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

The long-term effects of the 1988 algal bloom (Chrysochromulina polylepis M anton et Parke) along the Norwegian Skagerrak coast are evaluated and discu ssed on the basis of several monitoring programmes. Effects on individual g rowth 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 comm unity and the benthic communities. These communities were strongly affected on a short time scale, but recovered surprisingly fast. Populations of mos t organisms had recovered within months, and after 1 yr few traces of the t oxic bloom could be observed; after 4 to 5 yr all communities had essential ly 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 toxicit y of such blooms. We expect that even large perturbations are unlikely to l eave any profound long-lasting effects. The effects of the 1988 bloom are d iscussed 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 bee n impossible.