Abiotic hydrogen (H) sources and sinks near the Mid-Ocean Ridge (MOR) with implications for the subseafloor biosphere.

Free hydrogen (H) is a basal energy source underlying chemosynthetic activity within igneous ocean crust. In an attempt to systematically account for all H within young oceanic lithosphere (<10 Ma) near the Mid-Ocean Ridge (MOR), we construct a box model of this environment. Within this control volume, we assess abiotic H sources (∼6 × 10 mol H/y) and sinks (∼4 × 10 mol H/y) and then attribute the net difference (∼2 × 10 mol H/y) to microbial consumption in order to balance the H budget.