PerspectiveAquatic Ecosystems

Pesticide impacts through aquatic food webs

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Science  01 Nov 2019:
Vol. 366, Issue 6465, pp. 566-567
DOI: 10.1126/science.aaz6436

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Summary

Testing chemicals for toxicity is straightforward, but detecting their effects at the population, community, or ecosystem level is exceedingly difficult. As one moves to higher levels of ecological organization, the number of confounding factors and compensatory mechanisms increases (1). Standardized, laboratory studies of pesticides, required by regulatory agencies, typically focus on the short-term effects of acute exposure to individual model organisms with the results scaled up mathematically to estimate long-term and indirect effects. However, long-term and ecosystem-scale ecological studies frequently show surprises and emergent phenomena that couldn't be predicted by extrapolating from results at smaller temporal, spatial, and organizational scales (2). To understand the long-term ecosystem impacts of contaminants, one must study entire ecosystems for a long time. On page 620 of this issue, Yamamuro et al. (3) have done just this, demonstrating that neonicotinoid pesticides can affect entire food webs. Much of what we know about indirect food web impacts of contaminants comes from studies of oil spills. However, even oil spills that release millions of barrels of crude oil can have weak or undetectable effects at the population or community level. The Deepwater Horizon spill—the largest in United States history—is a good example. Extensive studies of nearshore fish populations following the spill have found little evidence of declines (1, 4), despite known toxicity and exposure (5). Pesticides present a challenge similar to that of oil spills, but a different kind of exposure: a continued “press” disturbance as they are repeatedly added to the environment rather than the discrete “pulse” disturbance of a major oil spill.

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