unleak

Coastal marine sediments are thought to be a substantial source of methane to the overlying water, with the potential for escape through the shallow water column to the atmosphere. Such effluxes are reduced by the oxidation of methane by methanotrophic microorganisms in both aerobic and anaerobic conditions. In marine sediments the primary electron acceptors for methane oxidation are oxygen and sulfate, respectively. Much of the focus on methane oxidation has been on anaerobic methane oxidation due to the great abundance of sulfate in sea- and pore-water and the co-location of the electron acceptor (sulfate) and electron donor (methane). As a result, comparatively little attention has been given to situations wherein anaerobic methane oxidation is overwhelmed and 1) aerobic methane oxidation must account for significant methane oxidation and 2) methane escapes from sediment into the water column. We will address this topic through a combination of in situ flux and chemical gradient analysis, geochemistry, microbial rate analysis, and reactive transport modeling.