Effects of Coral Bleaching and Coral Loss on the Structure and Function of Reef Fish Assemblages

Abstract

Climate-induced coral bleaching poses a significant threat to coral reef ecosystems, causing extensive coral loss and degradation of reef habitats. Moreover, many reef fishes exhibit declines in abundance following severe episodes of coral bleaching, attributable to loss of live coral and/or declines in the structural complexity of reef habitats. This chapter considers the effects of mass coral bleaching (and associated changes in the structure of tropical reef habitats) on the structure and function of reef fish assemblages, whereby significant declines in the biodiversity and abundance of reef fishes may jeopardise ecosystem function and fisheries productivity in coral reef systems. It is now clear that effects of coral bleaching and associated coral loss extend well beyond those species traditionally thought to have specific reliance on corals for food and shelter (e.g. butterflyfishes, damselfishes, gobies). In extreme cases, the abundance and species richness of fishes may decline >60% following extensive coral depletion and topographic collapse of reef habitats, combined with increasing dominance of non-coral biota. Negative effects of coral loss on reef fishes are apparent across 18 (out of 19) broadly defined functional groups, including scraping herbivores and piscivores. Coral bleaching and coral loss is also shown to have a wide range of sublethal effects on coral reef fishes, further affecting their individual behaviour, survivorship and fitness. Given the taxonomic extent and severity of effects, mass coral bleaching is likely to compromise the functioning and productivity of coral reefs, providing significant imperative to reduce greenhouse gas emissions.