Integrated risk assessment approach for eutrophication in coastal waters: Case of Baltic Sea

Eutrophication of coastal ecosystems is a global and rapidly intensifying environmental crisis. Efficient strategies are in great demand to adapt changes to coastal ecosystems and enhance the management. This study proposes a flexible methodology for quantifying the risk status of coastal subbasins. The proposed method integrates the characteristics of both a strong multi-criteria analysis and fuzzy set theory. Central to this methodology is the construction of a risk index for revealing the extent of cumulated nutrients discharges. The proposed model is applied to assess risk status in the Baltic Sea, showing an increasing trend of risk index over the years. Results also show good agreement with field observations and Helsinki Commission (HELCOM) predictions ─ the Bothnian Bay is ranked as a ‘Medium’ risk area while the Bornholm Bay shows a ‘Very High’ risk of eutrophication. The proposed approach not only evaluates the risk degree of nutrients enrichment, but also captures the extent of exogeneous contributions for the given area, leading to better management recommendations to reduce eutrophication risk.