Multiple stressors threatening the future of the Baltic Sea-Kattegat marine ecosystem: Implications for policy and management actions

- Multi-stressor effects can counteract abatement efforts in Baltic Sea.
- Strategies for setting environmental objectives in a changing climate are needed.
- Joint development of process understanding, modeling and monitoring is vital.

The paper discusses the combined effects of ocean acidification, eutrophication and climate change on the Baltic Sea and the implications for current management strategies. The scientific basis is built on results gathered in the BONUS+ projects Baltic-C and ECOSUPPORT. Model results indicate that the Baltic Sea is likely to be warmer, more hypoxic and more acidic in the future. At present management strategies are not taking into account temporal trends and potential ecosystem change due to warming and/or acidification, and therefore fulfilling the obligations specified within the Marine Strategy Framework Directive, OSPAR and HELCOM conventions and national environmental objectives may become significantly more difficult. The paper aims to provide a basis for a discussion on the effectiveness of current policy instruments and possible strategies for setting practical environmental objectives in a changing climate and with multiple stressors.