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High rates of anaerobic methane oxidation in freshwater wetlands reduce potential atmospheric methane emissions

2015; Nature Portfolio; Volume: 6; Issue: 1 Linguagem: Inglês

10.1038/ncomms8477

2041-1723

Katherine Eowyn Segarra, Florence Schubotz, Vladimir A. Samarkin, Marcos Y. Yoshinaga, Kai‐Uwe Hinrichs, Samantha B. Joye,

Hydrocarbon exploration and reservoir analysis

The role of anaerobic oxidation of methane (AOM) in wetlands, the largest natural source of atmospheric methane, is poorly constrained. Here we report rates of microbially mediated AOM (average rate=20 nmol cm−3 per day) in three freshwater wetlands that span multiple biogeographical provinces. The observed AOM rates rival those in marine environments. Most AOM activity may have been coupled to sulphate reduction, but other electron acceptors remain feasible. Lipid biomarkers typically associated with anaerobic methane-oxidizing archaea were more enriched in 13C than those characteristic of marine systems, potentially due to distinct microbial metabolic pathways or dilution with heterotrophic isotope signals. On the basis of this extensive data set, AOM in freshwater wetlands may consume 200 Tg methane per year, reducing their potential methane emissions by over 50%. These findings challenge precepts surrounding wetland carbon cycling and demonstrate the environmental relevance of an anaerobic methane sink in ecosystems traditionally considered strong methane sources. Freshwater wetlands are among the largest natural sources of methane to the atmosphere. Here, the authors report rates of anaerobic methane oxidation which rival those in marine environments, highlighting the importance of a long-overlooked anaerobic methane sink.