Patterns of mercury accumulation in northern Ontario walleye and relationship with watershed characteristics

Abstract

Mercury is a well known toxic contaminate that poses health risks to humans and wildlife. In Ontario 85% of consumption restrictions of fish from inland lakes is due to mercury contamination. The purpose of this study was to investigate the relationship between total mercury concentration in walleye and lake chemistry, watershed characteristics, and forest harvesting. Data from the Ministry of Natural Resources and Forestry Broad Scale Fisheries Monitoring Program, Land Information Ontario, and Ontario Land Cover 2000 were utilized for analysis in this study. Linear regressions showed that lake surface area (9.8%), total land area (6.1%), total forest area (4.1%), coniferous forest area (5.3%), dissolved organic carbon (8.9%), pH (16.4%), nitrate and nitrite (8.1%), and dissolved inorganic carbon (13.8%) had a significant relationship with total mercury. Further, multivariate regressions showed that lake surface area and coniferous forest area (13.3%), dissolved organic carbon and pH (23%), and dissolved organic carbon and nitrate and nitrite (12.6%) had a significant relationship with a higher R-square value. This study supports that lake chemistry variables and landscape variables including dissolved organic carbon, pH, nitrate and nitrite, dissolved inorganic carbon, coniferous forest area, total forest area, total land area, and total lake surface area played a larger role on the impacts on total mercury concentration in high predatory fish than harvest disturbance and wetlands within the watershed which showed no significant relationship with mercury concentrations.