Freshwater wetland sediments support substantial rates of anaerobic oxidation of methane (AOM)
Abstract
Freshwater wetlands are characterized by high rates of methanogenesis and are the single largest source of atmospheric methane. Anaerobic oxidation of methane (AOM), a previously underappreciated process in these systems, may be an important component in freshwater methane budgets. Here we report some of the first direct measurements of AOM in wetland sediments. We examined seasonal methane cycling within three freshwater wetlands (two peat wetlands and one tidal, freshwater creekbank) along the eastern coast of the US. Rates of AOM were high (up to 286 nmol per cubic cm per day) and varied on a seasonal basis. Despite low sulfate concentrations, rates of sulfate reduction were sufficient to support all the observed AOM activity, though rates of these two processes were not correlated. This study highlights the importance of AOM in freshwater sediments, where this process, in conjunction with sulfate reduction, may control emissions of methane to the atmosphere through competitive interactions with methanogens and the consumption of large fractions of the methane produced from acetate and hydrogen. The zone of maximum AOM activity was marked by enriched stable carbon isotopic signatures (δ13C) of methane and depleted signatures of DIC. However, the δ13C of archaeal and bacterial lipids were not indicative of methanotrophy. Studies that evaluate the role of AOM in wetlands using lipid and isotope-based approaches may therefore underestimate its importance.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.B24C..08S
- Keywords:
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- 0428 BIOGEOSCIENCES / Carbon cycling;
- 0465 BIOGEOSCIENCES / Microbiology: ecology;
- physiology and genomics;
- 0497 BIOGEOSCIENCES / Wetlands;
- 1615 GLOBAL CHANGE / Biogeochemical cycles;
- processes;
- and modeling