Pesticides and Their Metabolites in Amphibian Spawning Waters Are Positively Associated with Nearby Arable Land

Pesticides pose risks to human health and the environment. Monitoring schemes often exclude small sites with fluctuating water levels, inhabited by many species, including amphibians. We sampled for pesticides and their metabolites in 68 amphibian spawning waters in Austria. We analyzed the number of pesticides and concentrations in relation to the surrounding land use. We tested for 165 pesticides and metabolites and found 54; 46% were herbicides. The median total pesticide concentration per site was 0.097 µg/L (range: 0–20.419 µg/L). Pesticides found were generally of lower toxicity. We calculated the pesticide toxicity for aquatic invertebrates, fish, birds, and mammals, as proxies for amphibians and the overall ecosystems. Arable land was associated with pesticide number, concentration and toxicity according to the Boruta model selection. However, due to highly variable concentrations (and therefore also variable toxicity) only pesticide number showed significances in a generalized linear model. In this model arable land was positively associated with the number of pesticides detected, while the proportion of grassland, scrubs, artificial surfaces and tree cover had negative effects according to the linear model. Our results highlight (i) a widespread contamination of small temporary water bodies, (ii) the presence of multiple pesticide residues (cocktails), commonly more harmful than single pesticides, at amphibian spawning waters. These results provide a basis for future studies investigating the effects of common pesticide combinations in controlled settings using realistic scenarios and enable better assessment of the potential risks to wildlife.