Abstract
Coral reef ecosystems are increasingly subject to severe, large-scale disturbances caused by climate change (e.g., coral bleaching) and other more direct anthropogenic impacts. Many of these disturbances cause coral loss and corresponding changes in habitat structure, which has further important effects on abundance and diversity of coral reef fishes. Declines in the abundance and diversity of coral reef fishes are of considerable concern, given the potential loss of ecosystem function. This study explored the effects of coral loss, recorded in studies conducted throughout the world, on the diversity of fishes and also on individual responses of fishes within different functional groups. Extensive (>60%) coral loss almost invariably led to declines in fish diversity. Moreover, most fishes declined in abundance following acute disturbances that caused >10% declines in local coral cover. Response diversity, which is considered critical in maintaining ecosystem function and promoting resilience, was very low for corallivores, but was much higher for herbivores, omnivores and carnivores. Sustained and ongoing climate change thus poses a significant threat to coral reef ecosystems and diversity hotspots are no less susceptible to projected changes in diversity and function.
Highlights
Biodiversity varies greatly along latitudinal and longitudinal gradients [1,2], and may lead to important regional-scale differences in resilience and ecosystem function [3]
The maintenance of ecological functions depends upon functional redundancy and response diversity, rather than biodiversity per se [7]
Ecosystem functions performed by single species will be much more vulnerable to disturbances compared to functions performed by multiple species
Summary
Biodiversity varies greatly along latitudinal and longitudinal gradients [1,2], and may lead to important regional-scale differences in resilience and ecosystem function [3]. Species with common ecological functions will tend to have similar resource requirements and may be affected by most major disturbances [7] This suggests that functional groups with high redundancy may be highly vulnerable to disturbance, leading to loss of ecosystem function despite high levels of biodiversity [7,8]. The purpose of this review is to explore changes in the biodiversity and functioning of coral reef fish assemblages following distinct episodes of coral loss caused by acute disturbances, such as bleaching, severe tropical storms (cyclones), outbreaks of coral-feeding crown-of-thorns starfish (Acanthaster planci), or experimentally imposed disturbances. This study will aim to test whether high diversity among reef fish assemblages ensures the maintenance of key ecosystem functions during acute disturbances, and quantify response diversity among reef fishes within distinct functional groups (e.g., among different species of coral-feeding fishes). Previous studies have demonstrated marked variation in responses to coral loss amongst functional groups [22,23,24], but there has been limited consideration of differential responses among species within key groups [7]
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