Carbon and Sulfur Cycling in Prairie Pothole Wetland Sediments

This study aimed to provide the first information on coupled geochemistry and microbial communities in wetland sediments from the largest wetland ecosystem in the US, the Prairie Pothole Region (PPR). Wetlands in this region contain one of the highest concentrations of dissolved organic carbon (DOC) ever measured in freshwater systems and abundant sulfur (~ 20 mM sulfate, 6mM sulfide, and other sulfur species). The two analyzed wetlands are involved in massive methane fluxes (up to 162 mg methane/m2/hour in P7) and sustain sulfate reduction rates up to 22 umol sulfate/cm3/day. We used these 16S rRNA gene data to infer key microbial players in carbon and sulfur processing and to investigate why such active sulfate reduction did not inhibit methanogenesis. Abundant DOC and putative methanogens that utilize non-competitive substrates provide distinct mechanisms for bypassing thermodynamic inhibition. This work suggested that the PPR might play a unrecognized role in carbon mineralization and methane emissions, characterizing this wetlands as biogeochemical hotspots.