Long-Term Effects of Common Pesticides on Aquatic Species

16 November 2015

New research indicates that commonly-used insecticide mixtures continue to impact aquatic invertebrate species over multiple weeks, even when the chemicals are no longer detectable in water.

Through experiments meant to generally reflect runoff from a multiple-homeowner watershed, investigators found that pesticide mixtures had negative effects on the abundance of certain snails, water fleas, and crustaceans. “The effects we observed indicate that many species were affected at a sublethal level,” said Dr. Simone Hasenbein, lead author of the Environmental Toxicology & Chemistry study. “Thus, populations exposed to low concentrations of pesticides could be even more sensitive to other abiotic or biotic factors such as invasive species, or changes in salinity or temperature leading to a magnification of multi-stressor situations.” Access the press release:

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Full bibliographic information
Hasenbein, S., Lawler, S. P., Geist, J. and Connon, R. E. (2015), A long-term assessment of pesticide mixture effects on aquatic invertebrate communities.
Environ Toxicol Chem. doi:10.1002/etc.3187
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To understand the potential effects of pesticide mixtures on aquatic ecosystems, studies that incorporate increased ecological relevance are crucial. Using outdoor mesocosms, the authors examined long-term effects on aquatic invertebrate communities of tertiary mixtures of commonly used pesticides: 2 pyrethroids (permethrin, λ-cyhalothrin) and an organophosphate (chlorpyrifos). Application scenarios were based on environmentally relevant concentrations and stepwise increases of lethal concentrations from 10% (LC10) to 50% (LC50) based on laboratory tests on Hyalella azteca andChironomus dilutus; repeated applications were meant to generally reflect runoff events in a multiple-grower or homeowner watershed. Pyrethroids rapidly dissipated from the water column, whereas chlorpyrifos was detectable even 6wk after application. Twelve of 15 macroinvertebrate and 10 of 16 zooplankton taxa responded to contaminant exposures. The most sensitive taxa were the snail Radix sp., the amphipod H. azteca, the water flea Daphnia magna, and copepods. Environmentally relevant concentrations had acute effects on D. magna andH. azteca (occurring 24h after application), whereas lag times were more pronounced in Radixsp. snails and copepods, indicating chronic sublethal responses. Greatest effects on zooplankton communities were observed in environmentally relevant concentration treatments. The results indicate that insecticide mixtures continue to impact natural systems over multiple weeks, even when no longer detectable in water and bound to particles. Combinations of indirect and direct effects caused consequences across multiple trophic levels.

Environ Toxicol Chem 2015;9999:1–15.
© 2015 SETAC