The proposed CoBiOS project aims to integrate satellite products and ecological models into a really operational and user-relevant information service on high biomass blooms in Europe’s coastal waters. To this end CoBiOS will produce a harmonized and validated water transparency product based on satellite images for a large variety of coastal water types which will be used to force ecological models. While earth observation can provide information on the state of superficial algal blooms, the improved CoBiOS ecological models will make predictions on the fate of blooms, thus allowing assessment of e.g. the risks on hypoxia and dead zones. CoBiOS operates in overlapping model domains in the Northern part of Europe in order to derive uncertainty information from ensemble runs. During two extended trial runs and one operational demonstration phase the combined service will be demonstrated to groups of users and validated by a panel of key users. All facets of post-project sustainable commercial continuation of the services will be analysed in concert with the end-users. CoBiOS aims to make optimal use of MCS products and services and will provide feedback to this project.