Methylmercury Production in Two Northern Fen Peatlands

Northern peatlands provide conditions favourable for sulphate reducing bacteria, microorganisms responsible for producing methylmercury, an aquatic pollutant. An expected climate driven shift from moss- to sedge-dominance may alter mercury biogeochemistry. Observations from a moss-dominated poor fen and sedge-dominated intermediate fen were used to compare methylmercury to assess if contrasting plant communities, nutrients status and/or hydrologic regime control production. Chapter 2 compared porewater methylmercury and ancillary chemistry across two Northern Ontario fens. The lower water table, greater dissolved organic carbon, and lower pH in the poor fen resulted in 3.1 times greater methylmercury. Chapter 3, riparian zones in intermediate fen were evaluated to see if groundwater nutrient supply controlled methylmercury production and transport. Rather than groundwater supply, riparian zones with lower and greater water table fluctuations resulted in greater available sulphate and enhanced methylmercury. The proximity (≤ 2 m) of riparian zones to stream waters facilitated methylmercury transport to surface waters