Diverse methylotrophic methanogenic archaea cause high methane emissions from seagrass meadows

Significance Seagrass meadows colonize shallow coastlines around the world and represent sites of intense carbon cycling. Due to their capacity to produce methane, seagrass ecosystems constitute net sources of methane to the atmosphere. Here, we identify key processes and microorganisms responsible for methane formation in seagrass-covered sediments in the Mediterranean Sea. Our work shows that methane is solely formed from methylated compounds that are produced and released by the plant itself. Due to the persistence of these compounds in buried plant material, microbial methane production continues long after the death of the living plant. These results provide a comprehensive understanding of methane production in seagrass habitats, thereby contributing to our knowledge on these important blue carbon ecosystems.