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Marine Ecology Progress Series

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MEPS 207:201-218 (2000)  -  doi:10.3354/meps207201

A long-term perspective on the Chrysochromulina bloom on the Norwegian Skagerrak coast 1988: a catastrophe or an innocent incident?

Jakob Gjøsæter1, Kyrre Lekve2, Nils Chr. Stenseth1,2,*, Hans Petter Leinaas2, Hartvig Christie3, Einar Dahl1, Didrik S. Danielssen1, Bente Edvardsen4, Frode Olsgard5, Eivind Oug6, Eystein Paasche4

1Institute of Marine Research, Flødevigen Marine Research Station, 4817 His, Norway
2Division of Zoology, Department of Biology, University of Oslo, PO Box 1050 Blindern, 0316 Oslo, Norway
3Norwegian Institute for Nature Research, PO Box 736 Sentrum, 0105 Oslo, Norway
4Section for Marine Botany, Department of Biology, University of Oslo, PO Box 1069 Blindern, 0316 Oslo, Norway
5Division of Marine Chemistry and Marine Zoology, Department of Biology, University of Oslo, PO Box 1050 Blindern, 0316 Oslo, Norway
6Norwegian Institute for Water Research (NIVA), Regional Office Grimstad, Televeien 1, 4890 Grimstad, Norway
*Corresponding author. E-mail:

ABSTRACT: The long-term effects of the 1988 algal bloom (Chrysochromulina polylepis Manton et Parke) along the Norwegian Skagerrak coast are evaluated and discussed on the basis of several monitoring programmes. Effects on individual growth and survival of coastal cod and its population dynamics are analysed. Cod suffered a high mortality from June until November, and the 1988 year-class was strongly reduced. Growth was only slightly affected. Furthermore, the effects at the community level are evaluated for the coastal fish community and the benthic communities. These communities were strongly affected on a short time scale, but recovered surprisingly fast. Populations of most organisms had recovered within months, and after 1 yr few traces of the toxic bloom could be observed; after 4 to 5 yr all communities had essentially recovered. As part of the review we also discuss to what extent harmful blooms are likely to reoccur, and conclude that blooms have reoccurred and will continue to do so. However, nothing can be concluded about the toxicity of such blooms. We expect that even large perturbations are unlikely to leave any profound long-lasting effects. The effects of the 1988 bloom are discussed within a theoretical framework including stability, resilience and inertia. In conclusion we emphasise the importance of long-term monitoring data; without such data the analyses reported in this paper would have been impossible.

KEY WORDS: Coastal communities · Monitoring · Toxic effects · Stochasticity · Resilience

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