The evolvement of anaerobic oxidation of methane in fresh water sediments

Methane is a potent greenhouse gas that is produced naturally via microbial processes in anoxic environments (i.e. marine and lake sediments). The release of methane to the atmosphere from sediments is controlled by its aerobic and anaerobic oxidation. Anaerobic oxidation of methane (AOM) consumes up to 90% of the produced methane in marine sediments and over half of the produced methane in freshwater sediments. The most common electron acceptor in marine sediments for AOM is sulfate, however, in freshwater lake sediments, where sulfate concentrations are low, other electron acceptors can take its place (i.e. iron/manganese/nitrate). In lake Kinneret (Israel), iron-coupled AOM was evident by in-situ sedimentary profiles and in fresh sediment slurry incubations. Here we present geochemical and molecular analyses results of slurry experiments of long-term incubated lake Kinneret sediments with labeled 13C-methane, different potential electron acceptors and a few inhibitors. These experiments are part of an ongoing research to characterize the AOM processes in lake sediments, and indicate another possible type of AOM that has evolved in the long-term incubated lake sediments.