Abstract MICROBIAL DIVERSITY AND BIOGEOGRAPHY IN A SERPENTINITE-HOSTED ECOSYSTEM

The goal of this project was to characterize the taxonomic and functional diversity and document biogeographic patterns of microbial communities in an ecosystem influenced by active serpentinization. Serpentinization is a geochemical process which occurs when ultramafic rocks characteristic of the Earth’s mantle undergo aqueous alteration to produce altered mineral compositions (referred to as serpentines). This reaction results in highly-reduced, high pH fluids enriched in hydrogen, methane, and small organic acids, and depleted in dissolved carbonate. Serpentinization is common in environments such as slow-spreading mid-ocean ridges, where tectonic activity on the seafloor results in exposure of ultramafic rocks, and in ophiolites (sites where oceanic crust has been displaced onto continental margins). Environments associated with pervasive serpentinization tend to be anaerobic and highly alkaline (pH 10-12) and creates a range of unique niches for microbial colonization and diversification. While the process of serpentinization provides abundant fuels to support the growth of chemotrophic microorganisms, the highly alkaline, highly reducing environmental conditions challenge the limits of microbial physiology