In this project we aim to identify the molecules in complex, realistic water samples (river water, waste water) that are responsible for ecotoxicity to aquatic organisms, including algae and cyanobacteria. This is not restricted to known chemicals, such as active pharmaceutical ingredients, but also their transformation products.  It will not only focus on individual effects of single molecules but also combinations (mixtures) of multiple molecules, also considering heavy metals where relevant. To this end, we will combine effect-based monitoring and effect-directed analysis techniques with high-throughput ecotoxicological assays.