Wheat
C. Geoffrey
Wheat
C. Geoffrey
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ArticleA distinct and active bacterial community in cold oxygenated fluids circulating beneath the western flank of the Mid-Atlantic ridge(Nature Publishing Group, 2016-03-03) Meyer, Julie L. ; Jaekel, Ulrike ; Tully, Benjamin J. ; Glazer, Brian T. ; Wheat, C. Geoffrey ; Lin, Huei-Ting ; Hsieh, Chih-Chiang ; Cowen, James P. ; Hulme, Samuel M. ; Girguis, Peter R. ; Huber, Julie A.The rock-hosted, oceanic crustal aquifer is one of the largest ecosystems on Earth, yet little is known about its indigenous microorganisms. Here we provide the first phylogenetic and functional description of an active microbial community residing in the cold oxic crustal aquifer. Using subseafloor observatories, we recovered crustal fluids and found that the geochemical composition is similar to bottom seawater, as are cell abundances. However, based on relative abundances and functional potential of key bacterial groups, the crustal fluid microbial community is heterogeneous and markedly distinct from seawater. Potential rates of autotrophy and heterotrophy in the crust exceeded those of seawater, especially at elevated temperatures (25°C) and deeper in the crust. Together, these results reveal an active, distinct, and diverse bacterial community engaged in both heterotrophy and autotrophy in the oxygenated crustal aquifer, providing key insight into the role of microbial communities in the ubiquitous cold dark subseafloor biosphere. An Author Correction to this article was published on 16 April 2020
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ArticleIn situ enrichment of ocean crust microbes on igneous minerals and glasses using an osmotic flow-through device(American Geophysical Union, 2011-06-21) Smith, Amy ; Popa, Radu ; Fisk, Martin ; Nielsen, Mark ; Wheat, C. Geoffrey ; Jannasch, Hans W. ; Fisher, Andrew T. ; Becker, Keir ; Sievert, Stefan M. ; Flores, GilbertoThe 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.
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DatasetPore water chemical concentration data and location from push cores collected by the ROV Jason II on dive J2-773 from cruise MSM37 on R/V Maria S. Merian from March to April 2014(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-04-18) Wheat, C. GeoffreyPore water chemical concentration data and location from push cores collected by the ROV Jason II on dive J2-773 from cruise MSM37 on R/V Maria S. Merian on 11-April-2014. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/764875
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DatasetMinor ion concentrations in OsmoSamplers that were recovered on R/V Atlantis Expedition AT39-01 with the ROV Jason-II (Depart October 2, 2018 and returned 11/2/2017).(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2020-10-14) Wheat, C. GeoffreyMinor ion concentrations in OsmoSamplers that were recovered on R/V Atlantis Expedition AT39-01 with the ROV Jason-II (Depart October 2, 2018 and returned 11/2/2017). For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/820188
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ArticleMicrobial activity in the marine deep biosphere : progress and prospects(Frontiers Media, 2013-07-11) Orcutt, Beth N. ; LaRowe, Douglas E. ; Biddle, Jennifer F. ; Colwell, Frederick S. ; Glazer, Brian T. ; Kiel Reese, Brandi ; Kirkpatrick, John B. ; Lapham, Laura L. ; Mills, Heath J. ; Sylvan, Jason B. ; Wankel, Scott D. ; Wheat, C. GeoffreyThe vast marine deep biosphere consists of microbial habitats within sediment, pore waters, upper basaltic crust and the fluids that circulate throughout it. A wide range of temperature, pressure, pH, and electron donor and acceptor conditions exists—all of which can combine to affect carbon and nutrient cycling and result in gradients on spatial scales ranging from millimeters to kilometers. Diverse and mostly uncharacterized microorganisms live in these habitats, and potentially play a role in mediating global scale biogeochemical processes. Quantifying the rates at which microbial activity in the subsurface occurs is a challenging endeavor, yet developing an understanding of these rates is essential to determine the impact of subsurface life on Earth's global biogeochemical cycles, and for understanding how microorganisms in these “extreme” environments survive (or even thrive). Here, we synthesize recent advances and discoveries pertaining to microbial activity in the marine deep subsurface, and we highlight topics about which there is still little understanding and suggest potential paths forward to address them. This publication is the result of a workshop held in August 2012 by the NSF-funded Center for Dark Energy Biosphere Investigations (C-DEBI) “theme team” on microbial activity (www.darkenergybiosphere.org).
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PreprintChemistry of hot springs along the Eastern Lau Spreading Center( 2010-12-08) Mottl, Michael J. ; Seewald, Jeffrey S. ; Wheat, C. Geoffrey ; Tivey, Margaret K. ; Michael, Peter J. ; Proskurowski, Giora ; McCollom, Thomas M. ; Reeves, Eoghan P. ; Sharkey, Jessica ; You, Chen-Feng ; Chan, Lui-Heung ; Pichler, ThomasThe 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 229º to 363ºC 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 121ºC 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 δ7Li increase southward, and δ11B 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.
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ArticleA dynamic microbial community with high functional redundancy inhabits the cold, oxic subseafloor aquifer(Nature Publishing Group, 2017-11-03) Tully, Benjamin J. ; Wheat, C. Geoffrey ; Glazer, Brian T. ; Huber, Julie A.The rock-hosted subseafloor crustal aquifer harbors a reservoir of microbial life that may influence global marine biogeochemical cycles. Here we utilized metagenomic libraries of crustal fluid samples from North Pond, located on the flanks of the Mid-Atlantic Ridge, a site with cold, oxic subseafloor fluid circulation within the upper basement to query microbial diversity. Twenty-one samples were collected during a 2-year period to examine potential microbial metabolism and community dynamics. We observed minor changes in the geochemical signatures over the 2 years, yet the microbial community present in the crustal fluids underwent large shifts in the dominant taxonomic groups. An analysis of 195 metagenome-assembled genomes (MAGs) were generated from the data set and revealed a connection between litho- and autotrophic processes, linking carbon fixation to the oxidation of sulfide, sulfur, thiosulfate, hydrogen, and ferrous iron in members of the Proteobacteria, specifically the Alpha-, Gamma- and Zetaproteobacteria, the Epsilonbacteraeota and the Planctomycetes. Despite oxic conditions, analysis of the MAGs indicated that members of the microbial community were poised to exploit hypoxic or anoxic conditions through the use of microaerobic cytochromes, such as cbb3- and bd-type cytochromes, and alternative electron acceptors, like nitrate and sulfate. Temporal and spatial trends from the MAGs revealed a high degree of functional redundancy that did not correlate with the shifting microbial community membership, suggesting functional stability in mediating subseafloor biogeochemical cycles. Collectively, the repeated sampling at multiple sites, together with the successful binning of hundreds of genomes, provides an unprecedented data set for investigation of microbial communities in the cold, oxic crustal aquifer.
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ArticleCool, alkaline serpentinite formation fluid regime with scarce microbial habitability and possible abiotic synthesis beneath the South Chamorro Seamount(Springer, 2018-11-14) Kawagucci, Shinsuke ; Miyazaki, Junichi ; Morono, Yuki ; Seewald, Jeffrey S. ; Wheat, C. Geoffrey ; Takai, KenSouth Chamorro Seamount (SCS) is a blueschist-bearing serpentinite mud volcano in the Mariana forearc. Previous scientific drilling conducted at SCS revealed highly alkaline, sulfate-rich formation fluids resulting from slab-derived fluid upwelling combined with serpentinization both beneath and within the seamount. In the present study, a time-series of ROV dives spanning 1000 days was conducted to collect discharging alkaline fluids from the cased Ocean Drilling Program (ODP) Hole 1200C (hereafter the CORK fluid). The CORK fluids were analyzed for chemical compositions (including dissolved gas) and microbial community composition/function. Compared to the ODP porewater, the CORK fluids were generally identical in concentration of major ions, with the exception of significant sulfate depletion and enrichment in sulfide, alkalinity, and methane. Microbiological analyses of the CORK fluids revealed little biomass and functional activity, despite habitable temperature conditions. The post-drilling sulfate depletion is likely attributable to sulfate reduction coupled with oxidation of methane (and hydrogen), probably triggered by the drilling and casing operations. Multiple lines of evidence suggest that abiotic organic synthesis associated with serpentinization is the most plausible source of the abundant methane in the CORK fluid. The SCS formation fluid regime presented here may represent the first example on Earth where abiotic syntheses are conspicuous with little biotic processes, despite a condition with sufficient bioavailable energy potentials and temperatures within the habitable range.
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ArticleFluid transport and reaction processes within a serpentinite mud volcano: South Chamorro Seamount(Elsevier, 2020-01-15) Wheat, C. Geoffrey ; Seewald, Jeffrey S. ; Takai, KenNatural fluids with a pH (25 °C) up to 12.3 were collected from a sub-seafloor borehole observatory (Ocean Drilling Program (ODP) Hole 1200C) on South Chamorro Seamount, a serpentinite mud volcano in the Mariana forearc. We used systematic differences in the chemical compositions of pore waters from drilling operations during ODP Leg 195 and borehole fluids collected subsequently from Hole 1200C to define two endmember solutions, one of which was a sulfate-rich fluid with a methane concentration of 50 mM that ascends from the subduction channel and the other was a low-sulfate fluid. The sequence of sample collection and fluid compositions constrain subsurface hydrologic conditions. Deep-sourced, sulfate- and methane-rich, sterile fluids from the subduction channel can reach the seafloor unchanged within the central conduit, whereas other fluid pathways likely intersect the pelagic sediment that underlies the serpentinite mud volcano, providing potentially suitable conditions and inoculum for microbial anaerobic oxidation of methane (AOM). These AOM-affected, low-sulfate fluids also make it to the seafloor where they discharge. The source of the sulfate- and methane-rich fluid in the subduction channel is attributed to abiotic methane production fueled by hydrogen production from serpentinization and carbonate dissolution. This methane production includes a mechanism to raise the pH above values from serpentinization alone. Results from South Chamorro Seamount represent an end member along a transect defined by the distance from the trench. Results from this site are applied to other serpentinite mud volcanoes along this transect to speculate on likely chemical conditions within shallower and cooler portions of the subduction channel.
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ArticleCOBRA Master Class: Providing deep-sea expedition leadership training to accelerate early career advancement(Frontiers Media, 2023-10-05) Rotjan, Randi D. ; Bell, Katherine L. C. ; Huber, Julie A. ; Wheat, Charles Geoffrey ; Fisher, Andrew T. ; Sylvan, Rosalynn Lee ; McManus, James ; Bigham, Katharine T. ; Cambronero-Solano, Sergio ; Cordier, Tristan ; Goode, Savannah ; Leonard, Juliana ; Murdock, Sheryl ; Paula, Fabiana S. ; Ponsoni, Leandro ; Roa-Varon, Adela ; Seabrook, Sarah ; Shomberg, Russell ; Van Audenhaege, Loic ; Orcutt, Beth N.Leading deep-sea research expeditions requires a breadth of training and experience, and the opportunities for Early Career Researchers (ECRs) to obtain focused mentorship on expedition leadership are scarce. To address the need for leadership training in deep-sea expeditionary science, the Crustal Ocean Biosphere Research Accelerator (COBRA) launched a 14-week virtual Master Class with both synchronous and asynchronous components to empower students with the skills and tools to successfully design, propose, and execute deep-sea oceanographic field research. The Master Class offered customized and distributed training approaches and created an open-access syllabus with resources, including reading material, lectures, and on-line resources freely-available on the Master Class website (cobra.pubpub.org). All students were Early Career Researchers (ECRs, defined here as advanced graduate students, postdoctoral scientists, early career faculty, or individuals with substantial industry, government, or NGO experience) and designated throughout as COBRA Fellows. Fellows engaged in topics related to choosing the appropriate deep-sea research asset for their Capstone “dream cruise” project, learning about funding sources and how to tailor proposals to meet those source requirements, and working through an essential checklist of pre-expedition planning and operations. The Master Class covered leading an expedition at sea, at-sea operations, and ship-board etiquette, and the strengths and challenges of telepresence. It also included post-expedition training on data management strategies and report preparation and outputs. Throughout the Master Class, Fellows also discussed education and outreach, international ocean law and policy, and the importance and challenges of team science. Fellows further learned about how to develop concepts respectfully with regard to geographic and cultural considerations of their intended study sites. An assessment of initial outcomes from the first iteration of the COBRA Master Class reinforces the need for such training and shows great promise with one-quarter of the Fellows having submitted a research proposal to national funding agencies within six months of the end of the class. As deep-sea research continues to accelerate in scope and speed, providing equitable access to expedition training is a top priority to enable the next generation of deep-sea science leadership.