Prairie wetland ponds that stay wet all summer tend to have higher concentrations of neurotoxic methylmercury
Climate change in the Great Plains of North America may increase variability in the duration that wetland ponds remain wet over the course of a summer.
These wet-dry cycles in turn influence the concentration of neurotoxic methylmercury (MeHg) that may be available to biota in these biodiverse systems.
We measured MeHg concentrations in unfiltered water from 28 prairie wetland ponds in central Saskatchewan between 2006 and 2012.
Read this open access paper on the FACETS website.
These ponds fell into two categories: “Mainly Wet” ponds which stayed wet at least until October and “Mainly Dry” ponds which dried up early each summer.
The ponds received similar inputs of atmospheric Hg; however, average MeHg concentrations were higher in water from ponds that were “Mainly Wet”.
These ponds also had elevated concentrations of dissolved organic carbon (DOC) and sulphate (SO4–2 ). In many freshwater systems, the relative amount of MeHg produced can be estimated by measuring the DOC and SO4–2 concentrations in the water and prairie wetland ponds to fit this trend.
However, many ponds with high concentrations SO4–2 tend to have low MeHg concentrations because the formation of sulphide may inhibit MeHg production.
Our prairie wetland ponds, therefore, may not fit this accepted paradigm because we do not observe lower MeHg concentrations in high SO4–2 wetland ponds.
If wet-dry cycles are disrupted in the prairies due to climate change, our work suggests that there may be implications to the amount of MeHg produced in these important systems.
Read the paper — Wet–dry cycles influence methylmercury concentrations in water in seasonal prairie wetland ponds by Britt D. Hall, Sichen Liu, Cameron G.J. Hoggarth, Lara M. Bates, Stacy A. Boczulak, Jamie D. Schmidt, and Andrew M. Ireson.
