The ocean crust consists of basement rock formed at the mid-ocean ridges (MOR) plus the overlying sediments that accumulate over time as the basement rock ages and moves away from the MORs. There is growing evidence that a substantial biosphere exists throughout the immense volume of aging, sediment-buried basement underlying the global system of MOR flanks and ocean basins. The current project will exploit the unprecedented opportunities provided by long-term Ocean Drilling Program borehole observatories (CORKs) to collect uncontaminated samples of basement fluids for geochemical, microbiological and ecological characterization. Because water-rock reactions and associated microbial habitats vary with basement temperature and age, the geochemistry and molecular (genetic) diversity will be examined in basement fluids from multiple borehole observatories on the flanks of the Juan de Fuca Ridge (JFR), ranging in basement age (ca.1.24 to 3.5 million years) and in basement temperature (38 to 65degrees centigrade). The synergy between water-rock and aqueous (e.g., oxidation-reduction) reactions and the organisms living in proximity to them demands an interdisciplinary approach to research. In this project, the microbial community and metabolic diversity will be studied in close conjunction with geochemical processes. In situ, real-time analyses will simultaneously measure key dissolved reduction-oxidation (redox) species; such measurements will help to elucidate the metabolic climate of the basement fluids (e.g., how the microbes gain energy and fix carbon) and guide culturing portions of this study. These geochemical and biological studies will provide input data for thermodynamic calculations of numerous potential metabolic reactions (e.g., a sort of energy 'road map'), which will provide a 'reality-check' for the occurrence of certain metabolisms. Geochemical measurements and energetic calculations will provide a much-needed environmental context for realistic modeling of microbial community synergy.
The principal investigators and students from the participating institutions will interact closely with hydrogeologists, geochemists and technologists from numerous other institutions, as well as with staff of the International Ocean Drilling Program (IDOP) to both exploit existing CORK observatories and to influence development of new borehole observatories that are optimal for ocean basement microbial community studies. Multiple undergraduate, graduate and post-doctoral students will be intimately involved in all stages of the project, and will benefit from cross-institutional informal education and training. The project will actively interact with UH's NASA Astrobiology Institute (NAI), for which subseafloor biosphere studies is an increasingly significant component. Students and PIs will participate in educational outreach projects to K-12 schools and the general public, especially including continuation of the very successful ship-to-classroom and "Teacher at Sea" outreach programs; the latter will involve integrating K-12 science teachers directly into all aspects of the project from initial planning to field and laboratory work.
NSF project 1207880 – Microbial Ecology of Ocean Basement Aquifers: ODP Borehole Observatories – investigated the biosphere in the fluids that flow through the igneous basement rocks on the Juan de Fuca ridge flank system off the coast of Washington State. As co-investigator of the project, I led the efforts to evaluate the energy yields from a variety of potential metabolic reactions. The intellectual merits are reported in four peer-reviewed publications. Boettger et al. (2012) calculated values of Gibbs energy of chemolithotrophic processes in basement fluid and in zones where basement fluid and entrained seawater may mix. In pure basement fluid, energy yields from anaerobic processes are anemic; in mixed solutions, aerobic oxidations of hydrogen, methane, and sulfide are moderately energy yielding. Lin et al. (2012) and Lin et al. (2013) report the inorganic chemistry, gas composition, dissolved organic carbon, and dissolved amino acids in fluids from the sedimented basalt crust at Juan de Fuca. Thermodynamic calculations indicate that the ridge-flank basement environment is not conducive to the abiotic synthesis of free amino acids. Robador et al. (2013) focused on sulfate reducing microorganisms in these deep subseafloor basaltic fluids, reporting sulfate reduction rates that track with the age and temperature of the basaltic crust. The broader impacts include numerous presentations by the co-investigator at scientific conferences, university colloquia, and public forums. In addition, this project supported the training and professional development of two students (Jason Boettger, Tina Lin) and two post-doctoral fellows (Doug LaRowe, Alberto Robador).
