Regulators of coastal wetland methane production and responses to simulated global change

TitleRegulators of coastal wetland methane production and responses to simulated global change
Publication TypeJournal Article
Year of Publication2017
AuthorsVizza, C., West W. E., Jones S. E., Hart J. A., and Lamberti G. A.
Number of Pages431-446
Date PublishedJan
Type of ArticleArticle
Reprint Number1726-4170
LTER Accession NumberWOS:000395167800004
Keywordselevated co2; saltwater intrusion; northern wetlands; natural wetlands;, Environmental Sciences & Ecology; Geology, fresh-water wetland; sulfate reduction; organic-carbon; climate-change;, salt-marsh; methanogenesis

Wetlands are the largest natural source of methane (CH4) emissions to the atmosphere, which vary along salinity and productivity gradients. Global change has the potential to reshape these gradients and therefore alter future contributions of wetlands to the global CH4 budget. Our study examined CH4 production along a natural salinity gradient in fully inundated coastal Alaska wetlands. In the laboratory, we incubated natural sediments to compare CH4 production rates between non-tidal freshwater and tidal brackish wetlands, and quantified the abundances of methanogens and sulfate-reducing bacteria in these ecosystems. We also simulated seawater intrusion and enhanced organic matter availability, which we predicted would have contrasting effects on coastal wetland CH4 production. Tidal brackish wetlands produced less CH4 than non-tidal freshwater wetlands probably due to high sulfate availability and generally higher abundances of sulfate-reducing bacteria, whereas non-tidal freshwater wetlands had significantly greater methanogen abundances. Seawater addition experiments with freshwater sediments, however, did not reduce CH4 production, perhaps because the 14-day incubation period was too short to elicit a shift in microbial communities. In contrast, increased organic matter enhanced CH4 production in 75% of the incubations, but this response depended on the macrophyte species added, with half of the species treatments having no significant effect. Our study suggests that CH4 production in coastal wetlands, and therefore their overall contribution to the global CH4 cycle, will be sensitive to increased organic matter availability and potentially seawater intrusion. To better predict future wetland contributions to the global CH4 budget, future studies and modeling efforts should investigate how multiple global change mechanisms will interact to impact CH4 dynamics.

URL<Go to ISI>://WOS:000395167800004
Print Copy LocationBiogeosciences