Wet–dry cycles influence methylmercury concentrations in water in seasonal prairie wetland ponds

Methylmercury concentrations [MeHg] in whole water were measured 28 prairie wetland ponds central Saskatchewan between 2006 and 2012. Ponds fell into four land use categories (established grass, recent traditional cultivated, certified organic cultivated) two level patterns (“Mainly Wet” stayed wet at least until October “Mainly Dry” dried up each summer). Despite similar atmospheric Hg deposition, average proportion of total that was MeHg (%MeHg) higher from surrounded with established grass or farming; this trend may be driven by high one Organic site. A stronger relationship observed patterns. Average %MeHg significantly Mainly Wet compared to Dry ponds. Higher correlated much dissolved carbon (DOC) sulfate (SO 4 −2 ) specific UV absorbance DOC. We suggest not fit the accepted paradigm wetlands [SO ] show inhibition methylation. Our work suggests controls such as chemical nature DOC redox fluctuations hydrologically dynamic systems important determining net these sites.