Biogeochemical Consequences of the Sedimentary Subseafloor Biosphere

The water buried with sediment comprises by volume a substantial portion of the Earth's ocean. We explore the biogeochemical consequences of microbial activity in this subseafloor sedimentary ocean, the geochemistry of those sediments, and the overall biogeochemical cycles affecting the ocean. Biogeochemical processes resulting from deep subseafloor microbial activity, principally driven by organic carbon deposition and burial, leave a fundamental imprint on the interstitial water composition, the lithogenic and biogenic components of marine sediments, for example, the formation of diagenetic carbonate phases. Such non-steady state diagenetic formation of minerals and alteration of primary components by secondary reactions of metabolic products can reveal changes of the environmental conditions in the overlying water column over geological time. Furthermore, the long-term biogeochemical evolution of deep subseafloor sediment basins will expectedly affect the redox state of the ocean over geological timescales.