Collaborative Research: Microbial Ecology of Ocean Basement Aquifers: ODP Borehole Observatories

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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.