SCALING EUTROPHICATION EFFECTS BETWEEN SPECIES AND ECOSYSTEMS - THE IMPORTANCE OF VARIATION AND SIMILARITY AMONG SPECIES WITH SIMILAR FUNCTIONAL ROLES

Although eutrophication is frequently cited as an anthropogenic threat to coral-reef systems, very little is known about the effects of eutr ophication on coral-reef fishes. In this paper, I explore how variatio n and similarity among fish species, and among the species with which they interact, may determine when population-or system-level responses to nutrient enrichment are most likely. Where functionally similar sp ecies exhibit complementary responses to environmental stress, ecosyst em function may be maintained relatively unchanged although the relati ve abundance of species may shift dramatically. Alternatively, major c hanges in the ecosystem can occur if functionally similar species resp ond similarly to changes in the environment, if little functional comp lementarity or behavioural plasticity exists, or if feedback exists wh ereby changes in the fish assemblage cause further degradation of thei r coral habitat.