Pesticide contamination of small standing water bodies in the agricultural landscape of northeast Germany

Lentic small water bodies (LSWBs) play a crucial role in global freshwater ecology. Despite their ecological importance, LSWBs are often overlooked in many conservation strategies and scientific studies. A key problem for these ecosystems is anthropogenic stress, in particular the intensive use of pesticides in agriculture. The present study aimed to investigate the extent and variability of pesticide pollution in LSWBs at large spatial and temporal scales. It aimed to identify which substances are frequently detected in these waters and which have the greatest ecotoxicological impact. The study identified eight common pesticides that were detected in low concentrations in many samples at the regional scale. Nine substances also exceeded regulatory acceptable concentration levels (RACs), indicating potential ecological risks. Nicosulfuron, a widely used herbicide in maize growing areas, posed a particular threat as it frequently exceeded its RACs and is persistent in both soil and water. The constant herbicide contamination over three years in LSWBs shown in this study will most likely lead to cascading ecosystem-level effects by changed trophic interactions and altered habitat quality. Other substances, such as chlorpyrifos and clothianidin are no longer used in agriculture, but still showed similar exceedances of RACs. The study emphasizes that LSWBs are particularly prone to continuous pesticide contamination leading to serious ecological consequences that cannot be detected by one-off sampling, which could hold equally true for LSWBs in other agricultural regions of Germany.