Phase shifts and the role of herbivory in the resilience of coral reefs |
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Authors: | M H Ledlie N A J Graham J C Bythell S K Wilson S Jennings N V C Polunin J Hardcastle |
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Institution: | (1) School of Marine Science and Technology, Newcastle University, Newcastle-upon-Tyne, NE1 7RU, UK;(2) School of Biology, Newcastle University, Newcastle-upon-Tyne, NE1 7RU, UK;(3) Australian Institute of Marine Science, Townsville MC, Townsville, QLD, 4810, Australia;(4) Lowestoft Laboratory, Centre for Environment, Fisheries and Aquaculture Science, Lowestoft, NR33 0HT, UK;(5) Nature Seychelles, The Centre for Environment and Education, P.O. Box 1310, Roche Caiman, Mahé, Seychelles |
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Abstract: | Cousin Island marine reserve (Seychelles) has been an effectively protected no-take marine protected area (MPA) since 1968
and was shown in 1994 to support a healthy herbivorous fish assemblage. In 1998 Cousin Island reefs suffered extensive coral
mortality following a coral bleaching event, and a phase shift from coral to algal dominance ensued. By 2005 mean coral cover
was <1%, structural complexity had fallen and there had been a substantial increase in macroalgal cover, up to 40% in some
areas. No clear trends were apparent in the overall numerical abundance and biomass of herbivorous fishes between 1994 and
2005, although smaller individuals became relatively scarce, most likely due to the loss of reef structure. Analysis of the
feeding habits of six abundant and representative herbivorous fish species around Cousin Island in 2006 demonstrated that
epilithic algae were the preferred food resource of all species and that macroalgae were avoided. Given the current dominance
of macroalgae and the apparent absence of macroalgal consumers, it is suggested that the increasing abundance of macroalgae
is reducing the probability of the system reverting to a coral dominated state. |
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Keywords: | Recovery Coral bleaching Seychelles Marine protected areas Coral reef fishes Feeding observations |
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