Volatiles in submarine environments: Food for life

The recent recognition of a potentially vast, as yet unexplored hot microbial biosphere associated with active volcanism along the global mid-ocean ridge spreading center system has fundamentally shifted concepts of how planets and life may co-evolve. Central to this evolution is the transport of volatiles from the mantle to the hydrosphere because C-O-H-S fluids play a critical role in sustaining microbial communities in warm, porous subsurface and near vent environments. Although volatiles are critical to life forming processes and strongly influence formation of the oceanic crust, there is much yet to be discovered about their composition, evolution, and distribution in these dynamic environments. In this paper we present an overview of volatiles in the rock-and fluid-dominated portions of submarine environments and explore some of the linkages between geo-microbial processes. Questions are raised regarding the relative importance of microbial habitats sustained by volcanic activity and those supported by mantle systems in which exothermic serpentinization reactions drive fluid flow and generate fluids enriched in hydrogen, methane, and other hydrocarbons. The everchanging chemical and physical processes operating at the interfaces between the deep ocean and its underlying volcanically active crust make these ecosystems inherently difficult to study. Future advances in this research will require greater integration of microbiology and earth sciences.