Comparative bioaccumulation of mercury in two adjacent freshwater ecosystems

Mercury levels were determined in sediments, clams and representative fish species in two adjacent uncontaminated waterbodies situated on the Ontario Precambrian Shield. Food chain biomagnification of mercury occurred within both ecosystems. Significantly higher mercury levels were observed in most species resident in Tadenac Lake than in Tadenac Bay. For example, mean length adjusted fish mercury levels in Tadenac Lake and Tadenac Bay, respectively, were: smelt, 0.26 and 0.12 μg g −1; rockbass, 0.34 and 0.18 μg g −1; yellow perch, 0.29 and 0.12 μg g −1; smallmouth bass, 0.55 and 0.25 μg g −1 and northern pike 0.86 and 0.38 μg g −1. The observed differences in fish mercury levels between the two sites cannot be explained in terms of differences in fish growth rates, lake trophic status or fish selenium levels, but appeared to be related to sediment mercury levels and ambient water quality.