Impervious surface is not a strong predictor of contaminant accumulation in freshwater turtles in a rapidly urbanizing region

Abstract

Due to the relatively long lifespan and resilience of adults to environmental stressors, freshwater turtles are characterized as bioaccumulators of chronic contaminant exposure in urban ecosystems. Urbanization increases pollutants, resulting in subsequent runoff into streams. We evaluated the relationship between percent impervious surface and contaminant concentrations in turtles from 20 wetlands in Wake County, North Carolina, USA, one of the fastest-growing counties in the United States. We evaluated the concentrations of eight environmental contaminants known to cause human and environmental health issues listed under the U.S. Environmental Protection Agency's Resource Conservation and Recovery Act: arsenic (As), barium (Ba), cadmium (Cd), chromium (Cr), lead (Pb), mercury (Hg), selenium (Se), and silver (Ag), as well as vanadium (V) and copper (Cu) due to their presence in urban environments and bioaccumulation, in the blood and claws from Chelydra serpentina and Trachemys scripta. All contaminants, except for Cd and Ag, were detected in both species and both tissue types. Carnivorous Chelydra serpentina exhibited higher concentrations of Se and Hg than omnivorous Trachemys scripta. Partial redundancy analysis indicated that species accounted for more variance in the data than % impervious surface at a 2200-m scale. Robust mixed-effects models showed that % impervious surface was not correlated with contaminant concentrations in either species. Although we documented no relationship between urbanization and contaminant concentrations, we recommend additional research to investigate the effects of urbanization over time in this rapidly developing region.