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Marine Ecology Progress Series

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MEPS 337:1-13 (2007)  -  doi:10.3354/meps337001

Western Indian Ocean coral communities: bleaching responses and susceptibility to extinction

T. R. McClanahan1,*, M. Ateweberhan2, N. A. J. Graham3, S. K. Wilson3,4, C. Ruiz Sebastián5, M. M. M. Guillaume6,7, J. H. Bruggemann7

1Wildlife Conservation Society, Marine Programs, 2000 Southern Boulevard, Bronx, New York 10460-1099, USA
2Coral Reef Conservation Project, PO Box 99470, Mombasa, Kenya
3School of Marine Science & Technology, University of Newcastle, Newcastle upon Tyne, NE1 7RU, UK
4Australian Institute of Marine Science, TMC, Townsville, Queensland 4810, Australia
5Advanced Research Center for Applied Microbiology, University of the Western Cape, Belville, South Africa
6Département Milieux et Peuplements Aquatiques, UMR 5178 CNRS-UPMC-MNHN, BOME, Muséum National d’Histoire Naturelle, 61 rue Buffon, 75005 Paris, France
7Laboratoire d’Ecologie marine (ECOMAR), Université de la Réunion, BP 7151, 97715 Saint-Denis, La Réunion, France

ABSTRACT: A field study of coral bleaching and coral communities was undertaken spanning 8 countries and ~35° of latitude in 2005. This was combined with studies in southern Kenya and northeast Madagascar in 1998 and Mauritius in 2004 to develop a synoptic analysis of coral community structure, bleaching response, susceptibility of the communities to bleaching, and the relative risk of extinctions in western Indian Ocean coral reefs. Cluster analysis identified 8 distinct coral communities among the 91 sites sampled, with 2 distinct communities in northern South Africa and central Mozambique, a third in the central atolls of the Maldives, and 5 less differentiated groups, in a swath from southern Kenya to Mauritius, including Tanzania, the granitic islands of the Seychelles, northeast Madagascar, and Réunion. Massive Porites, Pavona, and Pocillopora dominated the central and northern Indian Ocean sites and, from historical records, replaced dominance by Acropora and Montipora. From southern Kenya to Mauritius, coral communities were less disturbed, with Acropora and Montipora dominating, and a mix of subdominants including branching Porites, Fungia, Galaxea, massive Porites, Pocillopora, and Synarea. The survey identified an area from southernmost Kenya to Tanzania as having the least disturbed and highest diversity reefs, and as being a regional priority for management. Taxa vulnerable to future extinction based on their response to warm water, population density, and commonness include largely low-diversity genera with narrow environmental ranges, such as Gyrosmilia interrupta, Plesiastrea versipora, Plerogyra sinuosa, and Physogyra lichtensteini.

KEY WORDS: ENSO · Biodiversity · Climate change · Degree Heating Weeks · Meta-population · Monitoring · Remote sensing · Seawater temperature

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