Polychlorinated Biphenyls and Organochlorine Pesticides in Plasma and the Embryonic Development in Lake Erie Water Snakes (Nerodia sipedon insularum) from Pelee Island, Ontario, Canada (1999)
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From three locations along a 34-km shoreline of Pelee Island, Ontario, 30 gravid female Lake Erie water snakes (Nerodia sipedon insularum) were sampled to determine the organochlorine (OC) contaminant levels in plasma and the number of live and dead embryos present in the body cavity. Plasma was analyzed for 59 polychlorinated biphenyl (PCB) congeners and 14 organochlorine pesticides. Concentrations of pesticides were low (≤0.1 ng/g wet wt) in all snakes, but there was significant variation in mean PCB concentrations in plasma from among the sampling locations on Pelee Island. Snakes (n = 5) from the West shore and dock area of the island had significantly higher PCB concentrations (90.4 ± 15.0 ng/g wet wt) in plasma than those from Lighthouse Point (n = 5; 34.4 ± 13 ng/g wet wt) and the south shore of the island (n = 5; 29.4 ± 16.3 ng/g wet wt). Body mass of the female snakes ranged from 252 to 880 g, and mean masses were not significantly different among sample sites. The number of live embryos found ranged from 13 to 46 female snakes and no dead embryos were detected. There were significant positive correlations among body mass, snout–vent length, and number of young per female. There were no significant correlations among body mass, snout–vent length, number of young per female, or per-gram body mass of female snakes and contaminant concentrations in plasma. It was concluded that an interim estimate of a no-effect level on embryonic survival in N. sipedon insularum may be a maximum average concentration of 90.4 ng/g wet wt PCBs and a maximum average concentration of 3.6 ng/g wet wt p,p′-dichloro-diphenyl-dichloroethylene in plasma.