Title:

Microbial Community Drivers of Porewater Methane Concentrations in Arctic Peatland Thaw Ponds

Arctic peatlands experiencing permafrost thaw are subject to increased greenhouse gas emissions, which contributes to a positive feedback loop. In this study, we used the relative abundance of methanogens and methane fluxes at different ponds and depths to analyze the drivers of methanogenesis. We extracted DNA from soil sediment samples from Stordalen Mire in Sweden, filtered the relative abundance of methanogens, linked the methane concentrations at different depths to these abundances. With this data, we derived conclusions about how different environmental conditions, such as the presence of dissolved organic carbon (DOC), methanotrophs, and changing oxygen levels, correlate with the methane production. We determined that methanogenesis (an anaerobic process) is limited at shallow depths with sufficient DOC and high oxygen levels (leading to decreased production of methane) and is subsequently limited at deeper depths with decreasing DOC levels and low oxygen concentrations. This creates an optimal zone, with low oxygen levels and sufficient DOC, for methanogenesis to occur. Further, it was observed that greater methanogen relative abundance is not necessarily correlated with higher CH4 production. This provides an insight into the complex peatland ecosystem, and more analyses should be performed using DOC measurements, oxygen concentrations, and different groups of microbes.

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