Size-dependent sensitivity of stream amphipods indicates population-level responses to chemical pollution

Global change assessments have typically ignored synthetic chemical pollution, despite the rapid increase of pharmaceuticals, pesticides, and industrial chemicals in the environment. The paucity of research on the ecological effects of these ‘micropollutants’ undermines our efforts to address the freshwater biodiversity crisis. Understanding the responses of individual organisms to chemical pollution can help address this knowledge gap because individual-level effects can cascade across populations, communities, and ecosystems with devastating consequences.

Inputs of treated municipal wastewater are a major source of micropollutants in receiving environments. Here we assessed population and individual-level influences of treated wastewater on freshwater gammarid amphipods (Gammarus spp.) in Swiss lowland streams in situ and tested effects of a micropollutant mixture on individual G. fossarum using a common garden laboratory experiment. We hypothesised that population-level effects of...