Abstract
Herbivorous and detritivorous fishes interact closely with the epilithic algal matrix (EAM) on coral reefs. While sediment and organic detrital loads within the EAM might influence this interaction, the responses of functionally distinct fishes to changing sediment and organic loads have not been investigated. Aquarium based feeding trials were performed to assess how different sediment and organic loads affected feeding by the highly abundant surgeonfishes, Ctenochaetus striatus, a detritivore, and Acanthurus nigrofuscus, a herbivore. C. striatus were highly sensitive to even small increases in sediment loads (of just 75 g m-2), displaying a significant decline in feeding rates as sediment loads increased. Although C. striatus is a specialised detritivore, changing organic loads had no effect and suggests that selection of feeding surfaces is primarily mediated by total sediment loads rather than organic loads. By contrast, A. nigrofuscus displayed no changes to its feeding behaviour regardless of sediment or organic load. These findings highlight the complex, species-specific way that sediments may mediate key ecological processes on coral reefs.
Highlights
There is increasing recognition that fishes help maintain coral reef resilience, by performing an extensive range of important ecosystem functions [1,2]
Recent research has revealed that the epilithic algal matrix (EAM) on coral reefs may shift from a state of short productive algal turfs (SPATs) to a less desirable state of unpalatable long sediment-laden algal turfs (LSATs), without any change in the abundance of PLOS ONE | DOI:10.1371/journal.pone
While C. striatus were highly sensitive to increasing sediment loads within the EAM, A. nigrofuscus were unaffected
Summary
There is increasing recognition that fishes help maintain coral reef resilience, by performing an extensive range of important ecosystem functions [1,2]. Herbivory is regarded as a core component of these ecosystem functions as it controls the growth and expansion of algal communities [1,3,4]. Transitions from coral dominated to algal dominated reef systems are regularly attributed to reductions in rates of herbivory [3,4,5,6]. Overfishing of herbivorous fishes is often identified as the main driver leading to reduced rates of herbivory on reefs [1,2,7]. Overfishing is just one of a number of factors which may lead to reductions in herbivory [8]. In some regions herbivorous fishes are not heavily targeted (e.g. the Great Barrier Reef [GBR]), declines in coral reef state and algal proliferation have still occurred [9,10,11]. Recent research has revealed that the epilithic algal matrix (EAM) on coral reefs may shift from a state of short productive algal turfs (SPATs) to a less desirable state of unpalatable long sediment-laden algal turfs (LSATs), without any change in the abundance of PLOS ONE | DOI:10.1371/journal.pone.0169479 January 3, 2017
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