The role of microbial Fe and Mn oxidation in submarine weathering of volcanic glass

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Researchers from the Scripps Institution of Oceanography in California will characterize changes in surface chemistry of seafloor basalts, in particular the rate of Fe and Mn release and oxidation, arising from microbial interaction with volcanic glasses. The research addresses the following questions: (1) do basaltic glasses support growth of chemolithoautotrophic bacteria in deep ocean environments, (2) how does the composition of the basaltic glass affect the microbial community composition, rates of glass alteration, and the formation of secondary phases, and (3) do Fe(II)- and Mn(II)-oxidizing bacteria participate in or accelerate the alteration of basaltic glass. The main goal of this work is to determine if the activity of microorganisms significantly accelerates the rates of basaltic glass dissolution in the marine environment. Motivation for this work comes from the fact that basaltic glass is one of the most abundant and reactive components of the ocean crust. The scientific program will include both field and laboratory components. Field investigations will include NOAA/NURP funded submersible dives on the flanks of Hawaii and Loihi seamount to study recent lava flows and carry out exposure experiments that will range from one to five years in duration. Sampling areas will include those with glasses that possess a range of Fe(II) or Mn(II) concentrations. Laboratory investigations will simulate biocorrosion of glass under controlled chemical conditions. The analytical program will entail investigation of changes in surface chemistry and in depths of Fe and Mn leaching and oxidation using novel synchrotron X-ray based analytical techniques developed by the research team. Biofilms grown by glass-colonizing bacteria will be studied as well as the diversity and composition of microbial communities growing on the glass. Characterization of natural and laboratory-grown Fe and Mn oxidizing microbes from sea floor basalts will be carried out using state-of-the-art molecular biological techniques (FISH, TRFLP). Geochemical analyses of weathered basalts will include examination by electron microprobe and a scanning electron microscope equipped with an energy dispersive chemical analyzer. This work will answer the question of whether microbes cause the weathering of volcanic glass and whether this process substantially impacts biogeochemical cycles in the oceans. It will also determine whether volcanic glass can serve as a viable substrate to support life in the deep ocean crust. Broader impacts include the development and refinement of new surface analytical techniques, support and training of a Postdoctoral Scholar and a Ph.D. student. It will also make available data and research resources for high/middle schoolteachers and students through the Internet via databases and websites.