Aerobic oxidation of methane significantly reduces global diffusive methane emissions from shallow marine waters

Methane is supersaturated in surface seawater and shallow coastal waters dominate global ocean methane emissions to the atmosphere. Aerobic methane oxidation (MOx) can reduce atmospheric evasion, but the magnitude and control of MOx remain poorly understood. Here we investigate methane sources and fates in the East China Sea and map global MOx rates in shallow waters by training machine-learning models. We show methane is produced during methylphosphonate decomposition under phosphate-limiting conditions and sedimentary release is also source of methane. High MOx rates observed in these productive coastal waters are correlated with methanotrophic activity and biomass. By merging the measured MOx rates with methane concentrations and other variables from a global database, we predict MOx rates and estimate that half of methane, amounting to 1.8 +/- 2.7 Tg, is consumed annually in near-shore waters (<50 m), suggesting that aerobic methanotrophy is an important sink that significantly constrains global methane emissions. Aerobic oxidation is a biological sink of methane that can reduce oceanic emissions to the atmosphere. This study estimates that half of methane from total loss, amounting to 1.8 +/- 2.7 Tg, is oxidized annually in global 0-50 m near-shore waters

Automated summary

This study investigated methane sources and fates in the East China Sea and estimated the global rates of aerobic methane oxidation (MOx) in shallow waters using machine-learning models. The results showed that methane is produced during methylphosphonate decomposition and sedimentary release. High MOx rates were observed in productive coastal waters and were correlated with methanotrophic activity and biomass. The study estimated that aerobic methanotrophy can consume around half of the methane annually in near-shore waters, significantly reducing global methane emissions.