Nutrient accumulation and nutrient retention in coastal waters – 30 years investigation in the Darss‐Zingst Bodden chain

Coastal waters are transitional zones between limnic waters and marine systems. The anthropogenic impact on these water bodies is high and a rapid change of trophic level was observed within the last 50 years. In the Darss-Zingst Bodden chain (southern Baltic Sea - Mecklenburg-West Pomerania, Germany), the change in trophic state during the last thirty years can be reconstructed by long-term monitoring of chemical, hydrographical and biological parameters with an up to daily resolution. Until the 1980s, increased input of the anthropogenic nutrient load from the catchment area has been documented. However, with the implementation of the HELCOM recommendations the input of phosphorus and nitrogen was reduced in the 1990s. In contrast to the reduction of nutrient inputs, a decrease in nutrient concentrations and primary production could not be observed. The reasons are a high internal nutrient load and the release of nutrients out of the sediments. Numerous research projects allowed the description and quantification of these processes. Today, the internal phosphorus pool exceeds the external phosphorus load several fold. These results are the scientific basis for the development of restoration strategies of coastal waters. The development of suitable management plans is necessary for the implementation of the EU Water Framework Directive to guarantee a good ecological state by 2015. The long time acquisition of monitoring data and voluminous complementary specific research projects was enabled by the local field research conditions of the Biological Station of the University of Rostock in Zingst.