##The International Joint Commission Plan 2014 guidelines for water level alteration at the Moses-Saunders power dam will likely mobilize hydric wetland soils and associated sediment into the nearshore of the St. Lawrence River. Given the legacy deposition of Hg and sulfur, as well as abundant organic matter and phosphorus sequestered by Typha, we predict that mercury-methylating microbes (MMMs) will play a major role in Hg cycling, and mobilization, in this region. Four wetland types were compared (barrier beaches, drowned river mouths, protected embayments and open embayments) to assess the presence of MMMs. Amplicon sequencing (16S rRNA) was used to investigate overall microbial diversity in these hydric soils, as well as targeted analysis of three major clades of known and predicted MMMs (viz., sulfate-reducing Deltaproteobacteria, Firmicutes and methanogenic Archaea). We find that wetland type was not a good predictor of microbial diversity, and we detected MMMs from all three clades in all of the samples we tested. Future studies are aimed at determining MMM activity in relation to redox status of hydric soils, which is related to water level management.