Methane Emissions across Aquatic Systems - From Headwater Streams to the Open Ocean

Aquatic systems are an important, but poorly constrained, source of methane (CH4) to the
atmosphere. The coastal ocean in particular has been insufficiently represented in global methane
budgets and assessments like the IPCC 5th report. Here, we present a new meta-analysis of CH4
emissions from the coastal ocean including inner estuaries, salt-marshes, mangroves, seagrass
meadows, tidal flats, aquaculture ponds, coral reefs and the continental shelf. Coastal ocean
emissions will be compared to those of the open ocean, and inland systems, including headwater streams, terrestrial permafrost thawing, rivers, lakes, natural ponds, reservoirs, non-tidal freshwater wetlands, and rice paddies. The main factors controlling CH4 emissions in different aquatic ecosystems, and research gaps, will also be discussed.