Eutrophication and contaminants in aquatic ecosystems

Eutrophication and persistent pollutants are two of the main environmental problems in European marine and freshwater ecosystems. As they tend to co-o ccur, interactive processes between eutrophication and contaminants are sug gested, that may lead to environmental effects that cannot be predicted fro m each process alone. In order to predict the consequences of remedial meas ures (changing the input of organic matter, nutrients and contaminants) it is important to understand mechanisms that alter the bioavailability and fa te of contaminants. The environmental risks will depend on the speciation o f contaminants and their association to media and matter and by that means affect exposure. Furthermore, the risks will depend on the mobility of the substances and their pathways in food chains. In 1995, the Swedish Environm ental Protection Agency initiated a 5-year research program Interactions be tween EUtrophication and CONtaminants (EUCON). A background document was pr epared listing a number of relevant questions and hypotheses. On the basis of this document a program was launched, addressing the problems related to the interaction between eutrophication and contaminants (persistent organi c compounds and trace metals) in the marine environment, with focus on the Baltic Sea, and in lakes. This paper summarizes the state-of-the-art, hypot heses and highlights from the research program with emphasis on the implica tions and applications of the results.