Environmental contaminants in Texas, USA, wetland reptiles: Evaluation using blood samples

Four species of reptiles (diamondback water snake [Nerodia rhombifer], blot ched water snake [N. erythrogaster], cottonmouth [Agkistrodon piscivorus], and red-eared slider [Trachemys scripta]) were collected at two contaminate d and three reference sites in Texas, USA. Old River Slough has received in tensive applications of agricultural chemicals since the 1950s. Municipal L ake received industrial arsenic wastes continuously from 1940 to 1993. Bloo d samples were analyzed for organochlorines, potentially toxic elements, ge netic damage, and plasma cholinesterase (ChE). Dichlorodiphenyldichloroethy lene (DDE) concentrations reached as high as 3.0 ppm (wet weight) in whole blood of a diamondback water snake at Old River Slough, a level probably ro ughly equivalent to the maximum concentration found in plasma of peregrine falcons (Falco peregrinus) in 1978 to 1979 when DDE peaked in this sensitiv e species. Possible impacts on diamondback water snakes are unknown, but at least one diamondback water snake was gravid when captured, indicating act ive reproduction. Arsenic was not found in red-eared sliders (only species sampled) from Municipal Lake. Red-eared sliders of both sexes at Old River Slough showed declining levels of ChE with increasing mass, suggesting a li fe-long decrease of ChE levels. Possible negative population consequences a re unknown, but no evidence was found in body condition (mass relative to c arapace length) that red-eared sliders at either contaminated site were har med.