This supporting material provides detailed methods and additional information for the study of manganese- and iron-dependent marine methane oxidation. The study was conducted using sediment samples from the Eel River Basin, collected during two cruises in 2005 and 2006. The samples were stored under anaerobic conditions and used for various experiments involving different electron acceptors such as sulfate, birnessite, ferrihydrite, nitrate, and ferric oxyhydroxide. Artificial seawater was prepared and used to incubate the sediments, with methane added to the headspace. The incubations were monitored for up to 10 months, with regular measurements of dissolved manganese and iron concentrations. Free energy calculations were performed to estimate the thermodynamic conditions under which methane oxidation occurs. Phylogenetic analysis of bacterial and archaeal clones was conducted to identify potential participants in the methane oxidation process. The study also discusses the potential contributions of aeolian dust and hydrothermal vents to the input of manganese and iron into the Eel River Basin, highlighting the significant role of these sources in methane oxidation.This supporting material provides detailed methods and additional information for the study of manganese- and iron-dependent marine methane oxidation. The study was conducted using sediment samples from the Eel River Basin, collected during two cruises in 2005 and 2006. The samples were stored under anaerobic conditions and used for various experiments involving different electron acceptors such as sulfate, birnessite, ferrihydrite, nitrate, and ferric oxyhydroxide. Artificial seawater was prepared and used to incubate the sediments, with methane added to the headspace. The incubations were monitored for up to 10 months, with regular measurements of dissolved manganese and iron concentrations. Free energy calculations were performed to estimate the thermodynamic conditions under which methane oxidation occurs. Phylogenetic analysis of bacterial and archaeal clones was conducted to identify potential participants in the methane oxidation process. The study also discusses the potential contributions of aeolian dust and hydrothermal vents to the input of manganese and iron into the Eel River Basin, highlighting the significant role of these sources in methane oxidation.