The central aim of the proposed Source to Sea (NAPSEA) CSA is to support national and local authorities in selecting effective nutrient load reduction measures and to gain political support for the implementation. The consortium partners have been closely involved in applied research and implementation of nutrient reduction measures at local, national and European level. In NAPSEA the current challenges to reduce nutrient pollution, eutrophication and its negative impacts on inland and coastal waters and their ecosystem services will be addressed by an integrated approach addressing nutrient pollution from river source to sea, using the Rhine and Elbe Rivers-North Sea coastal system as case study and integrating three complementary perspectives: governance, nutrient pathways & measures, and ecosystem health. Each of these perspectives provide an essential part of the solution to achieving a healthy ecosystem with measures that are societally acceptable and cost-effective. We will identify options to reach a harmonized approach in nutrient reduction measures across different geographical areas and policy frameworks (governance), select and evaluate nutrient reduction scenarios with an integrated modelling framework from source to sea (nutrient pathways) and define safe ecological boundaries for different types of ecosystems along the continuum from catchment to coast (ecosystem health). NAPSEA will showcase the best practices and consider obstacles on the implementation of socially acceptable, sustainable and effective measures for several local case studies within this geographical scope, also taking into account effects of climate change. These case studies accommodate the variability in potential threats of eutrophication as well as feasibility, effectiveness and implementation of potential measures to represent different ecosystem types, with varying eutrophication symptoms, and address different socio-economic and governance scales from local to European level.