John Wiley & Sons, Ltd.

Effects of environmentally realistic daily temperature variation on pesticide toxicity to aquatic invertebrates

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Toxicity of several agricultural chemicals to aquatic invertebrates has been shown to be temperature dependent, but the role of daily temperature variation has rarely been examined. We simulated a natural daily temperature pattern (a fluctuating cycle of 21 to 31 °C over a 24 h period) based on field‐collected data from Southern High Plains wetlands and have conducted a series of experiments comparing responses from this exposure scenario to a constant 24 ± 1 °C exposure. Results indicate alterations in pesticide toxicity under the fluctuating temperature regime compared to the constant temperature exposure. There was a significant interaction of temperature regime and bifenthrin on Chironomus dilutus survival and C. dilutus ash‐free dry mass was lower in the fluctuating temperature treatment. The 10 d median lethal concentration (LC50) for Hyalella azteca exposed to chlorothalonil was lower under the fluctuating temperature regime compared to the constant temperature regime. For Daphnia magna exposed to malathion, main effects of temperature regime and malathion were observed on cholinesterase (ChE) activity. This study demonstrates how environmentally relevant daily temperature variation influences contaminant effects on aquatic invertebrates. Environ Toxicol Chem © 2013 SETAC

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