Ecological Impacts of Popular Insecticide are Exacerbated by Stream Bed Sedimentation

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Author(s): Ana Chara-Serna &
John Richardson
Published in: Ecological Applications (January, 2018)

Chlorpyrifos interacts with other agricultural stressors to alter stream communities in laboratory microcosms

Sedimentation, nutrient enrichment, and insecticide pollution are some of the most pervasive stream ecosystem stressors associated with agriculture. However, despite their common co-occurrence, there is little information about their cumulative impacts on stream communities. We experimentally evaluated individual and combined effects of a popular insecticide (chlorpyrifos), nutrient enrichment, and sedimentation on stream invertebrate communities and ecosystem function. We found that sedimentation was the most detrimental stressor, with significant negative impacts on invertebrate communities and ecosystem processes. Even though chlorpyrifos alone did not cause significant invertebrate mortality, it still altered ecosystem functioning by lowering leaf decomposition rates. Furthermore, we observed that chlorpyrifos and sedimentation exacerbated each other’s impacts, as their combined effects were greater than the sum of their individual effects (abundance of small-sized invertebrates in sediment + insecticide treatment was 2.4 times lower than predicted by additivity). Our findings suggest that complex interactions among simultaneous disturbances may have unexpected, negative effects on aquatic life. Consideration of these potential interactions is important to protect freshwater ecosystems in agricultural landscapes.

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