was placed on defining growth kinetics, cell yields and growth energy demand (GE) across a range of conditions. The organism uses H-2 and CO2 as its sole carbon and energy sources. At various temperatures, pHs, and chlorinities, its growth rates and cell yields co-varied while GE remained uniform at 1.69x10(-11) J cell(-1)s(-1)+/- 0.68x10(-11) J cell(-1)s(-1) (s.d.
Keywords: HOV Alvin (Human Occupied Vehicle)

Low temperature geomicrobiology follows host rock composition along a geochemical gradient in Lau Basin - Sylvan, Jason B; Sia, Tiffany Y; Haddad, Amanda G; Briscoe, Lindsey J; Toner, Brandy M; Girguis, Peter R; Edwards, Katrina J (FRONTIERS IN MICROBIOLOGY, 2013)
The East Lau Spreading Center (ELSC) and Valu Fa Ridge (VFR) comprise a ridge segment in the southwest Pacific Ocean where rapid transitions in the underlying mantle chemistry manifest themselves as gradients in seafloor rock geochemistry. We studied the geology and microbial diversity of three silicate rock samples and three inactive sulfide chimney samples collected, from north to south, at the vent fields Kilo Moana, ABE, Tui Malila, and Mariner. This is the first study of microbial populations on basaltic andesite, which was sampled at Mariner vent field. Silicate rock geochemistry exhibits clear latitudinal trends that are mirrored by changes in bacterial community composition. alpha-proteobacteria, epsilon-proteobacteria, and Bacteroidetes are most common on a silicate collected from Kilo Moana and their proportions decrease linearly on silicates collected further south. Conversely, a silicate from Mariner vent field hosts high proportions of a unique lineage of Chloroflexi unrelated ({<}90{%} sequence similarity) to previously recovered environmental clones or isolates, which decrease at ABE and are absent at Kilo Moana. The exteriors of inactive sulfide structures are dominated by lineages of sulfur oxidizing alpha-proteobacteria, gamma-proteobacteria, and epsilon-proteobacteria, while the interior of one chimney is dominated by putative sulfur-reducing delta-proteobacteria. A comparison of bacterial communities on inactive sulfides from this and previous studies reveals the presence of a clade of uncultured Bacteroidetes exclusive to sulfidic environments, and a high degree of heterogeneity in bacterial community composition from one sulfide structure to another. In light of the heterogeneous nature of bacterial communities observed here and in previous studies of both active and inactive hydrothermal sulfide structures, the presence of numerous niches may be detected on these structures in the future by finer scale sampling and analysis.
Keywords: ROV Jason (Remotely Operated Vehicle)

A low-relief shield volcano origin for the South Kaua\''\}i Swell} - Ito, Garrett; Garcia, Michael O; Smith, John R; Taylor, Brian; Flinders, Ashton; Jicha, Brian; Yamasaki, Seiko; Weis, Dominique; Swinnard, Lisa; Blay, Chuck (GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 2013)
The South Kauai Swell (SKS) is a 110 km x 80 km ovoid bathymetric feature that stands {>}2 km high and abuts the southern flank of the island of Kauai. The origin of the SKS was investigated using multibeam bathymetry and acoustic backscatter, gravity data, radiometric ages, and geochemistry of rock samples. Most of the SKS rock samples are tholeiitic in composition with ages of 3.9-5.4 Ma indicating they were derived from shield volcanism. The ages and compositions of the SKS rocks partially overlap with those of the nearby Niihau, Kauai and West Kaena volcano complexes. The SKS was originally described as a landslide; however, this interpretation is problematic given the ovoid shape of SKS, its relatively smooth, flat-to-convex surface, and the lack of an obvious source region that could accommodate what would be one of Earth's most voluminous (6 x 10(3) km(3)) landslides. The morphology, size, and the surrounding gravity anomaly are more consistent with the SKS being a low-relief shield volcano, which was partially covered with a small volume of landside debris from south Kauai and later with some secondary volcanic seamounts. A shield origin would imply that Hawaiian and possibly other hotspot shield volcanoes can take on a wider variety of forms than is commonly thought, ranging from tall island-building shields, to smaller edifices such as Kaena Ridge and Mahukona, to even lower-relief volcanoes represented by the SKS and possibly the South West Oahu Volcanic Field.
Keywords: ROV Jason (Remotely Operated Vehicle)

Metagenome reveals potential microbial degradation of hydrocarbon coupled with sulfate reduction in an oil-immersed chimney from Guaymas Basin - He, Ying; Xiao, Xiang; Wang, Fengping (FRONTIERS IN MICROBIOLOGY, 2013)
Deep-sea hydrothermal vent chimneys contain a high diversity of microorganisms, yet the metabolic activity and the ecological functions of the microbial communities remain largely unexplored. In this study, a metagenomic approach was applied to characterize the metabolic potential in a Guaymas hydrothermal vent chimney and to conduct comparative genomic analysis among a variety of environments with sequenced metagenomes. Complete clustering of functional gene categories with a comparative metagenomic approach showed that this Guaymas chimney metagenome was clustered most closely with a chimney metagenome from Juan de Fuca. All chimney samples were enriched with genes involved in recombination and repair, chemotaxis and flagellar assembly, highlighting their roles in coping with the fluctuating extreme deep-sea environments. A high proportion of transposases was observed in all the metagenomes from deep-sea chimneys, supporting the previous hypothesis that horizontal gene transfer may be common in the deep-sea vent chimney biosphere. In the Guaymas chimney metagenome, thermophilic sulfate reducing microorganisms including bacteria and archaea were found predominant, and genes coding for the degradation of refractory organic compounds such as cellulose, lipid, pullullan, as well as a few hydrocarbons including toluene, ethylbenzene and o-xylene were identified. Therefore, this oil-immersed chimney supported a thermophilic microbial community capable of oxidizing a range of hydrocarbons that served as electron donors for sulphate reduction under anaerobic conditions.
Keywords: HOV Alvin (Human Occupied Vehicle)

Metatranscriptomics reveal differences in in situ energy and nitrogen metabolism among hydrothermal vent snail symbionts - Sanders, J G; Beinart, R A; Stewart, F J; Delong, E F; Girguis, P R (ISME JOURNAL, 2013)
Despite the ubiquity of chemoautotrophic symbioses at hydrothermal vents, our understanding of the influence of environmental chemistry on symbiont metabolism is limited. Transcriptomic analyses are useful for linking physiological poise to environmental conditions, but recovering samples from the deep sea is challenging, as the long recovery times can change expression profiles before preservation. Here, we present a novel, in situ RNA sampling and preservation device, which we used to compare the symbiont metatranscriptomes associated with Alviniconcha, a genus of vent snail, in which specific host-symbiont combinations are predictably distributed across a regional geochemical gradient. Metatranscriptomes of these symbionts reveal key differences in energy and nitrogen metabolism relating to both environmental chemistry (that is, the relative expression of genes) and symbiont phylogeny (that is, the specific pathways employed). Unexpectedly, dramatic differences in expression of transposases and flagellar genes suggest that different symbiont types may also have distinct life histories. These data further our understanding of these symbionts' metabolic capabilities and their expression in situ, and suggest an important role for symbionts in mediating their hosts' interaction with regional-scale differences in geochemistry.
Keywords: ROV Jason (Remotely Operated Vehicle)