The Darß-Zingst Bodden chain is a highly eutrophicated system even though phosphorus inputs were reduced 25 years ago. A long-term data set was analysed regarding phosphorus development in the system. A possible competition for phosphorus was analysed between submerged macrophytes and phytoplankton. This thesis reveals that the catchment area still dominates the phosphorus transport into the system. Submerged macrophytes had less influence on phytoplankton than expected. A redevelopment of the catchment area is favourable before considering restoring actions.<eng>