daNUbs - Nutrient Management in the Danube Basin and its Impact on the Black Sea

This report contains the scientific results of the daNUbs - Nutrient management in the danube basin and its impact on the black sea -project. This project links the emissions of nutrients from the sources (e.g. agriculture, waste water disposal, etc.) to the impact on groundwater, surface waters and the marine ecosystems. The project concentrates on the Danube as the main contributor to the nutrient pollution of the Western Black Sea shelf. Nutrient emission, transport and transformation models for river basins were successfully linked to physical and biological models for the Western Black Sea shelf area influenced by the Danube. Nutrient modelling in selected case study areas allow a much better understanding of the detailed processes influencing nutrient storage, transport and losses (denitrification). Based on the modelling results nutrient management is changed as a result of which the situation in the North-Western Black Sea shallow waters has improved considerably:

• reduced eutrophication, (reduced phytoplankton biomass, frequency of blooms and extension of high chlorophyll area),
• considerable increase in water transparency
• improvement of near bottom oxygen regime,
• regeneration of phytoplankton species (Diatoms) diversity,
• regeneration of phytobenthos,
• regeneration of macrozoobenthos (increase of species number and diversity). Scenario calculations clearly show that the economic 64 in the Danube Basin may reverse the improving situation of the quality of the North-Western and Western Black Sea ecosystem, if nutrients are not managed properly. This methodological approach is applicable to other rivers and coastal system