Aerobic methane production in marine ecosystems

Oceans are considered significant methane sources, but the origin of methane in oxic surface seawaters remains unknown. Here, we collected seawater from the Jiulong River Estuary, Taiwan Strait, and Arctic Ocean to explore the potential for aerobic methane production. 13 C labeling experiments revealed that methylphosphonate‐based methane production widely occurs in marine ecosystems, with the methane conversion efficiency varying depending on local conditions (14.4% in the Taiwan Strait, 2.5% in the Arctic Ocean, and 0.3% in the Jiulong River Estuary). The potential for methane production from methylphosphonate could account for 3–60% of global oceanic methane emissions. Changes in the microbial composition during the incubation experiments indicated that Rhodobacterales can cleave C–P bonds to produce methane. In contrast, microbes did not directly break down C–S/N bonds. Our findings suggest that the microbial use of methylated compounds represents a potential source of methane in marine ecosystems.