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Schernewski, G., Neumann, T. , Opitz, D.,Venohr, M. : Long-term eutrophication history and ecosystem changes in a large Baltic river basin â estuarine system. Transit. Waters Bull., 5(2): 21- 49, 2011.


The Odra river basin, the Szczecin Lagoon and its coastal waters in the southern Baltic region cover an area of about 150,000 km². We apply a spatial integrative approach to analyze the eutrophication history and functional changes of this area between early 1960s and 2000s. For this purpose, a river basin model is linked to a coastal and marine 3D-hydrodynamic ecosystem model. Annual riverine nutrient loads increase from the 1960s until the mid 1980s to 110,000 t nitrogen (N) and 15,000 t phosphorus (P) and decrease afterwards, but show a strong inter-annual variability. The contribution and location of emission sources in the catchment change significantly during the investigated 40 years. Nutrient and chlorophyll concentrations in the estuary follow changes in riverine N loads quickly. Therefore, river basin management measures should focus on both, P and N. Strong spatial concentration gradients in the estuary are always present. Nutrient availability, N/P ratios as well as processes like denitrification and N fixation show spatial and temporal changes during the 40 years. In the lagoon, N fixation does not play an important role and riverine N load reductions are not compensated by increased N fixation. The lagoon’s quantitative N retention is stable over the 40 years. However, in the early 1960s, about 26% of the total N load into the lagoon is removed by denitrification, compared to only about 15% during 1999–2002.

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