Multiple human-induced environmental stressors pose a major threat to global biodiversity and ecosystem functioning. Climate change and chemical pollution are two widespread stressors whose impact on freshwaters is likely to increase. We currently lack data and unified framework to predict responses of freshwater ecosystems to these combined stressors. To fill this knowledge gap, we used laboratory and mesocosm experiments to understand how commonly found pharmaceutically active compounds (PhACs) and pesticides affect whole ecosystems and energy flow in communities in small standing waters. Moreover, we explored if expected climate warming alters the presumed negative effects of anthropogenic pollution. We focused on three levels of organization that may affect ecosystems and the services they provide: (1) changes in community composition and ecosystem functioning that we linked to (2) changes in species interactions, and (3) alterations of individual physiology and behaviour. We collaborated on this project with the LECHB laboratory at the Faculty of Fisheries and Protection of Waters led by Prof. Tomáš Randák.