@article {ISI:000208863600280,
	title = {{Microbial communities at the borehole observatory on the Costa Rica Rift flank (Ocean Drilling Program Hole 896A)}},
	journal = {FRONTIERS IN MICROBIOLOGY},
	volume = {3},
	year = {2012},
	type = {Article},
	abstract = {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)},
	issn = {1664-302X},
	doi = {10.3389/fmicb.2012.00232},
	author = {Nigro, Lisa M and Harris, Kate and Orcutt, Beth N and Hyde, Andrew and Clayton-Luce, Samuel and Becker, Keir and Teske, Andreas}
}
@article {ISI:000280324500002,
	title = {{Subseafloor seawater-basalt-microbe reactions: Continuous sampling of borehole fluids in a ridge flank environment}},
	journal = {GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS},
	volume = {11},
	year = {2010},
	month = {jul},
	type = {Article},
	abstract = {Integrated Ocean Drilling Program (IODP) Hole 1301A was drilled, cased, and instrumented with a long-term, subseafloor observatory (CORK) on the eastern flank of the Juan de Fuca Ridge in summer 2004. This borehole is located 1 km south of ODP Hole 1026B and 5 km north of Baby Bare outcrop. Hole 1301A penetrates 262 m of sediment and 108 m of the uppermost 3.5 Ma basaltic basement in an area of warm (64 degrees C) hydrothermal circulation. The borehole was instrumented, and those instruments were recovered 4 years later. Here we report chemical data from two continuous fluid samplers (OsmoSamplers) and temperature recording tools that monitored changes in the state of borehole (formation) fluids. These changes document the effects of drilling, fluid overpressure and flow, seawater-basalt interactions, and microbial metababolic activity. Initially, bottom seawater flowed into the borehole through a leak between concentric CORK casing strings. Eventually, the direction of flow reversed, and warm, altered formation fluid flowed into the borehole and discharged at the seafloor. This reversal occurred during 1 week in September 2007, 3 years after drilling operations ceased. The composition of the formation fluid around Hole 1301A generally lies within bounds defined by springs on Baby Bare outcrop (to the south) and fluids that discharged from Hole 1026B (to the north); deviations likely result from reactions with drilling products. Simple conservative mixing of two end-member fluids reveals reactions occurring within the crust, including nitrate reduction presumably by denitrifying microbes. The observed changes in borehole fluid composition provide the foundation for a conceptual model of chemical and microbial change during recharge of a warm ridge-flank hydrothermal system. This model can be tested through future scientific ocean drilling experiments.},
	keywords = {HOV Alvin (Human Occupied Vehicle)},
	issn = {1525-2027},
	doi = {10.1029/2010GC003057},
	author = {Wheat, C Geoffrey and Jannasch, Hans W and Fisher, Andrew T and Becker, Keir and Sharkey, Jessica and Hulme, Samuel}
}
@article {ISI:000280049400003,
	title = {{Thermally stimulated {\textquoteleft}{\textquoteleft}runaway{\{}{\textquoteright}{\textquoteright}{\}} downhole flow in a superhydrostatic ocean crustal borehole: Observations, simulations, and inferences regarding crustal permeability}},
	journal = {JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH},
	volume = {115},
	year = {2010},
	month = {jul},
	type = {Article},
	abstract = {An array of boreholes, drilled through a regionally continuous hydrologically confining layer of sediments into extrusive igneous basement rocks of the Juan de Fuca Ridge eastern flank, has been instrumented with CORK hydrologic observatories for long-term monitoring and fluid sampling. Omission of seals between nested casing strings reaching into basement at one site created a low-resistance connection between basement and the overlying water column, and despite the natural superhydrostatic state of basement water at that location, a {\textquoteleft}{\textquoteleft}runaway{\{}{\textquoteright}{\textquoteright}{\}} condition of cold seawater downhole flow into the crust was established, which persisted for more than 4 years. The existence of this condition, along with perturbations generated by it and by initial drilling operations observed at a properly sealed hole 2.4 km away, have been used with analytic and finite element model solutions to constrain formation permeability. The minimum threshold permeability allowing stable downhole flow is roughly 4 x 10(-13) m(2). A value of permeability similar to this (3-4 x 10(-13) m(2)) is estimated on the basis of the elapsed time for initial perturbations to propagate between the sites (similar to 2.5 days). The amplitude of the long-term flow perturbation observed at the sealed site (roughly 1.7 kPa) is smaller than that predicted by modeling (5-10 kPa). Models for flow in an anisotropically permeable layer show that this could be the consequence of low vertical permeability (e. g., arising from massive volcanic or sediment interlayering) or high permeability in the direction of the tectonic fabric generated at the ridge axis. Disagreement between the permeabilities estimated here with previous large-scale estimates appropriate for the cross-strike direction (the primary direction between the borehole sites) (10(-10)-10(-9) m(2)) is difficult to reconcile; it is possible that the holes are poorly connected to zones of high permeability that facilitate the large lateral fluid and heat fluxes previously inferred at this young crustal site.},
	keywords = {HOV Alvin (Human Occupied Vehicle)},
	issn = {0148-0227},
	doi = {10.1029/2009JB006986},
	author = {Davis, Earl E and LaBonte, Alison and He, Jiangheng and Becker, Keir and Fisher, Andrew}
}
