Comparative assessment of a restored and natural wetland using 13C-DNA SIP reveals a higher potential for methane production in the restored wetland

Authors: HAMOVIT, N - University Of Maryland; ROYCHOWDHURY, T - Woodwell Climate Research Center; AKOB, D - Us Geological Survey (USGS); Zhang, Xuesong; McCarty, Gregory; YARWOOD, S - University Of Maryland

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/21/2025
Publication Date: 2/14/2025
Citation: Hamovit, N., Roychowdhury, T., Akob, D., Zhang, X., Mccarty, G.W., Yarwood, S. 2025. Comparative assessment of a restored and natural wetland using 13C-DNA SIP reveals a higher potential for methane production in the restored wetland. Applied and Environmental Microbiology. 91(3). https://doi.org/10.1128/aem.02161-24.
DOI: https://doi.org/10.1128/aem.02161-24

Interpretive Summary: Natural and restored wetlands can be a significant source of methane emissions within agricultural landscapes and understanding the biological controls on emissions of this potent greenhouse gas is important for controlling impacts of agriculture on global warming. We assessed the activities of methane generating microorganisms in natural and restored wetland soils using advanced stable isotope labeling and microbial population characterization. We found that restored wetlands had more active methane producing microbial populations than those of natural wetlands. This work suggests that wetland restoration approaches may need modification to reduce the methane emission potentials from agroecosystems.

Technical Abstract: Wetlands are the largest natural source of methane (CH4), a potent greenhouse gas produced by methanogens. Methanogenesis rates are controlled by environmental factors such as redox potential, temperature, and carbon and electron acceptor availability and are presumably dependent on the composition of the active methanogen community. We collected intact soil cores from a restored and natural freshwater depressional wetland on Maryland’s Delmarva Peninsula (USA) to assess the effects of wetland restoration and redox shifts on microbial processes. Intact soil cores were incubated under either saturated (anoxic) or unsaturated (oxic) conditions and amended with 13C-acetate for quantitative stable isotope probing (qSIP) of the 16S rRNA gene. Restored wetland cores supported a distinct community of methanogens compared to natural cores, and acetoclastic methanogens putatively identified in the genus Methanosarcina were among the most abundant taxa in restored anoxic and oxic cores. The active microbial communities in the restored wetland cores were also distinguished by the unique presence of facultatively anaerobic bacteria belonging to the orders Firmicutes and Bacteroidetes. In natural wetland incubations, methanogen populations were not among the most abundant taxa, and these communities were instead distinguished by the unique presence of aerobic bacteria in the phyla Acidobacteria, Actinobacteria, and class Alphaproteobacteria. Iron-reducing bacteria, in the genus Geobacter, were active across all redox conditions in both the restored and the natural cores, except the natural oxic–anoxic condition. These findings suggest an overall higher potential for methanogenesis in the restored wetland site compared to the natural wetland site, even when there is evidence of Fe reduction.