title: High rates of anaerobic methane oxidation in freshwater wetlands reduce potential atmospheric methane emissions.
abstract: 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 (13)C 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.
authors.affiliation: Department of Marine Sciences, University of Georgia, Athens, Georgia 30602, USA.
authors.forename: K E A
authors.initials: KE
authors.lastname: Segarra
authors.affiliation: MARUM Center for Marine Environmental Sciences and Department of Geosciences, University of Bremen, Bremen 28359, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Schubotz
authors.affiliation: Department of Marine Sciences, University of Georgia, Athens, Georgia 30602, USA.
authors.forename: V
authors.initials: V
authors.lastname: Samarkin
authors.affiliation: MARUM Center for Marine Environmental Sciences and Department of Geosciences, University of Bremen, Bremen 28359, Germany.
authors.forename: M Y
authors.initials: MY
authors.lastname: Yoshinaga
authors.affiliation: MARUM Center for Marine Environmental Sciences and Department of Geosciences, University of Bremen, Bremen 28359, Germany.
authors.forename: K-U
authors.initials: KU
authors.lastname: Hinrichs
authors.affiliation: Department of Marine Sciences, University of Georgia, Athens, Georgia 30602, USA.
authors.forename: S B
authors.initials: SB
authors.lastname: Joye
mesh_terms: D000393:Air Pollutants / Q000737:chemistry / Q000378:metabolism*; D000693:Anaerobiosis; D002247:Carbon Isotopes; D005431:Florida; D005618:Fresh Water; D005845:Georgia; D008281:Maine; D008697:Methane / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D053833:Wetlands
chemical_list: D000393:Air Pollutants; D002247:Carbon Isotopes; D008697:Methane