Population status of freshwater turtles across a PCB contamination gradient

Remarkably few studies on the effects of PCBs on wild turtles have been conducted. We contrasted population-level parameters of 2 species of freshwater turtles, the snapping turtle Chelydra serpentina and the painted turtle Chrysemys picta, across a strong PCB concentration gradient in the upper Hudson River, New York State, USA. Our study employed standardized capture methods that yielded 465 turtles during 1968 trap-nights over 2 yr (2006 and 2007) at 246 trapping sites. Individuals of both turtle species were relatively heavier in a contaminated river segment, but PCB concentration did not otherwise influence relative abundance of turtles, probabilities of habitat occupancy or detection, sex or age ratios, body size, incidence of deformities, external parasite occurrence, or several movement parameters in a manner consistent with adverse impacts to wild turtles. This lack of spatial trend in parameters of wild populations of aquatic turtles across a strong gradient of PCB contamination contrasts with predictions of adverse impacts derived from population modeling, dose-response studies, and tissue residue analyses.