The central objective of this project is to explore the impacts of microplastics on Irish fresh water aquatic organisms and ecosystems. This knowledge can inform monitoring programmes and regulatory policy by identifying those microplastics that pose the biggest risks to the freshwater environment. Microplastics are plastic particles smaller than 5mm. These particles are widespread in seas and oceans, and their harmful effects on many different marine animals are well known. In contrast, we know relatively little about microplastics in fresh water: its sources, environmental fate, and biological impacts. Several large scale projects are currently working to develop monitoring technology for these plastic particles, as well as creating models to explain its spread and build-up for the marine environment. However, microplastics can vary greatly in chemical composition, size, shape and concentration, and may have different toxic effects under fresh water conditions. Therefore, more information is needed to identify those microplastics posing the biggest risk for fresh water species and the freshwater environment.