We examined the influence of maternal mercury and selected lacustrine variables on the mercury content of eggs from yellow perch (Perca flavescens). Total mercury, methylmercury, and inorganic mercury were determined in eggs and carcasses (less eggs) from three seepage lakes with a pH range of 6.1a??7.0 and a fourth lake in which pH was experimentally increased from 5.5 to 6.8 by addition of alkaline groundwater. The concentration of total mercury in eggs was strongly correlated with that in the maternal carcass. Concentrations and burdens of mercury in eggs and carcasses were inversely correlated with lake water pH, acid-neutralizing capacity, calcium, and dissolved organic carbon. In eggs containing more than 30 ng/g dry weight (4.5 ng/g wet weight) of total mercury, methylmercury averaged 91% of total mercury and ranged from 85% to 96%. Mean burdens of total mercury in individual eggs varied greatly among lakes (range, 2.3a??63 pg), and the egg mass averaged 1.9% of the whole-body burden. We conclude that exposure of the developing yellow perch embryo to methylmercury is strongly affected by maternal bioaccumulation, which can vary substantially among and within lakes; however, the toxicological significance of the observed exposure of embryos to methylmercury is unclear.
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Methylmercury content of eggs in yellow perch related to maternal exposure in four Wisconsin lakes