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Geochimica et Cosmochimica Acta
Dissolved amino acids in oceanic basaltic basement fluids
Huei-Ting Lin*, Jan P. Amend*, Douglas E. LaRowe*, Jon-Paul Bingham, James P. Cowen*
*C-DEBI Contribution 262
The oceanic basaltic basement contains the largest aquifer on Earth and potentially plays an important role in the global carbon cycle as a net sink for dissolved organic carbon (DOC). However, few details of the organic matter cycling in the subsurface are known because great water depths and thick sediments typically hinder direct access to this environment. In an effort to examine the role of water-rock-microorganism interaction on organic matter cycling in the oceanic basaltic crust, basement fluid samples collected from three borehole observatories installed on the eastern flank of the Juan de Fuca Ridge were analyzed for dissolved amino acids. Our data show that dissolved free amino acids (1-13 nM) and dissolved hydrolyzable amino acids (43-89 nM) are present in the basement. The amino acid concentrations in the ridge-flank basement fluids are at the low end of all submarine hydrothermal fluids reported in the literature and are similar to those in deep seawater. Amino acids in recharging deep seawater, in situ amino acid production, and diffusional input from overlying sediments are potential sources of amino acids in the basement fluids. Thermodynamic modeling shows that amino acid synthesis in the basement can be sustained by energy supplied from inorganic substrates via chemolithotrophic metabolisms. Furthermore, an analysis of amino acid concentrations and compositions in basement fluids support the notion that heterotrophic activity is ongoing. Similarly, the enrichment of acidic amino acids and depletion of hydrophobic ones relative to sedimentary particulate organic matter suggests that surface sorption and desorption also alters amino acids in the basaltic basement. In summary, although the oceanic basement aquifer is a net sink for deep seawater DOC, similar amino acid concentrations in basement aquifer and deep seawater suggest that DOC is preferentially removed in the basement over dissolved amino acids. Our data also suggest that organic carbon cycling occurs in the oceanic basaltic basement, where an active subsurface biosphere is likely responsible for amino acid synthesis and degradation.
Estuarine, Coastal and Shelf Science
Cellular maintenance processes that potentially underpin the survival of subseafloor fungi over geological timescales
William D. Orsi*, Thomas A. Richards, Alyson E. Santoro
*C-DEBI Contribution 261
The subsurface environment of Earth contains a diverse and complex community comprised of >1028 microbial cells globally, with a significant portion of this biomass being present in continental margin sediment. The cellular functions, and the genes that encode them, enabling subsurface microbial survival over geological timescales are unknown. To better understand the cellular functions that enable microbial survival over geological timescales in subseafloor sediment, metatranscriptomes from subseafloor continental margin sediment (5-159 m below the seafloor) were compared to soil metatranscriptomes using fungal genomes from the genera Cryptococcus and Aspergillus, taxa known to occupy representative samples of each environment, as reference. Soil metatranscriptomes contain a relatively higher number of overexpressed representative fungal homologous genes involved in catabolism of labile substrates, reflecting the increased bioavailability of the soil substrate pool relative to subseafloor sediment. In contrast, many fungal homologs with overexpression in subseafloor samples encode proteasomes and autophagosomes that likely help conserve and recycle amino acids under reduced availability of labile organic matter. Genes associated with stationary phase were significantly overexpressed in the subseafloor suggesting a relatively higher investment into cellular maintenance energy. Such differences indicate that 1.) subseafloor fungal transcripts are not contaminants and 2.) subseafloor fungi are relatively dormant compared to soil fungi, and likely persist for long periods in stationary phase. Our findings provide insights into biochemical mechanisms enabling subseafloor survival for long periods, under extreme pressure, with relatively recalcitrant carbon sources.
Subsurface hydrothermal processes and the bioenergetics of chemolithoautotrophy at the shallow-sea vents off Panarea Island (Italy)
Roy E. Price*, Douglas E. LaRowe*, Francesco Italiano, Ivan Savov, Thomas Pichler, Jan P. Amend*
C-DEBI Contribution 266
The subsurface evolution of shallow-sea hydrothermal fluids is a function of many factors including fluid-mineral equilibria, phase separation, magmatic inputs, and mineral precipitation, all of which influence discharging fluid chemistry and consequently associated seafloor microbial communities. Shallow-sea vent systems, however, are understudied in this regard. In order to investigate subsurface processes in a shallow-sea hydrothermal vent, and determine how these physical and chemical parameters influence the metabolic potential of the microbial communities, three shallow-sea hydrothermal vents associated with Panarea Island (Italy) were characterized. Vent fluids, pore fluids and gases at the three sites were sampled and analyzed for major and minor elements, redox-sensitive compounds, free gas compositions, and strontium isotopes. The corresponding data were used to 1) describe the subsurface geochemical evolution of the fluids and 2) to evaluate the catabolic potential of 61 inorganic redox reactions for in situ microbial communities. Generally, the vent fluids can be hot (up to 135 °C), acidic (pH 1.9-5.7), and sulfidic (up to 2.5 mM H2S). Three distinct types of hydrothermal fluids were identified, each with higher temperatures and lower pH, Mg2+ and SO42-, relative to seawater. Type 1 was consistently more saline than Type 2, and both were more saline than seawater. Type 3 fluids were similar to or slightly depleted in most major ions relative to seawater. End-member calculations of conservative elements indicate that Type 1 and Type 2 fluids are derived from two different sources, most likely 1) a deeper, higher salinity reservoir and 2) a shallower, lower salinity reservoir, respectively, in a layered hydrothermal system. The deeper reservoir records some of the highest end-member Cl concentrations to date, and developed as a result of recirculation of brine fluids with long term loss of steam and volatiles due to past phase separation. No strong evidence for ongoing phase separation is observed. Type 3 fluids are suggested to be mostly influenced by degassing of volatiles and subsequently dissolution of CO2, H2S, and other gases into the aqueous phase. Gibbs energies (ΔGr) of redox reactions that couple potential terminal electron acceptors (O2, NO3–, MnIV, FeIII, SO42-, S0, CO2,) with potential electron donors (H2, NH4+, Fe2+, Mn2+, H2S, CH4) were evaluated at in situ temperatures and compositions for each site and by fluid type. When Gibbs energies of reaction are normalized per kilogram of hydrothermal fluid, sulfur oxidation reactions are the most exergonic, while the oxidation of Fe2+, NH4+, CH4, and Mn2+ are moderately energy yielding. The energetics calculations indicate that the most robust microbial communities in the Panarea hot springs combine H2S from deep water-rock-gas interactions with O2 that is entrained via seawater mixing to fuel their activities, regardless of site location or fluid type.
ROV Week-long Summer Camps for Middle School Students near Monterey, CA and the University of Mississippi
Motivated by the desire to address today’s technological workforce needs, SS-ROV Camp was started in 2013 through the collaborative efforts of C-DEBI Co-I Dr. Geoff Wheat and his team of program developers with funding from University of Mississippi, NIUST, NASA, NSF-USC (C-DEBI) and University of Alaska Fairbanks. They provide a hands-on, STEM, summer, learning opportunity that mimics a research ship mission – held in a classroom setting – where middle school students learn about the deep ocean and research equipment used. The camp is based on the premise that a research scientist going to sea needs a good plan and innovative tools, as well as the know-how and staff to utilize and fix them. Students engage in hands-on activities in the areas of robotics, sensor technology, programming, marine geology and ecology. Like professional ocean research, the SS-ROV Camp emphasizes purposeful engagement and vision, planning and preparation, teamwork and execution, and discovery and problem solving.
Consortium for Ocean Leadership: World Oceans Day Live Twitter Event, June 8, 1-5 PM ET
In celebration of World Oceans Day, Ocean Leadership will be conducting a live Twitter event to answer the public’s questions about the ocean and ocean life. As the organization representing the ocean research and education community, Ocean Leadership has the opportunity on World Oceans Day to engage with the public, provide them with unbiased scientific answers to their ocean questions, and create visibility for you, our Member institutions, by highlighting the important research and the expertise at your institutions, as well as hopefully driving interested individuals to your websites to learn more.
USC / Sea Grant / C-DEBI / Wrigley Institute: Summer Science Programs applications now open
Weeklong Summer Science Programs provide middle school and high school students the opportunity to visit the USC Phillip K. Wrigley Wrigley Institute for Environmental Studies on Catalina Island, and other coastal sites. Over the course of a week, students get amazing opportunities to work with local researchers, conduct their own research projects, learn about careers in marine science, build their own ROVs and explore the marine protected areas around the island. Applications for Summer 2015 are now available! Program dates are July 23- 29, 2015. The program is FREE to the students including transportation and will be limited to twenty applicants. It is offered in partnership by USC Sea Grant Program, Center for Dark Energy Biosphere Investigations, and Wrigley Institute for Environmental Studies. Applications are due by March 20, 2015.
The Data Incubator: Data Science Fellowship Opportunity
The next session will be from 06/01/15 to 07/17/15.
DCO: Call for Proposals Census of Deep Life Sequencing Opportunities
Application deadline: June 01, 2015.
NSF: Small Business Technology Transfer Program Phase I Solicitation (STTR)
Full proposal deadline: June 18, 2015.
NSF: Faculty Early Career Development Program (CAREER)
See also the FAQ. Full proposal deadlines: July 21-23, 2015.
Simons Foundation, Howard Hughes Medical Institute and Bill & Melinda Gates Foundation: 2016 Faculty Scholars Competition
Application deadline: July 28, 2015.
National Academies: Research Associateships for Graduate, Postdoctoral and Senior Researchers
There are four annual review cycles and the next closes August 01, 2015.
NSF: Geobiology and Low-Temperature Geochemistry Program Solicitation
Proposals accepted anytime.
IODP-USSSP: Proposals for Pre-Drilling Activities and Workshops
The U.S. Science Support Program (USSSP) accepts proposals on a rolling basis for pre-drilling activities and semi-annually for workshops, related to the International Ocean Discovery Program (IODP).
Bigelow: Postdoctoral Research Scientist – Geomicrobiology/Microbial Ecology
For full consideration, the application should be received by May 22, 2015.
MBARI: Principle Investigator
The Monterey Bay Aquarium Research Institute (MBARI) seeks a Principal Investigator (PI) to develop and direct a marine carbon cycle research team.
Bermuda Institute of Ocean Sciences: Chemical/Physical/Biological Oceanographer
Review of applications will begin April 15, 2015.
UTK: Professor and Head Department of Microbiology, The College of Arts & Sciences
Review of applications will begin on March 31, 2015 and will continue until the position is filled.
The review of materials will begin December 01, 2014, and will continue until the position is filled.
Skidaway Institute of Oceanography: Two Tenure Track Faculty Positions in Oceanography
The committee will begin to review applications on October 24, 014 and will continue until the positions are filled.
Don’t forget to email me with any items you’d like to share in future newsletters! You are what makes our deep biosphere community!