Acknowledgements
Analyses of abundances of phytoplankton and species of the order of Prymnesiales (Haptophyta) were financed by the Marine Monitoring Program of the Swedish Environmental Protection Agency. Surveys of nesting eiders in colonies in Sweden, Finland, Denmark and Estonia were performed as parts of different monitoring and research projects. Surveys on Gotland were financially supported by Nord Stream AG. Studies at Utklippan were financially supported by the County Administrative Board of Blekinge. Surveys in Estonia were financially supported by the State Environmental Monitoring Programme of the Estonian Ministry of Environment. The studies on Ertholmene were financed by Christiansö Fieldstation. For surveys at Tvärminne we thank Markus Öst and the Aronia eider team, Tvärminne Zoological station, and the LTER Welfin-site. The final analysis was financially supported by a research grant from Nord Stream AG to Gotland University and K. Larsson. We thank J. C. Coulson and an anonymous reviewer for their valuable comments on the manuscript.