Modeling Mercury Mass Balances and Accumulation in Fish in Lakes of the Muskoka River Watershed

摘要

Mercury (Hg) levels in fish can vary considerably between remote lakes of a region. We hypothesize that Hg concentrations in fish are correlated with Hg loading to remote lakes of a large region, the Muskoka River tertiary watershed (MRW, 5000 km~2, 859 lakes). Dissolved organic carbon (DOC) mobilizes Hg in aquatic systems because Hg forms soluble complexes with the humic portion of DOC. Watershed spatial attributes derived through Geographic Information System (GIS) techniques have been linked with DOC mass balance models to create a lake DOC concentration prediction model for the MRW. The model has given good predictions of DOC compared to measurements (slope = 1.084, y-intercept = 0.493, r~2= 0.46, p<0.001). Using a published relationship between DOC and Hg fluxes, semi-empirical Hg mass balance models at the landscape level will be developed. About 500 fish, mostly young-of-the-year and yearling yellow perch and pumpkinseed, were collected from 15 lakes from July to September (2003) in the study area. Total Hg levels ranged from ca. 0.10 to 0.90 mu g g~(-1) dry weight (0.02 to 0.16 mu g g~(-1) wet weight). Adult fish Hg concentrations are also available for ca. 100 lakes in the MRW. Fish concentrations will be compared empirically with Hg inputs. This is a useful GIS-based approach to estimating Hg inputs to lakes from a small number of easily obtained parameters, and links to Hg levels in fish.