Consistent Effects of Pesticides on Community Structure and Ecosystem Function in Freshwater Systems

Predicting ecological effects of contaminants remains challenging because of the sheer number of chemicals and their ambiguous role in biodiversity-ecosystem function relationships. We evaluated responses of pond ecosystems to standardized concentrations of 12 pesticides, nested in four pesticide classes and two pesticide types. We show consistent effects of herbicides and insecticides on ecosystem function, but slightly less consistent effects on community composition. Effects of pesticides on ecosystem functions were often mediated by changes to biodiversity, and our analyses show that consistency in effects of pesticide types on functions was driven by functional redundancy among species. These results suggest that risk assessment of the thousands of registered chemicals on ecosystem responses could be simplified to a smaller number of chemical groups and to groups of functionally redundant taxa.