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Chronic toxicity of the bromoxynil formulation Buctril® to Daphnia magna exposed continuously and intermittently

Kevin J. Buhl·Steven J. Hamilton·James C. Schmulbach
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Abstract

Two chronic toxicity tests were conducted in which Daphnia magna were either continuously or intermittently exposed to bromoxynil octanoate (BO; as Buctril ® ) for 28 d. In the intermittent exposure test, daphnids were exposed to daily pulses of BO with 24-h mean concentrations equal to those in the continuous exposure test, and the peak concentrations were three times the 24-h mean values. After 28 d of continuous exposure to BO, survival of daphnids was reduced at 80 μg/L, whereas mean number of young per adult, intrinsic rate of natural increase, and mean weight of adults were all reduced at ⩾40 μg/L. Intermittent exposures to daily pulses of BO for 28 d caused reduced survival of daphnids at 24-h mean concentrations ⩾40 μg/L and reduced mean number of young per adult, intrinsic rate of natural increase, and mean weight of adults at 24-h mean concentrations ⩾20 μg/L. The estimated geometric mean-maximum acceptable toxicant concentrations of BO based on 24-h mean nominal values were 28 μg/L for continuous exposures and 14 μg/L for intermittent exposures. These results demonstrated that continuous-exposure studies may not be adequate in assessing herbicide toxicity to aquatic biota when concentrations fluctuate temporally.

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Kevin J. Buhl, Steven J. Hamilton, James C. Schmulbach. 1993. Chronic toxicity of the bromoxynil formulation Buctril® to Daphnia magna exposed continuously and intermittently. https://doi.org/10.1007/bf00212126

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