This ProBleu Science Story invites your class to explore how every part of an ecosystem is linked and how even small changes can create big ripple effects. Using eutrophication as a real-world example, pupils will uncover the complexity of aquatic systems and see why scientists rely on models to study them. The resource introduces different types of models (conceptual vs. simulation), what they are used for, and how they help us make sense of environmental challenges. Your students will also meet Professor Kevin Flynn, a plankton ecologist at Plymouth Marine Laboratory. In the accompanying video, Kevin explains his role as a scientist, explains how he uses models in his work, and walks through a hands-on simulation model designed specifically for schools, so your class can try ecosystem modelling for themselves.