John Wiley & Sons, Ltd.

THE SPRING RUNOFF IN NEBRASKA'S ELKHORN RIVER WATERSHED AND ITS IMPACT ON TWO SENTINEL ORGANISMS

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The objectives of the present study were to determine 1) if temporal variability influenced the toxicity of Elkhorn River water and 2) if the toxic effect was consistent between two sentinel organisms, the fathead minnow (Pimephales promelas) and the northern leopard frog (Rana pipiens). During spring 2012, atrazine indicator strips were used to document the occurrence of agrichemical pulses in the Elkhorn River. Polar organic chemical integrative samplers (POCIS) were deployed for 14 d during both a pulse and post‐pulse period as indicated by the atrazine strips. Pesticide concentrations detected in the POCIS extracts ranged from 1.6 to 281 fold higher during the pulse period compared to the post‐pulse period. Fish and frog bioassays were conducted for 7 d, and hepatic mRNA expression of vitellogenin (Vtg) and estrogen receptor‐α (ERα) was determined by quantitative real‐time PCR (RT‐qPCR). Compared to lab water controls, fish exposed to water collected during an agrichemical pulse experienced significant reductions in Vtg and ERα, whereas exposed female frogs did not. Male leopard frogs, in contrast experienced significant increases in the expression of ERα, whereas pulse exposed male minnows did not. The significant effects observed following agrichemical pulse exposure demonstrate 1) that episodic agrichemical runoff adversely impacts sentinel organisms, and 2) that the adverse impacts observed depends upon the sex and species of the sentinel organism. Environ. Toxicol. Chem. © 2013 SETAC

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