Name
The Relationship Between Dissolved Organic Carbon Fluorophores and Methylmercury Concentrations in Prairie Wetland Ponds
Description
Methylmercury (MeHg), a neurotoxic compound derived from inorganic mercury (IHg), is a toxin of global concern because MeHg bioaccumulates in aquatic food webs. Natural wetland systems are sites for microbial MeHg production and rates of production are controlled by many environmental variables. These controls are poorly understood in wetland ponds in the Prairie Pothole Region (PPR) of the North American Great Plains. One such control variable is the concentration and composition of dissolved organic carbon (DOC) which has shown to both enhance and inhibit MeHg production. State-of-the-art emission excitation matrices (EEM) analysis has resulted in a greater understanding of DOC composition and its associations with MeHg in freshwater systems. Our work examines MeHg-DOC dynamics at the St. Denis National Wildlife Area (SDNWA) in central Saskatchewan where wetland ponds contain high concentrations of DOC and MeHg. We examined changes in the optical characteristics of DOC in 11 ponds in the SDNWA over the open water season using EEMs generated from the Horiba Duetta spectrofluorometer. Parallel factor analysis identified relevant fluorophores indicative of the chemical characteristics of the DOC samples. The relation of DOC fluorophores to geochemical data were established using principal component analysis and regression. Climate change impacts DOC through increased UV radiation, temperature, and resulting photodegradation, and better understanding the current characteristics of DOC and associations with IHg methylation will help in determination of future risks. Changes in DOC characteristics this could also impact MeHg bioaccumulation. Future mitigation must be informed by a better understanding of the Hg cycle.