The inter- and transdisciplinary project UBA-MoSEA utilizes high-resolution simulations with the 3D ecosystem model ERGOM-MOM to improve the assessment of eutrophication in the western Baltic Sea. On the one hand, causes for contradictory assessment results of the eutrophication indicators (nutrients and chlorophyll-a) are to be found in order to propose solutions for more reliable assessments in this area. As eutrophication is currently managed at many different levels, a harmonized approach between nutrient loads at the limnic-marine transfer point and the eutrophication status of the inner (EU-WFD) and outer coastal waters as well as the adjacent deep basins of the open Baltic Sea (EU-MSRL) will be investigated by a case study. In addition, the ability of the model to reproduce other indicators particularly relevant to shallow coastal waters, such as water transparency, will be investigated. Specifically for the proposed HELCOM indicator "shallow water oxygen", the model products are used to provide a better basis for the assessment of the indicator. Here, the provisional target and threshold values of the indicator need to be critically reviewed. The results generated by the model will be regularly discussed with national authorities (UBA, LUNG, LfU) in order to develop application-oriented solutions for improved water quality management in the western Baltic Sea.