Microplastics are a newly recognized type of environmental pollution in aquatic systems. This project assembles a multidisciplinary consortium of European experts from Germany, Sweden, Norway, and Belgium. Together, we are developing novel tools to study weathering of microplastics in a holistic manner. The toolbox includes analytical and (eco)toxicological methods, models and risk assessment. At ACESx, we focus on the ecological and ecotoxicological significance of biofilm growth on microplastics, its trophic transfer, and effects on consumers. We use state-of-the-art molecular and isotopic methods to trace plastic-associated microbiota in the laboratory experiments that will guide us in designing field surveys for microplastic transfer in food webs.