Anaerobic methane oxidation by manganese oxides - a new pathway for methane removal in marine sediments

This experiment aims at providing evidence for the coupling of the microbial oxidation of methane (CH4) to the reduction of Mn (oxyhydr)oxides (Mn-AOM) in marine sediments. Increased release of CH4 from marine sediments is a possible feedback mechanism of global warming and Mn-AOM is a potential pathway to prevent the escape of CH4 from the sediments, which has not been recognized so far. We plan to collect Mn and Fe XAS spectra of sediment samples for field sites where geochemical profiles suggest the occurrence of Mn-AOM and of sediment samples from incubation experiments, in which addition of Mn oxides increased CH4 oxidation. XAS analyses are expected to demonstrate that Mn-(oxyhydr)oxides (MnOx) are available in the sediment and that the oxidation of CH4 coincides with their reduction. Demonstrating that CH4 oxidation and Mn reduction are coupled in these sediments will provide strong evidence for the existence of Mn-AOM in marine systems.