The role of aquaculture in the eutrophication process of the Archipelago Sea, SW Finland

Summary

Eutrophication is the most severe environmental problem in the Archipelago Sea, SW Finland, as in the whole Baltic Sea. Over 80% of the total fish (rainbow trout, Oncorhynchus mykiss) farming of Finland occurs in its south-western coastal areas, and therefore it is often assumed that aquaculture is an important nutrient source. Although previous works have revealed that fish forming contributes only 8% of total phosphorus load and 2% of nitrogen, their relative importance remains unclear. Local studies extend the knowledge of the impacts of fish forming. Results clearly show that the methods used in monitoring are often poor, which is the main reason for the interpretation of ‘no effects’. However, local effects may be obvious if one conducts the appropriate analyses. Plankton, periphyton and sediment analyses are recommended, since changes in biota most accurately predict the potential changes at different trophic levels.