Stoichiometric Responses to an Agricultural Pesticide Are Modified by Predator Cues.

Lizanne Janssens, Lin Op de Beeck, Robby Stoks

Environmental science & technology 2017 Jan 03

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Current ecological risk assessment of pesticides fails to protect aquatic ecosystem health. To get better insight in how pesticides may affect aquatic ecosystems, we tested how sublethal pesticide concentrations modify body stoichiometry. Moreover, as interactions with natural stressors may cause underestimates of the impact of pesticides, we also tested whether this pathway depended on the presence of predator cues. Therefore, we exposed damselfly larvae to chlorpyrifos and cues from predatory dragonflies and focused on body stoichiometry and associated explanatory variables (growth rate, RNA:DNA, and energy storage molecules). The way the predator cues modulated the pesticide effects strongly differed between endpoints. Exposure to chlorpyrifos affected the key body stoichiometric ratios: chlorpyrifos consistently increased N:P, while its effects on C:N (decrease with predator cues) and C:P (increase without predator cues) strongly depended upon the presence of the natural stressor. These stoichiometric responses could be explained by associated changes in growth, RNA:DNA, and in C-rich fat and sugars and N-rich proteins. The observed changes in body stoichiometry may affect the damselflies' food quality and have the potential to cascade through the food web and shape nutrient cycling.

Citation

Lizanne Janssens, Lin Op de Beeck, Robby Stoks. Stoichiometric Responses to an Agricultural Pesticide Are Modified by Predator Cues. Environmental science & technology. 2017 Jan 03;51(1):581-588