Models of circumpolar mercury (Hg) storage indicate that the Hudson Bay Lowlands (Canada�s largest wetland) stores a significant amount of Hg (>150 mg Hg m-2) in the top 0-300 cm of the soil profile. Mercury is a chemical of concern as it speciates into organic methylmercury (MeHg), a neurotoxin that bioaccumulates and biomagnifies in aquatic ecosystems. This research seeks to: 1) understand the spatial distribution of total Hg (THg) and MeHg in continuous permafrost of the HBL; and 2) explore the impacts of permafrost thaw on microbial MeHg production in thawing environments. To assess THg distribution in the HBL, we collected 50 peat cores from 39 locations across the HBL, and analyzed subsamples for THg using a Milestone DMA-80 (n=980). To assess the impacts of permafrost thaw, we collected samples from palsas and peat plateaus (abundant permafrost features in the HBL) and newly thawed thermokarst fens (n = 188). Samples were analysed for MeHg concentrations following USEPA 1630, and microbial community structure was examined using 16s rRNA gene amplification and sequencing from soil eDNA. We found that Hg storage in the region was significantly lower than modelled estimates, with 9.23�1.65 mg Hg m-2 (mean�SD). Concentrations of THg were significantly higher in permafrost features compared to bogs, fens, and thermokarst fens, and MeHg was significantly higher (p <0.001) in subsamples from thermokarst fens. There was significant variation in microbial community structure between active layer, permafrost, and thermokarst environments, which potentially relates to higher MeHg concentrations in thermokarst fens.