Cross-shelf variation in the role of parrotfishes on the Great Barrier Reef

Hoey, A. S., and Bellwood, D. R. (2008) Cross-shelf variation in the role of parrotfishes on the Great Barrier Reef. Coral Reefs, 27 (1). pp. 37-47.

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Abstract

Herbivorous fishes are a key functional group on coral reefs. These fishes are central to the capacity of reefs to resist phase shifts and regenerate after disturbance. Despite this importance few studies have quantified the direct impact of these fishes on coral reefs. In this study the roles of parrotfishes, a ubiquitous group of herbivorous fishes, were examined on reefs in the northern Great Barrier Reef. The distribution of 24 species of parrotfish was quantified on three reefs in each of three cross-shelf regions. Functional roles (grazing, erosion, coral predation and sediment reworking) were calculated as the product of fish density, bite area or volume, bite rate, and the proportion of bites taken from various substrata. Inner-shelf reefs supported high densities but low biomass of parrotfishes, with high rates of grazing and sediment reworking. In contrast, outer-shelf reefs were characterised by low densities and high biomass of parrotfish, with high rates of erosion and coral predation. Mid-shelf reefs displayed moderate levels of all roles examined. The majority of this variation in functional roles was attributable to just two species. Despite being rare, Bolbometopon muricatum, the largest parrotfish species, accounted for 87.5% of the erosion and 99.5% of the coral predation on outer-shelf reefs. B. muricatum displayed little evidence of selectivity of feeding, with most substrata being consumed in proportion to their availability. In contrast, the high density of Scarus rivulatus accounted for over 70% of the total grazing and sediment reworking on inner-shelf reefs. This marked variation in the roles of parrotfishes across the continental shelf suggests that each shelf system is shaped by fundamentally different processes.

Item ID: 6149
Item Type: Article (Refereed Research - C1)
Keywords: reef fish ecology; ecosystem function; marine ecology; bioerosion; herbivory; sediment reworking; coral predation; ecosystem process; functional redundancy
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ISSN: 1432-0975
Date Deposited: 06 Apr 2010 03:18
FoR Codes: 06 BIOLOGICAL SCIENCES > 0602 Ecology > 060205 Marine and Estuarine Ecology (incl Marine Ichthyology) @ 50%
06 BIOLOGICAL SCIENCES > 0699 Other Biological Sciences > 069999 Biological Sciences not elsewhere classified @ 50%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960808 Marine Flora, Fauna and Biodiversity @ 100%
Citation Count from Web of Science Web of Science 66
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