This audit focused on whether Environment and Climate Change Canada and Agriculture and Agri-Food Canada took a coordinated and risk-based approach to reduce the impact of excess nutrients on ecosystem health in selected Canadian water basins. Our audit examined 3 water basins: Lake Erie, Lake Winnipeg, and Wolastoq, Saint John River. We selected these 3 water basins in part because they cross international or interprovincial borders and because each basin has significant or emerging harmful and nuisance algal blooms.