Methane is the second most important contributor to the global greenhouse effect. While emissions from anthropogenic sources are relatively well-constrained, natural sources such as aquatic environments, and in particular emissions from the coastal and open ocean, are insufficiently assessed in global methane budgets. To fill this knowledge gap, we need to better understand methane dynamics and underlying biogeochemical controls in marine aquatic systems including tidal freshwater wetlands, salt-marshes, mangroves, seagrass meadows, tidal flats, aquaculture ponds, tidal rivers, estuaries, coral reefs, continental margins and the open ocean. In this session we invite submissions related to methane production and consumption processes, methane transport mechanisms (diffusion, ebullition, upwelling), methane-associated biogeochemical reactions, microbial communities, fungi, and plant pathways, and other methane-related research of relevance to coastal and open ocean ecosystems under past, present and future climate. This session should be of interest to a range of scientific disciplines including chemical oceanographers, biogeochemists, microbiologists, organic chemists, ecologists, and atmospheric physicists.