The general scientific objectives of SESAME (Southern European Seas: Assessing and Modelling Ecosystem Changes ) are to assess and predict changes in the Mediterranean and Black Sea ecosystems as well as changes in the ability of these ecosystems to provide goods and services. The Mediterranean and Black Sea will be approached as a coupled climatic/ecosystem entity, with links and feedbacks to the world ocean. The assessment of ecosystem changes will be based on the identification of the major regime shifts in ecosystems that occurred during the last 50 years. Mathematical models, validated and upgraded using existing and new observations, will be used to predict ecosystem responses to changes in climate and anthropogenic forcing during the next five decades.