RAPID: Biologically-mediated methanogenesis and acetogenesis in the hydrothermally altered sediments of the Guaymas Basin

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AbstractIntellectual Merit. Sediment microbial communities recycle organic matter to inorganic building blocks throughout the sediment column. In deeply buried sediments, however, thermal cracking of organic matter plays an additional, but similar role. In the Guaymas basin, biologically-mediated and thermal decomposition processes co-occur, creating a complex mixture of organic matter breakdown products. In this project, the PI's will examine the processes of biologically-mediated methanogenesis and acetogenesis in Guaymas Basin sediments. Specifically, the PIs will evaluate rates of methanogenesis and acetogenesis in sediments collected from areas of active hydrothermal fluid venting and from flanking areas dominated by convective cooling (e.g. reduced hydrothermal flow). Additional experiments will quantify the impact of temperature and pressure on these important biologically-mediated processes that transform carbon dioxide and organic carbon into methane (methanogenesis) or carbon dioxide and hydrogen into acetate (acetogenesis).Broader Impact. This work will clarify the role of biological processes in producing methane and acetate in the organic rich, hydrothermally influenced sediments of the Guaymas Basin. While thermogenic processes are assumed to account for the majority of methane and acetate production in this Basin, the possibility of biological-mediation is underscored by the presence of methane producing archaea in a variety of habitats.