Methane-derived authigenic carbonates from modern and paleoseeps on the Cascadia margin: Mechanisms of formation and diagenetic signals - Joseph, C; Campbell, K A; Torres, M E; Martin, R A; Pohlman, J W; Riedel, M; Rose, K (Tracing Phanerozoic hydrocarbon seepage from local basins to the global Earth system, 2013)
Authigenic carbonate precipitation occurs within marine sediments where sulfate-dependent anaerobic methane oxidation occurs. Geochemical and isotopic analyses of authigenic carbonates are commonly used as indicators of carbon sources and environmental conditions present during carbonate formation, but burial diagenesis and recrystallization can overprint these signals. Plane polarized light (PPL) and cathodoluminescent (CL) petrography allows for detailed characterization of carbonate phases and their subsequent alteration. Petrographic, isotopic, and geochemical characteristics of modern offshore authigenic carbonates from central and northern Cascadia are compared with Oligocene–Pliocene fossil seep carbonates uplifted on the Olympic Peninsula. Coupled analyses show the value and complexity of separating primary vs. secondary signals with relevance to understanding fluid-burial history in methane seep provinces on tectonically active convergent margins. The modern, offshore, near-seafloor diagenetic environment (S. Hydrate Ridge and Barkley Canyon) is dominated by acicular and microcrystalline aragonite and high-Mg calcite (HMC, {>} 12 mol {%} Mg). PPL and CL data illustrate that aragonite and HMC phases recrystallize to intermediate-Mg calcite (IMC, 5–12 mol{%} Mg) during burial and diagenesis and eventually to low-Mg calcite (LMC, 18O attributable to elevated fluid temperatures during recrystallization.
Keywords: ROV Jason (Remotely Operated Vehicle)

Microbial diversity within basement fluids of the sediment-buried Juan de Fuca Ridge flank - Jungbluth, Sean P; Grote, Jana; Lin, Huei-Ting; Cowen, James P; Rappe, Michael S (ISME JOURNAL, 2013)
Despite its immense size, logistical and methodological constraints have largely limited microbiological investigations of the subseafloor basement biosphere. In this study, a unique sampling system was used to collect fluids from the subseafloor basaltic crust via a Circulation Obviation Retrofit Kit (CORK) observatory at Integrated Ocean Drilling Program borehole 1301A, located at a depth of 2667 m in the Pacific Ocean on the eastern flank of the Juan de Fuca Ridge. Here, a fluid delivery line directly accesses a 3.5 million years old basalt-hosted basement aquifer, overlaid by 262 m of sediment, which serves as a barrier to direct exchange with bottom seawater. At an average of 1.2 x 10(4) cells ml(-1), microorganisms in borehole fluids were nearly an order of magnitude less abundant than in surrounding bottom seawater. Ribosomal RNA genes were characterized from basement fluids, providing the first snapshots of microbial community structure using a high-integrity fluid delivery line. Interestingly, microbial communities retrieved from different CORKs (1026B and 1301A) nearly a decade apart shared major community members, consistent with hydrogeological connectivity. However, over three sampling years, the dominant gene clone lineage changed from relatives of Candidatus Desulforudis audaxviator within the bacterial phylum Firmicutes in 2008 to the Miscellaneous Crenarchaeotic Group in 2009 and a lineage within the JTB35 group of Gammaproteobacteria in 2010, and statistically significant variation in microbial community structure was observed. The enumeration of different phylogenetic groups of cells within borehole 1301A fluids supported our observation that the deep subsurface microbial community was temporally dynamic. The ISME Journal (2013) 7, 161-172; doi:10.1038/ismej.2012.73; published online 12 July 2012
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Microbial habitat connec ivity across spatial scales and hydrothermal temperature gradients at Guaymas Basin - Meyer, Stefanie; Wegener, Gunter; Lloyd, Karen G; Teske, Andreas; Boetius, Antje; Ramette, Alban (FRONTIERS IN MICROBIOLOGY, 2013)
The Guaymas Basin (Gulf of California) hydrothermal vent area is known as a dynamic and hydrothermally vented sedimentary system, where the advection and production of a variety of different metabolic substrates support a high microbial diversity and activity in the seafloor. The main objective of our study was to explore the role of temperature and other environmental factors on community diversity, such as the presence of microbial mats and seafloor bathymetry within one hydrothermally vented field of 200 x 250 m dimension. In this field, temperature increased strongly with sediment depth reaching the known limit of life within a few decimeters. Potential sulfate reduction rate as a key community activity parameter was strongly affected by in situ temperature and sediment depth, declining from high rates of 1-5 jimol m1-1 d-1 at the surface to the detection limit below 5 cm sediment depth, despite the presence of sulfate and hydrocarbons. Automated Ribosomal lntergenic Spacer Analysis yielded a high-resolution fingerprint of the dominant members of the bacterial community. Our analyses showed strong temperature and sediment depth effects on bacterial cell abundance and Operational Taxonomic Units (OTUs) number, both declining by more than one order of magnitude below the top 5 cm of the sediment surface. Another fraction of the variation in diversity and community structure was explained by differences in the local bathymetry and spatial position within the vent field. Nevertheless, more than 80{%} of all detected OTUs were shared among the different temperature realms and sediment depths, after being classified as cold (T {<} 10 C), medium (10 C {<} T {<} 40 C) or hot (T {>} 40 C) temperature conditions, with significant OTU overlap with the richer surface communities. Overall, this indicates a high connectivity of benthic bacterial habitats in this dynamic and heterogeneous marine ecosystem influenced by strong hydrothermalism.
Keywords: HOV Alvin (Human Occupied Vehicle)

Microbiological characterization of post-eruption “snowblower” vents at Axial Seamount, Juan de Fuca Ridge - Meyer, J L; Akerman, N H; Proskurowski, G; Huber, J A (Frontiers in Microbiology, 2013)
Microbial processes within the subseafloor can be examined during the ephemeral and uncommonly observed phenomena known as snowblower venting. Snowblowers are characterized by the large quantity of white floc that is expelled from the seafloor following mid-ocean ridge eruptions. During these eruptions, rapidly cooling lava entrains seawater and hydrothermal fluids enriched in geochemical reactants, creating a natural bioreactor that supports a subseafloor microbial “bloom.” Previous studies hypothesized that the eruption-associated floc was made by sulfide-oxidizing bacteria; however, the microbes involved were never identified. Here we present the first molecular analysis combined with microscopy of microbial communities in snowblower vents from samples collected shortly after the 2011 eruption at Axial Seamount, an active volcano on the Juan de Fuca Ridge. We obtained fluid samples and white flocculent material from active snowblower vents as well as orange flocculent material found on top of newly formed lava flows. Both flocculent types revealed diverse cell types and particulates when examined by phase contrast and scanning electron microscopy (SEM). Distinct archaeal and bacterial communities were detected in each sample type through Illumina tag sequencing of 16S rRNA genes and through sequencing of the sulfide oxidation gene, soxB. In fluids and white floc, the dominant bacteria were sulfur-oxidizing Epsilonproteobacteria and the dominant archaea were thermophilic Methanococcales. In contrast, the dominant organisms in the orange floc were Gammaproteobacteria and Thaumarchaeota Marine Group I. In all samples, bacteria greatly outnumbered archaea. The presence of anaerobic methanogens and microaerobic Epsilonproteobacteria in snowblower communities provides evidence that these blooms are seeded by subseafloor microbes, rather than from microbes in bottom seawater. These eruptive events thus provide a unique opportunity to observe subseafloor microbial communities.
Keywords: ROV Jason (Remotely Operated Vehicle)

Morphology, microanatomy and sequence data of Sclerolinum contortum (Siboglindae, Annelida) of the Gulf of Mexico - Eichinger, Irmgard; Hourdez, Stephane; Bright, Monika (ORGANISMS DIVERSITY {&} EVOLUTION, 2013)
Sclerolinum is a small genus of Siboglinidae (Annelida) living in an obligate mutualistic association with thiotrophic bacteria as adults. Its taxonomic position, based on morphology, has been controversial; however, molecular data point to a sister taxa relationship with vestimentiferans. 16S rRNA gene sequencing and comparative morphology revealed that the studied population from deep-sea hydrocarbon seeps of the Gulf of Mexico belongs to Sclerolinum contortum known from the Arctic Sea. Since no anatomical and microanatomical studies have been published yet, we conducted such a study on S. contortum using serial sectioning and light and transmission electron microscopy. We show that the Sclerolinum body, divided into a head, trunk, and opisthosoma, is very similar to that of the vestimentiferans, and therefore we propose that the body regions are homologous in both taxa.
Keywords: ROV Jason (Remotely Operated Vehicle)

Mylonitic deformation at the Kane oceanic core complex: Implications for the rheological behavior of oceanic detachment faults - Hansen, L N; Cheadle, M J; John, B E; Swapp, S M; Dick, H J B; Tucholke, B E; Tivey, M A (Geochemistry, Geophysics, Geosystems, 2013)
The depth extent, strength, and composition of oceanic detachment faults remain poorly understood because the grade of deformation-related fabrics varies widely among sampled oceanic core complexes (OCCs). We address this issue by analyzing fault rocks collected from the Kane oceanic core complex at 23°30′N on the Mid-Atlantic Ridge. A portion of the sample suite was collected from a younger fault scarp that cuts the detachment surface and exposes the interior of the most prominent dome. The style of deformation was assessed as a function of proximity to the detachment surface, revealing a ∼450 m thick zone of high-temperature mylonitization overprinted by a ∼200 m thick zone of brittle deformation. Geothermometry of deformed gabbros demonstrates that crystal-plastic deformation occurred at temperatures {>}700°C. Analysis of the morphology of the complex in conjunction with recent thermochronology suggests that deformation initiated at depths of ∼7 km. Thus we suggest the detachment system extended into or below the brittle-plastic transition (BPT). Microstructural evidence suggests that gabbros and peridotites with high-temperature fabrics were dominantly deforming by dislocation-accommodated processes and diffusion creep. Recrystallized grain size piezometry yields differential stresses consistent with those predicted by dry-plagioclase flow laws. The temperature and stress at the BPT determined from laboratory-derived constitutive models agree well with the lowest temperatures and highest stresses estimated from gabbro mylonites. We suggest that the variation in abundance of mylonites among oceanic core complexes can be explained by variation in the depth of the BPT, which depends to a first order on the thermal structure and water content of newly forming oceanic lithosphere.
Keywords: AUV ABE (Autonomous Benthic Explorer); ROV Jason (Remotely Operated Vehicle)

New glass sponges (Porifera: Hexactinellida) from deep waters of the central Aleutian Islands, Alaska - Reiswig, H M; Stone, R P (Zootaxa, 2013)
Hexactinellida from deep-water communities of the central Aleutian Islands, Alaska, are described. They were mostly collected by the remotely operated vehicle 'Jason II' from 494–2311 m depths during a 2004 RV 'Roger Revelle' expedition, but one shallow-water species collected with a shrimp trawl from 155 m in the same area is included. The excellent condition of the ROV-collected specimens enabled valuable redescription of some species previously known only from badly damaged specimens. New taxa include one new genus and eight new species in five families. Farreidae consist of two new species, Farrea aleutiana and F. aspondyla. Euretidae consists of only Pinulasma fistulosum n. gen., n. sp. Tretodictyidae include only Tretodictyum amchitkensis n. sp. Euplectellidae consists of only the widespread species Regadrella okinoseana Ijima, reported here over 3,700 km from its closest previously known occurrence. The most diverse family, Rossellidae, consists of Aulosaccus ijimai (Schulze), Aulosaccus schulzei Ijima, Bathydorus sp. (young stage not determinable to species), Caulophacus (Caulophacus) adakensis n. sp., Acanthascus koltuni n. sp., Staurocalyptus psilosus n. sp., Staurocalyptus tylotus n. sp. and Rhabdocalyptus mirabilis Schulze. We present argument for reinstatement of the abolished rossellid subfamily Acanthascinae and return of the subgenera Staurocalyptus Ijima and Rhabdocalyptus Schulze to their previous generic status. These fauna provides important complexity to the hard substrate communities that likely serve as nursery areas for the young stages of commercially important fish and crab species, refuge from predation for both young and adult stages, and also as a focal source of prey for juvenile and adult stages of those same species.
Keywords: ROV Jason (Remotely Operated Vehicle)

A new species of Lebbeus (Crustacea: Decapoda: Caridea: Hippolytidae) from the Von Damm Vent Field, Caribbean Sea - Nye, Verity; Copley, J; Plouviez, S; Van Dover, C L (Journal of the Marine Biological Association of the United Kingdom, 2013)
A new species of the hippolytid shrimp genus Lebbeus White, 1847 is described from the Von Damm Vent Field (VDVF) on the Mid-Cayman Spreading Centre, Caribbean Sea, at 2294 m water depth. Lebbeus virentova sp. nov. is defined and illustrated from seven specimens, with brief notes on its distribution and habitat. Molecular phylogenetic data from the COI mDNA region are used to analyse the species' phylogenetic position, and its morphology is compared with previously described species. This new species represents the second family of caridean shrimp to be reported from the VDVF. Lebbeus virentova sp. nov. is the eighth member of the genus to be described from hydrothermal vents and appears to be the first hippolytid shrimp at a vent field known from outside the Pacific Ocean.
Keywords: ROV Jason (Remotely Operated Vehicle)

Niche divergence by deep-sea octocorals in the genus Callogorgia across the continental slope of the Gulf of Mexico - Quattrini, Andrea M; Georgian, Samuel E; Byrnes, Luke; Stevens, Alex; Falco, Rosalia; Cordes, Erik E (MOLECULAR ECOLOGY, 2013)
Environmental variables that are correlated with depth have been suggested to be among the major forces underlying speciation in the deep sea. This study incorporated phylogenetics and ecological niche models (ENM) to examine whether congeneric species of Callogorgia (Octocorallia: Primnoidae) occupy different ecological niches across the continental slope of the Gulf of Mexico (GoM) and whether this niche divergence could be important in the evolution of these closely related species. Callogorgia americana americana, Callogorgia americana delta and Callogorgia gracilis were documented at 13 sites in the GoM (250-1000 m) from specimen collections and extensive video observations. On a first order, these species were separated by depth, with C. gracilis occurring at the shallowest sites, C. a. americana at mid-depths and C. a. delta at the deepest sites. Callogorgia a. delta was associated with areas of increased seep activity, whereas C. gracilis and C. a. americana were associated with narrow, yet warmer, temperature ranges and did not occur near cold seeps. ENM background and identity tests revealed little to no overlap in ecological niches between species. Temporal calibration of the phylogeny revealed the formation of the Isthmus of Panama was a vicariance event that may explain some of the patterns of speciation within this genus. These results elucidate the potential mechanisms for speciation in the deep sea, emphasizing both bathymetric speciation and vicariance events in the evolution of a genus across multiple regions.
Keywords: ROV Jason (Remotely Operated Vehicle)

Persistent effects of disturbance on larval patterns in the plankton after an eruption on the East Pacific Rise - Mills, S W; Mullineaux, L S; Beaulieu, S E; Adams, D K (Marine Ecology Progress Series, 2013)
To predict how benthic communities will respond to disturbance, it is necessary to understand how disturbance affects the planktonic larval supply available to recolonize the area. Deep-sea hydrothermal vent fauna along the East Pacific Rise (EPR) experience frequent local extinctions due to tectonic and magmatic events, but the effects on regional larval abundance and diversity are unknown. We had been monitoring larvae at 9°50'N on the EPR prior to the 2006 eruption and were able to resume collections shortly afterward. We found that many species that were common before the eruption became significantly less so afterward, whereas a few other species experienced a transient spike in abundance. Surprisingly, overall species richness in the plankton was high 9 mo after the eruption, but then decreased sharply after 1 yr and had not returned to pre-eruption levels after 2 yr. These results suggest that recovery from disturbance may continue to be affected by limited larval supply even several years after a disturbance event. This delay in recovery means that larvae of pioneer species may dominate potential colonists, even after benthic habitats have transitioned to conditions that favor later-successional species. Moreover, the combined effects of natural and anthropogenic disturbance (e.g. mining) would be likely to cause more profound and long-lasting changes than either event alone. Our results indicate that we do not have sufficient data to predict the timing of recovery after disturbance in the deep sea, even in a well-studied vent system.
Keywords: HOV Alvin (Human Occupied Vehicle)

Phylogenetic diversity and functional gene patterns of sulfur-oxidizing subseafloor Epsilonproteobacteria in diffuse hydrothermal vent fluids - Akerman, Nancy H; Butterfield, David A; Huber, Julie A (FRONTIERS IN MICROBIOLOGY, 2013)
Microorganisms throughout the dark ocean use reduced sulfur compounds for chemolithoautotrophy. In many deep-sea hydrothermal vents, sulfide oxidation is quantitatively the most important chemical energy source for microbial metabolism both at and beneath the seafloor. In this study, the presence and activity of vent endemic Epsilonproteobacteria was examined in six low-temperature diffuse vents over a range of geochemical gradients from Axial Seamount, a deep-sea volcano in the Northeast Pacific. PCR primers were developed and applied to target the sulfur oxidation soxB gene of Epsilonproteobacteria. soxB genes belonging to the genera Sulfurimonas and Sulfurovum are both present and expressed at most diffuse vent sites, but not in background seawater. Although Sulfurovum-like sox8 genes were detected in all fluid samples, the RNA profiles were nearly identical among the vents and suggest that Sulfurirnonas-like species are the primary Epsilonproteobacteria responsible for actively oxidizing sulfur via the Sox pathway at each vent. Community patterns of subseafloor Epsdonproteobactena 16S rRNA genes were best matched to methane concentrations in vent fluids, as well as individual vent locations, indicating that both geochemistry and geographical isolation play a role in structuring subseafloor microbial populations. The data show that in the subseafloor at Axial Seamount, Epsilonproteobacteria are expressing the soxB gene and that microbial patterns in community distribution are linked to both vent location and chemistry.
Keywords: ROV Jason (Remotely Operated Vehicle)

Population ecology of the tonguefish Symphurus thermophilus (Pisces; Pleuronectiformes; Cynoglossidae) at sulphur-rich hydrothermal vents on volcanoes of the northern Mariana Arc - Tunnicliffe, V; Tyler, J; Dower, J F (Deep-Sea Research. Part II: Topical Studies in Oceanography, 2013)
Flatfish are a major component of the hydrothermal vent community on three seamounts of the northern Mariana Volcanic Arc in the northwest Pacific. Nikko, Kasuga-2 and Daikoku seamounts host vent fields between 375 and 480 m depth where high temperature vents release molten sulphur. The small cynoglossid tonguefish, Symphurus thermophilus Munroe and Hashimoto, is ubiquitous in all vent habitats observed on these seamounts: among extensive fields of tubeworms and mussels and on solid sulphur surfaces on Nikko; on sulphur-rich sediments and barnacle-covered boulders on Kasuga-2; and on recent sulphur flows and on broad areas of loose and semi-consolidated sediments on Daikoku. We recorded repeated forays by individuals onto flows of molten sulphur as these surfaces cooled. Based on observations using ROVs, the mean density is 90 fish/m2 with maximum counts over 200 fish/m2 on Daikoku sediments. Compared to collected tonguefish from Daikoku and Kasuga-2, those from Nikko have significantly greater lengths and, on average, six times the mass. Otolith data indicate upper ages of 13 years with Nikko tonguefish growing significantly faster. Diets of tonguefish on the three seamounts reflect the different habitats and prey availability; in Daikoku specimens, small crustaceans and polychaetes are most common while on Nikko, gut contents are predominantly larger shrimp. We made the unusual observation of stunned midwater fish falling to the seafloor near the vents where S. thermophilus immediately attacked them. This tonguefish has a wide diet range and foraging behaviour that likely influence the differing growth rates and sizes of fish inhabiting the different vent sites. Limited genetic data suggest that larval exchange probably occurs among sites where the common habitat factor is high levels of elemental sulphur forming hard and partly unconsolidated substrata. Here, in the northern range of the Mariana Trench Marine National Monument, S. thermophilus, despite having an unusually broad habitat association, may be restricted in its overall range to this region of isolated volcanoes with active hydrothermalism.
Keywords: ROV Jason (Remotely Operated Vehicle)

Rare earth element geochemistry in cold-seep pore waters of Hydrate Ridge, northeast Pacific Ocean - Himmler, Tobias; Haley, Brian A; Torres, Marta E; Klinkhammer, Gary P; Bohrmann, Gerhard; Peckmann, Joern (GEO-MARINE LETTERS, 2013)
The concentrations of rare earth elements (REEs), sulphate, hydrogen sulphide, total alkalinity, calcium, magnesium and phosphate were measured in shallow ({<} 12 cm below seafloor) pore waters from cold-seep sediments on the northern and southern summits of Hydrate Ridge, offshore Oregon. Downward-decreasing sulphate and coevally increasing sulphide concentrations reveal sulphate reduction as dominant early diagenetic process from similar to 2 cm depth downwards. A strong increase of total dissolved REE (aREE) concentrations is evident immediately below the sediment-water interface, which can be related to early diagenetic release of REEs into pore water resulting from the re-mineralization of particulate organic matter. The highest pore water aREE concentrations were measured close to the sediment-water interface at similar to 2 cm depth. Distinct shale-normalized REE patterns point to particulate organic matter and iron oxides as main REE sources in the upper similar to 2-cm depth interval. In general, the pore waters have shale-normalized patterns reflecting heavy REE (HREE) enrichment, which suggests preferential complexation of HREEs with carbonate ions. Below similar to 2 cm depth, a downward decrease in aREE correlates with a decrease in pore water calcium concentrations. At this depth, the anaerobic oxidation of methane (AOM) coupled to sulphate reduction increases carbonate alkalinity through the production of bicarbonate, which results in the precipitation of carbonate minerals. It seems therefore likely that the REEs and calcium are consumed during vast AOM-induced precipitation of carbonate in shallow Hydrate Ridge sediments. The analysis of pore waters from Hydrate Ridge shed new light on early diagenetic processes at cold seeps, corroborating the great potential of REEs to identify geochemical processes and to constrain environmental conditions.
Keywords: HOV Alvin (Human Occupied Vehicle)

Reconstructing lava flow emplacement processes at the hot spot-affected Galapagos Spreading Center, 95 degrees W and 92 degrees W - McClinton, Tim; White, Scott M; Colman, Alice; Sinton, John M (GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 2013)
Volcanic eruptions at mid-ocean ridges (MORs) control the permeability, internal structure, and architecture of oceanic crust, thus establishing the foundation for the evolution of the ocean basins. To better understand the emplacement of submarine lava flows at MORs, we have integrated submersible-based geologic mapping with remote sensing techniques to characterize the lava flow morphology within previously mapped lava flow fields produced during single eruptive episodes at the Galapagos Spreading Center (GSC). Detailed attributes describing the surface geometry and texture of the lava flows have been extracted from high-resolution sonar data and combined with georeferenced visual observations from submersible dives and camera tows; based on signatures contained in these data, a fuzzy logic-based classification algorithm categorized lava flow morphology as pillows, lobates, or sheets. The resulting digital thematic maps offer an unprecedented view of GSC lava morphology, collectively covering 77 km(2) of ridge axis terrain at a resolution of 2 m x 2 m. Error assessments with independent visual reference data indicate approximately 90{%} agreement, comparable to subaerial classification studies. The digital lava morphology maps enable quantitative, spatially comprehensive measurements of the abundance and distribution of lava morphologies over large areas of seafloor and within individual eruptive units. A comparison of lava flow fields mapped at lower- and higher-magma-supply settings (95 degrees and 92 degrees W, respectively) indicates that effusion rates increase along with magma supply and independent of spreading rate at the GSC, although a complete range of eruptive behavior exists at each setting.
Keywords: HOV Alvin (Human Occupied Vehicle)

Sill to surface: Linking young off-axis volcanism with subsurface melt at the overlapping spreading center at 9°03′N East Pacific Rise - Waters, C L; Sims, K W W; Klein, E M; White, S M; Reagan, M K; Girard, G (Earth and Planetary Science Letters, 2013)
No young, off-axis, mid-ocean ridge lavas have yet been directly linked to underlying off-axis melt bodies. In this study, we present new measurements of 238U–230Th–226Ra–210Pb isotope compositions for a suite of lavas from the overlapping spreading center (OSC) at 9°03′N on the East Pacific Rise (EPR). These lavas span a large range of compositions, from basalt to dacite, and include both axial and off-axis samples recovered from a prominent, axis-parallel pillow ridge and a flat-topped seamount that overlie the westernmost extent of a 4-km-wide melt lens (Kent et al., 2000). We report 210Pb excesses in axial basalts and basaltic andesites, which we suggest results from gas-magma fractionation of 222Rn from 226Ra beneath dacite magmas. In addition, our U-series ages agree with visual observations, indicating that while most recent volcanic activity occurs at the spreading axis, active volcanism also occurs away from the axis. Specifically, the off-axis pillow ridge and seamount samples overlying the off-axis subsurface melt body have eruption ages of less than 8 ka, and likely as young as 1 ka, despite being located on crust that has a spreading age of {\~{}}75 ka. The young ages of these lavas, combined with existing geological, geochemical and geophysical constraints, provide evidence for a genetic link between the pillow ridge and seamount lavas and the seismically imaged, underlying off-axis melt lens. This link demonstrates that off-axis volcanism does not necessarily come from a sub-axial magma body and can be sourced directly from off-axis magma bodies.
Keywords: ROV Jason (Remotely Operated Vehicle)

Sulfide geochronology along the Endeavour Segment of the Juan de Fuca Ridge - Jamieson, J W; Hannington, M D; Clague, D A; Kelley, D S; Delaney, J R; Holden, J F; Tivey, M K; Kimpe, L E (Geochemistry, Geophysics, Geosystems, 2013)
Forty-nine hydrothermal sulfide-sulfate rock samples from the Endeavour Segment of the Juan de Fuca Ridge, northeastern Pacific Ocean, were dated by measuring the decay of 226Ra (half-life of 1600 years) in hydrothermal barite to provide a history of hydrothermal venting at the site over the past 6000 years. This dating method is effective for samples ranging in age from ∼200 to 20,000 years old and effectively bridges an age gap between shorter- and longer-lived U-series dating techniques for hydrothermal deposits. Results show that hydrothermal venting at the active High Rise, Sasquatch, and Main Endeavour fields began at least 850, 1450, and 2300 years ago, respectively. Barite ages of other inactive deposits on the axial valley floor are between ∼1200 and ∼2200 years old, indicating past widespread hydrothermal venting outside of the currently active vent fields. Samples from the half-graben on the eastern slope of the axial valley range in age from ∼1700 to ∼2925 years, and a single sample from outside the axial valley, near the westernmost valley fault scarp is ∼5850 ± 205 years old. The spatial relationship between hydrothermal venting and normal faulting suggests a temporal relationship, with progressive younging of sulfide deposits from the edges of the axial valley toward the center of the rift. These relationships are consistent with the inward migration of normal faulting toward the center of the valley over time and a minimum age of onset of hydrothermal activity in this region of 5850 years.
Keywords: HOV Alvin (Human Occupied Vehicle)

Sulfide oxidation, nitrate respiration, carbon acquisition, and electron transport pathways suggested by the draft genome of a single orange Guaymas Basin Beggiatoa (Cand. Maribeggiatoa) sp filament - MacGregor, Barbara J; Biddle, Jennifer F; Harbort, Christopher; Matthysse, Ann G; Teske, Andreas (MARINE GENOMICS, 2013)
A near-complete draft genome has been obtained for a single vacuolated orange Beggiatoa (Cand. Maribeggiatoa) filament from a Guaymas Basin seafloor microbial mat, the third relatively complete sequence for the Beggiatoaceae. Possible pathways for sulfide oxidation; nitrate respiration; inorganic carbon fixation by both Type II RuBisCO and the reductive tricarboxylic add cycle; acetate and possibly formate uptake; and energy-generating electron transport via both oxidative phosphorylation and the Rnf complex are discussed here. A role in nitrite reduction is suggested for an abundant orange cytochrome produced by the Guaymas strain; this has a possible homolog in Beggiatoa (Cand. Isobeggiatoa) sp. PS, isolated from marine harbor sediment, but not Beggiatoa alba B18LD, isolated from a freshwater rice field ditch. Inferred phylogenies for the Calvin-Benson-Bassham (CBB) cycle and the reductive (rTCA) and oxidative (TCA) tricarboxylic acid cycles suggest that genes encoding succinate dehydrogenase and enzymes for carboxylation and/or decarboxylation steps (including RuBisCO) may have been introduced to (or exported from) one or more of the three genomes by horizontal transfer, sometimes by different routes. Sequences from the two marine strains are generally more similar to each other than to sequences from the freshwater strain, except in the case of RuBisCO: only the Guaymas strain encodes a Type H enzyme, which (where studied) discriminates less against oxygen than do Type I RuBisCOs. Genes subject to horizontal transfer may represent key steps for adaptation to factors such as oxygen and carbon dioxide concentration, organic carbon availability, and environmental variability. (C) 2013 Elsevier B.V. All rights reserved.
Keywords: HOV Alvin (Human Occupied Vehicle)

Surficial permeability of the axial valley seafloor: Endeavour Segment, Juan de Fuca Ridge - Hearn, Casey K; Homola, Kira L; Johnson, H Paul (GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 2013)
Hydrothermal systems at mid-ocean spreading centers play a fundamental role in Earth's geothermal budget. One underexamined facet of marine hydrothermal systems is the role that permeability of the uppermost seafloor veneer plays in the distribution of hydrothermal fluid. As both the initial and final vertical gateway for subsurface fluid circulation, uppermost seafloor permeability may influence the local spatial distribution of hydrothermal flow. A method of deriving a photomosaic from seafloor video was developed and utilized to estimate relative surface permeability in an active hydrothermal area on the Endeavour Segment of the Juan de Fuca Ridge. The mosaic resolves seafloor geology of the axial valley seafloor at submeter resolution over an area greater than 1 km(2). Results indicate that the valley walls and basal talus slope are topographically rugged and unsedimented, providing minimal resistance to fluid transmission. Elsewhere, the axial valley floor is capped by an unbroken blanket of low-permeability sediment, resisting fluid exchange with the subsurface reservoir. Active fluid emission sites were restricted to the high-permeability zone at the base of the western wall. A series of inactive fossil hydrothermal structures form a linear trend along the western bounding wall, oriented orthogonal to the spreading axis. High-temperature vent locations appear to have migrated over 100 m along-ridge-strike over the decade between surveys. While initially an expression of subsurface faulting, this spatial pattern suggests that increases in seafloor permeability from sedimentation may be at least a secondary contributing factor in regulating fluid flow across the seafloor interface.
Keywords: ROV Jason (Remotely Operated Vehicle)

Sustained volcanically-hosted venting at ultraslow ridges: Piccard Hydrothermal Field, Mid-Cayman Rise - Kinsey, J C; German, C R (Earth and Planetary Science Letters, 2013)
At slow spreading mid-ocean ridges sustained submarine venting and the deposition of large seafloor massive sulfide deposits have previously been ascribed to tectonically-controlled hydrothermal circulation unrelated to young volcanic activity. Here, by contrast, we show that the Piccard Hydrothermal Field (PHF), on the ultraslow spreading Mid-Cayman Rise, represents a site of sustained fluid flow and sulfide formation hosted in a neovolcanic setting. The lateral extent and apparent longevity associated with the PHF are comparable to some of the largest tectonically-hosted vent sites known along the slow-spreading Mid-Atlantic Ridge. If such systems recur along all ultraslow ridges, which comprise ∼20{%} of the ∼55,000 km global ridge crest, potential implications would include (i) a higher probability of locating large, economically valuable, mineral deposits along ultraslow ridges together with (ii) larger fluxes than previously anticipated of chemicals released from high-temperature venting entering the oceans along the Atlantic–Indian Ocean sectors of the deep-ocean thermohaline conveyor.
Keywords: ROV Jason (Remotely Operated Vehicle)

Temporal trends in vent fluid iron and sulfide chemistry following the 2005/2006 eruption at East Pacific Rise, 9 degrees 50 ' N - Yuecel, M; Luther, G W (Geochemistry, Geophysics, Geosystems, 2013)
The chemistry of vent fluids that emanate to the seafloor undergoes dramatic changes after volcanic eruptions. Data on these changes are still limited, but the best studied example is the East Pacific Rise (EPR) at 9°50′N, where the temporal evolution of the vent fluid chemistry after the 1991/1992 eruption was documented. The area underwent another eruption sequence during late 2005/early 2006, and here we show that a similar evolution is recurring in the iron and sulfide contents of the high-temperature fluids sampled in June 2006, January 2007, and June 2008. The vents have had increasing dissolved iron and decreasing acid-volatile sulfide (free sulfide plus FeS) concentrations with 1 order of magnitude variation. In addition, chromium reducible sulfide (mainly pyrite) also had fivefold decreasing concentrations over the 3 years. Our results confirm a pattern that was noted only once before for 9°50′N EPR and emphasize the dramatic yearly variability in the concentrations of iron-sulfur species emanating from vents.
Keywords: HOV Alvin (Human Occupied Vehicle)

Trophic regions of a hydrothermal plume dispersing away from an ultramafic-hosted vent-system: Von Damm vent-site, Mid-Cayman Rise - Bennett, S A; Coleman, Max; Huber, J A; Reddington, E; Kinsey, J C; McIntyre, C; Seewald, J S; German, C R (Geochemistry, Geophysics, Geosystems, 2013)
Deep-sea ultramafic-hosted vent systems have the potential to provide large amounts of metabolic energy to both autotrophic and heterotrophic microorganisms in their dispersing hydrothermal plumes. Such vent-systems release large quantities of hydrogen and methane to the water column, both of which can be exploited by autotrophic microorganisms. Carbon cycling in these hydrothermal plumes may, therefore, have an important influence on open-ocean biogeochemistry. In this study, we investigated an ultramafic-hosted system on the Mid-Cayman Rise, emitting metal-poor and hydrogen sulfide-, methane-, and hydrogen-rich hydrothermal fluids. Total organic carbon concentrations in the plume ranged between 42.1 and 51.1 $μ$M (background = 43.2 ± 0.7 $μ$M (n = 5)) and near-field plume samples with elevated methane concentrations imply the presence of chemoautotrophic primary production and in particular methanotrophy. In parts of the plume characterized by persistent potential temperature anomalies but lacking elevated methane concentrations, we found elevated organic carbon concentrations of up to 51.1 $μ$M, most likely resulting from the presence of heterotrophic communities, their extracellular products and vent larvae. Elevated carbon concentrations up to 47.4 $μ$M were detected even in far-field plume samples. Within the Von Damm hydrothermal plume, we have used our data to hypothesize a microbial food web in which chemoautotrophy supports a heterotrophic community of microorganisms. Such an active microbial food web would provide a source of labile organic carbon to the deep ocean that should be considered in any future studies evaluating sources and sinks of carbon from hydrothermal venting to the deep ocean.
Keywords: ROV Jason (Remotely Operated Vehicle)

On the utility of radium isotopes as tracers of hydrocarbon discharge - Peterson, R N; Viso, R F; MacDonald, I R; Joye, S B (Marine Chemistry, 2013)
Natural seepage of hydrocarbons commonly occurs in the Gulf of Mexico and numerous other locations around the world's oceans. In-situ quantification of discharge and transport of these hydrocarbons through the water column is somewhat limited by a lack of available tracers. Here, we consider the utility of using radium isotopes, which are commonly enriched in formation fluids contained within hydrocarbon reservoirs, as tracers of hydrocarbons discharged into the deep ocean. During a cruise in November/December 2010 through the Gulf of Mexico, radium isotopes (224Ra and 226Ra) revealed anomalous concentrations in near-bottom samples associated with the presence of hydrocarbons at several sites where hydrocarbon seepage was known to occur and observed real-time via the human-occupied vehicle Alvin. These tracers also indicated the presence of near-bottom hydrocarbons in the vicinity of the Macondo wellhead where the Deepwater Horizon blowout occurred months earlier. These hydrocarbons are presumed to originate from nearby gas seeps later identified by water column sonar returns. The short half-life of 224Ra (3.66 days) suggests that anomalously high unsupported activities of this isotope must be derived from recent (days to weeks) discharge. Sampling at the sediment–water interface confirmed that the source of the water column radium isotope anomalies is likely benthic sources. These results suggest that radium isotopes may serve as useful tracers of hydrocarbons in such an environment, and we outline steps required to quantify discharge rates and transport time scales with these tracers.
Keywords: HOV Alvin (Human Occupied Vehicle)

Waning magmatic activity along the Southern Explorer Ridge revealed through fault restoration of rift topography - Deschamps, A; Tivey, M A; Chadwick, W W; Embley, R W (Geochemistry, Geophysics, Geosystems, 2013)
We combine high-resolution bathymetry acquired using the Autonomous Underwater Vehicle ABE with digital seafloor imagery collected using the remotely operated vehicle ROPOS across the axial valley of the Southern Explorer Ridge (SER) to infer the recent volcanic and tectonic processes. The SER is an intermediate spreading ridge located in the northeast Pacific. It hosts the Magic Mountain hydrothermal vent. We reconstruct the unfaulted seafloor terrain at SER based on calculations of the vertical displacement field and fault parameters. The vertical changes between the initial and the restored topographies reflect the integrated effects of volcanism and tectonism on relief-forming processes over the last 11,000–14,000 years. The restored topography indicates that the axial morphology evolved from a smooth constructional dome {>}500 m in diameter, to a fault-bounded graben, {\~{}}500 m wide and 30–70 m deep. This evolution has been accompanied by changes in eruptive rate, with deposition of voluminous lobate and sheet flows when the SER had a domed morphology, and limited-extent low-effusion rate pillow eruptions during graben development. Most of the faults shaping the present axial valley postdate the construction of the dome. Our study supports a model of cyclic volcanism at the SER with periods of effusive eruptions flooding the axial rift, centered on the broad plateau at the summit of the ridge, followed by a decrease in eruptive activity and a subsequent dominance of tectonic processes, with minor low-effusion rate eruptions confined to the axial graben. The asymmetric shape of the axial graben supports an increasing role of extensional processes, with a component of simple shear in the spreading processes.
Keywords: AUV ABE (Autonomous Benthic Explorer)

Why Orange Guaymas Basin Beggiatoa spp. Are Orange: Single-Filament-Genome-Enabled Identification of an Abundant Octaheme Cytochrome with Hydroxylamine Oxidase, Hydrazine Oxidase, and Nitrite Reductase Activities - MacGregor, Barbara J; Biddle, Jennifer F; Siebert, Jason R; Staunton, Eric; Hegg, Eric L; Matthysse, Ann G; Teske, Andreas (APPLIED AND ENVIRONMENTAL MICROBIOLOGY, 2013)
Orange, white, and yellow vacuolated Beggiatoaceae filaments are visually dominant members of microbial mats found near sea floor hydrothermal vents and cold seeps, with orange filaments typically concentrated toward the mat centers. No marine vacuolate Beggiatoaceae are yet in pure culture, but evidence to date suggests they are nitrate-reducing, sulfide-oxidizing bacteria. The nearly complete genome sequence of a single orange Beggiatoa ({\{}''{\}}Candidatus Maribeggiatoa{\{}''{\}}) filament from a microbial mat sample collected in 2008 at a hydrothermal site in Guaymas Basin (Gulf of California, Mexico) was recently obtained. From this sequence, the gene encoding an abundant soluble orange-pigmented protein in Guaymas Basin mat samples (collected in 2009) was identified by microcapillary reverse-phase high-performance liquid chromatography (HPLC) nano-electrospray tandem mass spectrometry (mu LC-MS-MS) of a pigmented band excised from a denaturing polyacrylamide gel. The predicted protein sequence is related to a large group of octaheme cytochromes whose few characterized representatives are hydroxylamine or hydrazine oxidases. The protein was partially purified and shown by in vitro assays to have hydroxylamine oxidase, hydrazine oxidase, and nitrite reductase activities. From what is known of Beggiatoaceae physiology, nitrite reduction is the most likely in vivo role of the octaheme protein, but future experiments are required to confirm this tentative conclusion. Thus, while present-day genomic and proteomic techniques have allowed precise identification of an abundant mat protein, and its potential activities could be assayed, proof of its physiological role remains elusive in the absence of a pure culture that can be genetically manipulated.
Keywords: HOV Alvin (Human Occupied Vehicle)

Adaptive radiation in extremophilic Dorvilleidae (Annelida): diversification of a single colonizer or multiple independent lineages? - Thornhill, D J; Struck, T H; Ebbe, B; Lee, R W; Mendoza, G F; Levin, L A; Halanych, K M (Ecology and Evolution, 2012)
Metazoan inhabitants of extreme environments typically evolved from forms found in less extreme habitats. Understanding the prevalence with which animals move into and ultimately thrive in extreme environments is critical to elucidating how complex life adapts to extreme conditions. Methane seep sediments along the Oregon and California margins have low oxygen and very high hydrogen sulfide levels, rendering them inhospitable to many life forms. Nonetheless, several closely related lineages of dorvilleid annelids, including members of Ophryotrocha, Parougia, and Exallopus, thrive at these sites in association with bacterial mats and vesicomyid clam beds. These organisms are ideal for examining adaptive radiations in extreme environments. Did dorvilleid annelids invade these extreme environments once and then diversify? Alternatively, did multiple independent lineages adapt to seep conditions? To address these questions, we examined the evolutionary history of methane-seep dorvilleids using 16S and Cyt b genes in an ecological context. Our results indicate that dorvilleids invaded these extreme habitats at least four times, implying preadaptation to life at seeps. Additionally, we recovered considerably more dorvilleid diversity than is currently recognized. A total of 3 major clades (designated “ Ophryotrocha,” “Mixed Genera” and “ Parougia”) and 12 terminal lineages or species were encountered. Two of these lineages represented a known species, Parougia oregonensis, whereas the remaining 10 lineages were newly discovered species. Certain lineages exhibited affinity to geography, habitat, sediment depth, and/or diet, suggesting that dorvilleids at methane seeps radiated via specialization and resource partitioning.
Keywords: HOV Alvin (Human Occupied Vehicle)

Advanced instrument system for real-time and time-series microbial geochemical sampling of the deep (basaltic) crustal biosphere - Cowen, J P; Copson, D A; Jolly, J; Hsieh, C -C; Lin, H -T; Glazer, B T; Wheat, C G (Deep-Sea Research. Part I: Oceanographic Research Papers, 2012)
Integrated Ocean Drilling Program borehole CORK (Circulation Obviation Retrofit Kit) observatories provide long-term access to hydrothermal fluids circulating within the basaltic crust (basement), providing invaluable opportunities to study the deep biosphere. We describe the design and application parameters of the GeoMICROBE instrumented sled, an autonomous sensor and fluid sampling system. The GeoMICROBE system couples with CORK fluid delivery lines to draw large volumes of fluids from crustal aquifers to the seafloor. These fluids pass a series of in-line sensors and an in situ filtration and collection system. GeoMICROBE's major components include a primary valve manifold system, a positive displacement primary pump, sensors (e.g., fluid flow rate, temperature, dissolved O2, electrochemistry-voltammetry analyzer), a 48-port in situ filtration and fluid collection system, computerized controller, seven 24 V–40 A batteries and wet-mateable (ODI) communications with submersibles. This constantly evolving system has been successfully connected to IODP Hole 1301A on the eastern flank of the Juan de Fuca Ridge. Also described here is a mobile pumping system (MPS), which possesses many of the same components as the GeoMICROBE (e.g., pump, sensors, controller), but is directly powered and controlled in real time via submersible operations; the MPS has been employed repeatedly to collect pristine basement fluids for a variety of geochemical and microbial studies.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Alvin Submersible's New Sphere Passes Pressure Tests (Sea Technology, 2012)
Keywords: HOV Alvin (Human Occupied Vehicle)

Anaerobic methane oxidation in metalliferous hydrothermal sediments: influence on carbon flux and decoupling from sulfate reduction - Wankel, Scott D; Adams, Melissa M; Johnston, David T; Hansel, Colleen M; Joye, Samantha B; Girguis, Peter R (ENVIRONMENTAL MICROBIOLOGY, 2012)
The anaerobic oxidation of methane (AOM) is a globally significant sink that regulates methane flux from sediments into the oceans and atmosphere. Here we examine mesophilic to thermophilic AOM in hydrothermal sediments recovered from the Middle Valley vent field, on the Juan de Fuca Ridge. Using continuous-flow sediment bioreactors and batch incubations, we characterized (i) the degree to which AOM contributes to net dissolved inorganic carbon flux, (ii) AOM and sulfate reduction (SR) rates as a function of temperature and (iii) the distribution and density of known anaerobic methanotrophs (ANMEs). In sediment bioreactors, inorganic carbon stable isotope mass balances results indicated that AOM accounted for between 16{%} and 86{%} of the inorganic carbon produced, underscoring the role of AOM in governing inorganic carbon flux from these sediments. At 90 degrees C, AOM occurred in the absence of SR, demonstrating a striking decoupling of AOM from SR. An abundance of Fe(III)-bearing minerals resembling mixed valent Fe oxides, such as green rust, suggests the potential for a coupling of AOM to Fe(III) reduction in these metalliferous sediments. While SR bacteria were only observed in cooler temperature sediments, ANMEs allied to ANME-1 ribotypes, including a putative ANME-1c group, were found across all temperature regimes and represented a substantial proportion of the archaeal community. In concert, these results extend and reshape our understanding of the nature of high temperature methane biogeochemistry, providing insight into the physiology and ecology of thermophilic anaerobic methanotrophy and suggesting that AOM may play a central role in regulating biological dissolved inorganic carbon fluxes to the deep ocean from the organic-poor, metalliferous sediments of the global mid-ocean ridge hydrothermal vent system.
Keywords: HOV Alvin (Human Occupied Vehicle)

Anaerobic oxidation of methane at different temperature regimes in Guaymas Basin hydrothermal sediments - Biddle, Jennifer F; Cardman, Zena; Mendlovitz, Howard; Albert, Daniel B; Lloyd, Karen G; Boetius, Antje; Teske, Andreas (ISME JOURNAL, 2012)
Anaerobic oxidation of methane (AOM) was investigated in hydrothermal sediments of Guaymas Basin based on delta C-13 signatures of CH4, dissolved inorganic carbon and porewater concentration profiles of CH4 and sulfate. Cool, warm and hot in-situ temperature regimes (15-20 degrees C, 30-35 degrees C and 70-95 degrees C) were selected from hydrothermal locations in Guaymas Basin to compare AOM geochemistry and 16S ribosomal RNA (rRNA), mcrA and dsrAB genes of the microbial communities. 16S rRNA gene clone libraries from the cool and hot AOM cores yielded similar archaeal types such as Miscellaneous Crenarchaeotal Group, Thermoproteales and anaerobic methane-oxidizing archaea (ANME)-1; some of the ANME-1 archaea formed a separate 16S rRNA lineage that at present seems to be limited to Guaymas Basin. Congruent results were obtained by mcrA gene analysis. The warm AOM core, chemically distinct by lower porewater sulfide concentrations, hosted a different archaeal community dominated by the two deep subsurface archaeal lineages Marine Benthic Group D and Marine Benthic Group B, and by members of the Methanosarcinales including ANME-2 archaea. This distinct composition of the methane-cycling archaeal community in the warm AOM core was confirmed by mcrA gene analysis. Functional genes of sulfate-reducing bacteria and archaea, dsrAB, showed more overlap between all cores, regardless of the core temperature. 16S rRNA gene clone libraries with Euryarchaeota-specific primers detected members of the Archaeoglobus clade in the cool and hot cores. A V6-tag high-throughput sequencing survey generally supported the clone library results while providing high-resolution detail on archaeal and bacterial community structure. These results indicate that AOM and the responsible archaeal communities persist over a wide temperature range. The ISME Journal (2012) 6, 1018-1031; doi:10.1038/ismej.2011.164; published online 17 November 2011
Keywords: HOV Alvin (Human Occupied Vehicle)

Archaea in metazoan diets: implications for food webs and biogeochemical cycling - Thurber, A R; Levin, L A; Orphan, V J; Marlow, J J (ISME Journal, 2012)
Although the importance of trophic linkages, including ‘top-down forcing', on energy flow and ecosystem productivity is recognized, the influence of metazoan grazing on Archaea and the biogeochemical processes that they mediate is unknown. Here, we test if: (1) Archaea provide a food source sufficient to allow metazoan fauna to complete their life cycle; (2) neutral lipid biomarkers (including crocetane) can be used to identify Archaea consumers; and (3) archaeal aggregates are a dietary source for methane seep metazoans. In the laboratory, we demonstrated that a dorvilleid polychaete, Ophryotrocha labronica, can complete its life cycle on two strains of Euryarchaeota with the same growth rate as when fed bacterial and eukaryotic food. Archaea were therefore confirmed as a digestible and nutritious food source sufficient to sustain metazoan populations. Both strains of Euryarchaeota used as food sources had unique lipids that were not incorporated into O. labronica tissues. At methane seeps, sulfate-reducing bacteria that form aggregations and live syntrophically with anaerobic-methane oxidizing Archaea contain isotopically and structurally unique fatty acids (FAs). These biomarkers were incorporated into tissues of an endolithofaunal dorvilleid polychaete species from Costa Rica (mean bulk $δ$13C=−92±4‰; polar lipids −116‰) documenting consumption of archaeal-bacterial aggregates. FA composition of additional soft-sediment methane seep species from Oregon and California provided evidence that consumption of archaeal-bacterial aggregates is widespread at methane seeps. This work is the first to show that Archaea are consumed by heterotrophic metazoans, a trophic process we coin as ‘archivory'.
Keywords: HOV Alvin (Human Occupied Vehicle)

Ascomycete phylotypes recovered from a Gulf of Mexico methane seep are identical to an uncultured deep-sea fungal clade from the Pacific - Thaler, A D; Van Dover, C L; Vilgalys, R (Fungal Ecology, 2012)
Deep-sea endemic fungi are one component of an under-sampled invisible biosphere whose contribution to benthic ecosystems is not yet understood. In the last decade, molecular techniques have facilitated the discovery of several new deep-sea fungal groups, especially in habitats such as hydrothermal vents and methane seeps. We assessed fungal diversity at a methane seep in the Gulf of Mexico by sequencing partial ITS and LSU gene regions from environmental DNA recovered from microoxic and anoxic sediment. While most phylotypes were closely allied with common fungal species, the dominant phylotype did not match any known terrestrial species and aligned with an uncultured deep-sea fungus found in oxygen-depleted sediment at multiple sites in the Pacific Ocean. Despite its apparently broad distribution and frequent occurrence in oxygen-depleted sediment, the ecological role of this phylotype is not yet known. (C) 2011 Elsevier Ltd and The British Mycological Society. All rights reserved.

Chemistry, Temperature, and Faunal Distributions at Diffuse-Flow Hydrothermal Vents Comparison of Two Geologically Distinct Ridge Systems - Luther, G W; Gartman, A; Yuecel, M; Madison, A S; Moore, T S; Nees, H A; Nuzzio, D B; Sen, A; Lutz, R A; Shank, T M; Fisher, C R (Oceanography, 2012)
Diffuse-flow, low-temperature areas near hydrothermal vents support life via chemosynthesis: hydrogen sulfide (and other reduced chemical compounds) emanating from the subsurface is oxidized with bottom-water oxygen through bacterial mediation to fix carbon dioxide and produce biomass. This article reviews the in situ diffuse-flow chemistry (mainly H2S and O2) and temperature data collected in 2006 and 2009 along the Eastern Lau Spreading Center (ELSC), and from 2004 to 2008 at 9°N along the East Pacific Rise (9 N EPR), predominantly around macrofauna that contain endosymbionts at these two hydrothermal vent regions. More than 48,000 and 20,000 distinct chemical and temperature data points were collected with a multi-analyte electrochemical analyzer in the diffuse-flow waters at 9 N EPR and the ELSC, respectively. Despite their different geological settings and different macrofauna (two different species of snails and mussels at the ELSC versus two different species of tubeworms and mussels at 9 N EPR), there are similarities in the temperature and chemistry data, as well as in the distributions of organisms. The pattern of water chemistry preferred by the provannid snails (Alviniconcha spp., Ifremeria nautilei) and Bathymodiolus brevior at the ELSC is similar to the water chemistry pattern found for the siboglinid tubeworms (Tevnia jerichonana, Riftia pachyptila) and the Bathymodiolus thermophilus mussels at 9 N EPR. The eruptions at 9 N EPR in 2005 and 2006 resulted in increased H2S concentrations, increased H2S/T ratios, and an initial change in the dominant tubeworm species from Riftia pachyptila to Tevnia jerichonana after the eruption created new vent habitats. In 2005, two sites at 9 N EPR showed major increases in the H2S/T ratio from 2004, which suggested a probable eruption in this basalt-dominated system. At the ELSC, there was a decrease in the H2S/T ratio from northern to southern sites, which reflects the change in geological setting from basalt to andesite and the shallower water depths at the southern sites.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Chrysogorgia from the New England and Corner Seamounts: Atlantic-Pacific connections - Pante, Eric; Watling, Les (JOURNAL OF THE MARINE BIOLOGICAL ASSOCIATION OF THE UNITED KINGDOM, 2012)
Recent exploration of the New England and Corner Seamounts revealed four new species of Chrysogorgia, described here using a combination of molecular and morphological data. These four species are characterized by a sinistral spiral, a character that, with one known exception, has only been reported for Pacific species. In addition, two species have a sclerite composition typical of the Pacific ('squamosae typicae'). This faunal connection between the Atlantic and the Pacific is confirmed by analysis of the mitochondrial msh1 gene. The exceptional preservation of specimens collected with remotely operated vehicles allows us to discuss the effect of growth on some morphological characters.
Keywords: HOV Alvin (Human Occupied Vehicle)

CO2 variability in mid-ocean ridge basalts from syn-emplacement degassing: Constraints on eruption dynamics - Soule, S A; Nakata, D S; Fornari, D J; Fundis, A T; Perfit, M R; Kurz, M D (Earth and Planetary Science Letters, 2012)
Basaltic glasses produced during mid-ocean ridge (MOR) eruptions display a wide range of dissolved CO2 concentrations with respect to equilibrium saturation at their eruption depth. This variability is thought to reflect the dynamics of magma ascent and emplacement, with rapid ascent and depressurization leading to supersaturated conditions and slower ascent resulting in equilibrium saturation. In this study we examine a suite of samples from the 2005–06 eruption of the East Pacific Rise (EPR), collected at {\~{}} 200 m intervals along two well-defined flow pathways within a single seafloor eruption to examine syn-emplacement degassing, using measurements of vesicularity, crystallinity, volatile contents, and helium. This new data set is unique because flow pathways of individual MOR lava flows have rarely been mapped and have never been systematically sampled. Here we show that a large range in dissolved CO2 concentrations exists within this single eruption that nearly spans that observed in tens of flows measured along this portion of the EPR crest. This lava flow experienced equilibrium degassing of dissolved CO2 from supersaturated conditions at the vent (and persisting over the first 750 m of flow) toward equilibrium with seafloor pressures along a {\~{}} 2.5 km-long flow path. This was accompanied by an increase in vesicularity and characteristic bubble radius along the flow, indicating the importance of bubble growth by diffusion for degassing. Nearly constant total helium concentrations (melt + vesicles) indicate that no bubbles were lost during emplacement. With a model of diffusion-controlled bubble growth constrained by observations from the samples along the largest flow lobe of the eruption, we calculate minimum ascent rates of 0.15 m/s, and – for this portion of the eruption – an eruption duration of {\~{}} 30 h and flow rates from 0.02 to 0.12 m/s. This study represents the first quantitative assessment of eruption dynamics using volatiles in a mid-ocean ridge lava flow.
Keywords: ROV Jason (Remotely Operated Vehicle)

Cold seep and oxygen minimum zone associated sources of margin heterogeneity affect benthic assemblages, diversity and nutrition at the Cascadian margin (NE Pacific Ocean) - Guilini, K; Levin, L A; Vanreusel, A (Progress in Oceanography, 2012)
Hydrate Ridge (HR), located on the northeastern Pacific margin off Oregon, is characterized by the presence of outcropping hydrates and active methane seepage. Additionally, permanent low oxygen conditions overlay the benthic realm. This study evaluated the relative influence of both seepage and oxygen minima as sources of habitat heterogeneity and potential stress-inducing features on the bathyal metazoan benthos (primarily nematodes) at three different seep and non-seep HR locations, exposed to decreasing bottom-water oxygen concentrations with increasing water depth. The nematode seep communities at HR exhibited low diversity with dominance of only one or two genera (Daptonema and Metadesmolaimus), elevated average individual biomass and $δ$13C evidence for strong dependance on chemosynthesis-derived carbon, resembling deep-sea seeps worldwide. Although the HR seep habitats harbored a distinct nematode community like in other known seep communities, they differed from deep-sea seeps in well-oxygenated waters based on that they shared the dominant genera with the surrounding non-seep sediments overlain by oxygen-deficient bottom water. The homogenizing effect of the oxygen minimum zone on the seep nematode assemblages and surrounding sediments was constant with increasing water depth and concomitant greater oxygen-deficiency, resulting in a loss of habitat heterogeneity.
Keywords: HOV Alvin (Human Occupied Vehicle)

Community study of tubeworm-associated epizooic meiobenthos from deep-sea cold seeps and hot vents - Degen, Renate; Riavitz, Laura; Gollner, Sabine; Vanreusel, Ann; Plum, Christoph; Bright, Monika (MARINE ECOLOGY PROGRESS SERIES, 2012)
The permanent metazoan meiofauna associated with vestimentiferan tubeworm aggregations from hydrocarbon seeps of the upper Louisiana slope in the Green Canyon (similar to 550 m) and the lower slope in Atwater Valley (similar to 2200 m) of the Gulf of Mexico was characterized. Meiofauna abundance, diversity, and community composition at genus level were compared between these seep sites, and with those of tubeworms from hydrothermal vents of the East Pacific Rise (Gollner et al. 2007; Mar Ecol Prog Ser 337: 39-49). The abundance was not significantly different between the 2 seep sites, and was also similar to those found at vents. A total of 150 meiobenthic genera were identified from the cold seep sites. While no significant difference in univariate measurements of diversity was detected, a shift in community composition between the shallow and the deep seep site was found. The hot vent communities included a total of only 17 genera and the diversity measurements were significantly lower at vents than at seeps. Also, Bray-Curtis dissimilarity was 97{%} between the meiobenthic communities from seeps and vents. The genera richness was negatively correlated with maximum temperature and maximum sulfide concentration, and positively correlated with minimum pH value. We conclude that the harsh conditions tubeworms experience at vents compared to the moderate conditions at cold seeps, as well as the longevity of cold seeps surrounded by sedimented deep-sea plains but short-lived vents on basaltic mid-ocean ridges, might explain the contrasting diversity patterns.
Keywords: ROV Jason (Remotely Operated Vehicle)

Comparative Composition, Diversity and Trophic Ecology of Sediment Macrofauna at Vents, Seeps and Organic Falls - Bernardino, A F; Levin, L A; Thurber, A R; Smith, C R (PLoS ONE, 2012)
Sediments associated with hydrothermal venting, methane seepage and large organic falls such as whale, wood and plant detritus create deep-sea networks of soft-sediment habitats fueled, at least in part, by the oxidation of reduced chemicals. Biological studies at deep-sea vents, seeps and organic falls have looked at macrofaunal taxa, but there has yet to be a systematic comparison of the community-level attributes of sediment macrobenthos in various reducing ecosystems. Here we review key similarities and differences in the sediment-dwelling assemblages of each system with the goals of (1) generating a predictive framework for the exploration and study of newly identified reducing habitats, and (2) identifying taxa and communities that overlap across ecosystems. We show that deep-sea seep, vent and organic-fall sediments are highly heterogeneous. They sustain different geochemical and microbial processes that are reflected in a complex mosaic of habitats inhabited by a mixture of specialist (heterotrophic and symbiont-associated) and background fauna. Community-level comparisons reveal that vent, seep and organic-fall macrofauna are very distinct in terms of composition at the family level, although they share many dominant taxa among these highly sulphidic habitats. Stress gradients are good predictors of macrofaunal diversity at some sites, but habitat heterogeneity and facilitation often modify community structure. The biogeochemical differences across ecosystems and within habitats result in wide differences in organic utilization (i.e., food sources) and in the prevalence of chemosynthesis-derived nutrition. In the Pacific, vents, seeps and organic-falls exhibit distinct macrofaunal assemblages at broad-scales contributing to ÃŸ diversity. This has important implications for the conservation of reducing ecosystems, which face growing threats from human activities.

The composition, origin and fate of complex mixtures in the maltene fractions of hydrothermal petroleum assessed by comprehensive two-dimensional gas chromatography - Ventura, G T; Simoneit, B R T; Nelson, R K; Reddy, C M (Organic Geochemistry, 2012)
Sedimentary organic matter in hydrothermal systems can be altered by high temperature fluids to generate petroleum. The saturated and aromatic fractions of these hydrothermal oils are compositionally similar to conventional oil with the exception that they often contain higher concentrations of polycyclic aromatic hydrocarbons (PAH) as well as substantial mixtures of coeluting organic compounds that produce dramatically rising signal on the baseline of gas chromatograms termed unresolved complex mixtures (UCMs). Little is known about the compounds that compose UCMs and why or how they form. This is in part due to an inability to discriminate between in situ and migrated components that characterize the petroleum generated in hydrothermal systems. However, UCMs are also a product of the limitations imbedded in analytical separation techniques. With the advent of comprehensive two-dimensional gas chromatography (GC × GC), a revision of what should constitute molecular complexity needs to be considered. We address these problems by comparing the molecular compositions of the maltene fractions of three previously published hydrothermal petroleum samples using time of flight-mass spectrometry (GC × GC–ToF-MS) and 12 hydrothermal petroleum samples in cores from three locales using comprehensive two-dimensional gas chromatography with flame ionization detection (GC × GC–FID). The sediment cores were collected from Middle Valley, located off the axis of the Juan de Fuca Ridge, and the Escanaba Trough, along the Gorda Ridge, both in the NE Pacific Ocean, as well as from the Guaymas Basin in the Gulf of California. We define a UCM in GC × GC data to be a condition in which ⩾25{%} of the detected peaks within a chromatographic area coelute in either the first or second dimension. In turn, complex (CM) and simple mixtures (SM) are defined as having 5–24{%} and and migrated components that characterize the petroleum generated in hydrothermal systems. However, UCMs are also a product of the limitations imbedded in analytical separation techniques. With the advent of comprehensive two-dimensional gas chromatography (GC × GC), a revision of what should constitute molecular complexity needs to be considered. We address these problems by comparing the molecular compositions of the maltene fractions of three previously published hydrothermal petroleum samples using time of flight-mass spectrometry (GC × GC–ToF-MS) and 12 hydrothermal petroleum samples in cores from three locales using comprehensive two-dimensional gas chromatography with flame ionization detection (GC × GC–FID). The sediment cores were collected from Middle Valley, located off the axis of the Juan de Fuca Ridge, and the Escanaba Trough, along the Gorda Ridge, both in the NE Pacific Ocean, as well as from the Guaymas Basin in the Gulf of California. We define a UCM in GC × GC data to be a condition in which ⩾25{%} of the detected peaks within a chromatographic area coelute in either the first or second dimension. In turn, complex (CM) and simple mixtures (SM) are defined as having 5–24{%} and
Keywords: HOV Alvin (Human Occupied Vehicle)

Comprehensive study of a heavy fuel oil spill : modeling and analytical approaches to understanding environmental weathering - Lemkau, K L (Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution, 2012)
Driven by increasingly heavy oil reserves and more efficient refining technologies, use of heavy fuel oils for power generation is rising. Unlike other refined products and crude oils, a large portion of these heavy oils is undetectable using the traditional gas chromatography-based techniques on which oil spill science has been based. In the current study, samples collected after the 2007 M/V Cosco Busan heavy fuel oil spill (San Francisco, CA) were analyzed using gas chromatography (GC)-based techniques, numerical modeling and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to examine natural weathering of the oil over a one and a half year period. Traditional GC techniques detected variable evidence of evaporation/ dissolution, biodegradation and photodegradation. Petroleum hydrocarbon compounds smaller than {\~{}}n-C16 were rapidly lost due to evaporation and dissolution. Significant biodegradation was not detected until one month post spill while photodegradation was only observed at one field site. To further examine the processes of evaporation and dissolution, samples were analyzed with comprehensive two-dimensional GC (GC×GC) and a physiochemical model developed to approximate quantitative apportionment of compounds lost to the atmosphere and water. Model results suggest temperature is the primary control of evaporation. Finally, to examine the prominent non-GC amenable component of the oil, samples were analyzed with FT-ICR MS. Results showed expected clustering of samples, with those samples collected sooner after the spill having the most compositional similarity to the unweathered oil. Analysis of dominant heteroatom classes within the oil showed losses of high molecular weight species and the formation of stable core structures with time. These results highlight the susceptibility to weathering of these higher molecular weight components, previously believed to be recalcitrant in the environment. Research findings indicate that environmental weathering results in removal or alteration of larger alkylated compounds as well as loss of lower molecular weight species through evaporation/dissolution, biodegradation and photodegradation, with a resultant fraction of stable compounds likely to remain in the environment years after the spill. This research demonstrates the advantages of combining multiple analytical and modeling approaches for a fuller understanding of oil spill chemistry.
Keywords: HOV Alvin (Human Occupied Vehicle)

Contributions to automated realtime underwater navigation - Stanway, M J (Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution, 2012)
This dissertation presents three separate–but related–contributions to the art of underwater navigation. These methods may be used in postprocessing with a human in the loop, but the overarching goal is to enhance vehicle autonomy, so the emphasis is on automated approaches that can be used in realtime. The three research threads are: i) in situ navigation sensor alignment, ii) dead reckoning through the water column, and iii) model-driven delayed measurement fusion. Contributions to each of these areas have been demonstrated in simulation, with laboratory data, or in the field–some have been demonstrated in all three arenas. The solution to the in situ navigation sensor alignment problem is an asymptotically stable adaptive identifier formulated using rotors in Geometric Algebra. This identifier is applied to precisely estimate the unknown alignment between a gyrocompass and Doppler velocity log, with the goal of improving realtime dead reckoning navigation. Laboratory and field results show the identifier performs comparably to previously reported methods using rotation matrices, providing an alignment estimate that reduces the position residuals between dead reckoning and an external acoustic positioning system. The Geometric Algebra formulation also encourages a straightforward interpretation of the identifier as a proportional feedback regulator on the observable output error. Future applications of the identifier may include alignment between inertial, visual, and acoustic sensors. The ability to link the Global Positioning System at the surface to precision dead reckoning near the seafloor might enable new kinds of missions for autonomous underwater vehicles. This research introduces a method for dead reckoning through the water column using water current profile data collected by an onboard acoustic Doppler current profiler. Overlapping relative current profiles provide information to simultaneously estimate the vehicle velocity and local ocean current–the vehicle velocity is then integrated to estimate position. The method is applied to field data using online bin average, weighted least squares, and recursive least squares implementations. This demonstrates an autonomous navigation link between the surface and the seafloor without any dependence on a ship or external acoustic tracking systems. Finally, in many state estimation applications, delayed measurements present an interesting challenge. Underwater navigation is a particularly compelling case because of the relatively long delays inherent in all available position measurements. This research develops a flexible, model-driven approach to delayed measurement fusion in realtime Kalman filters. Using a priori estimates of delayed measurements as augmented states minimizes the computational cost of the delay treatment. Managing the augmented states with time-varying conditional process and measurement models ensures the approach works within the proven Kalman filter framework–without altering the filter structure or requiring any ad-hoc adjustments. The end result is a mathematically principled treatment of the delay that leads to more consistent estimates with lower error and uncertainty. Field results from dead reckoning aided by acoustic positioning systems demonstrate the applicability of this approach to real-world problems in underwater navigation.
Keywords: AUV Sentry (Autonomous Underwater Vehicle); HOV Alvin (Human Occupied Vehicle)

Deep sea hydrothermal plumes and their interaction with oscillatory flows - Xu, Guangyu; Di Iorio, Daniela (GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 2012)
The acoustic scintillation method is applied to the investigation and monitoring of a vigorous hydrothermal plume from Dante within the Main Endeavour vent field (MEF) in the Endeavour Ridge segment. A 40 day time series of the plume's vertical velocity and temperature fluctuations provides a unique opportunity to study deep sea plume dynamics in a tidally varying horizontal cross flow. An integral plume model that takes into account ambient stratification and horizontal cross flows is established from the conservation equations of mass, momentum and density deficit. Using a linear additive entrainment velocity in the model ( E = alpha U-m + beta U-perpendicular to) that is a function of both the plume relative axial velocity (U-m) and the relative ambient flow perpendicular to the plume (U-perpendicular to) gives consistent results to the experimental data, suggesting entrainment coefficients alpha = 0.1 and beta = 0.6. Also from the integral model, the plume height in a horizontal cross flow ( U-a) is shown to scale as 1.8B(1/3)U(a)(-1/3)N(-2/3) for 0.01 {<}= U-a {<}= 0.1 m/s where B is the initial buoyancy transport and N is the ambient stratification, both of which are assumed constant.
Keywords: HOV Alvin (Human Occupied Vehicle)

Denitrification and environmental factors influencing nitrate removal in Guaymas Basin hydrothermally altered sediments - Bowles, Marshall W; Nigro, Lisa M; Teske, Andreas P; Joye, Samantha B (FRONTIERS IN MICROBIOLOGY, 2012)
We measured potential nitrate removal and denitrification rates in hydrothermally altered sediments inhabited by Beggiatoa mats and adjacent brown oil stained sediments from the Guaymas Basin, Gulf of California. Sediments with Beggiatoa maintained slightly higher rates of potential denitrification than did brown sediments at 31.2 +/- 12.1 versus 21.9 +/- 1.4 mu M N day-1, respectively. In contrast, the nitrate removal rates in brown sediments were higher than those observed in mat-hosting sediments at 418 +/- 145 versus 174 +/- 74 mu M N day-1, respectively. Additional experiments were conducted to assess the responses of denitrifying communities to environmental factors {\{}[{\}}i.e., nitrate, sulfide, and dissolved organic carbon (DOC) concentration)]. The denitrifying community had a high affinity for nitrate (Km = 137 +/- 91 mu M N day-1), in comparison to other environmental communities of denitrifiers, and was capable of high maximum rates of denitrification (Vmax = 1164 +/- 153 mu M N day-1). The presence of sulfide resulted in significantly lower denitrification rates. Microorganisms with the potential to perform denitrification were assessed in these sediments using the bacterial 16S rRNA gene and nitrous oxide reductase (nosZ) functional gene libraries. The bacterial 16S rRNA gene clone library was dominated by Epsilonproteobacteria (38{%}), some of which (e.g., Sulfurimonas sp.) have a potential for sulfide-dependent denitrification. The nosZ clone library did not contain clones similar to pure culture denitrifiers; these clones were most closely associated with environmental clones.
Keywords: HOV Alvin (Human Occupied Vehicle)

Distribution, abundance, and diversity patterns of the thermoacidophilic ``deep-sea hydrothermal vent euryarchaeota 2\''\}} - Flores, Gilberto E; Wagner, Isaac D; Liu, Yitai; Reysenbach, Anna-Louise (FRONTIERS IN MICROBIOLOGY, 2012)
Cultivation-independent studies have shown that taxa belonging to the ``deep-sea hydrothermal vent euryarchaeota 2{\{}''{\}} (DHVE2) lineage are widespread at deep-sea hydrothermal vents. While this lineage appears to be a common and important member of the microbial community at vent environments, relatively little is known about their overall distribution and phylogenetic diversity. In this study, we examined the distribution, relative abundance, co-occurrence patterns, and phylogenetic diversity of cultivable thermoacidophilic DHVE2 in deposits from globally distributed vent fields. Results of quantitative polymerase chain reaction assays with primers specific for the DHVE2 and Archaea demonstrate the ubiquity of the DHVE2 at deep-sea vents and suggest that they are significant members of the archaeal communities of established vent deposit communities. Local similarity analysis of pyrosequencing data revealed that the distribution of the DHVE2 was positively correlated with 10 other Euryarchaeota phylotypes and negatively correlated with mostly Crenarchaeota phylotypes. Targeted cultivation efforts resulted in the isolation of 12 axenic strains from six different vent fields, expanding the cultivable diversity of this lineage to vents along the East Pacific Rise and Mid-Atlantic Ridge. Eleven of these isolates shared greater than 97{%} 16S rRNA gene sequence similarity with one another and the only described isolate of the DHVE2, Aciduliprofundum boonei T469(T). Sequencing and phylogenetic analysis of five protein-coding loci, atpA, EF-2, radA, rpoB, and secY, revealed clustering of isolates according to geographic region of isolation. Overall, this study increases our understanding of the distribution, abundance, and phylogenetic diversity of the DHVE2.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

The East Pacific Rise Between 9 degrees N and 10 degrees N: Twenty-Five Years of Integrated, Multidisciplinary Oceanic Spreading Center Studies - Fornari, D J; Von Damm, K L; Bryce, Julia G; Cowen, J P; Ferrini, Vicki; Fundis, A; Lilley, M D; Luther, G W; Mullineaux, L S; Perfit, M R; Meana-Prado, M F; Rubin, K H; et al. (Oceanography, 2012)
The East Pacific Rise from {\~{}} 9–10°N is an archetype for a fast-spreading mid-ocean ridge. In particular, the segment near 9°50'N has been the focus of multidisciplinary research for over two decades, making it one of the best-studied areas of the global ridge system. It is also one of only two sites along the global ridge where two historical volcanic eruptions have been observed. This volcanically active segment has thus offered unparalleled opportunities to investigate a range of complex interactions among magmatic, volcanic, hydrothermal, and biological processes associated with crustal accretion over a full magmatic cycle. At this 9°50'N site, comprehensive physical oceanographic measurements and modeling have also shed light on linkages between hydrodynamic transport of larvae and other materials and biological dynamics influenced by magmatic processes. Integrated results of high-resolution mapping, and both in situ and laboratory-based geophysical, oceanographic, geochemical, and biological observations and sampling, reveal how magmatic events perturb the hydrothermal system and the biological communities it hosts.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Effects of variable magma supply on mid-ocean ridge eruptions: Constraints from mapped lava flow fields along the Galápagos Spreading Center - Colman, A; Sinton, J M; White, S M; McClinton, J T; Bowles, J A; Rubin, K H; Behn, M D; Cushman, B; Eason, D E; Gregg, T K P; Grönvold, Karl; Hidalgo, S; et al. (Geochemistry, Geophysics, Geosystems, 2012)
Mapping and sampling of 18 eruptive units in two study areas along the Galápagos Spreading Center (GSC) provide insight into how magma supply affects mid-ocean ridge (MOR) volcanic eruptions. The two study areas have similar spreading rates (53 versus 55 mm/yr), but differ by 30{%} in the time-averaged rate of magma supply (0.3 × 106 versus 0.4 × 106 m3/yr/km). Detailed geologic maps of each study area incorporate observations of flow contacts and sediment thickness, in addition to sample petrology, geomagnetic paleointensity, and inferences from high-resolution bathymetry data. At the lower-magma-supply study area, eruptions typically produce irregularly shaped clusters of pillow mounds with total eruptive volumes ranging from 0.09 to 1.3 km3. At the higher-magma-supply study area, lava morphologies characteristic of higher effusion rates are more common, eruptions typically occur along elongated fissures, and eruptive volumes are an order of magnitude smaller (0.002–0.13 km3). At this site, glass MgO contents (2.7–8.4 wt. {%}) and corresponding liquidus temperatures are lower on average, and more variable, than those at the lower-magma-supply study area (6.2–9.1 wt. {%} MgO). The differences in eruptive volume, lava temperature, morphology, and inferred eruption rates observed between the two areas along the GSC are similar to those that have previously been related to variable spreading rates on the global MOR system. Importantly, the documentation of multiple sequences of eruptions at each study area, representing hundreds to thousands of years, provides constraints on the variability in eruptive style at a given magma supply and spreading rate.
Keywords: HOV Alvin (Human Occupied Vehicle)

Evidence for the role of endosymbionts in regional-scale habitat partitioning by hydrothermal vent symbioses - Beinart, R A; Sanders, J G; Faure, B; Sylva, S P; Lee, R W; Becker, E L; Gartman, A; Luther, G W; Seewald, J S; Fisher, C R; Girguis, P R (Proceedings of the National Academy of Sciences of the United States of America, 2012)
Deep-sea hydrothermal vents are populated by dense communities of animals that form symbiotic associations with chemolithoautotrophic bacteria. To date, our understanding of which factors govern the distribution of host/symbiont associations (or holobionts) in nature is limited, although host physiology often is invoked. In general, the role that symbionts play in habitat utilization by vent holobionts has not been thoroughly addressed. Here we present evidence for symbiont-influenced, regional-scale niche partitioning among symbiotic gastropods (genus Alviniconcha) in the Lau Basin. We extensively surveyed Alviniconcha holobionts from four vent fields using quantitative molecular approaches, coupled to characterization of high-temperature and diffuse vent-fluid composition using gastight samplers and in situ electrochemical analyses, respectively. Phylogenetic analyses exposed cryptic host and symbiont diversity, revealing three distinct host types and three different symbiont phylotypes (one $ε$-proteobacteria and two $γ$-proteobacteria) that formed specific associations with one another. Strikingly, we observed that holobionts with $ε$-proteobacterial symbionts were dominant at the northern fields, whereas holobionts with $γ$-proteobacterial symbionts were dominant in the southern fields. This pattern of distribution corresponds to differences in the vent geochemistry that result from deep subsurface geological and geothermal processes. We posit that the symbionts, likely through differences in chemolithoautotrophic metabolism, influence niche utilization among these holobionts. The data presented here represent evidence linking symbiont type to habitat partitioning among the chemosynthetic symbioses at hydrothermal vents and illustrate the coupling between subsurface geothermal processes and niche availability.
Keywords: ROV Jason (Remotely Operated Vehicle)

Flux measurements of explosive degassing using a yearlong hydroacoustic record at an erupting submarine volcano - Dziak, R P; Baker, E T; Shaw, A M; Bohnenstiehl, D R; Chadwick, W W; Haxel, J H; Matsumoto, H; Walker, S L (Geochemistry, Geophysics, Geosystems, 2012)
The output of gas and tephra from volcanoes is an inherently disorganized process that makes reliable flux estimates challenging to obtain. Continuous monitoring of gas flux has been achieved in only a few instances at subaerial volcanoes, but never for submarine volcanoes. Here we use the first sustained (yearlong) hydroacoustic monitoring of an erupting submarine volcano (NW Rota-1, Mariana arc) to make calculations of explosive gas flux from a volcano into the ocean. Bursts of Strombolian explosive degassing at the volcano summit (520 m deep) occurred at 1–2 min intervals during the entire 12-month hydrophone record and commonly exhibited cyclic step-function changes between high and low intensity. Total gas flux calculated from the hydroacoustic record is 5.4 ± 0.6 Tg a−1, where the magmatic gases driving eruptions at NW Rota-1 are primarily H2O, SO2, and CO2. Instantaneous fluxes varied by a factor of ∼100 over the deployment. Using melt inclusion information to estimate the concentration of CO2 in the explosive gases as 6.9 ± 0.7 wt {%}, we calculate an annual CO2 eruption flux of 0.4 ± 0.1 Tg a−1. This result is within the range of measured CO2 fluxes at continuously erupting subaerial volcanoes, and represents ∼0.2–0.6{%} of the annual estimated output of CO2from all subaerial arc volcanoes, and ∼0.4–0.6{%} of the mid-ocean ridge flux. The multiyear eruptive history of NW Rota-1 demonstrates that submarine volcanoes can be significant and sustained sources of CO2 to the shallow ocean.

Geographic expansion of hermatypic and ahermatypic corals in the Gulf of Mexico, and implications for dispersal and recruitment - Sammarco, Paul W; Atchison, Amy D; Boland, Gregory S; Sinclair, James; Lirette, Angela (JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY, 2012)
The {>}3000 oil/gas platforms in the northern Gulf of Mexico (GOM) provide shallow hard-substratum in a soft-bottom dominated ecosystem. Excepting the Flower Garden Banks (FGB) and deeper mesophotic banks, no shallow hard substrate has been available offshore since the Holocene. Platforms have facilitated coral geographic expansion in this region. We determined the distribution, abundance, and species diversity patterns on 42 platforms in this region, at {<}= 37 m depth, along four cross-shelf transects: 1) S-SE from Corpus Christi, Texas; 2) S from Lake Sabine, Texas; 3) S from Terrebonne Bay, Louisiana; and 4) S-SW from Mobile, Alabama. Nine hermatypic, two ahermatypic, and one hydrozoan coral were found: hermatypes-Madracis decactis. Diploria strigosa, Montastraea cavernosa, Porites astreoides, Madracis formosa, Colpophyllia natans, Stephanocoenia intercepta, Stephanocoenia michelinii, and Millepora alcicornis (Hydrozoa); ahermatypes-Tubastraea cocci flea. Oculina diffusa, and Phyllangia americana. Pattern-seeking analyses identified four community types: one with no hermatypic corals (inner and mid-shelf); one high diversity set of platforms, dominated by abundant Madracis decactis, occurring with four other species per platform (outer shelf); and a third dominated by Madracis decactis, in low abundance, co-dominated by D. strigosa and Millepora alcicornis (outer shelf). Species diversity was highest around the Flower Garden Banks. Hermatypic density and D. strigosa (broadcaster) in particular, was maximum around the FGB, extending northwards. Madracis decactis (brooder) densities peaked at the shelf edge, off Terrebonne Bay, Louisiana. Montastraea cavernosa densities were bimodal, peaking near the FGB and east of the Mississippi River. The FGB appear to be the source of hermatypic corals for most platform populations. Differences between the distribution patterns of Madracis decactis and D. strigosa, Montastraea cavernosa, and O. diffusa suggest that the brooder effects longer recruitment distances by averaging larval dispersal over a broad range of hydrographic conditions throughout the year, while the broadcaster utilizes only one set of conditions over the same period. Averaging respective dispersal strategies over decades may have produced the observed disparate distribution patterns. Ahermatypic coral density exceeded hermatypic density by 10,000 fold, peaking south of Terrebonne Bay, Louisiana and Mobile, Alabama, due to T. coccinea. Ahermatypic diversity was highest off Matagorda Island, Texas, decreasing from west to east. Multi-variate pattern-seeking analysis (PATN) identified four ahermatypic community types: one dominated by O. diffusa and T. coccinea in low abundances (shelf-wide distribution); one characterized by the absence of ahermatypic corals (generally near-shore); one heavily dominated by T. coccinea, and also by O. diffusa in low abundances (mid-shelf to shelf edge); and one dominated by T. coccinea, co-dominated by both P. americana and O. diffusa in low abundances (shelf-edge). T. coccinea and P. americana appear to be derived from the southern GOM off Mexico or the Caribbean. Unlike shrinking coral populations in other parts of the world, corals have expanded their range substantially in the northern Gulf of Mexico, in areas previously devoid or near devoid of corals, facilitated by thousands of oil/gas platforms deployed for decades throughout the region. It is also possible that coral populations on these platforms may act as potential larval sources for the FGB in the event of a mass coral mortality there. (C) 2012 Elsevier B.V. All rights reserved.
Keywords: ROV Jason (Remotely Operated Vehicle)

Hippea jasoniae sp nov and Hippea alviniae sp nov., thermoacidophilic members of the class Deltaproteobacteria isolated from deep-sea hydrothermal vent deposits - Flores, Gilberto E; Hunter, Ryan C; Liu, Yitai; Mets, Anchelique; Schouten, Stefan; Reysenbach, Anna-Louise (INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY, 2012)
Thirteen novel, obligately anaerobic, thermoacidophilic bacteria were isolated from deep-sea hydrothermal vent sites. Four of the strains, designated EP5-r(T), KM1, Mar08-272r(T) and Mar08-368r, were selected for metabolic and physiological characterization. With the exception of strain EP5-r(T), all strains were short rods that grew between 40 and 72 degrees C, with optimal growth at 60-65 degrees C. Strain EP5-r(T) was more ovoid in shape and grew between 45 and 75 degrees C, with optimum growth at 60 degrees C. The pH range for growth of all the isolates was between pH 3.5 and 5.5 (optimum pH 4.5 to 5.0). Strain Mar08-272r(T) could only grow up to pH 5.0. Elemental sulfur was required for heterotrophic growth on acetate, succinate, Casamino acids and yeast extract. Strains EP5-r(T), Mar08-272r(T) and Mar08-368r could also use fumarate, while strains EP5-r(T), KM1 and Mar08-272r(T) could also use propionate. All isolates were able to grow chemolithotrophically on H-2, CO2, sulfur and vitamins. Phylogenetic analysis of 16S rRNA gene sequences placed all isolates within the family Desulfurellaceae of the class Deltaproteobacteria, with the closest cultured relative being Hippea maritima MH2T (similar to 95-98{%} gene sequence similarity). Phylogenetic analysis also identified several isolates with at least one intervening sequence within the 16S rRNA gene. The genomic DNA G+C contents of strains EP5-r(T), KM1, Mar08-272r(T) and Mar08-368r were 37.1, 42.0, 35.6 and 37.9 mol{%}, respectively. The new isolates differed most significantly from H. maritima MH2T in their phylogenetic placement and in that they were obligate thermoacidophiles. Based on these phylogenetic and phenotypic properties, the following two novel species are proposed: Hippea jasoniae sp. nov. (type strain Mar08-272r(T)=DSM 24585(T)=OCM 985(T)) and Hippea alviniae sp. nov. (type strain EP5-r(T)=DSM 24586(T)=OCM 986(T)).
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Hydrothermal Discharge During Submarine Eruptions THE IMPORTANCE OF DETECTION, RESPONSE, AND NEW TECHNOLOGY - Baker, E T; Chadwick, W W; Cowen, J P; Dziak, R P; Rubin, K H; Fornari, D J (Oceanography, 2012)
Submarine volcanic eruptions and intrusions construct new oceanic crust and build long chains of volcanic islands and vast submarine plateaus. Magmatic events are a primary agent for the transfer of heat, chemicals, and even microbes from the crust to the ocean, but the processes that control these transfers are poorly understood. The 1980s discovery that mid-ocean ridge eruptions are often associated with brief releases of immense volumes of hot fluids ("event plumes") spurred interest in methods for detecting the onset of eruptions or intrusions and for rapidly organizing seagoing response efforts. Since then, some 35 magmatic events have been recognized and responded to on mid-ocean ridges and at seamounts in both volcanic arc and intraplate settings. Field responses at mid-ocean ridges have found that event plumes occur over a wide range of eruption styles and sizes, and thus may be a common consequence of ridge eruptions. The source(s) of event plume fluids are still debated. Eruptions detected at ridges generally have high effusion rates and short durations (hours to days), whereas field responses at arc volcanic cones have found eruptions with very low effusion rates and durations on the scale of years. New approaches to the study of submarine magmatic events include the development of autonomous vehicles for detection and response, and the establishment of permanent seafloor observatories at likely future eruption sites.
Keywords: HOV Alvin (Human Occupied Vehicle)

A hydrothermal seep on the Costa Rica margin: middle ground in a continuum of reducing ecosystems - Levin, L A; Orphan, V J; Rouse, G W; Rathburn, A E; Ussler, W; Cook, G S; Goffredi, S K; Perez, Elena M; Waren, A; Grupe, B M; Chadwick, G; Strickrott, B (Proceedings of the Royal Society B: Biological Sciences, 2012)
Upon their initial discovery, hydrothermal vents and methane seeps were considered to be related but distinct ecosystems, with different distributions, geomorphology, temperatures, geochemical properties and mostly different species. However, subsequently discovered vents and seep systems have blurred this distinction. Here, we report on a composite, hydrothermal seep ecosystem at a subducting seamount on the convergent Costa Rica margin that represents an intermediate between vent and seep ecosystems. Diffuse flow of shimmering, warm fluids with high methane concentrations supports a mixture of microbes, animal species, assemblages and trophic pathways with vent and seep affinities. Their coexistence reinforces the continuity of reducing environments and exemplifies a setting conducive to interactive evolution of vent and seep biota.
Keywords: HOV Alvin (Human Occupied Vehicle)

Hydrothermal vent community zonation along environmental gradients at the Lau back-arc spreading center - Kim, S; Hammerstrom, K (Deep-Sea Research. Part I: Oceanographic Research Papers, 2012)
The Lau back-arc spreading center exhibits gradients in hydrothermal vent habitat characteristics from north to south. Biological zonation within a few meters of vents has been described as temperature driven. We constructed georeferenced photomosaics of the seafloor out to tens of meters beyond vents to describe peripheral zonation and explore correlations between environmental conditions and the biological community. Cluster analysis separated northern sites from southern sites, corresponding to a break in substrate from basalt in the north to andesite in the south. Northern sites were dominated by anemones, and southern by sponges. A previous suggestion that dominants may be dependent on friability of the substrate was not supported; when visually distinguishable, individual species within taxa showed different patterns. Northern sites hosted proportionally more suspension feeding species. Sulfide that can support microbial food sources is at higher concentrations at these sites, though bathymetry that may enhance bottom currents is less rugged. Northern sites had higher diversity that may result from the overall northwards flow, which would generally permit easier dispersal downcurrent, though we observed no difference in dispersal strategies at different sites.
Keywords: ROV Jason (Remotely Operated Vehicle); ROV Medea (Remotely Operated Vehicle)

Hydrothermal vent fields and chemosynthetic biota on the world's deepest seafloor spreading centre - Connelly, D P; Copley, J T; Murton, B J; Stansfield, K; Tyler, P A; German, C R; Van Dover, C L; Amon, D; Furlong, M; Grindlay, N; Hayman, N; Huehnerbach, V; et al. (Nature Communications, 2012)
The Mid-Cayman spreading centre is an ultraslow-spreading ridge in the Caribbean Sea. Its extreme depth and geographic isolation from other mid-ocean ridges offer insights into the effects of pressure on hydrothermal venting, and the biogeography of vent fauna. Here we report the discovery of two hydrothermal vent fields on the Mid-Cayman spreading centre. The Von Damm Vent Field is located on the upper slopes of an oceanic core complex at a depth of 2,300 m. High-temperature venting in this off-axis setting suggests that the global incidence of vent fields may be underestimated. At a depth of 4,960 m on the Mid-Cayman spreading centre axis, the Beebe Vent Field emits copper-enriched fluids and a buoyant plume that rises 1,100 m, consistent with {>}400 degrees C venting from the world's deepest known hydrothermal system. At both sites, a new morphospecies of alvinocaridid shrimp dominates faunal assemblages, which exhibit similarities to those of Mid-Atlantic vents.

Impact of the Deepwater Horizon oil spill on a deep-water coral community in the Gulf of Mexico - White, H K; Hsing, P-Y; Cho, W; Shank, T M; Cordes, E E; Quattrini, A M; Nelson, R K; Camilli, R; Demopoulos, A W J; German, C R; Brooks, J M; Roberts, H H; et al. (Proceedings of the National Academy of Sciences of the United States of America, 2012)
To assess the potential impact of the Deepwater Horizon oil spill on offshore ecosystems, 11 sites hosting deep-water coral communities were examined 3 to 4 mo after the well was capped. Healthy coral communities were observed at all sites {>}20 km from the Macondo well, including seven sites previously visited in September 2009, where the corals and communities appeared unchanged. However, at one site 11 km southwest of the Macondo well, coral colonies presented widespread signs of stress, including varying degrees of tissue loss, sclerite enlargement, excess mucous production, bleached commensal ophiuroids, and covering by brown flocculent material (floc). On the basis of these criteria the level of impact to individual colonies was ranked from 0 (least impact) to 4 (greatest impact). Of the 43 corals imaged at that site, 46{%} exhibited evidence of impact on more than half of the colony, whereas nearly a quarter of all of the corals showed impact to {>}90{%} of the colony. Additionally, 53{%} of these corals' ophiuroid associates displayed abnormal color and/or attachment posture. Analysis of hopanoid petroleum biomarkers isolated from the floc provides strong evidence that this material contained oil from the Macondo well. The presence of recently damaged and deceased corals beneath the path of a previously documented plume emanating from the Macondo well provides compelling evidence that the oil impacted deep-water ecosystems. Our findings underscore the unprecedented nature of the spill in terms of its magnitude, release at depth, and impact to deep-water ecosystems.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Inorganic chemistry, gas compositions and dissolved organic carbon in fluids from sedimented young basaltic crust on the Juan de Fuca Ridge flanks - Lin, H -T; Cowen, J P; Olson, E J; Amend, J P; Lilley, M D (Geochimica et Cosmochimica Acta, 2012)
The permeable upper oceanic basement serves as a plausible habitat for a variety of microbial communities. There is growing evidence suggesting a substantial subseafloor biosphere. Here new time series data are presented on key inorganic species, methane, hydrogen and dissolved organic carbon (DOC) in ridge flank fluids obtained from subseafloor observatory CORKs (Circulation Obviation Retrofit Kits) at Integrated Ocean Drilling Program (IODP) boreholes 1301A and 1026B. These data show that the new sampling methods (Cowen et al., 2012) employed at 1301A result in lower contamination than earlier studies. Furthermore, sample collection methods permitted most chemical analyses to be performed from aliquots of single large volume samples, thereby allowing more direct comparison of the data. The low phosphate concentrations (0.06–0.2 $μ$M) suggest that relative to carbon and nitrogen, phosphorus could be a limiting nutrient in the basement biosphere. Coexisting sulfate (17–18 mM), hydrogen sulfide (∼0.1 $μ$M), hydrogen (0.3–0.7 $μ$M) and methane (1.5–2 $μ$M) indicates that the basement aquifer at 1301A either draws fluids from multiple flow paths with different redox histories or is a complex environment that is not thermodynamically controlled and may allow co-occurring metabolic pathways including sulfate reduction and methanogenesis. The low DOC concentrations (11–18 $μ$M) confirm that ridge flank basement is a net DOC sink and ultimately a net carbon sink. Based on the net amounts of DOC, oxygen, nitrate and sulfate removed (∼30 $μ$M, ∼80 $μ$M, ∼40 $μ$M and ∼10 mM, respectively) from entrained bottom seawater, organic carbon may be aerobically or anaerobically oxidized in biotic and/or abiotic processes.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Links from Mantle to Microbe at the Lau Integrated Study Site:Insights from a Back-Arc Spreading Center - Tivey, M K; Becker, E; Beinart, R; Fisher, C R; Girguis, P R; Langmuir, C H; Michael, P J; Reysenbach, A -L (Oceanography, 2012)
The Lau Integrated Study Site (ISS) has provided unique opportunities for study of ridge processes because of its back-arc setting in the southwestern Pacific. Its location allows study of a biogeographical province distinct from those of eastern Pacific and mid-Atlantic ridges, and crustal compositions along the ridge lie outside the range of mid-ocean ridge crustal compositions. The Lau ISS is located above a subduction zone, at an oblique angle. The underlying mantle receives water and other elements derived from the downgoing lithospheric slab, with an increase in slab influence from north to south. Water lowers the mantle melting temperature and leads to greater melt production where the water flux is greater, and to distinctive regional-scale gradients along the ridge. There are deeper faulted axial valleys with basaltic volcanism in the north and inflated axial highs with andesites in the south. Differences in igneous rock composition and release of magmatic volatiles affect compositions of vent fluids and deposits. Differences in vent fluid compositions and small-scale diffuse-flow regimes correlate with regional-scale patterns in microbial and megafaunal distributions. The interdisciplinary research effort at the Lau ISS has successfully identified linkages between subsurface processes and deep-sea biological communities, from mantle to microbe to megafauna.
Keywords: AUV ABE (Autonomous Benthic Explorer); ROV Jason (Remotely Operated Vehicle)

Low-Temperature Hydrothermal Plumes in the Near-Bottom Boundary Layer at Endeavour Segment, Juan de Fuca Ridge - Hautala, Susan; Johnson, H Paul; Pruis, Matthew; Garcia-Berdeal, Irene; Bjorklund, Tor (OCEANOGRAPHY, 2012)
Keywords: ROV Jason (Remotely Operated Vehicle)

Meristic variation in males of the hydrothermal vent octopus, Muusoctopus hydrothermalis (Cephalopoda: Octopodidae) - Voight, Janet R (JOURNAL OF THE MARINE BIOLOGICAL ASSOCIATION OF THE UNITED KINGDOM, 2012)
Intraspecific variation in characters such as arm sucker and gill lamellae counts in octopodids is yet to be thoroughly investigated, potentially hampering our ability to recognize species. In this study, data from 13 specimens of Muusoctopus hydrothermalis collected at four hydrothermal vents on the East Pacific Rise between 8 degrees 38'N and 12 degrees 48'N are considered. Although the northern and southern octopuses differ minimally in size, mean sucker count by arm in the northern group is 11.7 to 22.8{%} higher than it is in the southern group; in addition these octopuses typically have an additional gill lamella and bulkier funnel organs. The arms of each individual carry a different number of suckers. The difference is significant on nonadjacent arms, a pattern that merits examination in a broader taxonomic context. Why these differences exist among conspecifics remains unknown, the incidence of parasitic copepods is not different between the groups and the between-group variation in arm suckers seen here compares well with a previous report of variation among 18 specimens from the type locality. Increases in meristic characters (counts) in fish are attributed to lower temperatures during embryonic development following Jordan's rule. Northern and southern vents offer the octopuses a wide temperature range, but vent fluid chemistry differs. Northern vent fluids may be more toxic; if so, developing octopus embryos may survive only minimal vent fluid exposure and therefore develop at low temperatures. At the less toxic southern vents, eggs may survive greater exposure to vent fluids and thus develop at higher temperatures.
Keywords: HOV Alvin (Human Occupied Vehicle)

Microbial communities at the borehole observatory on the Costa Rica Rift flank (Ocean Drilling Program Hole 896A) - Nigro, Lisa M; Harris, Kate; Orcutt, Beth N; Hyde, Andrew; Clayton-Luce, Samuel; Becker, Keir; Teske, Andreas (FRONTIERS IN MICROBIOLOGY, 2012)
The microbiology of subsurface, hydrothermally influenced basaltic crust flanking midocean ridges has remained understudied, due to the difficulty in accessing the subsurface environment. The instrumented boreholes resulting from scientific ocean drilling offer access to samples of the formation fluids circulating through oceanic crust. We analyzed the phylogenetic diversity of bacterial communities of fluid and microbial mat samples collected in situ from the observatory at Ocean Drilling Program Hole 896A, drilled into similar to 6.5 million-year-old basaltic crust on the flank of the Costa Rica Rift in the equatorial Pacific Ocean. Bacterial 16S rRNA gene sequences recovered from borehole fluid and from a microbial mat coating the outer surface of the fluid port revealed both unique and shared phylotypes. The dominant bacterial clones from both samples were related to the autotrophic, sulfur-oxidizing genus Thiomicrospira. Both samples yielded diverse gamma- and alphaproteobacterial phylotypes, as well as members of the Bacteroidetes, Planctomycetes, and Verrucomicrobia. Analysis of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) genes (cbbL and cbbM) from the sampling port mat and from the borehole fluid demonstrated autotrophic carbon assimilation potential for in situ microbial communities; most cbbL genes were related to those of the sulfur-oxidizing genera Thioalkalivibrio and Thiomicrospira, and cbbM genes were affiliated with uncultured phylotypes from hydrothermal vent plumes and marine sediments. Several 16S rRNA gene phylotypes from the 896A observatory grouped with phylotypes recovered from seawater-exposed basalts and sulfide deposits at inactive hydrothermal vents, but there is little overlap with hydrothermally influenced basaltic boreholes 1026B and U1301A on the Juan de Fuca Ridge flank, suggesting that site-specific characteristics of Hole 896A (i.e., seawater mixing into borehole fluids) affect the microbial community composition.
Keywords: HOV Alvin (Human Occupied Vehicle)

Microbial utilization of abiogenic carbon and hydrogen in a serpentinite-hosted system - Lang, S Q; Fruh-Green, G L; Bernasconi, S M; Lilley, M D; Proskurowski, G; Mehay, S; Butterfield, D A (Geochimica et Cosmochimica Acta, 2012)
Mantle rocks exposed on the seafloor constitute a highly reactive chemical and thermal system, in which interaction with seawater to produce serpentinite has major consequences for lithospheric cooling, global geochemical cycles, and microbial activity. Serpentinite-hosted hydrothermal activity is exemplified by the Lost City Hydrothermal Field (30°N, Mid-Atlantic Ridge) where fluid–rock reactions in the underlying ultramafic rocks result in high concentrations of abiotic hydrogen, methane, C2+ alkanes, and formate. Such systems have been proposed as possible analogs to the Early Earth environments that gave rise to the first biochemical pathways. Thus, characterizing the local microbial communities and their potential link with abiogenic compounds is of particular significance. Here we demonstrate that in active carbonate chimneys where microbial sulfate reduction is important, up to 50{%} of the microbial biomass is synthesized from mantle carbon. Conversely, mantle carbon contributes only ∼10{%} of the biomass in areas with minimal sulfate reduction. We attribute this difference to greater incorporation of formate or methane by the dominant microbial species, the Lost City Methanosarcinales, in locations where sulfate reducers are able to facilitate this assimilation. The ability of autotrophic communities at Lost City to capitalize on the steady stream of chemical products resulting from serpentinization reactions and to utilize abiogenic mantle carbon lend credence to the hypothesis that early biosynthetic pathways could have developed in similar environments.
Keywords: HOV Alvin (Human Occupied Vehicle)

Mineralogical and strontium isotopic record of hydrothermal processes in the lower ocean crust at and near the East Pacific Rise - Kirchner, Timo M; Gillis, Kathryn M (CONTRIBUTIONS TO MINERALOGY AND PETROLOGY, 2012)
Tectonic exposures of upper plutonics ({>} 800 m) that are part of a contiguous section of young East Pacific Rise (EPR) crust at the Hess Deep Rift provide the first regional-scale constraints on hydrothermal processes in the upper plutonic crust formed at a fast-spreading ridge. Submersible-collected samples recovered over a 4-km-wide region show that the sheeted dike complex is largely underlain by a 150- to 200-m-thick gabbro unit, followed by a more primitive gabbronorite unit. Gabbroic samples are variably altered by pervasive fluid flow along fracture networks to amphibole-dominated assemblages. The gabbroic rocks are significantly less altered (average 11{%} hydrous phases) than the overlying sheeted dike complex (average 24{%}), and the percentage of hydrous alteration diminishes with depth. Incipient, pervasive fluid flow occurred at amphibolite facies conditions (average 720A degrees C), with slightly higher temperatures in the lower 500 m of the section. The extent of subsequent lower-temperature alteration is generally low and regionally variable. The gabbroic samples are slightly elevated in Sr-87/Sr-86 relative to fresh rock values (0.7024) and less enriched than the overlying sheeted dike complex. Sr-87/Sr-86 for the pervasively altered gabbroic samples ranges from 0.70244 to 0.70273 (mean 0.70257), tonalites is 0.7038, and pyroxene hornfels ranges from 0.70259 to 0.70271. Sr-87/Sr-86 does not vary with depth, and there is a strong positive correlation with the percentage of hydrous phases. Strontium contents of igneous and hydrothermal minerals, combined with bulk rock Sr-87/Sr-86, indicate that Sr-isotopic exchange is largely controlled by the uptake of fluid Sr-87/Sr-86 in hydrous minerals and does not require Sr gain or loss. The minimum, time-integrated fluid-rock ratio for the sheeted dike complex and upper plutonics is 0.55-0.66, and the fluid flux calculated by mass balance is similar to 2.1 to 2.5 x 10(6) kg m(-2), 30-60{%} higher than fluid fluxes calculated in the same manner for sheeted dike complexes on their own at Hess and Pito Deeps, and Ocean Drilling Program Hole 504B. Alteration patterns within the upper plutonics evolved in response to axial magma chamber (AMC) dynamics at the EPR, such that magma replenishment led to assimilation and thermal metamorphism of the country rock, and the position of the hydrothermal root-zone tracked the vertical migration of the AMC. The freshness of the lowermost gabbroic rocks suggests that pervasive fluid flow does not lead to significant fluid and heat fluxes at and near fast-spreading ridges.
Keywords: HOV Alvin (Human Occupied Vehicle)

New digestive symbiosis in the hydrothermal vent amphipoda Ventiella sulfuris - Corbari, L; Durand, L; Cambon-Bonavita, M -A; Gaill, F; Compère, P (Comptes Rendus Biologies, 2012)
Ventiella sulfuris Barnard and Ingram, 1990 is the most abundant amphipod species inhabiting the Eastern Pacific Rise (EPR 9°N) vent fields. This vent-endemic species is frequently encountered near colonies of Pompeii worms Alvinella pompejana. V. sulfuris specimens were collected during the oceanographic cruise LADDER II at the Bio9 (9°50.3′ N, 2508 m depth) hydrothermal vent site. Main objectives were to highlight the occurrence of bacterial symbiosis in V. sulfuris and to hypothesise their implications in nutrition. Observations in light and electron microscopy (SEM, TEM) showed that the outer body surface and appendages are free of microorganisms. In contrast, the digestive system revealed two major microbial communities settled in the midgut and in the hindgut. Gut contents showed bacterial traces together with abundant fragments of Alvinellid cuticle and setae, from A. pompejana, suggesting that V. sulfuris could directly feed on Alvinellids and/or on their bacterial epibionts. Molecular analyses based on the 16S rRNA genes revealed the diversity of bacterial communities in the digestive system, of which, the Epsilonproteobacteria phylum, could be considered as one of the major bacterial group. Hypotheses were proposed on their symbiotic features and their implications in V. sulfuris nutrition.
Keywords: HOV Alvin (Human Occupied Vehicle)

Parvibaculum hydrocarboniclasticum sp. nov., a mesophilic, alkane-oxidizing alphaproteobacterium isolated from a deep-sea hydrothermal vent on the East Pacific Rise - Rosario-Passapera, Richard; Keddis, Ramaydalis; Wong, Ronald; Lutz, Richard A; Staroyoytov, Valentin; Vetriani, Costantino (INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY, 2012)
An aerobic, alkane-oxidizing bacterium, designated strain EPR92(T), was isolated from hydrothermal fluids that had been collected from a deep-sea vent on the East Pacific Rise (at 9 degrees 50' N 104 degrees 17' W). The cells of the novel strain were Gram-staining-negative rods that measured approximately 1.4 mu m in length and 0.4 mu m in width. Strain EPR92T grew at 20-40 degrees C (optimum 35 degrees C), with 1.0-5.0{%} (w/v) NaCl (optimum 2.5{%}), and at pH 4.0-8.5 (optimum pH 7.5). The generation time under optimal conditions was 63 min. Strain EPR92(T) grew aerobically in artificial seawater minimal medium with n-alkanes as sole carbon and energy sources, and also in artificial seawater medium supplemented with peptone and yeast extract. The predominant fatty acids were C-18:1 omega 7c, C-19:0 cyclo omega 8c, 11-methyl C-18:1 omega 7c and a putative C-12:0 aldehyde. The major polar lipids were phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and four unidentified aminolipids. The major respiratory quinone was Q-10 and the genomic DNA G+C content was 60.7 mol{%}. Phylogenetic analyses of the 16S rRNA gene showed that strain EPR92(T) belongs in the class Alphaproteobacteria and the recognized species that were most closely related to the novel strain were identified as Parvibaculum indicum P-31(T) (98.7{%} sequence similarity) and Parvibaculum lavamentivorans DS-1(T) (95.8{%}). In DNA-DNA hybridizations, the level of DNA-DNA relatedness observed between strain EPR92(T) and P. indicum P-31(T) was 47.7{%}, indicating that the two strains do not belong to the same species. Based on the phylogenetic, physiological, chemotaxonomic and genetic evidence, strain EPR92(T) represents a novel species within the genus Parvibaculum, for which the name Parvibaculum hydrocarboniclasticum sp. nov. is proposed. The type strain is EPR92(T) (=DSM 23209=JCM 16666(T)).
Keywords: HOV Alvin (Human Occupied Vehicle)

Phorcysia thermohydrogeniphila gen. nov., sp nov., a thermophilic, chemolithoautotrophic, nitrate-ammonifying bacterium from a deep-sea hydrothermal vent - Perez-Rodriguez, Ileana; Grosche, Ashley; Massenburg, Lynnicia; Starovoytov, Valentin; Lutz, Richard A; Vetriani, Costantino (INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY, 2012)
A novel hyperthermophilic, anaerobic, chemolithoautotrophic bacterium, designated strain HB-8(T), was isolated from the tube of Alvinella pompejana tubeworms collected from the wall of an actively venting sulfide structure on the East Pacific Rise at 13 degrees N. The cells were Gram-negative rods, approximately 1.0-1.5 mu m long and 0.5 mu m wide. Strain HB-8(T) grew between 65 and 80 degrees C (optimum 75 degrees C), 15 and 35 g NaCl l(-1) (optimum 30 gl(-1)) and pH 4.5 and 8.5 (optimum pH 6.0). Generation time under optimal conditions was 26 min. Growth occurred under chemolithoautotrophic conditions with H-2 as the energy source and CO2 as the carbon source. Nitrate and sulfur were used as electron acceptors, with concomitant formation of ammonium or hydrogen sulfide, respectively. The presence of lactate, formate, acetate or tryptone in the culture medium inhibited growth. The G+C content of the genomic DNA was 47.8 mol{%}. Phylogenetic analysis of the 16S rRNA gene and of the alpha subunit of the ATP citrate lyase of strain HB-8(T) indicated that this organism formed a novel lineage within the class Aquificae, equally distant from the type strains of the type species of the three genera that represent the family Desulfurobacteriaceae: Thermovibrio ruber ED11/3LLK8(T), Balnearium lithotrophicum 17S(T) and Desulfurobacterium thermolithotrophum BSA(T). The polar lipids of strain HB-8(T) differed substantially from those of other members of the Desulfurobacteriaceae, and this bacterium produced novel quinones. On the basis of phylogenetic, physiological and chemotaxonomic characteristics, it is proposed that the organism represents a novel genus and species within the family Desulfurobacteriaceae, Phorcysia thermohydrogeniphila gen. nov., sp. nov. The type strain of Phorcysia thermohydrogeniphila is HB-8(T) (=DSM 24425(T) =JCM 17384(T)).
Keywords: HOV Alvin (Human Occupied Vehicle)

Physiological homogeneity among the endosymbionts of Riftia pachyptila and Tevnia jerichonana revealed by proteogenomics - Gardebrecht, Antje; Markert, Stephanie; Sievert, Stefan M; Felbeck, Horst; Thuermer, Andrea; Albrecht, Dirk; Wollherr, Antje; Kabisch, Johannes; Le Bris, Nadine; Lehmann, Ruediger; Daniel, Rolf; Liesegang, Heiko; et al. (ISME JOURNAL, 2012)
The two closely related deep-sea tubeworms Riftia pachyptila and Tevnia jerichonana both rely exclusively on a single species of sulfide-oxidizing endosymbiotic bacteria for their nutrition. They do, however, thrive in markedly different geochemical conditions. A detailed proteogenomic comparison of the endosymbionts coupled with an in situ characterization of the geochemical environment was performed to investigate their roles and expression profiles in the two respective hosts. The metagenomes indicated that the endosymbionts are genotypically highly homogeneous. Gene sequences coding for enzymes of selected key metabolic functions were found to be 99.9{%} identical. On the proteomic level, the symbionts showed very consistent metabolic profiles, despite distinctly different geochemical conditions at the plume level of the respective hosts. Only a few minor variations were observed in the expression of symbiont enzymes involved in sulfur metabolism, carbon fixation and in the response to oxidative stress. Although these changes correspond to the prevailing environmental situation experienced by each host, our data strongly suggest that the two tubeworm species are able to effectively attenuate differences in habitat conditions, and thus to provide their symbionts with similar micro-environments. The ISME Journal (2012) 6, 766-776; doi: 10.1038/ismej.2011.137; published online 20 October 2011
Keywords: HOV Alvin (Human Occupied Vehicle)

`Pliocardia' krylovata, a new species of vesicomyid clam from cold seeps along the Costa Rica Margin - Martin, Alanna M; Goffredi, Shana K (JOURNAL OF THE MARINE BIOLOGICAL ASSOCIATION OF THE UNITED KINGDOM, 2012)
`Pliocardia' krylovata, sp. nov. (Bivalvia: Vesicomyidae: Pliocardiinae) is described from cold seeps off the coast of the Nicoya Peninsula, Costa Rica (700-1000 m depth). The phylogenetic position of `P.' krylovata was assessed by both morphological comparisons as well as nucleotide data from the cytochrome c oxidase I gene. Within the vesicomyids, `P.' krylovata belongs to the Pliocardiinae and its closest relative is `Calyptogena' ponderosa, which also bears some morphological resemblance to the genus Pliocardia, perhaps suggesting a need for reanalysis of not only its generic designation, but also the entire Pliocardiinae subfamily. `P.' krylovata has morphological similarities to `Pliocardia' bowdeniana and `Vesicomya' crenulomarginata, recently reassigned to the genus Pliocardia, including a thick shell, obvious rostrum, pointed posterior end, and a sculptured shell with concentric ribs on the outer surface, to name a few. It is morphologically distinguished, however, by having a complex pallial sinus and remarkably deep escutcheon.
Keywords: HOV Alvin (Human Occupied Vehicle)

On the Potential for Bioenergy and Biofuels from Hydrothermal Vent Microbes - Girguis, Peter R; Holden, James F (OCEANOGRAPHY, 2012)
Keywords: HOV Alvin (Human Occupied Vehicle)

Repeat bathymetric surveys at 1-metre resolution of lava flows erupted at Axial Seamount in April 2011 - Caress, D W; Clague, D A; Paduan, J B; Martin, J F; Dreyer, B M; Chadwick, W W; Denny, Alden; Kelley, D S (Nature Geoscience, 2012)
At sites with frequent submarine volcanic activity, it is difficult to discern between new and pre-existing lava flows. In particular, the distribution of the fissures from which lava erupts, the routes taken by lava flows and the relationship between the new flows and the pre-existing seafloor bathymetry are often unclear. The volcanic and hydrothermal systems of Axial Seamount submarine volcano in the Pacific Ocean have been studied intensively since eruptions were detected in 1998 (refs 1, 2) and 2011 (ref. 3). Here we combine pre- and post-eruption bathymetric surveys3, 4, 5, 6, 7, 8, with 1-m lateral resolution and 0.2-m vertical precision, to precisely map the extent and thickness of the lava flows, calculate the volume of lava and unambiguously identify eruptive fissures from the April 2011 eruption. Where the new lava flows extend beyond the boundaries of the repeated surveys, we use shipboard multibeam surveys to map the flows with lower resolution. We show that the eruption produced both sheet and lobate flows associated with high eruption rates and low-eruption-rate pillow mounds. We find that lava flows erupted from new as well as existing fissures and tended to reoccupy existing flow channels. This reoccupation makes it difficult to map submarine flows produced during one eruption without before-and-after bathymetric surveys.
Keywords: ROV Jason (Remotely Operated Vehicle)

Reply to Boehm and Carragher: Multiple lines of evidence link deep-water coral damage to Deepwater Horizon oil spill - White, H K; Hsing, P-Y; Cho, W; Shank, T M; Cordes, E E; Quattrini, A M; Nelson, R K; Camilli, R; Demopoulos, A W J; German, C R; Brooks, J M; Roberts, H H; et al. (Proceedings of the National Academy of Sciences of the United States of America, 2012)
Our original study (1) used visual inspection as well as biological and geochemical analyses of corals and the surrounding sediment to provide complementary and compelling evidence linking the Deepwater Horizon (DWH) oil spill to the presence of damaged deep-water corals and brittle stars 11 km from the site of the leaking oil.

Resilience of Cold-Water Scleractinian Corals to Ocean Acidification: Boron Isotopic Systematics of pH and Saturation State Up-Regulation - McCulloch, M; Trotter, J; Montagna, P; Falter, J; Dunbar, R; Freiwald, A; Försterra, G; Correa, M L; Maier, C; Rüggeberg, A; Taviani, M (Geochimica et Cosmochimica Acta, 2012)
The boron isotope systematics has been determined for azooxanthellate scleractinian corals from a wide range of both deep-sea and shallow-water environments. The aragonitic coral species, Caryophyllia smithii, Desmophyllum dianthus, Enallopsammia rostrata, Lophelia pertusa, and Madrepora oculata, are all found to have relatively high $δ$11B compositions ranging from 23.2‰ to 28.7‰. These values lie substantially above the pH-dependent inorganic seawater borate equilibrium curve, indicative of strong up-regulation of pH of the internal calcifying fluid (pHcf), being elevated by ∼0.6–0.8 units ($Δ$pH) relative to ambient seawater. In contrast, the deep-sea calcitic coral Corallium sp. has a significantly lower $δ$11B composition of 15.5‰, with a corresponding lower $Δ$pH value of ∼0.3 units, reflecting the importance of mineralogical control on biological pH up-regulation. The solitary coral D. dianthus was sampled over a wide range of seawater pHT and shows an approximate linear correlation with $Δ$pHDesmo = 6.43 − 0.71pHT (r2 = 0.79). An improved correlation is however found with the closely related parameter of seawater aragonite saturation state, where $Δ$pHDesmo = 1.09 − 0.14$Ømega$arag (r2 = 0.95), indicating the important control that carbonate saturation state has on calcification. The ability to up-regulate internal pHcf, and consequently $Ømega$cf, of the calcifying fluid is therefore a process present in both azooxanthellate and zooxanthellate aragonitic corals, and is attributed to the action of Ca2+-ATPase in modulating the proton gradient between seawater and the site of calcification. These findings also show that the boron isotopic compositions ($δ$11Bcarb) of aragonitic corals are highly systematic and consistent with direct uptake of the borate species within the biologically controlled extracellular calcifying medium. We also show that the relatively strong up-regulation of pH and consequent elevation of the internal carbonate saturation state ($Ømega$cf ∼8.5 to ∼13) at the site of calcification by cold-water corals, facilitates calcification at or in some cases below the aragonite saturation horizon, providing a greater ability to adapt to the already low and now decreasing carbonate ion concentrations. Although providing greater resilience to the effects of ocean acidification and enhancing rates of calcification with increasing temperature, the process of internal pHcf up-regulation has an associated energetic cost, and therefore growth-rate cost, of ∼10{%} per 0.1 pH unit decrease in seawater pHT. Furthermore, as the aragonite saturation horizon shoals with rapidly increasing pCO2 and $Ømega$arag
Keywords: ROV Jason (Remotely Operated Vehicle)

Response of hydrothermal vent vestimentiferan Riftia pachyptila to differences in habitat chemistry - Scott, Kathleen M; Boller, Amanda J; Dobrinski, Kimberly P; Le Bris, Nadine (MARINE BIOLOGY, 2012)
Vestimentiferan tubeworms, which rely on intracellular sulfide-oxidizing autotrophic bacteria for organic carbon, flourish at deep-sea hydrothermal vents despite the erratic nature of their habitat. To assess the degree to which differences in habitat chemistry (sulfide, pH/CO(2)) might impact host and symbiont metabolic activity, Riftia pachyptila tubeworms were collected from habitats with low (H(2)S {<} 0.0001 mM) and high (up to 0.7 mM) sulfide concentrations. The elemental sulfur content of the symbiont-containing trophosome organ was lower in specimens collected from the low-sulfide site. Symbiont abundance, RubisCO activity, and trophosome carbon fixation rates were not significantly different for individuals collected from low- versus high-sulfide habitats. Carbonic anhydrase activities were higher in the anterior gas exchange organs of R. pachyptila from the low-sulfide habitat. Despite large differences in habitat chemistry, symbiont abundance and autotrophic potential were consistent, while the host appears to tailor carbonic anhydrase activity to environmental CO(2) availability.
Keywords: HOV Alvin (Human Occupied Vehicle)

Reviews of power systems and environmental energy conversion for unmanned underwater vehicles - Wang, X -M; Shang, J -H; Luo, Zirong; Tang, Li; Zhang, X; Li, J (Renewable and Sustainable Energy Reviews, 2012)
The power supply for unmanned underwater vehicles has been an important research point since the vehicles were invented. The power systems and environmental energy conversions for the vehicles are reviewed in the paper. Several topics are represented: problems and general solutions for unmanned underwater vehicles power supplies; the mechanisms and structures of tether power system; characteristics of several batteries; the characterization of potential environmental energy, and energy conversion for unmanned underwater vehicles. Docking stations for underwater vehicles continuation are also represented in the paper. Some typical vehicles powered by the power systems and their performances are listed and analyzed.
Keywords: AUV ABE (Autonomous Benthic Explorer); ROV Medea (Remotely Operated Vehicle)

Satellite based remote management and operation of a 6000m AUV - Kaiser, C L; Kinsey, J C; Pinner, W; Yoerger, D R; German, C R; Van Dover, C L (Oceans, 2012, 2012)
During a July, 2012 expedition to the Hatteras Transverse Canyon, Blake Ridge, and Cape Fear Diapir, the AUV Sentry, aboard the NOAA Ship Okeanos, conducted experiments into remote operation of an AUV via satellite link. Remote launch, remote engineering, remote data processing and remote watch standing were all explored with varying degrees of success. Remote engineering and troubleshooting was found to be exceptionally promising and worthy of further effort. Remote data processing was a valuable addition for a telepresence enabled cruise where a substantial component of the science team was on shore. Remore watch standing and remote launch were both found to be viable though requiring improvement. Technology infrastructure is discussed along with successes, difficulties, and recommendations for future improvement.
Keywords: AUV Sentry (Autonomous Underwater Vehicle)

Scientific Gear as a Vector for Non-Native Species at Deep-Sea Hydrothermal Vents - Voight, J R; Lee, R W; Reft, A J; Bates, A E (Conservation Biology, 2012)
The fauna of deep-sea hydrothermal vents are among the most isolated and inaccessible biological communities on Earth. Most vent sites can only be visited by subsea vehicles, which can and do move freely among these communities. Researchers assume individuals of the regionally homogeneous vent fauna are killed by the change in hydrostatic pressure the animals experience when the subsea vehicles, which collected them, rise to the surface. After an Alvin dive, we found 38 apparently healthy individuals of a vent limpet in a sample from a hydrothermally inactive area. Prompted by our identification of these specimens as Lepetodrilus gordensis, a species restricted to vents 635 km to the south of our dive site, we tested whether they were from a novel population or were contaminants from the dive made 36 h earlier. The 16S gene sequences, morphology, sex ratio, bacterial colonies, and stable isotopes uniformly indicated the specimens came from the previous dive. We cleaned the sampler, but assumed pressure changes would kill any organisms we did not remove and that the faunas of the 2 areas were nearly identical and disease-free. Our failure to completely clean the gear on the subsea vehicle meant we could have introduced the species and any diseases it carried to a novel location. Our findings suggest that the nearly inaccessible biological communities at deep-sea vents may be vulnerable to anthropogenic alteration, despite their extreme physical conditions.
Keywords: HOV Alvin (Human Occupied Vehicle)

Seafloor deformation and forecasts of the April 2011 eruption at Axial Seamount - Chadwick, W W; Nooner, S L; Butterfield, D A; Lilley, M D (Nature Geoscience, 2012)
Axial Seamount is an active submarine volcano located at the intersection between the Cobb hotspot and the Juan de Fuca spreading centre in the northeast Pacific Ocean1, 2. The volcano has been closely monitored since it erupted in 1998 (refs 3, 4). Since then, Axial Seamount seemed to exhibit a similar inflation–deflation cycle to basaltic volcanoes on land and, on that basis, was expected to erupt again sometime before 2014 or 2020 (refs 5, 6). In April 2011 Axial Seamount erupted. Here we report continuous measurements of ocean bottom pressure that document the deflation–inflation cycle of Axial Seamount between 1998 and 2011. We find that the volcano inflation rate, caused by the intrusion of magma, gradually increased in the months leading up to the 2011 eruption. Sudden uplift occurred 40–55 min before the eruption onset, which we interpret as a precursor event. Based on our measurements of ground deformation through the entire eruption cycle at Axial Seamount, we suggest that another eruption could occur as early as 2018. We propose that the long-term eruptive cycle of Axial Seamount could be more predictable compared with its subaerial counterparts because the volcano receives a relatively steady supply of magma through the Cobb hotspot and because it is located on thin oceanic crust at a spreading plate boundary.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Seismic precursors and magma ascent before the April 2011 eruption at Axial Seamount - Dziak, R P; Haxel, J H; Bohnenstiehl, D R; Chadwick, W W; Nooner, S L; Fowler, M J; Matsumoto, H; Butterfield, D A (Nature Geoscience, 2012)
Volcanoes at spreading centres on land often exhibit seismicity and ground inflation months to years before an eruption, caused by a gradual influx of magma to the source reservoir1, 2, 3, 4. Deflation and seismicity can occur on time scales of hours to days, and result from the injection of magma into adjacent rift zones5, 6, 7, 8. Volcanoes at submarine rift zones, such as Axial Seamount in the northeast Pacific Ocean, have exhibited similar behaviour9, 10, 11, 12, but a direct link between seismicity, seafloor deformation and magma intrusion has never been demonstrated. Here we present recordings from ocean-bottom hydrophones and an established array of bottom-pressure recorders that reveal patterns of both microearthquakes and seafloor deformation at Axial Seamount on the Juan de Fuca Ridge, before it erupted in April 2011. Our observations show that the rate of seismicity increased steadily during a period of several years, leading up to an intrusion and eruption of magma that began on 6 April 2011. We also detected a sudden increase in seismo-acoustic energy about 2.6 h before the eruption began. Our data indicate that access to real-time seismic data, projected to be available in the near future, might facilitate short-term forecasting and provide sufficient lead-time to prepare in situ instrumentation before future intrusion and eruption events.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Simultaneous 16S and 18S rRNA fluorescence in situ hybridization (FISH) on LR White sections demonstrated in Vestimentifera (Siboglinidae) tubeworms - Schimak, M P; Toenshoff, E R; Bright, M (Acta Histochemica, 2012)
Traditional morphological identification of invertebrate marine species is limited in early life history stages for many taxa. In this study, we demonstrate, by example of Vestimentiferan tubeworms (Siboglinidae, Polychaeta), that the simultaneous fluorescence in situ hybridization (FISH) of both eukaryotic host and bacterial symbiont cells is possible on a single semi-thin (1 $μ$m) section. This allows the identification of host specimens to species level as well as offering visualization of bacteria distributed within the host tissue. Previously published 18S rRNA host-specific oligonucleotide probes for Riftia pachyptila, Tevnia jerichonana and a newly designed Oasisia alvinae probe, as well as a 16S rRNA probe targeting symbionts found in all host species, were applied. A number of standard fixation and hybridization parameters were tested and optimized for the best possible signal intensity and cellular resolution. Ethanol conserved samples embedded in LR White low viscosity resin yielded the best results with regard to both signal intensity and resolution. We show that extended storage times of specimens does not affect the quality of signals attained by FISH and use our protocol to identify morphologically unidentifiable tubeworm individuals from a small data set, conforming to previous findings in succession studies of the Siboglinidae family.
Keywords: HOV Alvin (Human Occupied Vehicle)

Small-scale thermal responses of hydrothermal vent polynoid polychaetes: Preliminary in situ experiments and methodological development - Robert, K; Onthank, K L; Juniper, S K; Lee, R W (Journal of Experimental Marine Biology and Ecology, 2012)
Hydrothermal vent systems represent a unique marine environment where high spatial variability allows the study of habitat selection with respect to small-scale temperature gradients. An autonomous time-lapse camera with a temperature logger array was deployed on four occasions to examine the thermal responses of two vent endemic polynoid polychaete taxa: Branchinotogluma sp. and Lepidonotopodium piscesae. Over a total deployment time of 52 h, we collected over 3,400 frames, in which 1,700 individuals were observed and monitored. Automated image processing and particle tracking routines were used to quickly process the imagery acquired in situ. Kriging interpolation was employed to create temperature maps (2.5–67 °C) of the field of view within which individual polynoids were tracked over time. Using the individual trajectories, we examined whether organisms selected for a narrower range of temperature than available in the environment and whether past information regarding the temperature encountered influenced subsequent movement decisions. A two state hidden Markov model was applied to predict behaviour based on movement patterns and examine whether areas characterized by different movement patterns differed in temperature. We found polynoids to be active over a wide range of temperatures and areas where different movement patterns were observed did not differ in temperature. Within their tolerated range of temperature, polynoids appear to thermoconform to the highly spatially variable thermal environment. Based on these preliminary deployments, we make suggestions for future studies over broader thermal regimes and longer time scales.
Keywords: HOV Alvin (Human Occupied Vehicle)

Spatial And Temporal Variations In Food Web Structure From Newly-Opened Habitat At Hydrothermal Vents - Gaudron, S M; Lefebvre, S; Jorge, A N; Gaill, F; Pradillon, F (Marine Environmental Research, 2012)
To highlight the spatio-temporal variability of the food web structure of hydrothermal vent fauna from newly-opened habitat, a series of Titanium Ring for Alvinellid Colonization devices (TRACs) was deployed at TICA site on the East Pacific Rise in 2006. This experiment was conducted for periods of 4 days, 13 days and one month and deployments were aligned along a gradient from the basaltic bottom to the vent openings. $δ$13C values of colonists revealed a narrower range of carbon sources in proximity to vent openings in Alvinella pompejana habitat than in Tevnia jerichonana habitat, separated by a distance of four meters. This was possibly due to a spatial change in available food sources with a possible higher contribution of particulate organic matter (POM) to the siboglinid habitat compared to a higher contribution of microbial primary producers such as Epsilonproteobacteria in the alvinellid habitat. Temporal variability was also observed during experimentation in the form of a shift in either $δ$13C and/or $δ$15N values for A. pompejana, Lepetodrilus elevatus, dirivultid copepods and polynoid polychaetes within a one-month window showing first of all, fast tissues turnover and secondly, a possible switch in feeding strategy or food sources. Lepidonotopodium riftense and Branchinotogluma sandersi may have to alternate between detritivorous and predatory feeding strategies. In addition, through the analysis of stable isotope composition of A. pompejana and its episymbionts, we provided evidence that these attached bacteria formed part of the worms' diet during the course of these colonization experiments.
Keywords: HOV Alvin (Human Occupied Vehicle)

Spatial heterogeneity and underlying geochemistry of phylogenetically diverse orange and white Beggiatoa mats in Guaymas Basin hydrothermal sediments - McKay, L J; MacGregor, B J; Biddle, J F; Albert, D B; Mendlovitz, H P; Hoer, D R; Lipp, J S; Lloyd, K G; Teske, A P (Deep-Sea Research. Part I: Oceanographic Research Papers, 2012)
Sulfide-oxidizing bacteria of the genus Beggiatoa are found in conspicuous, colorful mats on the seafloor above active hydrothermal seeps at Guaymas Basin. Guaymas Beggiatoa filaments fall into discrete size classes representing at least five separate 16S rRNA phylotypes, and appear either white, yellow, or orange. During two R/V Atlantis cruises to Guaymas Basin, 78 temperature profiles were taken near and within 15 different orange and white Beggiatoa mats by the Alvin submersible to investigate spatial relationships between mat color and hydrothermal fluid seeps, as indicated by elevated temperatures. The surface temperatures from 78 profiles are similar to each other (on average 8–12 °C, warmer than bare sediments at 3–4 °C), indicating that Guaymas Basin Beggiatoa spp., although relying on the hydrothermal system for energy and carbon sources, live within a relatively cool temperature range. Temperatures from 40 cm below orange Beggiatoa versus white Beggiatoa are the same, at 84 °C averaged across all mat systems. However, within a single mat system, temperatures are higher beneath the predominantly orange center of the mat than beneath the white mat periphery. Push core transects across the orange-to-white color change of three Beggiatoa mats showed stronger upward compression of isotherms and metabolic zones beneath the orange mat center than beneath white mat periphery. Hydrothermal temperature gradients push the microbial processes generating carbon and energy sources for Beggiatoa mats towards the sediment surface. The resulting steep gradients of hydrothermal electron donors and carbon sources to the sediment surface, rather than the in situ temperature by itself, control the relative positioning of orange and white filaments within a Guaymas Basin Beggiatoa mat. Given the wide spectrum of temperature and hydrothermal flux regimes between different mats, the orange/white pattern represents a relative preference or even a competitive balance among different Beggiatoa types that establishes itself within each hydrothermal hot spot.
Keywords: HOV Alvin (Human Occupied Vehicle)

Squat lobsters (Crustacea: Decapoda: Galatheoidea and Chirostyloidea) collected during the TALUD XIV cruise in the Gulf of California, Mexico, and rediscovery of Gastroptychus perarmatus (Haig, 1968) in the eastern Pacific - Hendrickx, Michel E (ZOOTAXA, 2012)
Seven species of squat lobsters were collected during the TALUD XIV cruise in the Gulf of California, Mexico. Gastroptychus perarmatus (Haig, 1968) was collected for the second time since it was described and represents a first record of the genus in the tropical eastern Pacific. Its association with gorgonians is also noted from color pictures taken during a deep-water dive in another cruise in the area. Janetogalathea californiensis (Benedict, 1902) was captured in four sampling stations, in the same area where it has been previously reported. Three species of Munida Leach, 1820 were collected (M. bapensis Hendrickx, 2000, M. mexicana Benedict, 1902, and M. tenella Benedict, 1902). Records of M. bapensis of this cruise combined with additional captures of this species in 2007 in the same area indicate that it is the most abundant deep-water species of squat lobster in the northern part of the central Gulf of California. Among the species of Munida, M. tenella was second in abundance and included specimens much larger than previously known. The single record for M. mexicana fits within the currently known depth and geographical ranges. Only one species of Munidopsis Whiteaves, 1874 (M. depressa Faxon, 1892) was collected, in one of the deeper sampling stations visited during the cruise and its northernmost distribution limit within the Gulf of California is increased by ca two degrees of latitude. The seventh species collected during this survey, Pleuroncodes planipes Stimpson, 1860, is a common inhabitant of the California Current and the Gulf of California.
Keywords: ROV Jason (Remotely Operated Vehicle)

Submarine landslide triggered by volcanic eruption recorded by in situ hydrophone - Chadwick, W W; Dziak, R P; Haxel, J H; Embley, R W; Matsumoto, H (Geology, 2012)
NW Rota-1 is a submarine volcano in the Mariana volcanic arc that is notable as the site where underwater explosive eruptions were first witnessed in A.D. 2004. After years of continuous low-level eruptive activity, a major landslide occurred at NW Rota-1 in August 2009, triggered by an unusually large eruption that produced 10 times the acoustic energy of the background level of activity. An anomalous earthquake swarm preceded the eruption, suggesting that the sequence started with a magmatic intrusion and associated faulting beneath the volcano. We quantify the size and extent of the landslide using bathymetric resurveys and interpret the timing of events using data from an in situ hydrophone. This is the first instrumental documentation of an earthquake-eruption-landslide sequence at a submarine volcano, and illustrates the close interaction between magmatic activity and mass wasting events in the growth of undersea arc volcanoes.
Keywords: ROV Jason (Remotely Operated Vehicle)

Subseafloor nitrogen transformations in diffuse hydrothermal vent fluids of the Juan de Fuca Ridge evidenced by the isotopic composition of nitrate and ammonium - Bourbonnais, Annie; Lehmann, Moritz F; Butterfield, David A; Juniper, S Kim (GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 2012)
Little is known about dissolved inorganic nitrogen (DIN) transformations in hydrothermal vent (HV) fluids. Here, we present the first isotopic measurements of nitrate (delta N-15 and delta O-18) and ammonium (delta N-15) from three HV fields on the Juan de Fuca ridge (NE-Pacific). The dominant process that drives DIN concentration variations in low-T diffuse fluids is water mass mixing below the seafloor, with no effect on the DIN isotope ratios. Strong inter-site variations in the concentration and delta N-15 of NH4+ in high-T fluids suggest different subsurface nitrogen (N) sources (deep-sea nitrate versus organic sediments) for hydrothermally discharged ammonium. Low NH4+ community N isotope effects ({<}3 parts per thousand) for net NH4+ consumption suggest an important contribution from gross ammonium regeneration in low-T fluids. Elevation of HV nitrate N-15/N-14 and O-18/O-16 over deep-sea mean isotope values at some sites, concomitant with decreased nitrate concentrations, indicate assimilatory or dissimilatory nitrate consumption by bacteria in the subsurface, with relatively low community N isotope effects ((15)epsilon(k) {<} 3 parts per thousand). The low N isotope effects suggest that nitrate assimilation or denitrification occur in bacterial mats, and/or in situ production of low delta N-15 nitrate. A significantly stronger relative increase for nitrate delta O-18 than for delta N-15 was observed at many sites, resulting in marked deviations from the 1:1 relationship for nitrate delta N-15 versus delta O-18 that is expected for nitrate reduction in marine settings. Simple box-model calculation show that the observed un-coupling of N and O nitrate isotope ratios is consistent with nitrate regeneration by either nitrite reoxidation and/or partial nitrification of hydrothermal ammonium (possibly originating from N-2 fixation). Our isotope data confirm the role of subsurface microbial communities in modulating hydrothermal fluxes to the deep ocean.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Subseafloor phase equilibria in high-temperature hydrothermal fluids of the Lucky Strike Seamount (Mid-Atlantic Ridge, 37°17'N) - Pester, N J; Reeves, E P; Rough, M E; Ding, K; Seewald, J S; Seyfried, W E (Geochimica et Cosmochimica Acta, 2012)
As part of an integrated study conducted at the Lucky Strike Seamount (Mid-Atlantic Ridge, 37°17′N) in 2008, gas-tight sampling devices were used to collect high-temperature (∼300 °C) hydrothermal fluids issuing from sulfide structures distributed throughout the vent field located in the summit depression. Compared with previous observations from 1993 to 1997, the most substantial changes in vent fluid compositions are dramatically increased CO2 concentrations (∼5×, up to 133 mmol/L) and the observation of vent fluids enriched in dissolved chloride relative to seawater. Combined with an increase in $δ$13CCO2$δ$13CCO2 values by ∼4‰ in 2008, the elevated CO2 indicates replenishment of the magmatic heat source and may be indicative of a recent magmatic event. The additional supporting fluid chemistry is, however, similar to that of the previous sampling intervals, necessitating a reassessment of the subseafloor controls on vent fluid chemistry at Lucky Strike in the context of recently obtained geophysical data that provides the depth/extent of a steady-state magma chamber. Two-phase behavior is indicated by the chloride variability in the vent fluids; and comparison with experimental data for the associated chloride-dependent partitioning of minor/trace elements suggests the possibility of a similar source fluid for all the vent structures, while limiting the likelihood of shallow phase separation and subseafloor mixing for the hydrothermal end-members. A recently calibrated Fe/Mn geothermometer indicates minimum subseafloor equilibration temperatures of 350–385 °C. However, constraints imposed by dissolved Si/Cl in conjunction with geophysical observations are consistent with peak reaction conditions at temperatures of 430–475 °C and pressures near the top of the axial magma chamber (∼410–480 bars), where magmatic CO2 becomes entrained in the circulating fluids. The distance between the magma chamber and the seafloor at Lucky Strike is substantially greater than at most faster spreading ridges; and we propose the resulting increased residence time in the up-flow zone leads to the re-equilibration of temperature sensitive transition metals at conditions less extreme than those associated with peak reaction. Agreement between experimental data, thermodynamic model calculations, and dissolved concentrations of Fe, Cu, Zn, H2, and H2S in the Lucky Strike fluids reinforce the hypothesis of pH-redox equilibria for transition metals at relatively oxidizing conditions and temperatures predicted by the empirical Fe/Mn geothermometer. In-situ pH measurements of the high-temperature fluids exiting the seafloor are also consistent with the model calculations.
Keywords: ROV Jason (Remotely Operated Vehicle)

Symbiont–host relationships in chemosynthetic mussels: A comprehensive lipid biomarker study - Kellermann, M Y; Schubotz, F; Elvert, M; Lipp, J S; Birgel, D; Prieto-Mollar, X; Dubilier, N; Hinrichs, K -U (Organic Geochemistry, 2012)
Symbiosis with chemosynthetic microorganisms allows invertebrates from hydrothermal vents and cold seeps, such as mussels, snails and tubeworms, to gain nutrition independently of organic input from photosynthetic communities. Lipid biomarkers and their compound specific stable carbon isotopes ($δ$13C) have greatly aided the elucidation of chemosynthetic symbiosis. Due to recent methodological advances in liquid chromatography it is now possible to obtain a more holistic view of lipid biomarkers, including the analysis of intact polar membrane lipids (IPLs) and bacteriohopanepolyols (BHPs). This study provides an extensive examination of polar and apolar lipids in combination with stable carbon isotope analysis of three Bathymodiolus mussels (Bathymodiolus childressi, Bathymodiolus cf. thermophilus, Bathymodiolus brooksi) hosting different types of bacterial symbiont (methane-oxidizing, sulfur-oxidizing and a dual symbiosis with methane- and sulfur-oxidizing symbionts, respectively). We propose that IPLs with C16:1 acyl side chains, and phosphatidylglycerol (PG), diphosphatidylglycerol (DPG) and phosphatidylethanolamine (PE) head groups, which were only detected in the gill tissue, can be used as symbiont-characteristic biomarkers. These putative symbiont-specific IPLs provide the opportunity to detect and quantify the methanotrophic and thiotrophic symbionts within the gill tissue. Additional characteristic markers for methanotrophic symbionts were found in B. childressi and B. brooksi, including the BHP derivatives aminotriol and aminotetrol, 4-methyl sterols and diagnostic fatty acids (FAs), such as C16:1$ømega$9, C16:1$ømega$8, and C18:1$ømega$8. In general, the $δ$13C values of FAs, alcohols and BHP-derived hopanols were in accordance with carbon assimilation pathways of the respective methanotrophic or thiotrophic symbionts in all three Bathymodiolus mussels. Differences in BHP distribution as well as $δ$13C values in the two mussels hosting a methanotrophic symbiont may indicate the presence of different methanotrophic symbionts and/or changes in the nutritional status. In all three mussel species the $δ$13C values of lipid biomarkers assigned to the symbionts were similar to those of the hosts, indicating the importance of the bacterial symbionts as the main carbon source for the mussel tissue.
Keywords: HOV Alvin (Human Occupied Vehicle)

Thermosulfurimonas dismutans gen. nov., sp nov., an extremely thermophilic sulfur-disproportionating bacterium from a deep-sea hydrothermal vent - Slobodkin, A I; Reysenbach, A -L.; Slobodkina, G B; Baslerov, R V; Kostrikina, N A; Wagner, I D; Bonch-Osmolovskaya, E A (INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY, 2012)
An extremely thermophilic, anaerobic, chemolithoautotrophic bacterium (strain S95(T)) was isolated from a deep-sea hydrothermal vent chimney located on the Eastern Lau Spreading Center, Pacific Ocean, at a depth of 1910 m. Cells of strain S95(T) were oval to short Gram-negative rods, 0.5-0.6 mu m in diameter and 1.0-1.5 mu m in length, growing singly or in pairs. Cells were motile with a single polar flagellum. The temperature range for growth was 50-92 degrees C, with an optimum at 74 degrees C. The pH range for growth was 5.5-8.0, with an optimum at pH 7.0. Growth of strain S95(T) was observed at NaCl concentrations ranging from 1.5 to 3.50/o (w/v). Strain S95(T) grew anaerobically with elemental sulfur as an energy source and bicarbonate/CO2 as a carbon source. Elemental sulfur was disproportionated to sulfide and sulfate. Growth was enhanced in the presence of poorly crystalline iron(III) oxide (ferrihydrite) as a sulfide-scavenging agent. Strain S95(T) was also able to grow by disproportionation of thiosulfate and sulfite. Sulfate was not used as an electron acceptor. Analysis of the 16S rRNA gene sequence revealed that the isolate belongs to the phylum Thermodesulfobacteria. On the basis of its physiological properties and results of phylogenetic analyses, it is proposed that the isolate represents the sole species of a new genus, Thermosulfurimonas dismutans gen. nov., sp. nov.; S95(T) (=DSM 24515(T)=VKM B-2683(T)) is the type strain of the type species. This is the first description of a thermophilic microorganism that disproportionates elemental sulfur.
Keywords: ROV Jason (Remotely Operated Vehicle)

The Transcriptome of Bathymodiolus azoricus Gill Reveals Expression of Genes from Endosymbionts and Free-Living Deep-Sea Bacteria - Egas, Conceicao; Pinheiro, Miguel; Gomes, Paula; Barroso, Cristina; Bettencourt, Raul (MARINE DRUGS, 2012)
Deep-sea environments are largely unexplored habitats where a surprising number of species may be found in large communities, thriving regardless of the darkness, extreme cold, and high pressure. Their unique geochemical features result in reducing environments rich in methane and sulfides, sustaining complex chemosynthetic ecosystems that represent one of the most surprising findings in oceans in the last 40 years. The deep-sea Lucky Strike hydrothermal vent field, located in the Mid Atlantic Ridge, is home to large vent mussel communities where Bathymodiolus azoricus represents the dominant faunal biomass, owing its survival to symbiotic associations with methylotrophic or methanotrophic and thiotrophic bacteria. The recent transcriptome sequencing and analysis of gill tissues from B. azoricus revealed a number of genes of bacterial origin, hereby analyzed to provide a functional insight into the gill microbial community. The transcripts supported a metabolically active microbiome and a variety of mechanisms and pathways, evidencing also the sulfur and methane metabolisms. Taxonomic affiliation of transcripts and 16S rRNA community profiling revealed a microbial community dominated by thiotrophic and methanotrophic endosymbionts of B. azoricus and the presence of a Sulfurovum-like epsilonbacterium.
Keywords: ROV Jason (Remotely Operated Vehicle)

Volcanic Eruptions in the Deep Sea - Rubin, K H; Soule, S A; Chadwick, W W; Fornari, D J; Clague, D A; Embley, R W; Baker, E T; Perfit, M R; Caress, D W; Dziak, R P (Oceanography, 2012)
Volcanic eruptions are important events in Earth's cycle of magma generation and crustal construction. Over durations of hours to years, eruptions produce new deposits of lava and/or fragmentary ejecta, transfer heat and magmatic volatiles from Earth's interior to the overlying air or seawater, and significantly modify the landscape and perturb local ecosystems. Today and through most of geological history, the greatest number and volume of volcanic eruptions on Earth have occurred in the deep ocean along mid-ocean ridges, near subduction zones, on oceanic plateaus, and on thousands of mid-plate seamounts. However, deep-sea eruptions ({>} 500 m depth) are much more difficult to detect and observe than subaerial eruptions, so comparatively little is known about them. Great strides have been made in eruption detection, response speed, and observational detail since the first recognition of a deep submarine eruption at a mid-ocean ridge 25 years ago. Studies of ongoing or recent deep submarine eruptions reveal information about their sizes, durations, frequencies, styles, and environmental impacts. Ultimately, magma formation and accumulation in the upper mantle and crust, plus local tectonic stress fields, dictate when, where, and how often submarine eruptions occur, whereas eruption depth, magma composition, conditions of volatile segregation, and tectonic setting determine submarine eruption style.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Volcanism on the flanks of the East Pacific Rise: Quantitative constraints on mantle heterogeneity and melting processes - Brandl, P A; Beier, C; Regelous, M; Abouchami, W; Haase, K M; Garbe-Schonberg, D; Galer, S J G (Chemical Geology, 2012)
We present major and trace element and Sr, Nd and triple-spike Pb isotope data for 17 fresh volcanic glasses from Seamount 6, a 10-km diameter seamount located 140 km east of the East Pacific Rise at 12°45′N. Geological and geochronological evidence show that magma compositions evolved from tholeiitic basalts to alkalic basalts and basaltic trachyandesites during the 1–2 Ma active lifetime of the seamount. Major and trace element compositions in Seamount 6 lavas vary systematically with isotope ratios; the youngest lavas with the highest incompatible trace element concentrations have the highest La/Yb, Nb/Zr, K2O/TiO2, 87Sr/86Sr, 206Pb/204Pb and the lowest 143Nd/144Nd, MgO and CaO. The range in element concentrations, incompatible element ratios, and isotope compositions in Seamount 6 lavas exceeds that observed in lavas erupted at the adjacent ridge axis, and is comparable to the range in lava compositions reported from all near-ridge seamounts studied to date. The observed range in lava compositions is consistent with mixing between enriched and depleted melts at shallow levels in the crust. The inferred difference in composition between these mixing endmembers cannot be explained by variable degrees of melting of a single source composition, and requires that the upper mantle is extremely heterogeneous on the scale of the melting region beneath a single seamount. We can show that the range in composition of EPR seamount lavas cannot be generated by melting of variably heterogeneous mantle in which enriched and depleted materials contribute equally to melting (source mixing). Instead, the trace element and isotope compositions of seamount lavas can be reproduced by melting models in which more enriched, fertile mantle lithologies are preferentially melted during mantle upwelling. At progressively lower degrees of melting, erupted lavas are thus more enriched in incompatible trace elements, have higher La/Yb, K/Ti, 87Sr/86Sr ratios and lower 143Nd/144Nd. If this is a common process, then mantle-derived magmas are unlikely to inherit the average incompatible trace element and isotope composition of their mantle source, which is likely to be significantly more depleted, nor will they display the full range of compositions present in the mantle melting region. These results have implications for the way in which oceanic basalts can be used to infer the composition of the upper mantle.
Keywords: HOV Alvin (Human Occupied Vehicle)

Widespread occurrence of two carbon fixation pathways in tubeworm endosymbionts: lessons from hydrothermal vent associated tubeworms from the Mediterranean Sea - Thiel, Vera; Hugler, M; Blümel, M; Baumann, H I; Gärtner, A; Schmaljohann, R; Strauss, H; Garbe-Schonberg, D; Petersen, S; Cowart, D A; Fisher, C R; Imhoff, J F (Frontiers in Microbiology, 2012)
Vestimentiferan tubeworms (siboglinid polychetes) of the genus Lamellibrachia are common members of cold seep faunal communities and have also been found at sedimented hydrothermal vent sites in the Pacific. As they lack a digestive system, they are nourished by chemoautotrophic bacterial endosymbionts growing in a specialized tissue called the trophosome. Here we present the results of investigations of tubeworms and endosymbionts from a shallow hydrothermal vent field in the Western Mediterranean Sea. The tubeworms, which are the first reported vent-associated tubeworms outside the Pacific, are identified as Lamellibrachia anaximandri using mitochondrial ribosomal and cytochrome oxidase I (COI) gene sequences. They harbor a single gammaproteobacterial endosymbiont. Carbon isotopic data, as well as the analysis of genes involved in carbon and sulfur metabolism indicate a sulfide-oxidizing chemoautotrophic endosymbiont. The detection of a hydrogenase gene fragment suggests the potential for hydrogen oxidation as alternative energy source. Surprisingly, the endosymbiont harbors genes for two different carbon fixation pathways, the Calvin-Benson-Bassham (CBB) cycle as well as the reductive tricarboxylic acid (rTCA) cycle, as has been reported for the endosymbiont of the vent tubeworm Riftia pachyptila. In addition to RubisCO genes we detected ATP citrate lyase (ACL – the key enzyme of the rTCA cycle) type II gene sequences using newly designed primer sets. Comparative investigations with additional tubeworm species (Lamellibrachia luymesi, Lamellibrachia sp. 1, Lamellibrachia sp. 2, Escarpia laminata, Seepiophila jonesi) from multiple cold seep sites in the Gulf of Mexico revealed the presence of acl genes in these species as well. Thus, our study suggests that the presence of two different carbon fixation pathways, the CBB cycle and the rTCA cycle, is not restricted to the Riftia endosymbiont, but rather might be common in vestimentiferan tubeworm endosymbionts, regardless of the habitat.
Keywords: ROV Jason (Remotely Operated Vehicle)

Abundance and distribution of fatty acids within the walls of an active deep-sea sulfide chimney - Li, J; Zhou, H Y; Peng, X T; Fu, M; Chen, Z Q; Yao, H Q (Journal of Sea Research, 2011)
Abundance and distribution of total fatty acids (TFAs) were examined along the physicochemical gradient within an active hydrothermal chimney collected from the Main Endeavour segment of Juan de Fuca Ridge. Approximately 27 fatty acids are identified with a chain-length ranging from C12 to C22. From the exterior to the interior of the chimney walls, the total concentrations of TFAs (∑ TFAs) show a trend of evident decrease. The observed compositions of TFAs are rich in bacterial biomarkers especially monounsaturated fatty acids (MUFAs) and minor branched and cyclopropyl FAs. On the basis of the species-specific FAs and bacterial 16SrRNA gene analysis (Li et al., unpublished data), sulfur-based metabolism appears to be the essential metabolic process in the chimney. Furthermore, the sulfur oxidizing bacteria (SOB) are identified as a basic component of microbial communities at the exterior of the hydrothermal chimney, and its proportion shows an inward decrease while the sulfate reducing bacteria (SRB) have an inverse distribution.
Keywords: HOV Alvin (Human Occupied Vehicle)

Anaerobic propane oxidation in marine hydrocarbon seep sediments - Quistad, S D; Valentine, D L (Geochimica et Cosmochimica Acta, 2011)
Propane (C3H8) is an abundant hydrocarbon in subsurface reservoirs with significance to atmospheric chemistry and to marine biogeochemistry. The anaerobic oxidation of propane coupled to sulfate reduction may prevent sub-seafloor accumulations of propane from entering the ocean and atmosphere. Anaerobic oxidation of propane has recently been demonstrated in cultures of novel sulfate-reducing bacteria, but has not been directly demonstrated or quantified in nature. In this work we describe a method involving incubation with 13C-propane to quantify rates of anaerobic oxidation of propane in anoxic sediment, and we conclusively demonstrate the oxidation of propane under sulfidic conditions in fresh sediments of a marine hydrocarbon seep. Observed rates of anaerobic oxidation of propane adhere to first-order kinetic behavior, enabling the modification of this method for whole core rate determinations. Whole core rates in nine cores from two hydrocarbon seeps measured 0.04–2100 nmoles C3H8 cm−3 day−1 by this method. The seep persistently supplied with more propane displayed substantially higher rates of anaerobic oxidation of propane, by 1–2 orders of magnitude when averaged over the top 10-cm, suggesting the development of the microbial community is strongly modulated by the availability of propane. This work is the first to estimate rates for anaerobic oxidation of propane in any environment, and demonstrates the potential importance of the process as a filter for preventing propane from entering the ocean and atmosphere.
Keywords: HOV Alvin (Human Occupied Vehicle)

Assessing the Deepwater Horizon oil spill with the Sentry autonomous underwater vehicle - Kinsey, J C; Yoerger, D R; Jakuba, M V; Camilli, Rich; Fisher, C R; German, C R (2011 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), 2011)
This paper reports the Sentry autonomous underwater vehicle and its deployment on two cruises in response to the Deepwater Horizon oil spill. The first cruise, in June 2010, coupled Sentry with the TETHYS mass spectrometer to track and localize a subsea hydrocarbon plume at a depth of approximately 1100m going at least 30km from the oil spill site. In December 2010, Sentry mapped and photographed deep-sea biological communities for follow-up observations and sampling with the Alvin manned submersible. These cruises demonstrate how robots and novel sensing technologies contributed to the oil spill assessment and the broader impact of technologies developed for basic research.
Keywords: AUV Sentry (Autonomous Underwater Vehicle)

Bacterial sulfur cycling shapes microbial communities in surface sediments of an ultramafic hydrothermal vent field - Schauer, Regina; Roy, Hans; Augustin, Nico; Gennerich, Hans-Hermann; Peters, Marc; Wenzhoefer, Frank; Amann, Rudolf; Meyerdierks, Anke (ENVIRONMENTAL MICROBIOLOGY, 2011)
The ultramafic-hosted Logatchev hydrothermal field (LHF) is characterized by vent fluids, which are enriched in dissolved hydrogen and methane compared with fluids from basalt-hosted systems. Thick sediment layers in LHF are partly covered by characteristic white mats. In this study, these sediments were investigated in order to determine biogeochemical processes and key organisms relevant for primary production. Temperature profiling at two mat-covered sites showed a conductive heating of the sediments. Elemental sulfur was detected in the overlying mat and metal-sulfides in the upper sediment layer. Micro-profiles revealed an intensive hydrogen sulfide flux from deeper sediment layers. Fluorescence in situ hybridization showed that filamentous and vibrioid, Arcobacter-related Epsilonproteobacteria dominated the overlying mats. This is in contrast to sulfidic sediments in basalt-hosted fields where mats of similar appearance are composed of large sulfur-oxidizing Gammaproteobacteria. Epsilonproteobacteria (7-21{%}) and Deltaproteobacteria (20-21{%}) were highly abundant in the surface sediment layer. The physiology of the closest cultivated relatives, revealed by comparative 16S rRNA sequence analysis, was characterized by the capability to metabolize sulfur components. High sulfate reduction rates as well as sulfide depleted in (34)S further confirmed the importance of the biogeochemical sulfur cycle. In contrast, methane was found to be of minor relevance for microbial life in mat-covered surface sediments. Our data indicate that in conductively heated surface sediments microbial sulfur cycling is the driving force for bacterial biomass production although ultramafichosted systems are characterized by fluids with high levels of dissolved methane and hydrogen.
Keywords: ROV Jason (Remotely Operated Vehicle)

Changing redox conditions at cold seeps as revealed by authigenic carbonates from Alaminos Canyon, northern Gulf of Mexico - Birgel, D; Feng, D; Roberts, H H; Peckmann, J (Chemical Geology, 2011)
Anaerobic oxidation of methane in anoxic sediments at cold seeps often leads to formation of authigenic carbonates close to the seafloor along continental margins. Recent work, however, indicated that the redox conditions in sediments may vary to some degree during seepage activity. In order to shed new light on the extent of this variability, authigenic carbonates from Alaminos Canyon lease block 645 of the northern Gulf of Mexico have been characterized by means of inorganic and organic geochemistry. The carbonates were collected from seep deposits representing various seafloor morphologies, including extensive pavements, mounds, fractured carbonate slabs surrounded by dense bivalve shells, and vestimentiferan tubeworm colonies. The deposits almost entirely consist of aragonite. The $δ$18O values of aragonite vary from + 2.6 to + 5.8‰ V-PDB, suggesting precipitation in slight disequilibrium with the surrounding pore fluids. The $δ$13C values of aragonite between − 33.9 and − 20.4‰ V-PDB agree with variable amounts of carbonate derived from oxidation of thermogenic methane and crude oil. Methane was primarily oxidized in an anaerobic process as revealed by the presence of 13C-depleted molecular fossils of methane-oxidizing archaea ($δ$13C values as negative as − 118‰) and sulfate-reducing bacteria ($δ$13C values as negative as − 97‰), the syntrophic partners in the anaerobic oxidation of methane. The observed inventories of molecular fossils in the authigenic carbonates mirror those of known consortia of anaerobic methane oxidizing archaea (ANME) and sulfate-reducing bacteria, namely the ANME-2/Desulfosarcina/Desulfococcus (DSS) and ANME-3/Desulfobulbus (DBB) consortia. In contrast, the same carbonates exhibit shale-normalized rare earth elements patterns that all display real negative Ce anomalies (Ce/Ce*  In contrast, the same carbonates exhibit shale-normalized rare earth elements patterns that all display real negative Ce anomalies (Ce/Ce* 13C values of the biomarkers of aerobic methanotrophs are as negative as − 58‰ and are consequently less 13C-depleted than the molecular fossils of the prokaryotes performing anaerobic oxidation of methane, a pattern in accord with culture experiments. Overall, our results suggest that redox conditions at cold seeps are variable. This variability probably reflects changes in seepage flux. The combination of an inorganic and an organic geochemical approach used here is promising to better assess the variability and diversity of past fluid and gas expulsion at seeps.
Keywords: ROV Jason (Remotely Operated Vehicle)

A characterization of a hydrothermal vent community from a diffuse flow vertical wall of "The tower" sulfide edifice at the Juan de Fuca Ridge - Grinar, M (Temple University, 2011)
The Juan de Fuca Ridge, located 400 km off the coast of Washington State, is home to unstable and unpredictable hydrothermal vent sites where chemosynthetic communities flourish. In 2007 the manned submersible ALVIN retrieved a Ridgeia piscesae tubeworm community in its entirety from the side of the Tower sulfide edifice from the Endeavor segment of the Juan de Fuca Ridge (47 55.416720 N, 129 6.487020 W, at a depth of 2269 m) using the Bushmaster Jr. collection device. The collection was analyzed for community structure and the data collected were compared to that from several other hydrothermal vent communities. It was determined that substrate composition is a factor that heavily influences community structure. The data were then compared to the community succession model developed by Sarrazin et. al. in 1997 and 1999 (Sarrazin et. al. 1997, Sarrazin and Juniper 1999). The Tower community was found to expand the model as a new community succession classification; that of community iii low flow. The Tower community was then analyzed for diversity, structure and tubeworm morphology in conjunction with two other communities from differing substrata. The Ridgeia piscesae tubeworms were found to be of the "long skinny" morphotype, one that was previously thought to only reside on basaltic substrate. The Tower community has similar species richness and higher species evenness than those from basaltic substrate, but similar richness and lower evenness that those from sulfide. This community type combines the characteristics of those from both substrata, resulting in a community with diversity and structure that is an intermediary between sulfide and basaltic substrates.
Keywords: HOV Alvin (Human Occupied Vehicle)

Chemistry of hot springs along the Eastern Lau Spreading Center - Mottl, M J; Seewald, J S; Wheat, C G; Tivey, M K; Michael, P J; Proskurowski, G; McCollom, T M; Reeves, E; Sharkey, J; You, C F; Chan, L H; Pichler, T (Geochimica et Cosmochimica Acta, 2011)
The Eastern Lau Spreading Center (ELSC) is the southernmost part of the back-arc spreading axis in the Lau Basin, west of the Tonga trench and the active Tofua volcanic arc. Over its 397-km length it exhibits large and systematic changes in spreading rate, magmatic/tectonic processes, and proximity to the volcanic arc. In 2005, we collected 81 samples of vent water from six hydrothermal fields along the ELSC. The chemistry of these waters varies both within and between vent fields, in response to changes in substrate composition, temperature and pressure, pH, water/rock ratio, and input from magmatic gases and subducted sediment. Hot-spring temperatures range from 229° to 363 °C at the five northernmost fields, with a general decrease to the south that is reversed at the Mariner field. The southernmost field, Vai Lili, emitted water at up to 334 °C in 1989 but had a maximum venting temperature of only 121 °C in 2005, due to waning activity and admixture of bottom seawater into the subseafloor plumbing system. Chloride varies both within fields and from one field to another, from a low of 528 mmol/kg to a high of 656 mmol/kg, and may be enriched by phase separation and/or leaching of Cl from the rock. Concentrations of the soluble elements K, Rb, Cs, and B likewise increase southward as the volcanic substrate becomes more silica-rich, especially on the Valu Fa Ridge. Iodine and $δ$7Li increase southward, and $δ$11B decreases as B increases, apparently in response to increased input from subducted sediment as the arc is approached. Species that decrease southward as temperature falls are Si, H2S, Li, Na/Cl, Fe, Mn, and 87Sr/86Sr, whereas pH, alkalinity, Ca, and Sr increase. Oxygen isotopes indicate a higher water/rock ratio in the three systems on Valu Fa Ridge, consistent with higher porosity in more felsic volcanic rocks. Vent waters at the Mariner vent field on the Valu Fa Ridge are significantly hotter, more acid and metal-rich, less saline, and richer in dissolved gases and other volatiles, including H2S, CO2, and F, than the other vent fields, consistent with input of magmatic gases. The large variations in geologic and geophysical parameters produced by back-arc spreading along the ELSC, which exceed those along mid-ocean ridge spreading axes, produce similar large variations in the composition of vent waters, and thus provide new insights into the processes that control the chemistry of submarine hot springs.
Keywords: ROV Jason (Remotely Operated Vehicle)

Cold seeps in Monterey Bay, California: Geochemistry of pore waters and relationship to benthic foraminiferal calcite - Gieskes, J M; Rathburn, A E; Martin, J B; Perez, M E; Mahn, C; Bernhard, J M; Day, S (Applied Geochemistry, 2011)
An extensive geochemical and biogeochemical examination of CH4 seeps in the Clam Flats area of Monterey Bay provides insight into the character of relationships between seep geochemistry and benthic foraminiferal geochemistry. The area is characterized by sulfide-rich fluids. Sulfide increases are associated with large increases in alkalinity, as well as small decreases in dissolved Ca and Mg. In addition, only small increases in NH4 are observed, but values of $δ$13C of dissolved inorganic C are as low as −60‰ at shallow depths (C of dissolved inorganic C are as low as −60‰ at shallow depths (4, which is transported upward by slow seepage of pore fluids. The geochemistry of the pore fluids should be relevant to the geochemistry of the carbonate tests of living and dead foraminifera. However, a profound disequilibrium of approximately an order of magnitude occurs between the $δ$13C values of stained (cytoplasm-containing) foraminiferal carbonate and the C isotope values of ambient pore water dissolved inorganic C. Reasons are unclear for this isotopic disequilibrium, but have important implications for interpretations of foraminiferal carbonate as a paleoenvironmental proxy. Much fine scale work is needed to fully understand the relationships between the biogeochemistry of benthic foraminifera and the geochemistry of the pore waters where they live.
Keywords: ROV Jason (Remotely Operated Vehicle)

Comparative metagenomics of microbial communities inhabiting deep-sea hydrothermal vent chimneys with contrasting chemistries - Xie, Wei; Wang, Fengping; Guo, Lei; Chen, Zeling; Sievert, Stefan M; Meng, Jun; Huang, Guangrui; Li, Yuxin; Yan, Qingyu; Wu, Shan; Wang, Xin; Chen, Shangwu; et al. (ISME JOURNAL, 2011)
Deep-sea hydrothermal vent chimneys harbor a high diversity of largely unknown microorganisms. Although the phylogenetic diversity of these microorganisms has been described previously, the adaptation and metabolic potential of the microbial communities is only beginning to be revealed. A pyrosequencing approach was used to directly obtain sequences from a fosmid library constructed from a black smoker chimney 4143-1 in the Mothra hydrothermal vent field at the Juan de Fuca Ridge. A total of 308 034 reads with an average sequence length of 227 bp were generated. Comparative genomic analyses of metagenomes from a variety of environments by two-way clustering of samples and functional gene categories demonstrated that the 4143-1 metagenome clustered most closely with that from a carbonate chimney from Lost City. Both are highly enriched in genes for mismatch repair and homologous recombination, suggesting that the microbial communities have evolved extensive DNA repair systems to cope with the extreme conditions that have potential deleterious effects on the genomes. As previously reported for the Lost City microbiome, the metagenome of chimney 4143-1 exhibited a high proportion of transposases, implying that horizontal gene transfer may be a common occurrence in the deep-sea vent chimney biosphere. In addition, genes for chemotaxis and flagellar assembly were highly enriched in the chimney metagenomes, reflecting the adaptation of the organisms to the highly dynamic conditions present within the chimney walls. Reconstruction of the metabolic pathways revealed that the microbial community in the wall of chimney 4143-1 was mainly fueled by sulfur oxidation, putatively coupled to nitrate reduction to perform inorganic carbon fixation through the Calvin-Benson-Bassham cycle. On the basis of the genomic organization of the key genes of the carbon fixation and sulfur oxidation pathways contained in the large genomic fragments, both obligate and facultative autotrophs appear to be present and contribute to biomass production. The ISME Journal (2011) 5, 414-426; doi: 10.1038/ismej.2010.144; published online 7 October 2010
Keywords: HOV Alvin (Human Occupied Vehicle)

Deciphering the ocean bottom pressure variation in the Logatchev hydrothermal field at the eastern flank of the Mid-Atlantic Ridge - Gennerich, Hans-Hermann; Villinger, Heinrich (GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 2011)
Ocean bottom pressure data from the Logatchev hydrothermal field (LHF) are presented and analyzed. The data were collected with two ocean bottom pressure meters (OBPs), constructed at the University of Bremen, that are capable of recording signals with frequencies up to 0.25 Hz. Over the long-term, a nearly 2.5 kPa (25 cm water column equivalent) pressure variation over 3.7 years is observed, which is consistent with uplift followed by subsidence, but cannot unequivocally be discerned from instrumental drift. Medium-term pressure variations are compared with satellite surface topography, satellite gravity, ocean modeling, and in situ data from an OBP 700 km away. It is shown that fluctuations in the oceanic mass distribution dominate the variations in this frequency range and that oceanic modeling and data from a 700 km distant OBP are positively correlated with the LHF bottom pressure time series. The short-term variations are dominated by microseisms originating from sea surface waves and pressure waves from earthquakes as can be shown by comparison with weather buoy and teleseismic data.
Keywords: ROV Jason (Remotely Operated Vehicle)

Dimorphism in methane seep-dwelling ecotypes of the largest known bacteria - Bailey, J V; Salman, V; Rouse, G W; Schulz-Vogt, H; Levin, L A; Orphan, V J (ISME Journal, 2011)
We present evidence for a dimorphic life cycle in the vacuolate sulfide-oxidizing bacteria that appears to involve the attachment of a spherical Thiomargarita-like cell to the exteriors of invertebrate integuments and other benthic substrates at methane seeps. The attached cell elongates to produce a stalk-like form before budding off spherical daughter cells resembling free-living Thiomargarita that are abundant in surrounding sulfidic seep sediments. The relationship between the attached parent cell and free-living daughter cell is reminiscent of the dimorphic life modes of the prosthecate Alphaproteobacteria, but on a grand scale, with individual elongate cells reaching nearly a millimeter in length. Abundant growth of attached Thiomargarita-like bacteria on the integuments of gastropods and other seep fauna provides not only a novel ecological niche for these giant bacteria, but also for animals that may benefit from epibiont colonization.
Keywords: HOV Alvin (Human Occupied Vehicle)

Dissolved and particulate organic carbon in hydrothermal plumes from the East Pacific Rise, 9 degrees 50′N - Bennett, S A; Statham, P J; Green, D R H; Le Bris, N; McDermott, J M; Prado, F; Rouxel, O J; Von Damm, K L; German, C R (Deep-Sea Research. Part I: Oceanographic Research Papers, 2011)
Chemoautotrophic production in seafloor hydrothermal systems has the potential to provide an important source of organic carbon that is exported to the surrounding deep-ocean. While hydrothermal plumes may export carbon, entrained from chimney walls and biologically rich diffuse flow areas, away from sites of venting they also have the potential to provide an environment for in-situ carbon fixation. In this study, we have followed the fate of dissolved and particulate organic carbon (DOC and POC) as it is dispersed through and settles beneath a hydrothermal plume system at 9°50′N on the East Pacific Rise. Concentrations of both DOC and POC are elevated in buoyant plume samples that were collected directly above sites of active venting using both DSV Alvin and a CTD-rosette. Similar levels of POC enrichment are also observed in the dispersing non-buoyant plume, ∼500 m downstream from the vent-site. Further, sediment-trap samples collected beneath the same dispersing plume system, show evidence for a close coupling between organic carbon and Fe oxyhydroxide fluxes. We propose, therefore, a process that concentrates POC into hydrothermal plumes as they disperse through the deep-ocean. This is most probably the result of some combination of preferential adsorption of organic carbon onto Fe-oxyhydroxides and/or microbial activity that preferentially concentrates organic carbon in association with Fe-oxyhydroxides (e.g. through the microbial oxidation of Fe(II) and Fe sulfides). This potential for biological production and consumption within hydrothermal plumes highlights the importance of a multidisciplinary approach to understanding the role of the carbon cycle in deep-sea hydrothermal systems as well as the role that hydrothermal systems may play in regulating global deep-ocean carbon budgets.
Keywords: HOV Alvin (Human Occupied Vehicle)

Drilling constraints on lithospheric accretion and evolution at Atlantis Massif, Mid-Atlantic Ridge 30 degrees N - Blackman, D K; Ildefonse, B; John, B E; Ohara, Y; Miller, D J; Abe, N; Abratis, M; Andal, E S; Andreani, M; Awaji, S; Beard, J S; Brunelli, D; et al. (Journal of Geophysical Research: Solid Earth, 2011)
Expeditions 304 and 305 of the Integrated Ocean Drilling Program cored and logged a 1.4 km section of the domal core of Atlantis Massif. Postdrilling research results summarized here constrain the structure and lithology of the Central Dome of this oceanic core complex. The dominantly gabbroic sequence recovered contrasts with predrilling predictions; application of the ground truth in subsequent geophysical processing has produced self-consistent models for the Central Dome. The presence of many thin interfingered petrologic units indicates that the intrusions forming the domal core were emplaced over a minimum of 100-220 kyr, and not as a single magma pulse. Isotopic and mineralogical alteration is intense in the upper 100 m but decreases in intensity with depth. Below 800 m, alteration is restricted to narrow zones surrounding faults, veins, igneous contacts, and to an interval of locally intense serpentinization in olivine-rich troctolite. Hydration of the lithosphere occurred over the complete range of temperature conditions from granulite to zeolite facies, but was predominantly in the amphibolite and greenschist range. Deformation of the sequence was remarkably localized, despite paleomagnetic indications that the dome has undergone at least 45 degrees rotation, presumably during unroofing via detachment faulting. Both the deformation pattern and the lithology contrast with what is known from seafloor studies on the adjacent Southern Ridge of the massif. There, the detachment capping the domal core deformed a 100 m thick zone and serpentinized peridotite comprises similar to 70{%} of recovered samples. We develop a working model of the evolution of Atlantis Massif over the past 2 Myr, outlining several stages that could explain the observed similarities and differences between the Central Dome and the Southern Ridge.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Argo (Remotely Operated Vehicle); ROV DSL-120 (Remotely Operated Vehicle)

Early to Middle Devonian granitic and volcanic rocks from the central Gulf of Maine - Barr, S M; Mortensen, J K; Thompson, M D; Hermes, O D; White, C E (Lithos, 2011)
Cashes Ledge igneous suite in the central Gulf of Maine is represented by 10 granitic and two felsic tuff samples collected from bedrock outcrops using the submersible Alvin in 1971–1972 and archived at the Woods Hole Oceanographic Institute. Laser ablation ICP-MS analyses of zircon grains yielded crystallization ages of 414.9 ± 1.1 Ma and 399.7 ± 1.5 Ma for two alkali feldspar granite samples, 407.0 ± 1.9 Ma for a syenogranite sample, and 384.4 ± 2.3 Ma and 383.9 ± 1.6 Ma for two felsic tuff samples. The samples contain iron-rich mafic minerals, including aegirine-augite, grunerite/ferroedenite, and annite. Most of the samples are alkaline to slightly peralkaline, with high concentrations of SiO2, Y, Zr, Nb, and REE, strong negative Eu anomalies, and positive epsilon Nd values (1.8 to 3.7). The suite resembles part of a belt of similar Silurian–Devonian rocks with ages between 426 and 370 Ma now recognized in the central part of Avalonia in southeastern New England. They formed in a long-lived, likely extensional regime linked to subduction and subsequent complex transcurrent motions among Ganderia, Avalonia, and Meguma, culminating in the closure of the Rheic Ocean.
Keywords: HOV Alvin (Human Occupied Vehicle)

Effects of chronic low carbonate saturation levels on the distribution, growth and skeletal chemistry of deep-sea corals and other seamount megabenthos - Thresher, Ronald E; Tilbrook, Bronte; Fallon, Stewart; Wilson, Nick C; Adkins, Jess (MARINE ECOLOGY PROGRESS SERIES, 2011)
Ocean acidification has been predicted to reduce the ability of marine organisms to produce carbonate skeletons, threatening their long-term viability and severely impacting marine ecosystems. Corals, as ecosystem engineers, have been identified as particularly vulnerable and important. To determine the sensitivity of corals and allied taxa to long-term exposure to very low carbonate concentrations, we examined the distribution and skeletal characteristics of coral taxa along a natural deep-sea concentration gradient on seamounts of SW Australia. Carbonate under-saturation had little evident effect on the depth distribution, growth or skeletal composition of live scleractinians or gorgonians, with corals growing, often abundantly, in waters as much as 20 to 30{%} under-saturated. Developmental anomalies in the deepest skeleton-forming anthozoan collected (an isidid gorgonian, at nearly 4 km depth) suggest an absolute low tolerance limit of about 40{%} under-saturation. Evidence for an effect of acidification on the accumulation of reef structure is ambiguous, with clear indications of dissolution of high-magnesium calcite (HMC) gorgonian skeletons at depths below 2300 m, but also abundant, old scleractinian skeletons well below the aragonite saturation horizon. The latter might be the result of ferromanganese deposition on exposed skeletons, which, however, may render them inhospitable for benthic organisms.
Keywords: AUV ABE (Autonomous Benthic Explorer); ROV Jason (Remotely Operated Vehicle)

Evidence for episodic aseismic slip across the subduction seismogenic zone off Costa Rica: CORK borehole pressure observations at the subduction prism toe - Davis, E; Heesemann, M; Wang, K (Earth and Planetary Science Letters, 2011)
Slow slip events, or “silent” earthquakes, may relieve a significant amount of stress at many subduction plate boundaries, both downdip of the limit of seismogenesis, and within the seismogenic zone itself in cases where seismic energy release accounts for only a fraction of the plate tectonic displacement rate (Schwartz and Rokosky, 2007). Slow slip has been identified in several instances downdip of the landward limit of the seismogenic zone and is often accompanied by seismic tremor or low-frequency earthquake activity along and above the plate interface (referred to as “episodic tremor and slip”, or ETS). Little is known, however, about the spatial distribution and history of slip between great earthquakes along the seismogenic thrust interface itself which lies mostly offshore. In this article we present formation pressure transients observed in two deep-sea boreholes near the toe of the subduction prism off Nicoya Peninsula, Costa Rica, which followed ETS events observed on shore by 1–2 weeks. The signatures of the transients are consistent with local slip on the shallow part of the thrust interface, with the underthrusting plate experiencing relaxation and the outer prism experiencing contraction. The delay between the tremor activity and the pressure transients observed c. 100 km seaward at the prism toe suggests either slow propagation across the seismogenic zone or delayed deformation at the outer part of the prism triggered by the slip beneath Nicoya. Such slip may serve generally to relieve stress at subduction zones, but also to increase stress in parts of the plate boundary where interseismic slip does not occur.
Keywords: HOV Alvin (Human Occupied Vehicle)

Excesses of seawater-derived 234U in volcanic glasses from Loihi Seamount due to crustal contamination - Pietruszka, A J; Keyes, M J; Duncan, J A; Hauri, E H; Carlson, R W; Garcia, M O (Earth and Planetary Science Letters, 2011)
The effects of crustal contamination on the chemistry of oceanic basalts are commonly assumed to be negligible due to the compositional similarity between the erupted basalt and the underlying oceanic crust or volcanic edifice. Here we evaluate this assumption with high-precision measurements of the 234U–238U and 230Th–238U disequilibria, Cl/K2O ratios, and 87Sr/86Sr ratios of volcanic glasses from Loihi Seamount, a submarine Hawaiian volcano with an active hydrothermal system. The samples, including one from the volcano's 1996 eruption, have small to moderate amounts of excess 234U ({\~{}} 0.2–1.0{%}) and variable, elevated Cl/K2O ratios. These excesses of 234U and enrichments in Cl are thought to result from contamination with seawater-derived U and Cl, but neither of these signatures can be explained by syn- or post-eruptive interaction between lava and seawater. Instead, mantle-derived magmas at Loihi appear to be variably contaminated with two distinct crustal materials: hydrothermal brines (which create enrichments in Cl) and U-enriched hydrothermally altered rocks (which create excesses of 234U). Both of these materials are expected to be found within the volcanic edifice as complementary parts of the volcano's hydrothermal system. The Loihi glasses display a wide measured range in the amount of excess 230Th from {\~{}}1 to 7{%} (due to the addition of seawater-derived U) that overlaps with lavas from Kilauea Volcano ({\~{}} 2{%} excess 230Th). We correct the 230Th–238U disequilibria of the Loihi glasses back to their original pre-contamination values using their 234U–238U disequilibria and a simple mass-balance calculation. This correction suggests that mantle-derived magmas at Loihi have a narrow range of {\~{}} 6–9{%} excess 230Th, which is significantly larger than observed for lavas from the neighboring volcano, Kilauea. This difference is consistent with the idea that Loihi is tapping mantle that is upwelling slowly ({\~{}} 5–6 cm/yr) on the margin of the Hawaiian plume.
Keywords: HOV Alvin (Human Occupied Vehicle)

Extraordinarily high biomass benthic community on Southern Ocean seamounts - Thresher, R E; Adkins, J; Fallon, S J; Gowlett-Holmes, K; Althaus, F; Williams, A (SCIENTIFIC REPORTS, 2011)
We describe a previously unknown assemblage of seamount-associated megabenthos that has by far the highest peak biomass reported in the deep-sea outside of vent communities. The assemblage was found at depths of 2-2.5 km on rocky geomorphic features off the southeast coast of Australia, in an area near the Sub-Antarctic Zone characterised by high rates of surface productivity and carbon export to the deep-ocean. These conditions, and the taxa in the assemblage, are widely distributed around the Southern mid-latitudes, suggesting the high-biomass assemblage is also likely to be widespread. The role of this assemblage in regional ecosystem and carbon dynamics and its sensitivities to anthropogenic impacts are unknown. The discovery highlights the lack of information on deep-sea biota worldwide and the potential for unanticipated impacts of deep-sea exploitation.
Keywords: AUV ABE (Autonomous Benthic Explorer); ROV Jason (Remotely Operated Vehicle)

Fluid elemental and stable isotope composition of the Nibelungen hydrothermal field (8 degrees18'S, Mid-Atlantic Ridge): Constraints on fluid-rock interaction in heterogeneous lithosphere - Schmidt, K; Garbe-Schonberg, D; Koschinsky, A; Strauss, H; Jost, C L; Klevenz, V; Koniger, P (Chemical Geology, 2011)
Depending on the geological setting, the interaction of submarine hydrothermal fluids with the host rock leads to distinct energy and mass transfers between the lithosphere and the hydrosphere. The Nibelungen hydrothermal field is located at 8°18′S, about 9 km off-axis of the Mid-Atlantic Ridge (MAR). At 3000 m water depth, 372 °C hot, acidic fluids emanate directly from the bottom, without visible sulfide chimney formation. Hydrothermal fluids obtained in 2009 are characterized by low H2S concentrations (1.1 mM), a depletion of B (192 $μ$M) relative to seawater, lower Si (13.7 mM) and Li (391 $μ$M) concentrations relative to basaltic-hosted hydrothermal systems and a large positive Eu anomaly, and display a distinct stable isotope signature of hydrogen (∆2HH2O = 7.6–8.7‰) and of oxygen (∆18OH2O = 2.2–2.4‰). The heavy hydrogen isotopic signature of the Nibelungen fluids is a specific feature of ultramafic-hosted hydrothermal systems and is mainly controlled by the formation of OH-bearing alteration minerals like serpentine, brucite, and tremolite during pervasive serpentinization. New isotopic data obtained for the ultramafic-hosted Logatchev I field at 14°45′N, MAR (∆2HH2O = 3.8–4.2‰) display a similar trend, being clearly distinguished from other, mafic-hosted hydrothermal systems at the MAR. The fluid geochemistry at Nibelungen kept stable since the first sampling campaign in 2006 and is evident for a hybrid alteration of mafic and ultramafic rocks in the subseafloor. Whereas the ultramafic-fingerprint parameters Si, Li, B, Eu anomaly and ∆2HH2O distinguish the Nibelungen field from other hydrothermal systems venting in basaltic settings at similar physico-chemical conditions and are related to the interaction with mantle rocks, the relatively high concentrations of trace alkali elements, Pb, and Tl can only be attributed to the alteration of melt-derived gabbroic rocks. The elemental and isotopic composition of the fluid suggest a multi-step alteration sequence: (1) low- to medium-temperature alteration of gabbroic rocks, (2) pervasive serpentinization at moderate to high temperatures, and (3) limited high-temperature interaction with basaltic rocks during final ascent of the fluid. The integrated water/rock ratio for the Nibelungen hydrothermal system is about 0.5. The fluid compositional fingerprint at Nibelungen is similar to the ultramafic-hosted Logatchev I fluids with respect to key parameters. Some compositional differences can be ascribed to different alteration temperatures and other fluid pathways involving a variety of source rocks, higher water/rock ratios, and sulfide precipitation in the sub-seafloor at Logatchev I.
Keywords: ROV Jason (Remotely Operated Vehicle)

Geochemistry of hydrothermal fluids from the PACMANUS, Northeast Pual and Vienna Woods hydrothermal fields, Manus Basin, Papua New Guinea - Reeves, E; Seewald, J S; Saccocia, P J; Walsh, E; Bach, W; Craddock, P R; Shanks, W C; Sylva, S P; Pichler, T; Rosner, M (Geochimica et Cosmochimica Acta, 2011)
Processes controlling the composition of seafloor hydrothermal fluids in silicic back-arc or near-arc crustal settings remain poorly constrained despite growing evidence for extensive magmatic–hydrothermal activity in such environments. We conducted a survey of vent fluid compositions from two contrasting sites in the Manus back-arc basin, Papua New Guinea, to examine the influence of variations in host rock composition and magmatic inputs (both a function of arc proximity) on hydrothermal fluid chemistry. Fluid samples were collected from felsic-hosted hydrothermal vent fields located on Pual Ridge (PACMANUS and Northeast (NE) Pual) near the active New Britain Arc and a basalt-hosted vent field (Vienna Woods) located farther from the arc on the Manus Spreading Center. Vienna Woods fluids were characterized by relatively uniform endmember temperatures (273–285 °C) and major element compositions, low dissolved CO2 concentrations (4.4 mmol/kg) and high measured pH (4.2–4.9 at 25 °C). Temperatures and compositions were highly variable at PACMANUS/NE Pual and a large, newly discovered vent area (Fenway) was observed to be vigorously venting boiling (358 °C) fluid. All PACMANUS fluids are characterized by negative $δ$DH2O$δ$DH2O values, in contrast to positive values at Vienna Woods, suggesting substantial magmatic water input to circulating fluids at Pual Ridge. Low measured pH (25 °C) values (∼2.6–2.7), high endmember CO2 (up to 274 mmol/kg) and negative $δ$34SH2S$δ$34SH2S values (down to −2.7‰) in some vent fluids are also consistent with degassing of acid-volatile species from evolved magma. Dissolved CO2 at PACMANUS is more enriched in 13C (−4.1‰ to −2.3‰) than Vienna Woods (−5.2‰ to −5.7‰), suggesting a contribution of slab-derived carbon. The mobile elements (e.g. Li, K, Rb, Cs and B) are also greatly enriched in PACMANUS fluids reflecting increased abundances in the crust there relative to the Manus Spreading Center. Variations in alkali and dissolved gas abundances with Cl at PACMANUS and NE Pual suggest that phase separation has affected fluid chemistry despite the low temperatures of many vents. In further contrast to Vienna Woods, substantial modification of PACMANUS/NE Pual fluids has taken place as a result of seawater ingress into the upflow zone. Consistently high measured Mg concentrations as well as trends of increasingly non-conservative SO4 behavior, decreasing endmember Ca/Cl and Sr/Cl ratios with increased Mg indicate extensive subsurface anhydrite deposition is occurring as a result of subsurface seawater entrainment. Decreased pH and endmember Fe/Mn ratios in higher Mg fluids indicate that the associated mixing/cooling gives rise to sulfide deposition and secondary acidity production. Several low temperature (⩽80 °C) fluids at PACMANUS/NE Pual also show evidence for anhydrite dissolution and water–rock interaction (fixation of B) subsequent to seawater entrainment. Hence, the evolution of fluid compositions at Pual Ridge reflects the cumulative effects of water/rock interaction, admixing and reaction of fluids exsolved from silicic magma, phase separation/segregation and seawater ingress into upflow zones.
Keywords: ROV Jason (Remotely Operated Vehicle)

Hydrothermal vents as a kinetically stable source of iron-sulphide-bearing nanoparticles to the ocean - Yucel, M; Gartman, A; Chan, Clara S; Luther, G W (Nature Geoscience, 2011)
Hydrothermal vents emit sulphur and metals to the ocean(1). Particular attention has been paid to hydrothermal fluxes of iron(2-4), a limiting micronutrient of marine primary production(5). Vent-derived iron was previously thought to rapidly oxidize and precipitate around vents(6). However, organic matter can bind to and stabilize dissolved and particulate iron in hydrothermal plumes(7-9), facilitating its dispersion into the open ocean(10). Here, we report measurements of the chemical speciation of sulphide and iron in high-temperature fluids emanating from vents in the East Pacific Rise and the Eastern Lau Spreading Center. We show that pyrite nanoparticles-composed of iron and sulphur-account for up to 10{%} of the filterable iron (less than 200nm in size) in these fluids. We suggest that these particles form before the discharge of the vent fluid. We estimate that pyrite nanoparticles sink more slowly than larger plume particles, and are more resistant to oxidation than dissolved Fe(II) and FeS. We suggest that the discharge of iron in the form of pyrite nanoparticles increases the probability that vent-derived iron will be transported over long distances in the deep ocean.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

In situ enrichment of ocean crust microbes on igneous minerals and glasses using an osmotic flow-through device - Smith, A; Popa, R; Fisk, M; Nielsen, M; Wheat, C G; Jannasch, H W; Fisher, A T; Becker, K; Sievert, S M; Flores, G (Geochemistry, Geophysics, Geosystems, 2011)
The Integrated Ocean Drilling Program (IODP) Hole 1301A on the eastern flank of Juan de Fuca Ridge was used in the first long-term deployment of microbial enrichment flow cells using osmotically driven pumps in a subseafloor borehole. Three novel osmotically driven colonization systems with unidirectional flow were deployed in the borehole and incubated for 4 years to determine the microbial colonization preferences for 12 minerals and glasses present in igneous rocks. Following recovery of the colonization systems, we measured cell density on the minerals and glasses by fluorescent staining and direct counting and found some significant differences between mineral samples. We also determined the abundance of mesophilic and thermophilic culturable organotrophs grown on marine R2A medium and identified isolates by partial 16S or 18S rDNA sequencing. We found that nine distinct phylotypes of culturable mesophilic oligotrophs were present on the minerals and glasses and that eight of the nine can reduce nitrate and oxidize iron. Fe(II)-rich olivine minerals had the highest density of total countable cells and culturable organotrophic mesophiles, as well as the only culturable organotrophic thermophiles. These results suggest that olivine (a common igneous mineral) in seawater-recharged ocean crust is capable of supporting microbial communities, that iron oxidation and nitrate reduction may be important physiological characteristics of ocean crust microbes, and that heterogeneously distributed minerals in marine igneous rocks likely influence the distribution of microbial communities in the ocean crust.
Keywords: HOV Alvin (Human Occupied Vehicle)

In situ measurements of hydrogen sulfide, oxygen, and temperature in diffuse fluids of an ultramafic-hosted hydrothermal vent field (Logatchev, 14 degrees 45 ` N, Mid-Atlantic Ridge): Implications for chemosymbiotic bathymodiolin mussels - Zielinski, Frank U; Gennerich, Hans-Hermann; Borowski, Christian; Wenzhoefer, Frank; Dubilier, Nicole (GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 2011)
The Logatchev hydrothermal vent field (14 degrees 45'N, Mid-Atlantic Ridge) is located in a ridge segment characterized by mantle-derived ultramafic outcrops. Compared to basalt-hosted vents, Logatchev high-temperature fluids are relatively low in sulfide indicating that the diffuse, low-temperature fluids of this vent field may not contain sufficient sulfide concentrations to support a chemosymbiotic invertebrate community. However, the high abundances of bathymodiolin mussels with bacterial symbionts related to free-living sulfur-oxidizing bacteria suggested that bioavailable sulfide is present at Logatchev. To clarify, if diffuse fluids above mussel beds of Bathymodiolus puteoserpentis provide the reductants and oxidants needed by their symbionts for aerobic sulfide oxidation, in situ microsensor measurements of dissolved hydrogen sulfide and oxygen were combined with simultaneous temperature measurements. High temporal fluctuations of all three parameters were measured above the mussel beds. H2S and O-2 coexisted with mean concentrations between 9 and 31 mu M (H2S) and 216 and 228 mu M (O-2). Temperature maxima ({<}= 7.4 degrees C) were generally concurrent with H2S maxima ({<}= 156 mu M) and O-2 minima ({>}= 142 mu M). Long-term measurements for 250 days using temperature as a proxy for oxygen and sulfide concentrations indicated that the mussels were neither oxygen limited nor sulfide limited. Our in situ measurements at Logatchev indicate that sulfide may also be bioavailable in diffuse fluids from other ultramafic-hosted vents along slow and ultraslow spreading ridges. Components: 12,100 words, 9 figures, 4 tables.
Keywords: ROV Jason (Remotely Operated Vehicle)

Microbial Ecology of the Dark Ocean above, at, and below the Seafloor - Orcutt, B N; Sylvan, J B; Knab, N J; Edwards, K J (Microbiology and Molecular Biology Reviews, 2011)
The majority of life on Earth—notably, microbial life—occurs in places that do not receive sunlight, with the habitats of the oceans being the largest of these reservoirs. Sunlight penetrates only a few tens to hundreds of meters into the ocean, resulting in large-scale microbial ecosystems that function in the dark. Our knowledge of microbial processes in the dark ocean—the aphotic pelagic ocean, sediments, oceanic crust, hydrothermal vents, etc.—has increased substantially in recent decades. Studies that try to decipher the activity of microorganisms in the dark ocean, where we cannot easily observe them, are yielding paradigm-shifting discoveries that are fundamentally changing our understanding of the role of the dark ocean in the global Earth system and its biogeochemical cycles. New generations of researchers and experimental tools have emerged, in the last decade in particular, owing to dedicated research programs to explore the dark ocean biosphere. This review focuses on our current understanding of microbiology in the dark ocean, outlining salient features of various habitats and discussing known and still unexplored types of microbial metabolism and their consequences in global biogeochemical cycling. We also focus on patterns of microbial diversity in the dark ocean and on processes and communities that are characteristic of the different habitats.
Keywords: HOV Alvin (Human Occupied Vehicle)

Mineralogical and stable isotopic characterization of authigenic carbonate from a hydrocarbon seep site, Gulf of Mexico slope: Possible relation to crude oil degradation - Mansour, A S; Sassen, R (Marine Geology, 2011)
One of the characteristic features on the cold deep seafloor on Atwater Valley (AT) Block 425 (1930 m water depth) in the Gulf of Mexico is the occurrence of seepage of crude oil and hydrocarbon gases associated with thermogenic gas hydrate and authigenic carbonate deposits. Mineralogical, petrographic and isotopic analyses revealed that the precipitation of these carbonates was related to the microbial oxidation of hydrocarbons. Carbonate deposits are composed of heavily oil-stained, small nodules to large cobbles of dense limestones of fine-grained textures. Other carbonate fragments are composed of small intraclasts, pellets and some bivalve shell fragments cemented together by aragonite cement. XRD analysis and petrographic investigations revealed that the authigenic carbonate is predominantly composed of aragonite that occurs as microcrystalline matrix and cement. Microcrystalline, sparitic and botryoidal acicular aragonite crystals are observed as void-filling cement. The $δ$18O values of the authigenic carbonate (3.80 to 4.16‰ V-PDB) suggest that the precipitating fluid has equilibrated with the cold bottom seawater. The calculated $δ$18O values (0.18 to 0.54‰ SMOW) of the precipitating fluid show subtle deviation from the values reported for the present bottom seawater. This is attributed possibly to the precipitation from pore water with temperature ranged from 3.3 to 1.7 °C, which is less than the measured bottom seawater (4 °C). However, the mixing of the marine pore water with some deep hydrocarbon-rich brines or hydrate-water would provide a source of 18O-enrichment fluid for the precipitation of the authigenic carbonates. Based on the predominance of aragonite with botryoidal and clotted fabric, the occurrence of pyrite and from the oxygen isotopic data, it is plausible that the authigenic carbonates may have formed near the sediment/water interface in an oxygen-depleted environment with low temperature. The narrow range of the $δ$13C values of the authigenic carbonate (− 23.88 to − 28.62‰ V-PDB) suggests that a single source of carbon is predominant. Based on the moderately low $δ$13C values and the occurrence of spots of crude oil coatings of the carbonate samples, in addition to the application of a carbon isotope mass balance model, the carbon involving in the formation of the carbonates of the AT 425 seep site could be mainly derived from microbial degradation of crude oil. Microbial oxidation of non-methane thermogenic hydrocarbon gases such as ethane, propane and isobutane would play some role as a source of carbonate-carbon.
Keywords: HOV Alvin (Human Occupied Vehicle)

Modal analysis of the deep-water solitary scleractinian, Desmophyllum dianthus, on SW Pacific seamounts: inferred recruitment periodicity, growth, and mortality rates - Thresher, R E; Adkins, J; Thiagarajan, N (CORAL REEFS, 2011)
Little is known about the demography of corals inhabiting deep-sea features due to the logistical difficulties of working at the extreme depths they inhabit. To obtain basic information about growth, mortality, and recruitment dynamics for such a coral, we applied modal analysis to the size frequency distributions of live-caught and sub-fossil specimens of the widely distributed solitary cup coral, Desmophyllum dianthus, collected on SW Pacific seamounts. Comparison of live-caught material collected in 1997 and 2007-2009 indicated modal progression over time and an implied maximum age of approximately 190 years, which is similar to ages determined previously for D. dianthus using radiometric techniques. A log-linear decline in the number of individuals with increasing size further implies a constant adult mortality rate, of 15.1{%} per annum in 1997 and 9.2{%} per annum in 2007-2009. The spacing of size modes in the 2007-2009 samples suggests regularly episodic recruitment events, at 22- to 32-year intervals, which may relate to periodic variability in large-scale Southern Ocean circulation. Preliminary analyses of size frequency distributions of the sub-fossil material suggest that the trophodynamics, growth, and adult mortality schedules of D. dianthus in the SW Pacific have remained basically similar throughout the Holocene.
Keywords: AUV ABE (Autonomous Benthic Explorer); ROV Jason (Remotely Operated Vehicle)

Nautiliniellidae (Annelida) from Costa Rican cold seeps and a western Pacific hydrothermal vent, with description of four new species - Teresa Aguado, M; Rouse, Greg W (SYSTEMATICS AND BIODIVERSITY, 2011)
Four genera and five species of Nautiliniellidae (Phyllodocida; Annelida), representing four new species and one new record, were found in association with bivalves belonging to Mytilidae (Bathymodiolus spp.), Solemyidae (Acharax sp.) and Vesicomyidae (Calyptogena and Vesicomya) from hydrothermal vents of the western Pacific (Lau back-arc basin) and cold seeps of the eastern Pacific (Costa Rica). Iheyomytilidicola lauensis n. sp. is characterized by the presence of unidentate hooks; Laubierus alvini n. sp. has long dorsal cirri and notoacicula not protruding in any segment; Natsushima sashai n. sp has bifurcate chaetae with distal teeth markedly different in length and width between each other; and Shinkai fontefridae n. sp. differs in having posterior hooks with subdistal spines. Sexual dimorphism is described for Shinkai and Natsushima species and confirmed by DNA sequencing (Cytochrome c oxidase subunit I sequences). In addition, one specimen of N. bifurcata Miura {&} Laubier, 1990 from the Gulf of Cadiz has been studied to compare it morphologically and genetically with N. sashai n. sp. Scanning electron and optical microscopy images are provided for each species, as well as pictures of live animals. Morphological features described and documented for the first time include the presence of internal longitudinal chambers within chaetae and possible evidence that the simple chaetae, characteristic of nautiliniellids, may be derived from compound chaetae.
Keywords: ROV Jason (Remotely Operated Vehicle)

A new Fe/Mn geothermometer for hydrothermal systems: Implications for high-salinity fluids at 13°N on the East Pacific Rise - Pester, N J; Rough, M; Ding, K; Seyfried, W E (Geochimica et Cosmochimica Acta, 2011)
Field and experimental investigations demonstrate the chemistry of mid-ocean ridge hydrothermal vent fluids reflects fluid–mineral reaction at higher temperatures than those typically measured at the seafloor. To account for this and, in turn, be able to better constrain sub-seafloor hydrothermal processes, we have developed an empirical geothermometer based on the dissolved Fe/Mn ratio in high-temperature fluids. Using data from basalt alteration experiments, the relationship; T (°C) = 331.24 + 112.41*log[Fe/Mn] has been calibrated between 350 and 450 °C. The apparent Fe–Mn equilibrium demonstrated by the experimental data is in good agreement with natural vent fluids, suggesting broad applicability. When used in conjunction with constraints imposed by quartz solubility, associated sub-seafloor pressures can be estimated for basalt-hosted systems. As an example, this methodology is used to interpret new data from 13°N on the East Pacific Rise, where high-temperature fluids both enriched and depleted in chloride (339–646 mmol/kg), relative to seawater, are actively venting within a close proximity. Accounting for these variable salinities, active phase separation is clearly taking place at 13°N, yet the fluid Fe/Mn ratios and the silica concentrations suggest equilibration at temperatures less than those coinciding with the two-phase region. These data show the chloride-enriched fluid reflects the highest temperature and pressure (∼432 °C, 400 bars) of equilibration, consistent with circulation near the top of the inferred magma chamber. This is in agreement with the elevated CO2 concentration relative to the chloride-depleted fluids. The noted temperature derived from the Fe/Mn geothermometer is higher than the critical temperature for a fluid of equivalent salinity. This carries the important implication that, despite being chloride-enriched relative to seawater, these fluids evolved as the vapor component of even higher salinity brine.
Keywords: HOV Alvin (Human Occupied Vehicle)

Observations of eruptive plume dynamics and pyroclastic deposits from submarine explosive eruptions at NW Rota-1, Mariana arc - Deardorff, N D; Cashman, K V; Chadwick, W W (Journal of Volcanology and Geothermal Research, 2011)
Observations at the submarine volcano NW Rota-1, Mariana arc, have provided a unique opportunity to study basaltic explosive eruptions at {\~{}} 550 m below sea level. In particular, during one week of observations in 2006, the active vent evolved from a region of diffuse gas venting and slow lava effusion to a focused vent that emitted a nearly continuous stream of gas with entrained juvenile pyroclasts. The eruptions were small, strombolian bursts that ejected bomb-sized pyroclasts meters above the vent and produced buoyant plumes that rose tens of meters above the vent and contained variable amounts of ash. Sampled pyroclasts are dominantly coarse ash and lapilli with fluidal textures that provide evidence of magmatic fragmentation. However, the blocky morphologies of some clasts, combined with visual evidence of secondary fragmentation, suggest that quench granulation due to rapid cooling was also important in pyroclast formation. Rapid cooling is also suggested by the slow rise of buoyant plumes (which indicates a low heat content and small density contrast with surrounding seawater). Rapid plume deceleration in seawater limited deposition of coarse ash, lapilli, and bombs to within a few meters of the vent, and allowed recycling of ≤{\~{}}15{%} of the ejected clasts. Petrologic evidence for pyroclast recycling is provided by numerous microcrystalline inclusions incorporated within microlite-poor matrix glass. The matrix glass within these inclusions is strongly enriched in chlorine (
Keywords: ROV Jason (Remotely Operated Vehicle)

Organization and Microanatomy of the Sclerolinum contortum Trophosome (Polychaeta, Siboglinidae) - Eichinger, Irmgard; Klepal, Waltraud; Schmid, Markus; Bright, Monika (BIOLOGICAL BULLETIN, 2011)
The trophosome-an organ especially evolved to accommodate symbiotic bacteria-is a key character of the polychaete family Siboglinidae. Astonishingly, the trophosomes vary in organization and origin between the different siboglinid taxa. The trophosome of the small genus Sclerolinum was nearly unknown until now. Here we investigated the trophosome of S. contortum from the Gulf of Mexico, using light and electron microscopy. We show that this organ derives from the visceral mesoderm and propose that the trophosome of the sister clade Vestimentifera and Sclerolinum is a homologous character. Like that of juvenile vestimentiferans, the trophosome of Sclerolinum trophosome is simply organized. This study reveals that the Sclerolinum trophosome exhibits two regions that differ in the organization of host tissue and the size and shape of the symbionts. We suggest that a specific cell cycle within the symbiont-housing organ is directed along the longitudinal body axis, with a region of proliferation anteriorly and a region of degradation posteriorly. Using Raman microspectroscopy we demonstrate that the endosymbionts of S. contortum from the Gulf of Mexico contain sulfur vesicles, and we argue for a chemoautotrophic sulfur-oxidizing metabolism.
Keywords: ROV Jason (Remotely Operated Vehicle)

Precious corals (Coralliidae) from north-western Atlantic Seamounts - Simpson, Anne; Watling, Les (JOURNAL OF THE MARINE BIOLOGICAL ASSOCIATION OF THE UNITED KINGDOM, 2011)
Two new species belonging to the precious coral genus Corallium were collected during a series of exploratory cruises to the New England and Corner Rise Seamounts in 2003-2005. One red species, Corallium bathyrubrum sp. nov., and one white species, C. bayeri sp. nov., are described. Corallium bathyrubrum is the first red Corallium to be reported from the western Atlantic. An additional species, C. niobe Bayer, 1964 originally described from the Straits of Florida, was also collected and its description augmented.
Keywords: HOV Alvin (Human Occupied Vehicle)

The relative effects of particles and turbulence on acoustic scattering from deep-sea hydrothermal vent plumes - Xu, Guangyu; Di Iorio, Daniela (JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA, 2011)
Acoustic methods are applied to the investigation and monitoring of a vigorous hydrothermal plume within the Main Endeavor vent field at the Endeavor segment of the Juan de Fuca Ridge. Forward propagation and scattering from suspended particulates using Rayleigh scattering theory is shown to be negligible (log-amplitude variance sigma(2)(chi) similar to 10(-7)) compared to turbulence induced by temperature fluctuations (sigma(2)(chi) similar to 0.1). The backscattering from turbulence is then quantified using the forward scattering derived turbulence level, which gives a volume backscattering strength of s(V) = 6.5 x 10(-8) m(-1). The volume backscattering cross section from particulates can range from s(V) = 3.3 x 10(-6) to 7.2 x 10(-10) m(-1) depending on the particle size. These results show that forward scatter acoustic methods in hydrothermal vent applications can be used to quantify turbulence and its effect on backscatter measurements, which can be a dominant factor depending on the particle size and its location within the plume. (C) 2011 Acoustical Society of America. {\{}[{\}}DOI: 10.1121/1.3624816]
Keywords: ROV Jason (Remotely Operated Vehicle)

Reproductive traits of pioneer gastropod species colonizing deepsea hydrothermal vents after an eruption - Bayer, S (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2011)
The colonization dynamics and life histories of pioneer species are vital components in understanding the early succession of nascent hydrothermal vents. The reproductive ecology of pioneer species at deep-sea hydrothermal vents may provide insight into their dispersal, population connectivity, and ability to colonize after disturbance. An opportunity to study the reproductive traits of two pioneer gastropod species, Ctenopelta porifera and Lepetodrilus tevnianus, presented itself in 2006 after an eruption on the East Pacific Rise (EPR) eliminated vent communities near 9°50ʹ′N. Standard histological techniques were used to determine whether reproductive characteristics, such as timing of gamete release, fecundity, or time to maturation, differed from other vent gastropods in ways that might explain arrival of these two species as early colonizers. Both species exhibited two-component oocyte size frequency distributions that indicated they were quasi-continuous reproducers with high fecundity. In C. porifera, the oocyte size distributions differed slightly between two collection dates, suggesting that environmental cues may introduce some variability in gamete release. In samples collected within one year of the estimated eruption date, individuals in populations of both C. porifera and L. tevnianus were reproductively mature. The smallest reproducing C. porifera were 4.2 mm (males) and 5.4 mm (females) in shell length, whereas reproductive L. tevnianus were smaller (2.3 and 2.4 mm in males and females respectively). Most C porifera in the population were large ({>} 6.0 mm) compared to their settlement size and reproductively mature. In contrast, most L tevnianus were small (
Keywords: HOV Alvin (Human Occupied Vehicle)

Seabed search boost - Gross, M G (Current Biology, 2011)
Oceanography's newest deep-sea research submersible is also its oldest.
Keywords: HOV Alvin (Human Occupied Vehicle)

Stable isotopes provide new insights into vestimentiferan physiological ecology at Gulf of Mexico cold seeps - Becker, E L; Macko, S A; Lee, R W; Fisher, C R (Naturwissenschaften, 2011)
On the otherwise low-biomass seafloor of the Gulf of Mexico (GoM) continental slope, natural oil and gas seeps are oases of local primary production that support lush animal communities. Hundreds of seep communities have been documented on the continental slope, and nutrition derived from seeps could be an important link in the overall GoM food web. Here, we present a uniquely large and cohesive data set of $δ$13C, $δ$15N, and $δ$34S compositions of the vestimentiferan tubeworms Escarpia laminata and Lamellibrachia sp. 1, which dominate biomass at GoM seeps and provide habitat for hundreds of other species. Our sampling design encompassed an entire region of the GoM lower slope, allowing us for the first time to assess spatial variability in isotope compositions and to robustly address long-standing hypotheses about how vestimentiferans acquire and cycle nutrients over their long lifespan (200+ years). Tissue $δ$13C values provided strong evidence that larger adult vestimentiferans use their buried roots to take up dissolved inorganic carbon from sediment pore water, while very small individuals use their plume to take up carbon dioxide from the seawater. $δ$34S values were extremely variable among individuals of the same species within one location (S values were extremely variable among individuals of the same species within one location (2 area), indicating high variability in the inorganic sulfur pools on a very small spatial scale. This finding supports the hypothesis that vestimentiferans use their roots to cycle sulfate and sulfide between their symbionts and free-living consortia of sulfate-reducing archaea in the sediment. Finally, consistent differences in $δ$15N between two cooccurring vestimentiferan species provided the first strong evidence for partitioning of inorganic resources, which has significant implications for the ecology and evolution of this taxonomic group.
Keywords: HOV Alvin (Human Occupied Vehicle)

Sulfide Oxidation across Diffuse Flow Zones of Hydrothermal Vents - Gartman, A; Yucel, M; Madison, A S; Chu, D W; Ma, S; Janzen, C P; Becker, E L; Beinart, R A; Girguis, P R; Luther, G W (Aquatic Geochemistry, 2011)
The sulfide (H(2)S/HS(-)) that is emitted from hydrothermal vents begins to oxidize abiotically with oxygen upon contact with ambient bottom water, but the reaction kinetics are slow. Here, using in situ voltammetry, we report detection of the intermediate sulfur oxidation products polysulfides [S(x)(2-)] and thiosulfate [S(2)O(3)(2-)], along with contextual data on sulfide, oxygen, and temperature. At Lau Basin in 2006, thiosulfate was identified in less than one percent of approximately 10,500 scans and no polysulfides were detected. Only five percent of 11,000 voltammetric scans taken at four vent sites at Lau Basin in May 2009 show either thiosulfate or polysulfides. These in situ data indicate that abiotic sulfide oxidation does not readily occur as H(2)S contacts oxic bottom waters. Calculated abiotic potential sulfide oxidation rates are
Keywords: ROV Jason (Remotely Operated Vehicle)

Surface-generated mesoscale eddies transport deep-sea products from hydrothermal vents - Adams, D K; McGillicuddy, D J; Zamudio, L; Thurnherr, A M; Liang, X; Rouxel, O J; German, C R; Mullineaux, L S (Science, 2011)
Atmospheric forcing, which is known to have a strong influence on surface ocean dynamics and production, is typically not considered in studies of the deep sea. Our observations and models demonstrate an unexpected influence of surface-generated mesoscale eddies in the transport of hydrothermal vent efflux and of vent larvae away from the northern East Pacific Rise. Transport by these deep-reaching eddies provides a mechanism for spreading the hydrothermal chemical and heat flux into the deep-ocean interior and for dispersing propagules hundreds of kilometers between isolated and ephemeral communities. Because the eddies interacting with the East Pacific Rise are formed seasonally and are sensitive to phenomena such as El Niño, they have the potential to introduce seasonal to interannual atmospheric variations into the deep sea.
Keywords: HOV Alvin (Human Occupied Vehicle)

Thermodynamics and kinetics of sulfide oxidation by oxygen: a look at inorganically controlled reactions and biologically mediated processes in the environment - Luther III, George W; Findlay, Alyssa J; MacDonald, Daniel J; Owings, Shannon M; Hanson, Thomas E; Beinart, Roxanne A; Girguis, Peter R (FRONTIERS IN MICROBIOLOGY, 2011)
The thermodynamics for the first electron transfer step for sulfide and oxygen indicates that the reaction is unfavorable as unstable superoxide and bisulfide radical ions would need to be produced. However, a two-electron transfer is favorable as stable S(0) and peroxide would be formed, but the partially filled orbitals in oxygen that accept electrons prevent rapid kinetics. Abiotic sulfide oxidation kinetics improve when reduced iron and/or manganese are oxidized by oxygen to form oxidized metals which in turn oxidize sulfide. Biological sulfur oxidation relies on enzymes that have evolved to overcome these kinetic constraints to affect rapid sulfide oxidation. Here we review the available thermodynamic and kinetic data for H2S and HS center dot as well as O-2, reactive oxygen species, nitrate, nitrite, and NOx species. We also present new kinetic data for abiotic sulfide oxidation with oxygen in trace metal clean solutions that constrain abiotic rates of sulfide oxidation in metal free solution and agree with the kinetic and thermodynamic calculations. Moreover, we present experimental data that give insight on rates of chemolithotrophic and photolithotrophic sulfide oxidation in the environment. We demonstrate that both anaerobic photolithotrophic and aerobic chemolithotrophic sulfide oxidation rates are three or more orders of magnitude higher than abiotic rates suggesting that in most environments biotic sulfide oxidation rates will far exceed abiotic rates due to the thermodynamic and kinetic constraints discussed in the first section of the paper. Such data reshape our thinking about the biotic and abiotic contributions to sulfide oxidation in the environment.
Keywords: ROV Jason (Remotely Operated Vehicle)

Thermodynamics and kinetics of sulfide oxidation by oxygen: a look at inorganically controlled reactions and biologically mediated processes in the environment - Luther, G W; Findlay, A J; MacDonald, D J; Owings, S M; Hanson, T E; Beinart, R A; Girguis, P R (Frontiers in Microbiology, 2011)
The thermodynamics for the first electron transfer step for sulfide and oxygen indicates that the reaction is unfavorable as unstable superoxide and bisulfide radical ions would need to be produced. However, a two-electron transfer is favorable as stable S(0) and peroxide would be formed, but the partially filled orbitals in oxygen that accept electrons prevent rapid kinetics. Abiotic sulfide oxidation kinetics improve when reduced iron and/or manganese are oxidized by oxygen to form oxidized metals which in turn oxidize sulfide. Biological sulfur oxidation relies on enzymes that have evolved to overcome these kinetic constraints to affect rapid sulfide oxidation. Here we review the available thermodynamic and kinetic data for H2S and HS center dot as well as O-2, reactive oxygen species, nitrate, nitrite, and NOx species. We also present new kinetic data for abiotic sulfide oxidation with oxygen in trace metal clean solutions that constrain abiotic rates of sulfide oxidation in metal free solution and agree with the kinetic and thermodynamic calculations. Moreover, we present experimental data that give insight on rates of chemolithotrophic and photolithotrophic sulfide oxidation in the environment. We demonstrate that both anaerobic photolithotrophic and aerobic chemolithotrophic sulfide oxidation rates are three or more orders of magnitude higher than abiotic rates suggesting that in most environments biotic sulfide oxidation rates will far exceed abiotic rates due to the thermodynamic and kinetic constraints discussed in the first section of the paper. Such data reshape our thinking about the biotic and abiotic contributions to sulfide oxidation in the environment.
Keywords: ROV Jason (Remotely Operated Vehicle)

Thermophilic anaerobic oxidation of methane by marine microbial consortia - Holler, Thomas; Widdel, Friedrich; Knittel, Katrin; Amann, Rudolf; Kellermann, Matthias Y; Hinrichs, Kai-Uwe; Teske, Andreas; Boetius, Antje; Wegener, Gunter (ISME JOURNAL, 2011)
The anaerobic oxidation of methane (AOM) with sulfate controls the emission of the greenhouse gas methane from the ocean floor. AOM is performed by microbial consortia of archaea (ANME) associated with partners related to sulfate-reducing bacteria. In vitro enrichments of AOM were so far only successful at temperatures {<}= 25 degrees C; however, energy gain for growth by AOM with sulfate is in principle also possible at higher temperatures. Sequences of 16S rRNA genes and core lipids characteristic for ANME as well as hints of in situ AOM activity were indeed reported for geothermally heated marine environments, yet no direct evidence for thermophilic growth of marine ANME consortia was obtained to date. To study possible thermophilic AOM, we investigated hydrothermally influenced sediment from the Guaymas Basin. In vitro incubations showed activity of sulfate-dependent methane oxidation between 5 and 70 degrees C with an apparent optimum between 45 and 60 degrees C. AOM was absent at temperatures {>}= 75 degrees C. Long-term enrichment of AOM was fastest at 50 degrees C, yielding a 13-fold increase of methane-dependent sulfate reduction within 250 days, equivalent to an apparent doubling time of 68 days. The enrichments were dominated by novel ANME-1 consortia, mostly associated with bacterial partners of the deltaproteobacterial HotSeep-1 cluster, a deeply branching phylogenetic group previously found in a butane-amended 60 degrees C-enrichment culture of Guaymas sediments. The closest relatives (Desulfurella spp.; Hippea maritima) are moderately thermophilic sulfur reducers. Results indicate that AOM and ANME archaea could be of biogeochemical relevance not only in cold to moderate but also in hot marine habitats. The ISME Journal (2011) 5, 1946-1956; doi: 10.1038/ismej.2011.77; published online 23 June 2011
Keywords: HOV Alvin (Human Occupied Vehicle)

Three new species of pennatulacean octocorals with the ability to attach to rocky substrata (Cnidaria: Anthozoa: Pennatulacea) - Williams, Gary C; Alderslade, Philip (ZOOTAXA, 2011)
All sea pens have been thought to anchor in soft sediment using a basal, sausage-shaped, muscular peduncle. Based on underwater images and examination of specimens, we report an adaptation of the proximal portion of the peduncle for attachment to solid surfaces. We document four species with this adaptation, three new, Anthoptilum lithophilum sp. nov. (California, 669-700 m), A. gowlettholmesae sp. nov. (Tasmania, 729-1803 m), and Calibelemnon francei sp. nov. (the Bahamas, 1969 m), and one known, A. decipiens Thomson {&} Henderson, 1906 (Sri Lanka, 925 m). The peduncle of a colony with this adaptation is greatly expanded by an outgrowth of the coenenchyme that forms a sucker-like structure, beneath which a conical mass of tough tissue surrounds the proximal end of the internal axis. We infer this structure affects suction, increasing or decreasing the strength of adhesion to the substratum, and discuss the systematics and functional morphology of this new ecological phenomenon-pennatulaceans fastened to hard substrata. We alter the definition of the genus Anthoptilum to accommodate this morphology, reporting on specimens of the type species, A. grandiflorum; compare the two sea pen families-Anthoptilidae and Scleroptilidae- and the two genera; and present a key to the known rock-inhabiting species.
Keywords: ROV Jason (Remotely Operated Vehicle)

Tracing iron-fueled microbial carbon production within the hydrothermal plume at the Loihi Seamount - Bennett, S A; Hansman, R L; Sessions, A L; Nakamura, K; Edwards, K J (Geochimica et Cosmochimica Acta, 2011)
The Loihi hydrothermal plume provides an opportunity to investigate iron (Fe) oxidation and microbial processes in a system that is truly Fe dominated and distinct from mid-ocean ridge spreading centers. The lack of hydrogen sulfide within the Loihi hydrothermal fluids and the presence of an oxygen minimum zone at this submarine volcano's summit, results in a prolonged presence of reduced Fe within the dispersing non-buoyant plume. In this study, we have investigated the potential for microbial carbon fixation within the Loihi plume. We sampled for both particulate and dissolved organic carbon in hydrothermal fluids, microbial mats growing around vents, and the dispersing plume, and carried out stable carbon isotope analysis on the particulate fraction. The $δ$13C values of the microbial mats ranged from −23‰ to −28‰, and are distinct from those of deep-ocean particulate organic carbon (POC). The mats and hydrothermal fluids were also elevated in dissolved organic carbon (DOC) compared to background seawater. Within the hydrothermal plume, DOC and POC concentrations were elevated and the isotopic composition of POC within the plume suggests mixing between background seawater POC and a 13C-depleted hydrothermal component. The combination of both DOC and POC increasing in the dispersing plume that cannot solely be the result of entrainment and DOC adsorption, provides strong evidence for in-situ microbial productivity by chemolithoautotrophs, including a likelihood for iron-oxidizing microorganisms.
Keywords: ROV Jason (Remotely Operated Vehicle)

Using CRISPRs as a metagenomic tool to identify microbial hosts of a diffuse flow hydrothermal vent viral assemblage - Anderson, Rika E; Brazelton, William J; Baross, John A (FEMS MICROBIOLOGY ECOLOGY, 2011)
Metagenomic analyses of viruses have revealed widespread diversity in the viriosphere, but it remains a challenge to identify specific hosts for a viral assemblage. To address this problem, we analyze the viral metagenome of a northeast Pacific hydrothermal vent with a comprehensive database of spacers derived from the clustered regularly interspaced short palindromic repeat (CRISPR) putative immune system. CRISPR spacer matches to the marine vent virome suggest that viruses infecting hosts from diverse taxonomic groups are present in this vent environment. Comparative virome analyses show that CRISPR spacers from vent isolates and from thermophiles in general have a higher percentage of matches to the vent virome than to other marine or terrestrial hot spring viromes. However, a high percentage of hits to spacers from mesophilic hosts, combined with a moderately high modeled alpha diversity, suggest that the marine vent virome is comprised of viruses that have the potential to infect diverse taxonomic groups of multiple thermal regimes in both the bacterial and the archaeal domains.
Keywords: HOV Alvin (Human Occupied Vehicle)

U-Th systematics and ages of carbonate chimneys at the Lost City Hydrothermal Field - Ludwig, K A; Shen, C C; Kelley, D S; Cheng, H; Edwards, R L (Geochimica et Cosmochimica Acta, 2011)
The Lost City Hydrothermal Field (LCHF) is a serpentinite-hosted vent field located 15 km west of the spreading axis of the Mid-Atlantic Ridge. In this study, uranium–thorium (U–Th) geochronological techniques have been used to examine the U–Th systematics of hydrothermal fluids and the 230Th ages of hydrothermally-precipitated carbonate chimneys at the LCHF. Fluid sample analyses indicate that endmember fluids likely contain only 0.0073 ng/g U or less compared to 3.28 ± 0.03 ng/g of U in ambient seawater. For fluid samples containing only 2–21{%} ambient seawater (1.1–11 mmol/kg Mg), Th concentration is 0.11–0.13 pg/g and surrounding seawater concentrations average 0.133 ± 0.016 pg/g. The 230Th/232Th atomic ratios of the vent fluids range from 1 (±10) × 10−6 to 11 (±5) × 10−6, are less than those of seawater, and indicate that the vent fluids may contribute a minor amount of non-radiogenic 230Th to the LCHF carbonate chimney deposits. Chimney 238U concentrations range from 1 to 10 $μ$g/g and the average chimney corrected initial $δ$234U is 147.2 ± 0.8, which is not significantly different from the ambient seawater value of 146.5 ± 0.6. Carbonate 232Th concentrations range broadly from 0.0038 ± 0.0003 to 125 ± 16 ng/g and 230Th/232Th atomic ratios vary from near seawater values of 43 (±8) × 10−6 up to 530 (±25) × 10−3. Chimney ages, corrected for initial 230Th, range from 17 ± 6 yrs to 120 ± 13 kyrs. The youngest chimneys are at the intersection of two active, steeply-dipping normal faults that cut the Atlantis Massif; the oldest chimneys are located in the southwest portion of the field. Vent deposits on a steep, fault-bounded wall on the east side of the field are all Th, range from 17 ± 6 yrs to 120 ± 13 kyrs. The youngest chimneys are at the intersection of two active, steeply-dipping normal faults that cut the Atlantis Massif; the oldest chimneys are located in the southwest portion of the field. Vent deposits on a steep, fault-bounded wall on the east side of the field are all
Keywords: HOV Alvin (Human Occupied Vehicle)

Vent fluid chemistry of the Rainbow Hydrothermal System (36 degrees N, MAR): Phase equilibria and in-situ pH controls on subseafloor alteration processes - Seyfried, W E; Pester, N J; Ding, K; Rough, M (Geochimica et Cosmochimica Acta, 2011)
The Rainbow hydrothermal field is located at 36°13.8′N–33°54.15′W at 2300 m depth on the western flank of a non-volcanic ridge between the South AMAR and AMAR segments of the Mid-Atlantic Ridge. The hydrothermal field consists of 10–15 active chimneys that emit high-temperature (∼365 °C) fluid. In July 2008, vent fluids were sampled during cruise KNOX18RR, providing a rich dataset that extends in time information on subseafloor chemical and physical processes controlling vent fluid chemistry at Rainbow. Data suggest that the Mg concentration of the hydrothermal end-member is not zero, but rather 1.5–2 mmol/kg. This surprising result may be caused by a combination of factors including moderately low dissolved silica, low pH, and elevated chloride of the hydrothermal fluid. Combining end-member Mg data with analogous data for dissolved Fe, Si, Al, Ca, and H2, permits calculation of mineral saturation states for minerals thought appropriate for ultramafic-hosted hydrothermal systems at temperatures and pressures in keeping with constraints imposed by field observations. These data indicate that chlorite solid solution, talc, and magnetite achieve saturation in Rainbow vent fluid at a similar pH(T,P) (400 °C, 500 bar) of approximately 4.95, while higher pH values are indicated for serpentine, suggesting that serpentine may not coexist with the former assemblage at depth at Rainbow. The high Fe/Mg ratio of the Rainbow vent fluid notwithstanding, the mole fraction of clinochlore and chamosite components of chlorite solid solution at depth are predicted to be 0.78 and 0.22, respectively. In situ pH measurements made at Rainbow vents are in good agreement with pH(T,P) values estimated from mineral solubility calculations, when the in situ pH data are adjusted for temperature and pressure. Calculations further indicate that pH(T,P) and dissolved H2 are extremely sensitive to changes in dissolved silica owing to constraints imposed by chlorite solid solution-fluid equilibria. Indeed, the predicted correlation between dissolved silica and H2 defines a trend that is in good agreement with vent fluid data from Rainbow and other high-temperature ultramafic-hosted hydrothermal systems. We speculate that the moderate concentrations of dissolved silica in vent fluids from these systems result from hydrothermal alteration of plagioclase and olivine in the form of subsurface gabbroic intrusions, which, in turn are variably replaced by chlorite + magnetite + talc ± tremolite, with important implications for pH lowering, dissolved sulfide concentrations, and metal mobility.
Keywords: ROV Jason (Remotely Operated Vehicle)

Volatile abundances and oxygen isotopes in basaltic to dacitic lavas on mid-ocean ridges: The role of assimilation at spreading centers - Wanless, V D; Perfit, M R; Ridley, W I; Wallace, P J; Grimes, C B; Klein, E M (Chemical Geology, 2011)
Most geochemical variability in MOR basalts is consistent with low- to moderate-pressure fractional crystallization of various mantle-derived parental melts. However, our geochemical data from MOR high-silica glasses, including new volatile and oxygen isotope data, suggest that assimilation of altered crustal material plays a significant role in the petrogenesis of dacites and may be important in the formation of basaltic lavas at MOR in general. MOR high-silica andesites and dacites from diverse areas show remarkably similar major element trends, incompatible trace element enrichments, and isotopic signatures suggesting similar processes control their chemistry. In particular, very high Cl and elevated H2O concentrations and relatively light oxygen isotope ratios ({\~{}} 5.8‰ vs. expected values of {\~{}} 6.8‰) in fresh dacite glasses can be explained by contamination of magmas from a component of ocean crust altered by hydrothermal fluids. Crystallization of silicate phases and Fe-oxides causes an increase in $δ$18O in residual magma, but assimilation of material initially altered at high temperatures results in lower $δ$18O values. The observed geochemical signatures can be explained by extreme fractional crystallization of a MOR basalt parent combined with partial melting and assimilation (AFC) of amphibole-bearing altered oceanic crust. The MOR dacitic lavas do not appear to be simply the extrusive equivalent of oceanic plagiogranites. The combination of partial melting and assimilation produces a distinct geochemical signature that includes higher incompatible trace element abundances and distinct trace element ratios relative to those observed in plagiogranites.
Keywords: ROV DSL-120 (Remotely Operated Vehicle); ROV Jason (Remotely Operated Vehicle)

Volcanic morphology of West Mata Volcano, NE Lau Basin, based on high-resolution bathymetry and depth changes - Clague, D A; Paduan, J B; Caress, D W; Thomas, Hans; Chadwick, W W; Merle, S G (Geochemistry, Geophysics, Geosystems, 2011)
High-resolution (1.5 m) mapping from the autonomous underwater vehicle (AUV) D. Allan B. of West Mata Volcano in the northern Lau Basin is used to identify the processes that construct and modify the volcano. The surface consists largely of volcaniclastic debris that forms smooth slopes to the NW and SE, with smaller lava flows forming gently sloping plateaus concentrated along the ENE and WSW rift zones, and more elongate flows radiating from the summit. Two active volcanic vents, Prometheus and Hades, are located ∼50 and ∼150 m WSW of the 1159 m summit, respectively, and are slightly NW of the ridgeline so the most abundant clastic deposits are emplaced on the NW flank. This eruptive activity and the location of vents appears to have been persistent for more than a decade, based on comparison of ship-based bathymetric surveys in 1996 and 2008–2010, which show positive depth changes up to 96 m on the summit and north flank of the volcano. The widespread distribution of clastic deposits downslope from the rift zones, as well as from the current vents, suggests that pyroclastic activity occurs at least as deep as 2200 m. The similar morphology of additional nearby volcanoes suggests that they too have abundant pyroclastic deposits.
Keywords: ROV Jason (Remotely Operated Vehicle)

Abyssogena: a new genus of the family Vesicomyidae (Bivalvia) from deep-water vents and seeps - Krylova, Elena M; Sahling, Heiko; Janssen, Ronald (JOURNAL OF MOLLUSCAN STUDIES, 2010)
A new genus Abyssogena is established for A. phaseoliformis ( Metivier, Okutani {&} Ohta, 1986) and A. kaikoi ( Okutani {&} Metivier, 1986), which were previously assigned to the genus Calyptogena Dall, 1891, and also for two new species, A. southwardae and A. novacula. The most characteristic features of Abyssogena are an elongate shell up to about 280 mm in length; a pallial line starting from the ventral margin of the anterior adductor scar; secondary pallial attachment scars developed dorsal to the pallial line; radially arranged hinge teeth with a reduced anterior cardinal tooth in the right valve; and presence of an inner ctenidial demibranch only. Abyssogena occurs in deep water from 2,985 to 6,400 m and is distributed in the Pacific and Atlantic Oceans at cold seeps along continental margins and hydrothermal vents at mid-oceanic ridges. Some species have a remarkably wide geographic distribution; A. southwardae is present throughout the Atlantic and A. phaseoliformis is present in Japan, Kuril-Kamchatka, as well as Aleutian Trenches. No fossils of Abyssogena are known.
Keywords: HOV Alvin (Human Occupied Vehicle)

Alvin gets an interior re-design: sub's new sphere will provide a little more room and comfort - Nevala, A E (Oceanus, 2010)
Keywords: HOV Alvin (Human Occupied Vehicle)

Archaea and bacteria with surprising microdiversity show shifts in dominance over 1,000-year time scales in hydrothermal chimneys - Brazelton, W J; Ludwig, K A; Sogin, M L; Andreishcheva, E N; Kelley, D S; Shen, C C; Edwards, R L; Baross, J A (Proceedings of the National Academy of Sciences of the United States of America, 2010)
The Lost City Hydrothermal Field, an ultramafic-hosted system located 15 km west of the Mid-Atlantic Ridge, has experienced at least 30,000 years of hydrothermal activity. Previous studies have shown that its carbonate chimneys form by mixing of ∼90 °C, pH 9–11 hydrothermal fluids and cold seawater. Flow of methane and hydrogen-rich hydrothermal fluids in the porous interior chimney walls supports archaeal biofilm communities dominated by a single phylotype of Methanosarcinales. In this study, we have extensively sampled the carbonate-hosted archaeal and bacterial communities by obtaining sequences of {>}200,000 amplicons of the 16S rRNA V6 region and correlated the results with isotopic (230Th) ages of the chimneys over a 1,200-year period. Rare sequences in young chimneys were commonly more abundant in older chimneys, indicating that members of the rare biosphere can become dominant members of the ecosystem when environmental conditions change. These results suggest that a long history of selection over many cycles of chimney growth has resulted in numerous closely related species at Lost City, each of which is preadapted to a particular set of reoccurring environmental conditions. Because of the unique characteristics of the Lost City Hydrothermal Field, these data offer an unprecedented opportunity to study the dynamics of a microbial ecosystem's rare biosphere over a thousand-year time scale.
Keywords: HOV Alvin (Human Occupied Vehicle)

Asphalt volcanoes as a potential source of methane to late Pleistocene coastal waters - Valentine, D L; Reddy, C M; Farwell, C; Hill, T M; Pizarro, O; Yoerger, D R; Camilli, R; Nelson, R K; Peacock, E E; Bagby, S C; Clarke, B A; Roman, C N; et al. (Nature Geoscience, 2010)
Every year, natural petroleum seepage emits 0.2–2 Tg of oil to the ocean1. Significant oil seepage can build large underwater mounds, consisting of tar deposits with morphologies similar to volcanic lava flows, known as asphalt volcanoes2, 3. Such events are typically accompanied by large fluxes of the greenhouse gas methane4, 5. Marine sediments from the Santa Barbara basin, California, contain a record of elevated methane concentrations6, anoxia and tar deposition7 during the Pleistocene epoch that had been attributed to dissolution of methane hydrates. However, the region is known to have exhibited oil seepage in the past7. Here, we document the discovery of seven extinct asphalt volcanoes off the coast of southern California. The morphology of the deposits and geochemistry of samples taken from the two largest structures supports their classification as asphalt volcanoes, derived from a common source. We estimate that the two structures resulted from seepage of 0.07–0.4 Tg of oil, accompanied by the emission of 0.35–1.8 Tg of methane. Radiocarbon dating of carbonate deposits entrained with the asphalt indicates formation of the volcanoes between 44 and 31 kyr ago. The timing and volume of erupted hydrocarbons from the asphalt structures can explain some or all of the documented methane release and tar accumulation in the Santa Barbara basin during the Pleistocene.
Keywords: AUV Sentry (Autonomous Underwater Vehicle); HOV Alvin (Human Occupied Vehicle)

Autonomous underwater vehicles as tools for deep-submergence archaeology - Roman, C; Mather, R (Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment, 2010)
Marine archaeology beyond the capabilities of scuba divers is a technologically enabled field. The tool suite includes ship-based systems such as towed side-scan sonars and remotely operated vehicles, and more recently free-swimming autonomous underwater vehicles (AUVs). Each of these platforms has various imaging and mapping capabilities appropriate for specific scales and tasks. Broadly speaking, AUVs are becoming effective tools for locating, identifying, and surveying archaeological sites. This paper discusses the role of AUVs in this suite of tools, outlines some specific design criteria necessary to maximize their utility in the field, and presents directions for future developments. Results are presented for a recent joint AUV—towed system survey and a demonstration of current mine-hunting technologies applied to archaeology.
Keywords: AUV ABE (Autonomous Benthic Explorer); ROV Jason (Remotely Operated Vehicle)

Axial Seamount - Chadwick, W W; Butterfield, D A; Embley, R W; Tunnicliffe, V; Huber, J A; Nooner, S L; Clague, D A (Oceanography, 2010)
Axial Seamount is a hotspot volcano superimposed on the Juan de Fuca Ridge (JdFR) in the Northeast Pacific Ocean. Due to its robust magma supply, it rises {\~{}} 800 m above the rest of JdFR and has a large elongate summit caldera with two rift zones that parallel and overlap with adjacent segments of the spreading center (Figure 1). Submersible dives at Axial in 1983–1984 discovered the first active black smoker vents in the Northeast Pacific (Chase et al., 1985). The New Millennium Observatory (NeMO; http://www.pmel.noaa.gov/vents/nemo) was established at Axial in 1996 to study volcanic events and the perturbations they cause to hydrothermal and biological systems. As if on cue, Axial erupted in January 1998 and was the first seafloor eruption detected remotely and monitored by in situ instruments (Embley et al., 1999). In fact, one instrument caught in a 1998 lava flow was later recovered with data intact, providing new insight into the emplacement of submarine lavas (Chadwick, 2003). Initially, research focused on mapping, sampling, and documenting the impact of the eruption on the hydrothermal vents and biological communities (Figure 2). The emphasis has gradually shifted to long-term geophysical, geochemical, and biological monitoring of the volcano in anticipation of its next eruption.

Beaked whale foraging areas inferred by gouges in the seafloor - Auster, Peter J; Watling, Les (MARINE MAMMAL SCIENCE, 2010)
Keywords: HOV Alvin (Human Occupied Vehicle)

Biogeochemical signatures and microbial activity of different cold-seep habitats along the Gulf of Mexico deep slope - Joye, S B; Bowles, M W; Samarkin, V A; Hunter, K S; Niemann, H (Deep-Sea Research. Part II: Topical Studies in Oceanography, 2010)
Microorganisms and the processes they mediate serve as the metabolic foundation of cold seeps. We characterized a suite of biogeochemical constituents and quantified rates of two key microbial processes, Sulfate Reduction (SR) and Anaerobic Oxidation of Methane (AOM), to assess variability between habitats at water depths exceeding 1000 m in the northern Gulf of Mexico. Rates of SR were highest in sediments beneath microbial mats, lower in brine-influenced and oil-influenced sediments, and lowest in animal habitats. Sediments collected near tubeworms had the highest SR rates for animal habitats. Rates of AOM generally were low, but higher rates were associated with brine-influenced, oil-influenced, tubeworm- and urchin-inhabited sediments. Rates of both SR and AOM were orders of magnitude lower at deep-slope sites compared to upper-slope sites examined previously. As observed at upper-slope sites, SR and AOM rates were often loosely coupled. At one site, AOM rates exceeded SR rates, suggesting that an alternate electron acceptor for AOM is possible. Extremely depleted $δ$13C values in methane illustrated the broad significance of biogenic methane production at deep-slope sites. Brine-influenced habitats were characterized by extremely high concentrations of ammonium and dissolved organic carbon, serving as important focused sources of these chemicals to adjacent environments.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Biogeography and Potential Exchanges Among the Atlantic Equatorial Belt Cold-Seep Faunas - Olu, K; Cordes, E E; Fisher, C R; Brooks, J M; Sibuet, M; Desbruyeres, D (PLoS ONE, 2010)
Like hydrothermal vents along oceanic ridges, cold seeps are patchy and isolated ecosystems along continental margins, extending from bathyal to abyssal depths. The Atlantic Equatorial Belt (AEB), from the Gulf of Mexico to the Gulf of Guinea, was one focus of the Census of Marine Life ChEss (Chemosynthetic Ecosystems) program to study biogeography of seep and vent fauna. We present a review and analysis of collections from five seep regions along the AEB: the Gulf of Mexico where extensive faunal sampling has been conducted from 400 to 3300m, the Barbados accretionary prism, the Blake ridge diapir, and in the Eastern Atlantic from the Congo and Gabon margins and the recently explored Nigeria margin. Of the 72 taxa identified at the species level, a total of 9 species or species complexes are identified as amphi-Atlantic. Similarity analyses based on both Bray Curtis and Hellinger distances among 9 faunal collections, and principal component analysis based on presence/absence of megafauna species at these sites, suggest that within the AEB seep megafauna community structure is influenced primarily by depth rather than by geographic distance. Depth segregation is observed between 1000 and 2000m, with the middle slope sites either grouped with those deeper than 2000m or with the shallower sites. The highest level of community similarity was found between the seeps of the Florida escarpment and Congo margin. In the western Atlantic, the highest degree of similarity is observed between the shallowest sites of the Barbados prism and of the Louisiana slope. The high number of amphi-atlantic cold-seep species that do not cluster according to biogeographic regions, and the importance of depth in structuring AEB cold-seep communities are the major conclusions of this study. The hydrothermal vent sites along the Mid Atlantic Ridge (MAR) did not appear as “stepping stones” for dispersal of the AEB seep fauna, however, the south MAR and off axis regions should be further explored to more fully test this hypothesis.

Biogeography, Ecology and Vulnerability of Chemosynthetic Ecosystems in the Deep Sea - Baker, M C; Ramirez-Llodra, E; Tyler, P A; German, C R; Boetius, A; Cordes, E E; Dubilier, N; Fisher, C R; Levin, L A; Metaxas, A; Rowden, R; Santos, R S; et al. (Life in the World's Oceans: Diversity, Distribution, and Abundance, 2010)

Biotic and abiotic factors affecting distributions of megafauna in diffuse flow on andesite and basalt along the Eastern Lau Spreading Center, Tonga - Podowski, E L; Ma, S; Luther, G W; Wardrop, D; Fisher, C R (Marine Ecology Progress Series, 2010)
Imagery and environmental data from 7 diffuse flow hydrothermal vent sites along the Eastern Lau Spreading Center (ELSC) are used to constrain the effects of lava type, temperature, chemistry, and biological interactions on faunal distributions. Of the species with chemoautotrophic endosymbionts, the snail Alviniconcha spp. occupies habitats with the greatest exposure to vent fluids. Temperatures exceeding 45°C define its upper limit of exposure to vent flow, and minimum sulfide requirements constrain its lower limits. The mussel Bathymodiolus brevior experiences the least exposure to vent flow; temperatures of about 20°C determine its upper limit, while its lower limit is defined by its minimum sulfide requirements. The snail Ifremeria nautilei inhabits areas with intermediate exposure to vent fluids and biological interactions are likely the most important factor shaping this snail's realized niche. Microhabitats of non-symbiont-containing fauna were defined in terms of symbiont-containing faunal distributions. The crab Austinograea spp. occupies areas with the greatest exposure to vent flow; shrimp, the snail Eosipho desbruyeresi, and anemones inhabit intermediate zones of vent flow; and the squat lobster Munidopsis lauensis dominates the periphery of diffuse flow areas, with little exposure to vent fluids. The physical structure of different lava types along the ELSC differentially affects the diffusion of vent fluids, which has a variety of implications for fauna, particularly distributions of zoanthids, anemones, and mixed communities of I. nautilei and B. brevior.
Keywords: ROV Jason (Remotely Operated Vehicle)

Building the next-generation Alvin: plan offers a roadmap to extend sub's diving capacity to 6,500 meters - Nevala, A E (Oceanus, 2010)
Keywords: HOV Alvin (Human Occupied Vehicle)

Carbon release from submarine seeps at the Costa Rica fore arc: Implications for the volatile cycle at the Central America convergent margin - Fueri, E; Hilton, D R; Tryon, M D; Brown, K M; McMurtry, G M; Brueckmann, W; Wheat, C G (Geochemistry, Geophysics, Geosystems, 2010)
We report total dissolved inorganic carbon (DIC) abundances and isotope ratios, as well as helium isotope ratios (3He/4He), of cold seep fluids sampled at the Costa Rica fore arc in order to evaluate the extent of carbon loss from the submarine segment of the Central America convergent margin. Seep fluids were collected over a 12 month period at Mound 11, Mound 12, and Jaco Scar using copper tubing attached to submarine flux meters operating in continuous pumping mode. The fluids show minimum 3He/4He ratios of 1.3 RA (where RA is air 3He/4He), consistent with a small but discernable contribution of mantle-derived helium. At Mound 11, $δ$13C∑CO2 values between −23.9‰ and −11.6‰ indicate that DIC is predominantly derived from deep methanogenesis and is carried to the surface by fluids derived from sediments of the subducting slab. In contrast, at Mound 12, most of the ascending dissolved methane is oxidized due to lower flow rates, giving extremely low $δ$13C∑CO2 values ranging from −68.2‰ to −60.3‰. We estimate that the carbon flux (CO2 plus methane) through submarine fluid venting at the outer fore arc is 8.0 × 105 g C km−1 yr−1, which is virtually negligible compared to the total sedimentary carbon input to the margin and the output at the volcanic front. Unless there is a significant but hitherto unidentified carbon flux at the inner fore arc, the implication is that most of the carbon being subducted in Costa Rica must be transferred to the (deeper) mantle, i.e., beyond the depth of arc magma generation.
Keywords: HOV Alvin (Human Occupied Vehicle)

Characterization of 12 polymorphic microsatellite loci in Ifremeria nautilei, a chemoautotrophic gastropod from deep-sea hydrothermal vents - Thaler, A D; Zelnio, K; Jones, R; Carlsson, J; Van Dover, C L; Schultz, T F (Conservation Genetics Resources, 2010)
{Ifremeria nautilei is deep-sea provannid gastropod endemic to hydrothermal vents at southwest Pacific back-arc spreading centers. Twelve, selectively neutral and unlinked polymorphic microsatellite loci were developed for this species. Three loci deviated significantly from Hardy-Weinberg expectations. Average observed heterozygosity ranged from 0.719 to 0.906 (mean H-O = 0.547

Cold-seep carbonates of the middle and lower continental slope, northern Gulf of Mexico - Roberts, H H; Feng, D; Joye, S B (Deep-Sea Research. Part II: Topical Studies in Oceanography, 2010)
Authigenic carbonates from cold seeps on the middle and lower continental slope of the northern Gulf of Mexico (GOM) exhibit a wide range of mineralogical and stable isotopic compositions. These carbonates consist of concretions and nodules in surface sediments, hardgrounds of crusts and isolated slabs, and mounded buildups of blocks and slabs of up to over 10 meters in relief above the surrounding seafloor. Mineralogically, the carbonates are dominated by high-Mg calcite (HMC) and aragonite. However, low levels ({<}5 wt{%}) of dolomite are present in most samples. Petrographically, Mg-calcite peloidal matrix and acicular to botryoidal aragonitic void-filling cements are the most frequent associations. The carbon isotopic compositions of the carbonates range from −60.8 to 14.0‰ PDB, indicating complex carbon sources that include 13C-depleted biogenic and thermogenic methane, biodegraded crude oil, seawater CO2, and 13C-enriched residual CO2 from methanogenesis. A similarly large variability in $δ$18O values (2.5 to 6.7‰ PDB) demonstrates the geochemical complexity of the slope, with some samples pointing toward an 18O-enriched oxygen source that is possibly related to advection of 18O-enriched formation water and/or to the decomposition of gas hydrate. A considerable range of mineralogical and isotopic variations in cold-seep carbonate composition was noted even within individual study sites. However, common trends occur across multiple geographic areas. This situation suggests that local controls on fluid and gas flux, types of seep hydrocarbons, the presence or absence of gas hydrate in the near-surface sediment, and chemosynthetic communities, as well as the temporal evolution of the local hydrocarbon reservoir, all may play a part in determining carbonate mineralogy and isotope geochemistry. The carbon isotope data clearly indicate that between-site variation is greater than within-site variation. Seep carbonates formed on the middle and lower continental slope of the GOM do not appear to be substantially different from those found on the upper slope ({<}1000-m water depth). The highly variable fluids and gases that leave their geochemical imprints on seep carbonate of the middle and lower continental slope are similar to their outer shelf and upper slope counterparts.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Combined carbonate carbon isotopic and cellular ultrastructural studies of individual benthic foraminifera : 2. Toward an understanding of apparent disequilibrium in hydrocarbon seeps - Bernhard, J M; Martin, J B; Rathburn, A E (Paleoceanography, 2010)
Numerous previous studies show disequilibrium between stable carbon isotope ratios of foraminiferal calcite and pore water dissolved inorganic carbon in hydrocarbon seeps, calling into question the utility of this widely used paleoceanographic tracer as a proxy. We use a recently developed method to compare stable carbon isotope ratios of foraminiferal carbonate with cell ultrastructural observations from individual benthic foraminifera from seep (under chemosynthetic bivalves) and nonseep habitats in Monterey Bay, California, to better understand control(s) of benthic foraminiferal carbon isotope ratios. Two attributes previously proposed to cause the isotopic offsets are diet and symbionts. Ultrastructural analysis shows that positive staining with Rose Bengal indicates presence of foraminiferal cytoplasm, bacterial biomass, or a combination of both and, thus, is not an unequivocal indicator of viability. We also show for the first time that some living seep foraminifera have endobionts. Results from our unique, yet limited, data set are consistent with suggestions that, in our sites, several foraminiferal species collected from seep clam beds may not survive there, diet and symbiont presence do not appear to be major contributors to disequilibrium, little calcification of seep-tolerant foraminiferal species occurs while seep conditions prevail, and microscale variability in habitats could influence $δ$13C of benthic foraminiferal carbonate. Results further suggest that our knowledge of benthic foraminiferal ecology and biomineralization, especially in extreme habitats such as seeps, must be bolstered before we fully understand the fidelity of paleoenvironmental records derived from benthic foraminiferal test $δ$13C data.
Keywords: ROV Jason (Remotely Operated Vehicle)

Combined carbonate carbon isotopic and cellular ultrastructural studies of individual benthic foraminifera: Method description - Martin, J B; Bernhard, J M; Curtis, J; Rathburn, A E (Paleoceanography, 2010)
Carbon isotopes of foraminiferal tests provide a widely used proxy for past oceanographic environmental conditions. This proxy can be calibrated using live specimens, which are reliably identified with observations of cell ultrastructure. Observations of ultrastructures can also be used for studies of biological characteristics such as diet and presence of symbionts. Combining biological and isotopic studies on individual foraminifera could provide novel information, but standard isotopic methods destroy ultrastructures by desiccating specimens and observations of ultrastructure require removal of carbonate tests, preventing isotope measurements. The approach described here preserves cellular ultrastructure during isotopic analyses by keeping the foraminifera in an aqueous buffer (Phosphate Buffered Saline (PBS)). The technique was developed and standardized with 36 aliquots of NBS-19 standard of similar weight to foraminiferal tests (5 to 123 $μ$g). Standard errors ranged from ± 0.06 to ± 0.85‰ and were caused by CO2 contaminants dissolved in the PBS. The technique was used to measure $δ$13C values of 96 foraminifera, 10 of which do not precipitate carbonate tests. Calcareous foraminiferal tests had corrected carbon isotope ratios of −8.5 to +3.2‰. This new technique allows comparisons of isotopic compositions of tests made by foraminifera known to be alive at the time of collection with their biological characteristics such as prey composition and presence or absence of putative symbionts. The approach may be applied to additional biomineralizing organisms such as planktonic foraminifera, pteropods, corals, and coccolithophores to elucidate certain biological controls on their paleoceanographic proxy signatures.
Keywords: ROV Jason (Remotely Operated Vehicle)

Community composition and temporal change at deep Gulf of Mexico cold seeps - Lessard-Pilon, S; Porter, M D; Cordes, E E; MacDonald, I R; Fisher, C R (Deep-Sea Research. Part II: Topical Studies in Oceanography, 2010)
Specialized cold-seep communities have been known to exist in the Gulf of Mexico (GOM) since the mid-1980s, but only recently has extensive research been carried out on sites at depths {>}1000 m. This study uses a combination of imagery and analyses within a Geographic Information Systems (GIS) framework to examine the composition of mussel and tubeworm communities at depths between 2200 and 2800 m in the Gulf of Mexico, spatial relations among the fauna, and changes in these communities over time. Photomosaics at three discrete seep communities were obtained in 2006 and a video mosaic of another community was obtained in 1992. Each of these communities was re-imaged in 2007. In addition, quantitative physical collections were made within two of the photomosaic sites and used to confirm the identification of megafauna, quantify the occurrence of smaller and cryptic macrofauna, and allow first-order calculations of biomass within the sites. Substrate type had a significant effect on community composition. Significant associations were identified between live mussels with anemones, shrimp, and sea cucumbers, and between tubeworm aggregations and Munidopsis sp. crabs and encrusting fauna, indicating differences in the composition of megafauna associated with adjacent mussel and tubeworm aggregations. Little change was seen in the total area colonized by foundation fauna (tubeworms and mussels) between years at any site. However, significant changes occurred in the positions of mussels, even over periods of a single year, at all sites, and evidence for the establishment of new tubeworm aggregations between 1992 and 2007 was noted at one site. These photomosaics provide data suggesting that environmental conditions can change over small spatial and temporal scales and mussels move in response to these changes. The successional trends are examined and compared to the patterns that have been documented in shallow ({<}1000-m depth) Gulf of Mexico seep communities.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Community structure comparisons of lower slope hydrocarbon seeps, northern Gulf of Mexico - MacDonald, I R; Smith, M; Huffer, F W (Deep-Sea Research. Part II: Topical Studies in Oceanography, 2010)
Photographic sampling collected from ROV JASON III on randomized transects (generally 10 per site) was used to compare seven suspected hydrocarbon seeps on the lower continental slope at depths of 956 to 2330 m. The study design focused on areas containing high-amplitude reflectance patterns in seismic returns from the bottom. Animal samples nested in these areas and high-resolution photographic mosaics permitted fine-scale description of the community components and their associations with each other. The transect results showed three types of chemosynthetic community: carbonate prone, brine pool prone, and low-density. These communities are characterized by, respectively, abundant carbonate rubble and tubeworm clusters, bacterial mats and brine pools, and relatively sparse chemosynthetic fauna that tended to be overlooked by the photographic survey plan. These differences were not clearly related to depth or longitude because the sites are at the opposite eastern and western extents of the project region. Photographic survey is a statistically reliable method for detecting the carbonate rubble and bacterial mat types of community, but may be unreliable for sparse or clustered fauna such as seep mussels. Photographic survey results provided relatively low taxonomic resolution, but were sufficient to distinguish statistical differences in the abundance of characteristic faunal groups, such as the Echinoidea and Gorgonacea, associated with hydrocarbon seeps. Initial studies of statistical power indicate that future photographic surveys of suspected seep communities, if conducted with an equivalent level of effort, might detect the presence of more abundant habitat, including carbonate rubble, bacterial mats, and tubeworms, but could miss less abundant indicators.
Keywords: ROV Jason (Remotely Operated Vehicle)

Community structure of infaunal macrobenthos around vestimentiferan thickets at the San Clemente cold seep, NE Pacific - Bernardino, A F; Smith, C R (Marine Ecology, 2010)
The San Clemente cold seep lies within 100–200 km of other reducing habitats in the NE Pacific, offering an opportunity to compare diversity and species overlap among reducing habitats (i.e. whale-, kelp-, and wood-falls) at similar depths within a single region. Video observations from the research submersible Alvin at the San Clemente seep (1800 m depth) indicated clumps (‘thickets') of vestimentiferans distributed as meter-scale patches interspersed with vesicomyid clam beds and black sediments. Sediment-core samples were collected at distances of 0 to 80–200 m along randomly oriented transects radiating outward from vestimentiferan thickets to evaluate changes in macrofaunal community structure from thickets into the background community. Macrofaunal abundance was elevated at distances of 0–1 m compared to 80–200 m (i.e. the ‘background' community). The tube-building frenulate worms Siboglinum spp., along with peracarid crustaceans, dominated sediments within 1 m of vestimentiferan thickets. Species diversity was depressed within 1 m of thickets but with high rates of species accumulation, suggesting that seep sites greatly increase sediment heterogeneity and facilitate colonization by non-background macrofaunal species. Stable isotope data indicate chemosynthetic nutrition for some dominant macrofaunal species within 1 m of tubeworm thickets. The macrofaunal community near vestimentiferan thickets in San Clemente seep contains intermediate levels of species richness and diversity compared to other deep-sea seep areas in the northeast Pacific. There was low species overlap between the San Clemente seep macrofauna and communities in reducing habitats near wood-, whale-, and kelp-falls at similar depths within the region, suggesting that seeps harbor a distinct infaunal community.
Keywords: HOV Alvin (Human Occupied Vehicle)

Deep-sea coral aragonite as a recorder for the neodymium isotopic composition of seawater - van de Flierdt, T; Robinson, L F; Adkins, J F (Geochimica et Cosmochimica Acta, 2010)
Deep-sea corals have been shown to be useful archives of rapid changes in ocean chemistry during the last glacial cycle. Their aragonitic skeleton can be absolutely dated by U–Th data, freeing radiocarbon to be used as a water-mass proxy. For certain species of deep-sea corals, the growth rate allows time resolution that is comparable to ice cores. An additional proxy is needed to exploit this opportunity and turn radiocarbon data into rates of ocean overturning in the past. Neodymium isotopes in seawater can serve as a quasi-conservative water-mass tracer and initial results indicate that deep-sea corals may be reliable archives of seawater Nd isotopes. Here we present a systematic study exploring Nd isotopes as a water-mass proxy in deep-sea coral aragonite. We investigated five different genera of modern deep-sea corals (Caryophyllia, Desmophyllum, Enallopsamia, Flabellum, Lophelia), from global locations covering a large potential range of Nd isotopic compositions. Comparison with ambient seawater measurements yields excellent agreement and suggests that deep-sea corals are reliable archives for seawater Nd isotopes. A parallel study of Nd concentrations in these corals yields distribution coefficients for Nd between seawater and coral aragonite of 1–10, omitting one particular genus (Enallopsamia). The corals and seawater did however not come from exactly the same location, and further investigations are needed to reach robust conclusions on the incorporation of Nd into deep-sea coral aragonite. Lastly, we studied the viability of extracting the Nd isotope signal from fossil deep-sea corals by carrying out stepwise cleaning experiments. Our results show that physical removal of the ferromanganese coating and chemical pre-cleaning have the highest impact on Nd concentrations, but that oxidative/reductive cleaning is also needed to acquire a seawater Nd isotope signal.
Keywords: HOV Alvin (Human Occupied Vehicle)

Dispersion of a tracer on the East Pacific Rise (9 degrees N–10 degrees N), including the influence of hydrothermal plumes - Jackson, P R; Ledwell, J R; Thurnherr, A M (Deep-Sea Research. Part I: Oceanographic Research Papers, 2010)
On 12 November 2006, 3 kg of sulfur hexafluoride were released in a 1.2 km long streak in the axial summit trough of the East Pacific Rise at 9°30′N to study how circulation and mixing affect larval dispersion. The first half of a tracer survey performed approximately 40 days after the injection found a small percentage of the tracer on the ridge axis between 9°30′N and 10°10′N, with the main concentration near 9°50′N, a site of many active hydrothermal vents. These observations provide evidence of larval connectivity between vent sites on the ridge. The latter half of the survey detected the primary patch of tracer west of the ridge and just south of the Lamont Seamounts, as a majority of the tracer had been transported off the ridge. However, by the end of the survey, the eastern edge of this patch was transported back to within 10 km of the ridge crest at 9°50′N by a reversal in the subinertial flow, suggesting another pathway for larvae between points along the ridge. Both the horizontal and vertical distributions of the tracer were complex and were likely heavily influenced by topography and vents in the area. Elevated tracer concentrations within the axial summit trough and an adjacent depression on the upper ridge flank suggest that tracers may be detained in such depressions. Correlated tracer/turbidity profiles provide direct evidence of entrainment of the tracer into vent plumes from 9°30′N to 10°N. A comparison of the vertical tracer inventory with neutral density vent-plume observations suggests that on the order of 10{%} of the tracer injected was entrained into vent plumes near the injection site. The results imply that effluent from diffuse hydrothermal sources and larvae of hydrothermal vent fauna can be entrained in significant quantities into plumes from discrete sources and dispersed in the neutrally buoyant plumes.
Keywords: HOV Alvin (Human Occupied Vehicle)

Dive site geology: DSV ALVIN (2006) and ROV JASON II (2007) dives to the middle-lower continental slope, northern Gulf of Mexico - Roberts, H H; Shedd, W; Hunt, J (Deep-Sea Research. Part II: Topical Studies in Oceanography, 2010)
Use of DSV ALVIN (2006) and ROV JASON II (2007) provided access to never observed or sampled sites of fluid-gas expulsion from the little-studied middle and lower continental slope of the northern Gulf of Mexico (below water depths of 1000 m). Dives were focused on 15 locations selected by 3-D seismic surface attributes and shallow subsurface geologic analyses. The linkage between highly positive seafloor reflectivity and hard bottoms proved to be an efficient indicator of potential sites of interest. Through observation and sampling of reflective sites, starting in the mid-1980s, it has become apparent that most hard bottoms on the northern Gulf's continental slope are created by the precipitation of authigenic carbonates at hydrocarbon seep sites. Access to the Bureau of Ocean Energy Management, Regulation and Enforcement's extraordinary archive of slope-wide 3-D seismic data made efficient site selection possible. From thousands of sites that display the characteristics of fluid-gas expulsion, 15 were observed and sampled during the 2006 and 2007 cruises. Water depths in which these 15 sites were located ranged from ∼2750 to ∼970 m. All sites exhibited evidence of hydrocarbon seepage or more rapid venting. Chemosynthetic organisms, authigenic carbonates, barite, gas hydrates, highly anoxic surface sediments, brine pools, and hydrocarbon-laced brine flows were identified and sampled. High-resolution acoustic Autonomous Underwater Vehicle (AUV) data, including multibeam bathymetry, side-scan sonar swaths, and chirp sonar subbottom profiles, were collected at four locations (AC601, WR269, GC852, and AT340). Data sets from the 2006 and 2007 dives resulted in a greatly improved understanding of both cross-slope and along-slope variability in the characteristics of fluid-gas expulsion sites and associated habitats. Our studies confirmed the importance of fluid-gas expulsion processes for sustaining chemosynthetic communities and impacting seabed geology on the middle and lower continental slope of the northern Gulf of Mexico.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Diverse styles of submarine venting on the ultraslow spreading Mid-Cayman Rise - German, C R; Bowen, A; Coleman, M L; Honig, D L; Huber, J A; Jakuba, M V; Kinsey, J C; Kurz, M D; Leroy, S; McDermott, J M; de Lepinay, B M; Nakamura, K; et al. (Proceedings of the National Academy of Sciences of the United States of America, 2010)
Thirty years after the first discovery of high-temperature submarine venting, the vast majority of the global mid-ocean ridge remains unexplored for hydrothermal activity. Of particular interest are the world's ultraslow spreading ridges that were the last to be demonstrated to host high-temperature venting but may host systems particularly relevant to prebiotic chemistry and the origins of life. Here we report evidence for previously unknown, diverse, and very deep hydrothermal vents along the similar to 110 km long, ultraslow spreading Mid-Cayman Rise (MCR). Our data indicate that the MCR hosts at least three discrete hydrothermal sites, each representing a different type of water-rock interaction, including both mafic and ultramafic systems and, at similar to 5,000 m, the deepest known hydrothermal vent. Although submarine hydrothermal circulation, in which seawater percolates through and reacts with host lithologies, occurs on all mid-ocean ridges, the diversity of vent types identified here and their relative geographic isolation make the MCR unique in the oceans. These new sites offer prospects for an expanded range of vent-fluid compositions, varieties of abiotic organic chemical synthesis and extremophile microorganisms, and unparalleled faunal biodiversity-all in close proximity.
Keywords: HOV Alvin (Human Occupied Vehicle)

Diversity of bathyal macrofauna on the northeastern Pacific margin: the influence of methane seeps and oxygen minimum zones - Levin, L A; Mendoza, G F; Gonzalez, J P; Thurber, A R; Cordes, E E (Marine Ecology, 2010)
The upper continental slope in the northeastern Pacific Ocean is intercepted by a deep oxygen minimum zone (OMZ; 650–1100 m) and punctuated by conduits of methane seepage. We examined the effects of these two dominant sources of heterogeneity on the density, composition and diversity of heterotrophic macrofauna off Hydrate Ridge, Oregon (OR; 800 m water depth), where the seeps co-occur within an OMZ, and off the Eel River, Northern California (CA; 500 m), where seeps are overlain by better oxygenated waters. We hypothesized that seeps (containing clam beds and microbial mats) should contribute a suite of distinct species to the regional margin species pool but that OMZ-associated hypoxia would dampen seep-related heterogeneity. Macrofaunal densities were highest (23,000–33,510 ind·m−2) in the CA seep sediments and in the OR near-seep samples, intermediate in the OR seep, CA near seep and CA and OR 500-m margin sediments (10,054–19,777 ind·m−2), and lowest in the CA and OR OMZ habitats at 800 m (4269–7847 ind·m−2). Annelids constituted over 50{%} of the taxa in all but the CA clam bed and OR microbial mat sediments, where mollusks were abundant. Approximately 50{%} of seep species appeared to be habitat endemic; species present in microbial mats largely formed a subset of those present in the clam beds. Dorvilleid and ampharetid polychaetes were dominant in the seep sediments; non-seep margin sediments at 500 and 800 m were populated heavily by branchiate polychaetes including cossurids and paraonids. Alpha diversity (Es[20] calculated per core) was lowest and rank 1 dominance was highest in the CA and OR microbial mat habitats. Pooled analyses of Es[100] revealed highest species richness in the CA clam bed and near-seep habitats (30.3 and 29.6, respectively), and lowest species richness in the OR microbial mat and near-seep habitats (16.5 and 17.9, respectively). Non-seep sediments (500 and 800 m) off both CA and OR were more homogeneous (55–57{%} within-habitat similarity) than clam bed and microbial mat sediments (only 32–37{%} within-habitat similarity). CA sediment macrofauna generally exhibit higher alpha diversity, and as habitats are combined, a higher rate of increase in the slope of the species accumulation curves than do OR margin macrofauna. Methane seeps in the NE Pacific introduce significant heterogeneity that increases margin biodiversity at multiple spatial scales. However, our hypothesis that the OMZ would lessen the seep contributions to diversity was not supported. The better oxygenated CA seeps at 500 m shared more of the background margin fauna (at 500 m) than did the OR seeps at 800 m (with OMZ fauna at 800 m). Geographical differences in the fluxes of methane-rich fluids and the increased reliance on chemosynthetic food sources with increased depth could explain these results.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Elevated concentrations of formate, acetate and dissolved organic carbon found at the Lost City Hydrothermal Field - Lang, S Q; Butterfield, D A; Schulte, M; Kelley, D S; Lilley, M D (Geochimica et Cosmochimica Acta, 2010)
Fluids from the ultramafic-hosted Lost City hydrothermal field were analyzed for total dissolved organic carbon and dissolved organic acids. Formate (36–158 $μ$mol/kg) and acetate (1–35 $μ$mol/kg) concentrations are higher than in other fluids from unsedimented hydrothermal vents, and are a higher ratio of the total dissolved organic carbon than has been found in most marine geothermal systems. Isotopic evidence is consistent with an abiotic formation mechanism for formate, perhaps during serpentinization processes in the sub-surface. Further support comes from previous studies where the abiological formation of low molecular weight organic acids has been shown to be thermodynamically favorable during hydrothermal alteration of olivine, and laboratory studies in which the reduction of carbon dioxide to formate has been confirmed. As the second most prevalent carbon species after methane, formate may be an important substrate to microbial communities in an environment where dissolved inorganic carbon is limited. Acetate is found in locations where sulfate reduction is believed to be important and is likely to be a microbial by-product, formed either directly by autotrophic metabolic activity or indirectly during the fermentative degradation of larger organic molecules. Given the common occurrence of exposed ultramafic rocks and active serpentinization within the worlds ocean basins, the abiotic formation of formate may be an important process supporting life in these high pH environments and may have critical implications to understanding the organic precursors from which life evolved.
Keywords: HOV Alvin (Human Occupied Vehicle)

Enumeration of viruses and prokaryotes in deep-sea sediments and cold seeps of the Gulf of Mexico - Kellogg, C A (Deep-Sea Research. Part II: Topical Studies in Oceanography, 2010)
Little is known about the distribution and abundance of viruses in deep-sea cold-seep environments. Like hydrothermal vents, seeps support communities of macrofauna that are sustained by chemosynthetic bacteria. Sediments close to these communities are hypothesized to be more microbiologically active and therefore to host higher numbers of viruses than non-seep areas. Push cores were taken at five types of Gulf of Mexico habitats at water depths below 1000 m using a remotely operated vehicle (ROV). The habitats included non-seep reference sediment, brine seeps, a microbial mat, an urchin field, and a pogonophoran worm community. Samples were processed immediately for enumeration of viruses and prokaryotes without the addition of a preservative. Prokaryote counts were an order of magnitude lower in sediments directly in contact with macrofauna (urchins, pogonophorans) compared to all other samples (107 vs. 108 cells g−1 dry weight) and were highest in areas of elevated salinity (brine seeps). Viral-Like Particle (VLP) counts were lowest in the reference sediments and pogonophoran cores (108 VLP g−1 dry wt), higher in brine seeps (109 VLP g−1 dry wt), and highest in the microbial mats (1010 VLP g−1 dry wt). Virus-prokaryote ratios (VPR) ranged from {<}5 in the reference sediment to {>}30 in the microbial mats and {>}60 in the urchin field. VLP counts and VPR were all significantly greater than those reported from sediments in the deep Mediterranean Sea and in most cases were higher than recent data from a cold-seep site near Japan. The high VPR suggest that greater microbial activity in or near cold-seep environments results in greater viral production and therefore higher numbers of viruses.
Keywords: ROV Jason (Remotely Operated Vehicle)

Epizooic metazoan meiobenthos associated with tubeworm and mussel aggregations from cold seeps of the northern Gulf of Mexico - Bright, M; Plum, C; Riavitz, L A; Arbizu, P M; Cordes, E E; Gollner, S (Deep-Sea Research. Part II: Topical Studies in Oceanography, 2010)
The abundance and higher taxonomic composition of epizooic metazoan meiobenthic communities associated with mussel and tubeworm aggregations of hydrocarbon seeps at Green Canyon, Atwater Valley, and Alaminos Canyon in depths between 1400 and 2800 m were studied and compared to the infaunal community of non-seep sediments nearby. Epizooic meiofaunal abundances of associated meiobenthos living in tubeworm bushes and mussel beds at seeps were extremely low (usually {<}100 ind. 10 cm−2), similar to epizooic meiofauna at deep-sea hydrothermal vents, and the communities were composed primarily of nematodes, copepods, ostracods, and halacarids. In contrast, epizooic meiobenthic abundance is lower than previous studies have reported for infauna from seep sediments. Interestingly, non-seep sediments contained higher abundances and higher taxonomic diversity than epizooic seep communities, although in situ primary production is restricted to seeps.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Expanding dispersal studies at hydrothermal vents through species identification of cryptic larval forms - Adams, D K; Mills, S W; Shank, T M; Mullineaux, L S (MARINE BIOLOGY, 2010)
The rapid identification of hydrothermal vent-endemic larvae to the species level is a key limitation to understanding the dynamic processes that control the abundance and distribution of fauna in such a patchy and ephemeral environment. Many larval forms collected near vents, even those in groups such as gastropods that often form a morphologically distinct larval shell, have not been identified to species. We present a staged approach that combines morphological and molecular identification to optimize the capability, efficiency, and economy of identifying vent gastropod larvae from the northern East Pacific Rise (NEPR). With this approach, 15 new larval forms can be identified to species. A total of 33 of the 41 gastropod species inhabiting the NEPR, and 26 of the 27 gastropod species known to occur specifically in the 9A degrees 50' N region, can be identified to species. Morphological identification efforts are improved by new protoconch descriptions for Gorgoleptis spiralis, Lepetodrilus pustulosus, Nodopelta subnoda, and Echinopelta fistulosa. Even with these new morphological descriptions, the majority of lepetodrilids and peltospirids require molecular identification. Restriction fragment length polymorphism digests are presented as an economical method for identification of five species of Lepetodrilus and six species of peltospirids. The remaining unidentifiable specimens can be assigned to species by comparison to an expanded database of 18S ribosomal DNA. The broad utility of the staged approach was exemplified by the revelation of species-level variation in daily planktonic samples and the identification and characterization of egg capsules belonging to a conid gastropod Gymnobela sp. A. The improved molecular and morphological capabilities nearly double the number of species amenable to field studies of dispersal and population connectivity.
Keywords: HOV Alvin (Human Occupied Vehicle)

Flatfish at seamount hydrothermal vents show strong genetic divergence between volcanic arcs - Tunnicliffe, V; Koop, B F; Tyler, J; So, Stacy (Marine Ecology-an Evolutionary Perspective, 2010)
Hydrothermal vents near the summits of seamounts in Western Pacific volcanic arcs foster dense populations of flatfishes, a group otherwise unknown at vents. We examined genetic divergence among populations of a symphurine tonguefish described as Symphurus thermophilus Munroe {&} Hashimoto from sites up to 6000 km apart in the Western Pacific to explore connectivity patterns among seamounts. Average genetic divergence between individuals from the Mariana Arc and the Tonga-Kermadec Arcs was 14.2{%} (COI) and 9.0{%} (16S), whereas within-arc divergences were {<}0.3{%}. We found that the Tonga-Kermadec individuals represent a cryptic species, Symphurus sp. A, displaying similar phenotypic features and behaviour to the Mariana Arc S. thermophilus. We also sequenced another distinctive symphurine species; Symphurus sp. B. Collections and image records from three expeditions to the Tonga and Kermadec arcs revealed characteristics of the distribution, dispersion, behaviour and morphology of these flatfish species. These two new Symphurus species inhabit vents where native sulphur occurs in excess and depths are {<}600 m. Substratum range of Symphurus sp. A was wide, including mussel beds, rock surfaces and sediments in densities that may exceed 100 m−2. Reproductive females were present. The complex and diverse nature of volcanic settings of hydrothermalism introduces a wide variety of habitat conditions that likely augments diversity of faunas on seamounts in distinct biogeographic provinces.
Keywords: ROV Jason (Remotely Operated Vehicle)

Flow rate perturbations in a black smoker hydrothermal vent in response to a mid-ocean ridge earthquake swarm - Crone, Timothy J; Wilcock, William S D; McDuff, Russell E (GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 2010)
Although there is indirect evidence for strong connections between tectonic processes and mid-ocean ridge hydrothermal flow, there are no direct observations of these links, primarily because measuring flow in these systems is difficult. Here we use an optical analysis technique to obtain a 44 day record of flow rate changes in a black smoker vent in the Main Endeavour field of the Juan de Fuca Ridge. We show that variations in the flow rate coincide with an earthquake swarm observed using an ocean bottom seismometer array. These observations indicate that connections between tectonics and flow are indeed strong, that hydraulic connections within this hydrothermal system are long ranging, and that enhanced tidal pumping of fluids may be initiated by earthquake activity. Because the effects of the swarm cross over an intervening vent field, we infer that the upflow zones feeding this field are narrow. Using the time lag between the swarm onset and the flow rate changes we estimate that the bulk permeability of the crust on the Endeavour segment ranges from 3.0 x 10(-13) m(2) to 6.0 x 10(-12) m(2).
Keywords: HOV Alvin (Human Occupied Vehicle)

Fluid sources and pathways of the Costa Rica erosional convergent margin - Tryon, Michael D; Wheat, C Geoffrey; Hilton, David R (GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 2010)
The margins community has only relatively recently begun to examine the tectonics and associated hydrologic systems of erosive convergent margins, which are substantially different as compared with accretionary margins. In this respect, the type example erosive margin is the Costa Rica system, which has been the subject of numerous recent large-scale investigations. Here pore fluids expelled at the wedge toe and at midslope mounds and mud volcanoes have been interpreted to have a common deep source of dehydrating clays, analogous to that at accretionary margins. However, we report unusually high B/Li molar ratios in pore fluids from a recent mudflow on Mound 11, offshore Costa Rica, which, together with unusually low B/Li ratios previously reported at the wedge toe, reveal that alternative fluid sources and/or processes must be operating at the Costa Rica margin. As serpentine formation is the only subduction zone process that significantly fractionates B and Li, we propose that the difference in fluid chemical composition is the result of erosion of upper plate serpentinites, ongoing serpentinization, and serpentine mineral phase transitions in the subduction channel. These processes provide both a source of fluids and fluid pathways that lead to the unique geochemical signature observed at this erosional margin. This conclusion is compatible with, and supported by, the current view of the tectonics, geology, and hydrogeology of the Costa Rica margin and the similarity of the pore fluid to that of two other convergent margins, both with known fluid/serpentinite interactions.
Keywords: HOV Alvin (Human Occupied Vehicle)

Functional genes as markers for sulfur cycling and CO2 fixation in microbial communities of hydrothermal vents of the Logatchev field - Huegler, Michael; Gaertner, Andrea; Imhoff, Johannes F (FEMS MICROBIOLOGY ECOLOGY, 2010)
Life at deep-sea hydrothermal vents depends on chemolithoautotrophic microorganisms as primary producers mediating the transfer of energy from hydrothermal fluids to higher trophic levels. A comprehensive molecular survey was performed with microbial communities in a mussel patch at the Irina II site of the Logatchev hydrothermal field by combining the analysis of 16S rRNA gene sequences with studies of functional key genes involved in biochemical pathways of sulfur oxidation-reduction (soxB, aprA) and autotrophic carbon fixation (aclB, cbbM, cbbL). Most significantly, major groups of chemoautotrophic sulfur oxidizers in the diffuse fluids differed in their biosynthetic pathways of both carbon fixation and sulfur oxidation. One important component of the community, the Epsilonproteobacteria, has the potential to grow chemoautotrophically by means of the reductive tricarboxylic acid cycle and to gain energy through the oxidation of reduced sulfur compounds using the Sox pathway. The majority of soxB and all retrieved aclB gene sequences were assigned to this group. Another important group in this habitat, the Gammaproteobacteria, may use the adenosine 5'-phosphosulfate pathway and the Calvin-Benson-Bassham cycle, deduced from the presence of aprA and cbbM genes. Hence, two important groups of primary producers at the investigated site might use different pathways for sulfur oxidation and carbon fixation.
Keywords: ROV Jason (Remotely Operated Vehicle)

Genetic and anatomic relationships among three morphotypes of the echinoid Echinocrepis rostrata - Vardaro, Michael F (INVERTEBRATE BIOLOGY, 2010)
Three morphotypes-purple, tan, and white-of an irregular echinoid of the genus Echinocrepis are commonly observed in the deep North Pacific Ocean. Mitochondrial (mt) 16S DNA and cytochrome c oxidase subunit I (COI) DNA sequences were amplified from gonadal tissue samples from specimens of each morphotype. These portions of the mitochondrial genome are commonly used in species barcoding, and their similarities were compared and placed in 95{%} connection limit parsimony networks. All three morphotypes have similar 16S mtDNA and COI mtDNA sequences, and are thus likely representatives of the same species, Echinocrepis rostrata. Specimens of the white morphotype were smaller than the specimens of the other two morphotypes, had less gonad tissue, and had a different body shape, suggesting that it represents the juvenile form of E. rostrata. Resolving the three morphotypes into one species simplifies the identification of E. rostrata from photographs and leads to a greater understanding of the life history and reproductive cycle of a species vital to deep-sea bioturbation and carbon sequestration.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Geochemistry of lavas from the 2005-2006 eruption at the East Pacific Rise, 9 degrees 46'N-9 degrees 56'N: Implications for ridge crest plumbing and decadal changes in magma chamber compositions - Goss, A R; Perfit, M R; Ridley, W I; Rubin, K H; Kamenov, G D; Soule, S A; Fundis, A; Fornari, D J (Geochemistry, Geophysics, Geosystems, 2010)
Detailed mapping, sampling, and geochemical analyses of lava flows erupted from an ∼18 km long section of the northern East Pacific Rise (EPR) from 9°46′N to 9°56′N during 2005–2006 provide unique data pertaining to the short-term thermochemical changes in a mid-ocean ridge magmatic system. The 2005–2006 lavas are typical normal mid-oceanic ridge basalt with strongly depleted incompatible trace element patterns with marked negative Sr and Eu/Eu* anomalies and are slightly more evolved than lavas erupted in 1991–1992 at the same location on the EPR. Spatial geochemical differences show that lavas from the northern and southern limits of the 2005–2006 eruption are more evolved than those erupted in the central portion of the fissure system. Similar spatial patterns observed in 1991–1992 lavas suggest geochemical gradients are preserved over decadal time scales. Products of northern axial and off-axis fissure eruptions are consistent with the eruption of cooler, more fractionated lavas that also record a parental melt component not observed in the main suite of 2005–2006 lavas. Radiogenic isotopic ratios for 2005–2006 lavas fall within larger isotopic fields defined for young axial lavas from 9°N to 10°N EPR, including those from the 1991–1992 eruption. Geochemical data from the 2005–2006 eruption are consistent with an invariable mantle source over the spatial extent of the eruption and petrogenetic processes (e.g., fractional crystallization and magma mixing) operating within the crystal mush zone and axial magma chamber (AMC) before and during the 13 year repose period. Geochemical modeling suggests that the 2005–2006 lavas represent differentiated residual liquids from the 1991–1992 eruption that were modified by melts added from deeper within the crust and that the eruption was not initiated by the injection of hotter, more primitive basalt directly into the AMC. Rather, the eruption was driven by AMC pressurization from persistent or episodic addition of more evolved magma from the crystal mush zone into the overlying subridge AMC during the period between the two eruptions. Heat balance calculations of a hydrothermally cooled AMC support this model and show that continual addition of melt from the mush zone was required to maintain a sizable AMC over this time interval.
Keywords: HOV Alvin (Human Occupied Vehicle)

Hydrothermal circulation within the Endeavour Segment, Juan de Fuca Ridge - Johnson, H P; Tivey, M A; Bjorklund, T A; Salmi, M S (Geochemistry, Geophysics, Geosystems, 2010)
Areas of the seafloor at mid-ocean ridges where hydrothermal vents discharge are easily recognized by the dramatic biological, physical, and chemical processes that characterize such sites. Locations where seawater flows into the seafloor to recharge hydrothermal cells within the crustal reservoir are by contrast almost invisible but can be indirectly identified by a systematic grid of conductive heat flow measurements. An array of conductive heat flow stations in the Endeavour axial valley of the Juan de Fuca Ridge has identified recharge zones that appear to represent a nested system of fluid circulation paths. At the scale of an axial rift valley, conductive heat flow data indicate a general cross-valley fluid flow, where seawater enters the shallow subsurface crustal reservoir at the eastern wall of the Endeavour axial valley and undergoes a kilometer of horizontal transit beneath the valley floor, finally exiting as warm hydrothermal fluid discharge on the western valley bounding wall. Recharge zones also have been identified as located within an annular ring of very cold seafloor around the large Main Endeavour Hydrothermal Field, with seawater inflow occurring within faults that surround the fluid discharge sites. These conductive heat flow data are consistent with previous models where high-temperature fluid circulation cells beneath large hydrothermal vent fields may be composed of narrow vertical cylinders. Subsurface fluid circulation on the Endeavour Segment occurs at various crustal depths in three distinct modes: (1) general east to west flow across the entire valley floor, (2) in narrow cylinders that penetrate deeply to high-temperature heat sources, and (3) supplying low-temperature diffuse vents where seawater is entrained into the shallow uppermost crust by the adjacent high-temperature cylindrical systems. The systematic array of conductive heat flow measurements over the axial valley floor averaged ∼150 mW/m2, suggesting that only about 3{%} of the total energy flux of ocean crustal formation is removed by conductive heat transfer, with the remainder being dissipated to overlying seawater by fluid advection.
Keywords: ROV Jason (Remotely Operated Vehicle)

Identification of chemoautotrophic microorganisms from a diffuse flow hydrothermal vent at EPR 9 degrees North using 13C DNA Stable Isotope Probing and Catalyzed Activated Reporter Deposition-Fluorescence in situ Hybridization - Richberg, K P (Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution, 2010)
At deep‐sea hydrothermal vents chemolithoautotrophic microbes mediate the transfer of geothermal chemical energy to higher trophic levels. To better understand these underlying processes and the organisms catalyzing them, this research used DNA Stable Isotope Probing (SIP) combined with Catalyzed Activated Reporter Deposition‐Fluorescence in situ Hybridization (CARD‐FISH) to identify the microorganisms chemoautotrophically supporting the food web at a diffuse flow hydrothermal vent. Both anaerobic and aerobic shipboard incubations containing various augmented electron donor and acceptor species showed that Epsilonproteobacteria were the dominant chemoautotrophs with greater than 70{%} of the cells counted within the first 24 hours. 13C DNA SIP identified unique organisms not previously characterized from low temperature diffuse flow venting: green sulfur bacteria (Chlorobi‐like organisms) possibly utilizing photoautotrophy, aerobic Lutibacter litoralis‐like organisms growing under anaerobic conditions, and Epsilonproteobacterial Thioreductor sp. at temperatures above maximum known tolerances. This research illustrates both the promise and pitfalls of the SIP technique applied to hydrothermal systems, concluding that timing of the incubation experiments is the critical step in eliminating undesired 13C labeling. These results set the stage for a more thorough future examination of diffuse flow microorganisms by presenting interesting questions that second generation experiments could be designed to answer.
Keywords: HOV Alvin (Human Occupied Vehicle)

Incongruent patterns of genetic connectivity among four ophiuroid species with differing coral host specificity on North Atlantic seamounts - Cho, W W; Shank, T M (Marine Ecology, 2010)
Seamounts are considered to play a defining role in the evolution and diversity of marine fauna, acting as ‘stepping-stones' for dispersal, regional centers of genetic isolation and speciation, and refugia for deep-sea populations. This study focused on the patterns of dispersal and genetic connectivity of four seamount ophiuroid species (Asteroschema clavigera, Ophiocreas oedipus, Ophioplinthaca abyssalis, and Ophioplinthaca chelys) displaying differing levels of associative (epifaunal) specificity to cold-water coral hosts inhabiting the New England and Corner Rise Seamount chains, and Muir Seamount in the Northwestern Atlantic. Analyses of mt16S and mtCOI revealed evidence for recent population expansion and high gene flow for all four species. However, species-specific genetic differentiation was significant based on seamount region and depth. Significant differences were found among regional seamount groups for A. clavigera, within seamount regions and seamounts for O. chelys, among 250-m depth intervals for A. clavigera, among 100-m depth intervals for O. oedipus, and there were indications of isolation by distance for A. clavigera and O. oedipus. In addition, A. clavigera and O. oedipus, broadcast spawners with high fidelity to specific coral hosts, displayed predominantly westward historical migration, whereas the ophioplinthacids, with lower host-specificity, displayed predominantly eastward migration. No congruent patterns of historical migration were evident among species and seamounts, yet these patterns can be correlated with species-specific host specificity, specific depth strata, and dispersal strategies. Conservation efforts to protect seamount ecosystems should promote multi-species approaches to genetic connectivity, and consider the impact of the ‘dependence' of biodiversity on host fauna in these vulnerable marine ecosystems.
Keywords: HOV Alvin (Human Occupied Vehicle)

Indigenous ectosymbiotic bacteria associated with diverse hydrothermal vent invertebrates - Goffredi, Shana K (ENVIRONMENTAL MICROBIOLOGY REPORTS, 2010)
P{>}Symbioses involving bacteria and invertebrates contribute to the biological diversity and high productivity of both aquatic and terrestrial environments. Well-known examples from chemosynthetic deep-sea hydrothermal vent environments involve ectosymbiotic microbes associated with the external surfaces of marine invertebrates. Some of these ectosymbioses confer protection or defence from predators or the environment itself, some are nutritional in nature, and many still are of unknown function. Several recently discovered hydrothermal vent invertebrates, including two populations of yeti crab (Kiwa spp.), a limpet (Symmetromphalus aff. hageni), and the scaly-foot snail (as yet undescribed), support a consortium of diverse bacteria. Comparisons of these ectosymbioses to those previously described revealed similarities among the associated microorganisms, suggesting that certain microbes are indigenous to the surfaces of marine invertebrates. In particular, members of the Thiovulgaceae (epsilonproteobacteria) and Thiotrichaceae (gammaproteobacteria) appear to preferentially form ectosymbioses with vent crustaceans and gastropods. Interactions between specific Proteobacteria and the surfaces of many marine invertebrates likely have ecological and evolutionary significance at these chemically challenging habitats.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Influence of foundation species, depth, and location on diversity and community composition at Gulf of Mexico lower-slope cold seeps - Cordes, E E; Becker, E L; Hourdez, S; Fisher, C R (Deep-Sea Research. Part II: Topical Studies in Oceanography, 2010)
Efforts to understand and preserve the seep communities of the deep Gulf of Mexico (GOM) begin with a comprehensive survey of the biodiversity of these communities. Previous studies have provided a conceptual model of the physiology, population, and community ecology of upper continental slope seeps. However, seeps at water depths below 1000 m in the Gulf of Mexico remain relatively unknown. In this study, data from 47 samples of tubeworm- and mussel-associated communities at depths of 1005–2750 m are examined. Other than tubeworms and mussels, 66 taxa of macro- and megafauna were collected, 43 of which appear to be restricted to water depths of over 1000 m, and 39 that have not been reported previously from the Gulf of Mexico. Diversity in mussel beds was highest at mid-slope depths, but tubeworm-associated communities did not show clear bathymetric trends in diversity. Diversity was higher in tubeworm aggregations at the alpha level (per sample), but higher in mussel beds at the beta level (species turnover among collections). Although both community types were often numerically dominated by the endemic shrimp Alvinocaris muricola, broad differences in the communities hosted by tubeworm aggregations and mussel beds were apparent. The most important factors explaining community similarity within community type were the depth, relative abundance of different mussel species in a bed, and the average size of tubeworms in an aggregation. The high proportion of deep-seep species that were found for the first time in the Gulf of Mexico emphasizes the importance of conservation efforts for these patchy communities.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Initial results of comparing cold-seep carbonates from mussel- and tubeworm-associated environments at Atwater Valley 340, northern Gulf of Mexico - Feng, D; Roberts, H H (Deep-Sea Research. Part II: Topical Studies in Oceanography, 2010)
Chemosymbiotic macrofauna (such as mussels and tubeworms) and authigenic carbonates are typical of many hydrocarbon seeps. To address whether mussels and tubeworms could impact the sediment geochemistry of their habitat where authigenic carbonates are precipitated, a comparative study of petrographic and geochemical features of the authigenic carbonates from mussel- and tubeworm-associated environments at hydrocarbon seeps in Atwater Valley lease area block 340 (AT340) of the Gulf of Mexico was undertaken. Both mussel- and tubeworm-associated carbonates are dominated by high-magnesium calcite (HMC) and aragonite, and two tubeworm-associated carbonate samples have minor amounts of dolomite. The $δ$13C values of all carbonates are low, ranging from −60.8‰ to −35.5‰ PDB. Although there is much overlap, surprisingly the $δ$13C values of mussel-associated carbonates are generally higher than those of tubeworm-associated carbonates (−51.8‰ vs. −54.8‰ for an average of over 60 subsamples). It is suggested that (1) carbon isotopic vital effect of seep mussels and tubeworms, (2) fluid physical pumping of mussels, and (3) release of sulfate by tubeworm roots may be responsible for the relatively lower $δ$13C values of tubeworm-associated carbonates. It has been suggested that the heterogeneities in mineralogy and stable carbon isotope geochemistry of the seep carbonates may be attributed to the activity of macrofauna (mussels and tubeworms) and associated microbes. Our observations also suggest that at AT340 the geochemical evolution of seep macrofauna is from a mussel-dominated environment to a mixed mussel-tubeworm environment, and finally to a mostly tubeworm-dominated environment. This evolution is controlled mainly by the habitat, e.g., hydrocarbon seep flux.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Insights into the behaviour of sulphur in mid-ocean ridge axial hydrothermal systems from the composition of the sheeted dyke complex at Pito Deep - Barker, A K; Coogan, L A; Gillis, K M (Chemical Geology, 2010)
The behaviour of seawater sulphate in hydrothermal systems at intermediate- to fast-spreading ridges is investigated using new analyses of the $δ$34S, sulphur concentration and Fe2O3/Fe2O3total, combined with existing 87Sr/86Sr, of sheeted dykes from the Pito Deep tectonic window. The Pito Deep sheeted dyke complex has a similar composition to the sheeted dykes drilled at ODP Hole 504B suggesting that the measured compositions are representative of sheeted dyke complexes at intermediate- to fast-spreading ridges. The dykes show only small increases in $δ$34S which, combined with the rock dominated $δ$34S of vent fluids, requires the majority of seawater sulphate to be precipitated as anhydrite before the fluid reacts with the sheeted dyke complex. This loss of sulphate from the fluid means that a much higher Fe2O3 in the sheeted dyke complex than in fresh MORB glasses cannot be explained by oxidation due to seawater sulphate reduction during fluid–rock reaction. Instead, oxidation probably occurs due to degassing of reduced species, largely H2, during dyke emplacement and solidification. A mass balance model that accounts for anhydrite precipitation and Sr partitioning into the anhydrite, as well as fitting the concentration and isotopic ratios of S and Sr in the sheeted dykes and vent fluids, suggests water/rock ratios of ∼ 1. For a 1 km thick sheeted dyke complex this is equivalent to a fluid flux of ∼ 3 × 106 kg m− 2, sufficient to remove ∼ 60{%} of the latent heat of crystallization from the lower crust.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

Insights to magmatic–hydrothermal processes in the Manus back–arc Basin as recorded by anhydrite - Craddock, P R; Bach, W (Geochimica et Cosmochimica Acta, 2010)
Microchemical analyses of rare earth element (REE) concentrations and Sr and S isotope ratios of anhydrite are used to identify sub-seafloor processes governing the formation of hydrothermal fluids in the convergent margin Manus Basin, Papua New Guinea. Samples comprise drill-core vein anhydrite and seafloor massive anhydrite from the PACMANUS (Roman Ruins, Snowcap and Fenway) and SuSu Knolls (North Su) active hydrothermal fields. Chondrite-normalized REE patterns in anhydrite show remarkable heterogeneity on the scale of individual grains, different from the near uniform REEN patterns measured in anhydrite from mid-ocean ridge deposits. The REEN patterns in anhydrite are correlated with REE distributions measured in hydrothermal fluids venting at the seafloor at these vent fields and are interpreted to record episodes of hydrothermal fluid formation affected by magmatic volatile degassing. 87Sr/86Sr ratios vary dramatically within individual grains between that of contemporary seawater and that of endmember hydrothermal fluid. Anhydrite was precipitated from a highly variable mixture of the two. The intra-grain heterogeneity implies that anhydrite preserves periods of contrasting hydrothermal versus seawater dominant near-seafloor fluid circulation. Most sulfate $δ$34S values of anhydrite cluster around that of contemporary seawater, consistent with anhydrite precipitating from hydrothermal fluid mixed with locally entrained seawater. Sulfate $δ$34S isotope ratios in some anhydrites are, however, lighter than that of seawater, which are interpreted as recording a source of sulfate derived from magmatic SO2 degassed from underlying felsic magmas in the Manus Basin. The range of elemental and isotopic signatures observed in anhydrite records a range of sub-seafloor processes including high-temperature hydrothermal fluid circulation, varying extents of magmatic volatile degassing, seawater entrainment and fluid mixing. The chemical and isotopic heterogeneity recorded in anhydrite at the inter- and intra-grain scale captures the dynamics of hydrothermal fluid formation and sub-seafloor circulation that is highly variable both spatially and temporally on timescales over which hydrothermal deposits are formed. Microchemical analysis of hydrothermal minerals can provide information about the temporal history of submarine hydrothermal systems that are variable over time and cannot necessarily be inferred only from the study of vent fluids.
Keywords: ROV Jason (Remotely Operated Vehicle)

Isolated communities of Epsilonproteobacteria in hydrothermal vent fluids of the Mariana Arc seamounts - Huber, Julie A; Cantin, Holly V; Huse, Susan M; Welch, David B Mark; Sogin, Mitchell L; Butterfield, David A (FEMS MICROBIOLOGY ECOLOGY, 2010)
Low-temperature hydrothermal vent fluids represent access points to diverse microbial communities living in oceanic crust. This study examined the distribution, relative abundance, and diversity of Epsilonproteobacteria in 14 low-temperature vent fluids from five volcanically active seamounts of the Mariana Arc using a 454 tag sequencing approach. Most vent fluids were enriched in cell concentrations compared with background seawater, and quantitative PCR results indicated that all fluids were dominated by bacteria. Operational taxonomic unit-based statistical tools applied to 454 data show that all vents from the northern end of the Mariana Arc grouped together, to the exclusion of southern arc seamounts, which were as distinct from one another as they were from northern seamounts. Statistical analysis also showed a significant relationship between seamount and individual vent groupings, suggesting that community membership may be linked to geographical isolation and not geochemical parameters. However, while there may be large-scale geographic differences, distance is not the distinguishing factor in the microbial community composition. At the local scale, most vents host a distinct population of Epsilonproteobacteria, regardless of seamount location. This suggests that there may be barriers to exchange and dispersal for these vent endemic microorganisms at hydrothermal seamounts of the Mariana Arc.
Keywords: ROV Jason (Remotely Operated Vehicle)

Low-molecular weight hydrocarbons in vent fluids from the Main Endeavour Field, northern Juan de Fuca Ridge - Cruse, A M; Seewald, J S (Geochimica et Cosmochimica Acta, 2010)
Despite its location on sediment-free basalt, vent fluids from the Main Endeavour Field (MEF) contain chemical species that indicate fluids have interacted with sediments during circulation. We report on the distribution and isotopic abundances of organic compounds (C1–C3 alkanes and alkenes, benzene and toluene) in fluids collected from the Main Endeavour Field (MEF) in July, 2000, to understand the processes that regulate their abundances and characterize fluid sources. Aqueous organic compounds are derived from the thermal alteration of sedimentary organic matter and subsequently undergo further oxidation reactions during fluid flow. Fluid:sediment mass ratios calculated using $Σ$NH4 concentrations indicate that the sediments are distal to the MEF, resulting in a common reservoir of fluids for all of the vents. Following the generation from sediment alteration, aqueous organic compounds undergo secondary alteration reactions via a stepwise oxidation reaction mechanism. Alkane distributions and isotopic compositions indicate that organic compounds in MEF fluids have undergone a greater extent of alteration as compared to Middle Valley fluids, either due to differences in subsurface redox conditions or the residence time of fluids at subsurface conditions. The distributions of the aromatic compounds benzene and toluene are qualitatively consistent with the subsurface conditions indicated by equilibration of aqueous alkanes and alkanes. However, benzene and toluene do not achieve chemical equilibrium in the subsurface. Methane and CO2 also do not equilibrate chemically or isotopically at reaction zone temperatures, a likely result of an insufficient reaction time after addition of CO2 from magmatic sources during upflow. The organic geochemistry supports the assumption that the sediments with which MEF fluids interact has the same composition as sediments present in Middle Valley itself, and highlight differences in subsurface reaction zone conditions and fluid flow pathways at these two sites.
Keywords: HOV Alvin (Human Occupied Vehicle)

Malaguana-Gadao Ridge: Identification and implications of a magma chamber reflector in the southern Mariana Trough - Becker, Nathan C; Fryer, Patricia; Moore, Gregory F (GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 2010)
Six-channel seismic reflection data reveal a magma chamber reflector beneath the Malaguana-Gadao Ridge, the southernmost segment of the spreading center in the Mariana Trough. For most of its length the spreading center in this active back-arc basin is morphologically similar to slow spreading mid-ocean ridges, having a deep central graben flanked by a zone of abyssal hill fabric. This southernmost segment, however, has a broad, smooth cross section, lacks a deep central graben, and is thus similar in morphology to fast spreading ridges (e.g., the East Pacific Rise). We identify a magma chamber at 1.5 s two-way travel time below the crest of the ridge. Observations from remotely operated vehicles along the ridge reveal not only fresh pillows, lobate, and sheet lava flows but also an abundance of volcaniclastic debris and intense hydrothermal activity. These observations, together with the ``fast spreading{\{}''{\}} morphology of the ridge, suggest that this segment has a considerably higher magma supply than is typical in the Mariana Trough. We suggest that the volcanic arc or enhanced melting of a hydrated mantle is supplying volatile-rich magma as evidenced by a highly negative coefficient of reflection, -0.42, for this MCR and the presence of evolved, highly vesicular lava and volcaniclastic materials. The southeastern Mariana back-arc basin spreading ridge does not compare readily with mechanical models for global mid-ocean ridge data sets because of marked asymmetry in both volcanism and deformation that may be the consequence of slab-related geometry in this part of the convergent margin system.
Keywords: ROV Jason (Remotely Operated Vehicle)

Mantle melting, melt transport, and delivery beneath a slow-spreading ridge: the paleo-MAR from 23 degrees15′N to 23 degrees 45′N - Dick, H J B; Lissenberg, C J; Warren, J M (Journal of Petrology, 2010)
Kane Megamullion, an oceanic core complex near the Mid-Atlantic Ridge (MAR) abutting the Kane Transform, exposes nearly the full plutonic foundation of the MARK paleo-ridge segment. This provides the first opportunity for a detailed look at the patterns of mantle melting, melt transport and delivery at a slow-spreading ridge. The Kane lower crust and mantle section is heterogeneous, as a result of focused mantle melt flow to different points beneath the ridge segment in time and space, over an ∼300–400 kyr time scale. The association of residual mantle peridotite, dunite and troctolite with a large ∼1 km+ thick gabbro section at the Adam Dome Magmatic Center in the southern third of the complex probably represents the crust–mantle transition. This provides direct evidence for local melt accumulation in the shallow mantle near the base of the crust as a result of dilation accompanying corner flow beneath the ridge. Dunite and troctolite with high-Mg Cpx represent melt–rock reaction with the mantle, and suggest that this should be taken into account in modeling the evolution of mid-ocean ridge basalt (MORB). Despite early precipitation of high-Mg Cpx, wehrlites similar to those in many ophiolites were not found. Peridotite modes from the main core complex and transform wall define a depletion trend coincident with that for the SW Indian Ridge projecting toward East Pacific Rise mantle exposed at Hess Deep. The average Kane transform peridotite is a lherzolite with 5·2{%} Cpx, whereas that from the main core complex is a harzburgite with only 3·5{%} Cpx. As the area corresponds to a regional bathymetric low, and the crust is apparently thin, it is likely that most residual mantle along the MAR is significantly more depleted. Thus, harzburgitic and lherzolitic ophiolite subtypes cannot be simply interpreted as slow- and fast-spreading ridges respectively. The mantle peridotites are consistent with a transform edge effect caused by juxtaposition of old cold lithosphere against upwelling mantle at the ridge–transform intersection. This effect is far more local, confined to within 10 km of the transform slip zone, and far smaller than previously thought, corresponding to ∼8{%} as opposed to 12·5{%} melting of a pyrolitic mantle away from the transform. Excluding the transform, the overall degree of melting over 3 Myr indicated by the peridotites is uniform, ranging from ∼11·3 to 13·8{%}. Large variations in composition for a single dredge or ROV dive, however, reflect local melt transport through the shallow mantle. This produced variable extents of melt–rock reaction, dunite formation, and melt impregnation. At least three styles of late mantle metasomatism are present. Small amounts of plagioclase with elevated sodium and titanium and alumina-depletion in pyroxene relative to residual spinel peridotites represent impregnation by a MORB-like melt. Highly variable alumina depletion in pyroxene rims in spinel peridotite probably represents cryptic metasomatism by small volumes of late transient silica-rich melts meandering through the shallow mantle. Direct evidence for such melts is seen in orthopyroxenite veins. Finally, a late hydrous fluid may be required to explain anomalous pyroxene sodium enrichment in spinel peridotites. The discontinuous thin lower crust exposed at Kane Megamullion contrasts with the {>}700 km2 1·5 km+ thick Atlantis Bank gabbro massif at the SW Indian Ridge (SWIR), clearly showing more robust magmatism at the latter. However, the SWIR spreading rate is 54{%} of the MAR rate, the offset of the Atlantis II Fracture Zone is 46{%} greater and Na8 of the spatially associated basalts 16{%} greater—all of which predict precisely the opposite. At the same time, the average compositions of Kane and Atlantis II transform peridotites are nearly identical. This is best explained by a more fertile parent mantle beneath the SWIR and demonstrates that crustal thickness predicted by simply inverting MORB compositions can be significantly in error.
Keywords: ROV Jason (Remotely Operated Vehicle)

Mapping elemental distributions in submarine hydrothermal sulfide smokers using proton induced X-ray emission - Yeats, C; Belton, D; Laird, J S; Ryan, C G (Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2010)
PIXE analysis using a 3 MeV proton beam on the CSIRO Nuclear Microprobe was carried out on samples of four typical undersea sulfide chimneys from the Rogers Ruins and Fenway hydrothermal sites, PACMANUS field, Eastern Manus Basin, Papua New Guinea. The ability of PIXE to map the spatial association of trace elements within the sulfides across multiple mineralogical zones provides important insights into the mode of formation of structures and the nature of interaction between ∼250 and 350 °C hydrothermal fluids and 3–4 °C ambient seawater within the chimney walls.
Keywords: AUV ABE (Autonomous Benthic Explorer); ROV Jason (Remotely Operated Vehicle)

Molecular systematics of the bubblegum coral genera (Paragorgiidae, Octocorallia) and description of a new deep-sea species - Herrera, S; Baco, A R; Sanchez, J A (Molecular Phylogenetics and Evolution, 2010)
Bubblegum octocorals (Paragorgia and Sibogagorgia) play an important ecological role in many deep-sea ecosystems. However, these organisms are currently threatened by destructive fishing methods such as bottom trawling. Taxonomic knowledge of conservation targets is necessary for the creation and implementation of efficient conservation strategies. However, for most deep-sea coral groups this knowledge remains incomplete. For instance, despite its similarities with Paragorgia, Sibogagorgia is particular in lacking polyp sclerites, which are present in groups like Paragorgia and the Coralliidae. Although two kinds of sclerites are very similar between Paragorgia and Sibogagorgia, other characters challenge the monophyly of these genera. Here we help to clarify the taxonomy and evolutionary relationships of the bubblegum octocorals and related taxa by examining molecular data. We employed nucleotide sequences of mitochondrial (ND6, ND6-ND3 intergenic spacer, ND3, ND2, COI, msh1 and 16S) and nuclear (28S and ITS2) genomic regions from several taxa to infer molecular phylogenetics and to examine the correspondence of morphological features with the underlying genetic information. Our data strongly supported the monophyly of the genus Paragorgia, the family Coralliidae (precious corals), and a group of undescribed specimens resembling Sibogagorgia. Further morphological observations were congruent regarding the uniqueness of the undescribed specimens, here defined as a new species, Sibogagorgia cauliflora sp. nov., which occurs in both sides of the North American landmass at depths below 1700 m. This new species resembles S. dennisgordoni with branching in one plane but has fairly different radiate sclerites and significantly divergent DNA sequences. The existence of several diagnostic characters of Sibogagorgia in S. cauliflora indicates that they indeed belong to this genus. It is however remarkable that a small number of medullar canals are also found in this species; medullar canals have been considered as the main diagnostic character of Paragorgia. Thus, the evidence generated here indicates that the presence or absence of these canals per se is not a conclusively diagnostic character for either genus. The lack of internal-node resolution in the inferred phylogenetic hypotheses of these genera does not allow us to propose a clear scenario regarding the evolution of these traits.
Keywords: ROV Jason (Remotely Operated Vehicle)

Multiple scales of diversification within natural populations of archaea in hydrothermal chimney biofilms - Brazelton, W J; Sogin, M L; Baross, J A (Environmental Microbiology Reports, 2010)
Corroborative data collected from 16S rRNA clone libraries, intergenic transcribed spacer (ITS) region clone libraries, and 16S rRNA hypervariable region tag pyrosequencing demonstrate microdiversity within single-species archaeal biofilms of the Lost City Hydrothermal Field. Both 16S rRNA clone libraries and pyrosequencing of the V6 hypervariable region show that Lost City Methanosarcinales (LCMS) biofilms are dominated by a single sequence, but the pyrosequencing data set also reveals the presence of an additional 1654 rare sequences. Clone libraries constructed with DNA spanning the V6 hypervariable region and ITS show that multiple ITS sequences are associated with the same dominant V6 sequence. Furthermore, ITS variability differed among three chimney samples, and the sample with the highest ITS diversity also contained the highest V6 diversity as measured by clone libraries as well as tag pyrosequencing. These results indicate that the extensive microdiversity detected in V6 tag sequences is an underestimate of genetic diversity within the archaeal biofilms.
Keywords: HOV Alvin (Human Occupied Vehicle)

Nautilia nitratireducens sp nov., a thermophilic, anaerobic, chemosynthetic, nitrate-ammonifying bacterium isolated from a deep-sea hydrothermal vent - Perez-Rodriguez, Ileana; Ricci, Jessica; Voordeckers, James W; Starovoytov, Valentin; Vetriani, Costantino (INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY, 2010)
A thermophilic, anaerobic, chemosynthetic bacterium, designated strain MB-1(T), was isolated from the walls of an active deep-sea hydrothermal vent chimney on the East Pacific Rise at 9 degrees 50' N 10 degrees 17' W. The cells were Gram-negative-staining rods, approximately 1-1.5 mu m long and 0.3-0.5 mu m wide. Strain MB-1(T) grew at 25-65 degrees C (optimum 55 degrees C), with 10-35 g NaCl l(-1) (optimum 20 g l(-1)) and at pH 4.5-8.5 (optimum pH 7.0). Generation time under optimal conditions was 45.6 min. Growth occurred under chemolithoautotrophic conditions with H(2) as the energy source and CO(2) as the carbon source. Nitrate was used as the electron acceptor, with resulting production of ammonium. Thiosulfate, sulfur and selenate were also used as electron acceptors. No growth was observed in the presence of lactate, peptone or tryptone. Chemo-organotrophic growth occurred in the presence of acetate, formate, Casamino acids, sucrose, galactose and yeast extract under a N(2)/CO(2) gas phase. The G+C content of the genomic DNA was 36.0 mol{%}. Phylogenetic analysis of the 16S rRNA gene sequence indicated that this organism is closely related to Nautilia profundicola AmH(T), Nautilia abyssi PH1209(T) and Nautilia lithotrophica 525(T) (95, 94 and 93{%} sequence identity, respectively). On the basis of phylogenetic, physiological and genetic considerations, it is proposed that the organism represents a novel species within the genus Nautilia, Nautilia nitratireducens sp. nov. The type strain is MB-1(T) (=DSM 22087(T) =JCM 15746(T)).
Keywords: HOV Alvin (Human Occupied Vehicle)

New constraints on methane fluxes and rates of anaerobic methane oxidation in a Gulf of Mexico brine pool via in situ mass spectrometry - Wankel, S D; Joye, S B; Samarkin, V A; Shah, S R; Friederich, G; Melas-Kyriazi, J; Girguis, P R (Deep-Sea Research. Part II: Topical Studies in Oceanography, 2010)
Deep-sea biogeochemical cycles are, in general, poorly understood owing to the difficulties of making measurements in situ, recovering samples with minimal perturbation, and, in many cases, coping with high spatial and temporal heterogeneity. In particular, biogeochemical fluxes of volatiles such as methane remain largely unconstrained because of the difficulties with accurate quantification in situ and the patchiness of point sources such as seeps and brine pools. To better constrain biogeochemical fluxes and cycling, we have developed a deep-sea in situ mass spectrometer (ISMS) to enable high-resolution quantification of volatiles in situ. Here we report direct measurements of methane concentrations made in a Gulf of Mexico brine pool located at a depth of over 2300 m. Concentrations of up to 33 mM methane were observed within the brine pool, whereas concentrations in the water directly above were three orders of magnitude lower. These direct measurements enabled us to make the first accurate estimates of the diffusive flux from a brine pool, calculated to be 1.1±0.2 mol m−2 yr−1. Integrated rate measurements of aerobic methane oxidation in the water column overlying the brine pool were ∼320 $μ$mol m−2 yr−1, accounting at most for just 0.03{%} of the diffusive methane flux from the brine pool. Calculated rates of anaerobic methane oxidation were 600–1200 $μ$M yr−1, one to two orders of magnitude higher than previously published values of AOM in anoxic fluids. These findings suggest that brine pools are enormous point sources of methane in the deep sea, and may, in aggregate, have a pronounced impact on the global marine methane cycle.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

A new coral species introduced into the Atlantic Ocean - Tubastraea micranthus (Ehrenberg 1834) (Cnidaria, Anthozoa, Scleractinia): An invasive threat? - Sammarco, Paul W; Porter, Scott A; Cairns, Stephen D (AQUATIC INVASIONS, 2010)
Over the past 60-70 years, the invasive Indo-Pacific coral Tubastraea coccinea (Lesson 1830; Cnidaria, Scleractinia) has colonized the western tropical Atlantic Ocean - the Americas, the Antilles, northern Gulf of Mexico (GOM), and many of its 3,600 oil/gas platforms. It is now the single, most abundant coral on artificial substrata in the GOM, with hundreds of thousands of colonies on a single platform. Here, we report for the first time the observation of a closely related congener in the western Atlantic - the Indo-Pacific azooxanthellate Tubastraea micranthus (Ehrenberg 1834) - and suggest that it may pose a threat similar to T. coccinea. A total of 83 platforms, including deep-water, toppled, Rigs-to-Reefs structures, were surveyed in the northern Gulf of Mexico between 2000 and 2009, from Matagorda Island, Texas to Mobile, Alabama, USA, between the depths of 7 and 37 m, by SCUBA divers. Five platforms were surveyed by Remotely Operated Vehicle (ROV) to depths of up to 117 m. T. micranthus was found on only one platform - Grand Isle 93 (GI-93), off Port Fourchon, Louisiana, near the Mississippi River mouth, at the cross-roads of two major safety fairways/shipping lanes transited by large international commercial ships. The introduction appears to be recent, probably derived from the ballast water or hull of a vessel from the Indo-Pacific. If the growth and reproductive rates of T. micranthus, both sexual and asexual, are similar to those of T. coccinea, this species could dominate this region like its congener. It is not known whether this species is an opportunist/pioneer species, like T. coccinea, a trait protecting benthic communities from its dominance. The question of rapid-response eradication is raised.
Keywords: ROV Jason (Remotely Operated Vehicle)

Northwest Rota-1 Seamount - Chadwick, W W; Embley, R W; Baker, E T; Resing, J A; Lupton, J E; Cashman, K V; Dziak, R P; Tunnicliffe, V; Butterfield, D A; Tamura, Y (Oceanography, 2010)
Northwest Rota-1 Seamount is the first place on Earth where a submarine volcanic eruption was witnessed in 2004, and, remarkably, it appears that the volcano has been erupting continuously ever since. NW Rota-1 is located {\~{}} 100 km north of Guam in the western Pacific, within the newly designated Mariana Trench Marine National Monument (http://www.fws.gov/marianastrenchmarinemonument). With a summit depth of 520 m, it is a symmetrical cone of basaltic andesite composition (Figure 1) formed in the subduction zone setting of the Mariana volcanic arc. It was identified as a site of particular interest in 2003 when sampling of its overlying hydrothermal plume showed very high magmatic volatile input (Resing et al., 2007). Consequently, it was one of several seamounts targeted for dives with a remotely operated vehicle the following year. During these dives, an actively erupting vent was discovered at a depth of 550 m; lava, fluid, and gas samples were collected; and colonies of shrimp, limpets, and crabs (some of them new species) were found living in the volcano summit's harsh conditions (Embley et al., 2006; Limén et al., 2006).

A novel trigger-based method for hydrothermal vents prospecting using an autonomous underwater robot - Ferri, G; Jakuba, M V; Yoerger, D R (Autonomous Robots, 2010)
In this paper we address the problem of localizing active hydrothermal vents on the seafloor using an Autonomous Underwater Vehicle (AUV). The plumes emitted by hydrothermal vents are the result of thermal and chemical inputs from submarine hot spring systems into the overlying ocean. The Woods Hole Oceanographic Institution's Autonomous Benthic Explorer (ABE) AUV has successfully localized previously undiscovered hydrothermal vent fields in several recent vent prospecting expeditions. These expeditions utilized the AUV for a three-stage, nested survey strategy approach (German et al. in Deep Sea Res. I 55:203–219, 2008). Each stage consists of a survey flown at successively deeper depths through easier to detect but spatially more constrained vent fluids. Ideally this sequence of surveys culminates in photographic evidence of the vent fields themselves. In this work we introduce a new adaptive strategy for an AUV's movement during the first, highest-altitude survey: the AUV initially moves along pre-designed tracklines but certain conditions can trigger an adaptive movement that is likely to acquire additional high value data for vent localization. The trigger threshold is changed during the mission, adapting the method to the different survey profiles the robot may find. The proposed algorithm is vetted on data from previous ABE missions and measures of efficiency presented.
Keywords: AUV ABE (Autonomous Benthic Explorer)

Paving the seafloor: Volcanic emplacement processes during the 2005-2006 eruptions at the fast spreading East Pacific Rise, 9 degrees 50 ` N - Fundis, A T; Soule, S A; Fornari, D J; Perfit, M R (GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 2010)
The 2005-2006 eruptions near 9 degrees 50'N at the East Pacific Rise (EPR) marked the first observed repeat eruption at a mid-ocean ridge and provided a unique opportunity to deduce the emplacement dynamics of submarine lava flows. Since these new flows were documented in April 2006, a total of 40 deep-towed imaging surveys have been conducted with the Woods Hole Oceanographic Institution's (WHOI) TowCam system. More than 60,000 digital color images and high-resolution bathymetric profiles of the 2005-2006 flows from the TowCam surveys were analyzed for lava flow morphology and for the presence of kipukas, collapse features, faults and fissures. We use these data to quantify the spatial distributions of lava flow surface morphologies and to investigate how they relate to the physical characteristics of the ridge crest, such as seafloor slope, and inferred dynamics of flow emplacement. We conclude that lava effusion rate was the dominant factor controlling the observed morphological variations in the 2005-2006 flows. We also show that effusion rates were higher than in previously studied eruptions at this site and varied systematically along the length of the eruptive fissure. This is the first well-documented study in which variations in seafloor lava morphology can be directly related to a well documented ridge-crest eruption where effusion rate varied significantly.
Keywords: HOV Alvin (Human Occupied Vehicle)

Phylogenetic diversity of sediment bacteria from the deep Northeastern Pacific Ocean: a comparison with the deep Eastern Mediterranean Sea - Kouridaki, Ioanna; Polymenakou, Paraskevi N; Tselepides, Anastasios; Mandalakis, Manolis; Smith Jr., Kenneth L (INTERNATIONAL MICROBIOLOGY, 2010)
The variability of bacterial community composition and diversity was studied by comparative analysis of five 16S rRNA gene clone libraries from deep-sea sediments (water column depth: 4000 m) of the Northeastern Pacific Ocean and Eastern Mediterranean Sea. This is the first comparison of the bacterial communities living in these deep-sea ecosystems. The estimated chlorophyll a, organic carbon, and C/N ratio provided evidence of significant differences in the trophic state of the sediments between the Northeastern Pacific Ocean and the much warmer Eastern Mediterranean Sea. A diverse range of 16S rRNA gene phylotypes was found in the sediments of both regions. These were represented by 11 different taxonomic groups, with Gammaproteobacteria predominating in the Northeastern Pacific Ocean sediments and Acidobacteria in the Eastern Mediterranean microbial community. In addition, several 16S rRNA gene phylotypes only distantly related to any of the previously identified sequences (non-affiliated rRNA genes) represented a significant fraction of the total sequences. The potential diversity at the two sites differs but remains largely unexplored and remains of continuing scientific interest. {\{}[{\}}Int Microbiol 2010; 13(3):143-150]
Keywords: HOV Alvin (Human Occupied Vehicle)

Pore water chemistry of the Mariana serpentinite mud volcanoes: A window to the seismogenic zone - Hulme, S M; Wheat, C G; Fryer, P; Mottl, M J (Geochemistry, Geophysics, Geosystems, 2010)
In 2003, we conducted a survey of 11 serpentinite mud volcanoes in the Mariana fore arc. Here we report sediment pore water data from navigated gravity and piston cores and from push cores collected by the ROV system Jason2-Medea. Systematic variations in profiles of pore water chemical compositions from these mud volcanoes are consistent with models that include active upflow of pore water relative to the surrounding serpentinite matrix. The speed of upwelling, based on fits of an advection-diffusion model to observed data (K, Na, Rb, and Cs), reaches a maximum of 36 cm/yr at Big Blue Seamount. Results from these simulations constrain the pore water composition at depth and the degree of additional alteration as the pore water ascends through the sampled section. For example, the transition metals (e.g., Mn, Fe, Co, Ni, Cu, and Mo) are mobilized under conditions of low upwelling speeds and microbial activity. Similarly, the rare earth elements (REE) show evidence of near-surface alteration. In addition to these surficial reactions, distinctive pore water compositional patterns exist as a function of the distance from the trench axis, which is a proxy for the depths of water generation from the downgoing plate below each seamount. Systematic trends in the chemical composition of these slab-sourced fluids are consistent with increasing temperature and pressure at depth west of the trench. These trends include an increase in K, sulfate, carbonate alkalinity, Na/Cl, B, Mn, Fe, Co, Rb, Cs, Gd/Tb, Eu, and light REE (LREE) and a decrease in Ca, Sr, and Y with increasing distance from the trench. Mg and U are universally depleted in the upwelling water. We constrain the thermal conditions along the décollement using concentrations of fluid mobile elements (K, B, Cs, and Rb) and the mobilization of LREE relative to heavy REE (HREE). The 80°C isotherm is estimated at a depth of 15 km between Blue Moon Seamount and Cerulean Springs. At slab depths of 17 to 24 km, pore waters lack significant Rb and K enrichments relative to seawater, suggesting an upper bound near 150°C. There is an observed enrichment in LREE relative to HREE at Big Blue Seamount (slab depth 25 km) indicating that the décollement at this site is ∼200°C. The relative mobilization of Cs outpaced that of Rb at all seamounts sampled in this survey. On the basis of laboratory experiments, this observation sets an upper limit of ∼350°C at a depth of 30 km below the seafloor.
Keywords: ROV Jason (Remotely Operated Vehicle); ROV Medea (Remotely Operated Vehicle)

Pseudofossils in relict methane seep carbonates resemble endemic microbial consortia - Bailey, J V; Raub, T D; Meckler, A N; Harrison, B K; Raub, T M D; Green, A M; Orphan, V J (Palaeogeography, Palaeoclimatology, Palaeoecology, 2010)
Pleistocene-age methane seep carbonates from the Eel River Basin, California contain aggregate-like structures composed of tightly-packed hollow spheres that morphologically resemble syntrophic archaeal–bacterial consortia known to catalyze the anaerobic oxidation of methane (AOM). Tetragonal microstructures also present in the carbonates resemble seep-endemic Methanosarcinales cell clusters. Despite morphological similarities to the seep-endemic microbes that likely mediated the authigenesis of Eel River Basin carbonates and sulfides, detailed petrographic, SEM, and magnetic microscopic imaging, remanence rock magnetism, laser Raman, and energy dispersive X-ray spectroscopy, suggest that these microstructures are not microfossils, but rather mineral structures that result from the diagenetic alteration of euhedral Fe-sulfide framboids. Electron microscopy shows that during diagenesis, reaction rims composed of Fe oxide form around framboid microcrystalites. Subsequent dissolution of greigite or pyrite crystals leaves behind hollow cell-like casings (external molds) — a transformation that occurs on timescales of ∼100 kyr or less. Despite their superficial resemblance to morphologically-distinctive extant microbes in local sediments, the presence of acellular precursor grains, as well as of partially-altered transitional forms, complicate the interpretation of these and other framboidal microstructures that have been reported from the rock record.
Keywords: HOV Alvin (Human Occupied Vehicle)

Rapid dispersal of a hydrothermal plume by turbulent mixing - Walter, M; Mertens, C; Stober, U; German, C R; Yoerger, D R; Sultemfub, J; Rhein, M; Melchert, B; Baker, E T (Deep-Sea Research. Part I: Oceanographic Research Papers, 2010)
The water column imprint of the hydrothermal plume observed at the Nibelungen field (8°18′S 13°30′W) is highly variable in space and time. The off-axis location of the site, along the southern boundary of a non-transform ridge offset at the joint between two segments of the southern Mid-Atlantic Ridge, is characterized by complex, rugged topography, and thus favorable for the generation of internal tides, subsequent internal wave breaking, and associated vertical mixing in the water column. We have used towed transects and vertical profiles of stratification, turbidity, and direct current measurements to investigate the strength of turbulent mixing in the vicinity of the vent site and the adjacent rift valley, and its temporal and spatial variability in relation to the plume dispersal. Turbulent diffusivities K$ρ$K$ρ$ were calculated from temperature inversions via Thorpe scales. Heightened mixing (compared to open ocean values) was observed in the whole rift valley within an order of K$ρ$K$ρ$ around 10−3 m2 s−1. The mixing close to the vent site was even more elevated, with an average of View the MathML sourceK$ρ$=4×10−2m2s−1. The mixing, as well as the flow field, exhibited a strong tidal cycle, with strong currents and mixing at the non-buoyant plume level during ebb flow. Periods of strong mixing were associated with increased internal wave activity and frequent occurrence of turbulent overturns. Additional effects of mixing on plume dispersal include bifurcation of the particle plume, likely as a result of the interplay between the modulated mixing strength and current speed, as well as high frequency internal waves in the effluent plume layer, possibly triggered by the buoyant plume via nonlinear interaction with the elevated background turbulence or penetrative convection.
Keywords: AUV ABE (Autonomous Benthic Explorer)

Rare earth element abundances in hydrothermal fluids from the Manus Basin, Papua New Guinea: indicators of sub-seafloor hydrothermal processes in back-arc basins - Craddock, P R; Bach, W; Seewald, J S; Rouxel, O J; Reeves, E; Tivey, M K (Geochimica et Cosmochimica Acta, 2010)
Rare earth element (REE) concentrations are reported for a large suite of seafloor vent fluids from four hydrothermal systems in the Manus back-arc basin (Vienna Woods, PACMANUS, DESMOS and SuSu Knolls vent areas). Sampled vent fluids show a wide range of absolute REE concentrations and chondrite-normalized (REEN) distribution patterns (LaN /SmN ∼ 0.6–11; LaN /YbN ∼ 0.6 – 71; View the MathML sourceEuN/EuN∗∼1–55). REEN distribution patterns in different vent fluids range from light-REE enriched, to mid- and heavy-REE enriched, to flat, and have a range of positive Eu-anomalies. This heterogeneity contrasts markedly with relatively uniform REEN distribution patterns of mid-ocean ridge hydrothermal fluids. In Manus Basin fluids, aqueous REE compositions do not inherit directly or show a clear relationship with the REE compositions of primary crustal rocks with which hydrothermal fluids interact. These results suggest that the REEs are less sensitive indicators of primary crustal rock composition despite crustal rocks being the dominant source of REEs in submarine hydrothermal fluids. In contrast, differences in aqueous REE compositions are consistently correlated with differences in fluid pH and ligand (chloride, fluoride and sulfate) concentrations. Our results suggest that the REEs can be used as an indicator of the type of magmatic acid volatile (i.e., presence of HF, SO2) degassing in submarine hydrothermal systems. Additional fluid data suggest that near-seafloor mixing between high-temperature hydrothermal fluid and locally entrained seawater at many vent areas in the Manus Basin causes anhydrite precipitation. Anhydrite effectively incorporates REE and likely affects measured fluid REE concentrations, but does not affect their relative distributions.
Keywords: ROV Jason (Remotely Operated Vehicle)

Remote-sensing evaluation of geophysical anomaly sites in the outer continental slope, northern Gulf of Mexico - Garcia-Pineda, O; MacDonald, I R; Zimmer, B; Shedd, B; Roberts, H (Deep-Sea Research. Part II: Topical Studies in Oceanography, 2010)
Synthetic Aperture Radar (SAR) images obtained from satellites are a reliable tool for localizing natural hydrocarbon seeps. For this study, we used the Texture Classifier Neural Network Algorithm (TCNNA) to interpret SAR data from the RADARSAT satellite and a geostatistical clustering analysis to compare seeps detected in 579 SAR images covering the northern Gulf of Mexico (GOM). Geostatistical analysis results indicate that, in a typical active seep formation, oil vents would be found within a seep formation ∼2.5 km in diameter. Repeated observations of slicks at a given seep formation indicate that advection of rising oil in the water column causes an offset from the vent depending on water depth. At 500 m, the radial offset is up to 1400 m; at 2000 m, it is up to 3270 m. Observations with submersibles showed that, in 100{%} of the cases, the calculated seep formations that are matched with active oil seeps correspond to anomalies interpreted from surface amplitude maps and migration pathways in the seismic data. However, episodically, larger releases from persistent seeps occurred, and also some other seep formations showed intermittent releases. Our analysis indicates that active oil seeps detected with SAR represent a subset of the total array of geophysical features generated by hydrocarbon migration on the northern continental slope of the Gulf of Mexico.
Keywords: HOV Alvin (Human Occupied Vehicle); ROV Jason (Remotely Operated Vehicle)

ROV records deepest explosive eruption on the seafloor (Sea Technology, 2010)
Keywords: ROV Jason (Remotely Operated Vehicle)