Every day, more microplastics (< 5 mm) are introduced into the aquatic environment, but where do they end up and do they influence natural processes? Increasing microplastic concentrations threaten ecosystems and the navigability of our waterways, as microplastics likely increase the settling of sediments by ‘gluing’ them together. This project will shed light on this aggregation process, by combining laboratory experiments, field studies and computer models. Ports will be used as practical examples, as they are heavily polluted. The results will inform scientists, practitioners and politicians on how to tackle plastic pollution of our rivers, ports and seas.