Observations of a new source of coral mortality along the Kenyan coast Timothy R. McClanahan 1, *, Shawn M. McLaughlin 2 , Joanne E. Davy 3,7 , William H. Wilson 3,4 , Esther C. Peters 5 , Kathy L. Price 2 & Joseph Maina 6 l The Wildlife Conservation Society, Bronx, NY 10460, USA 2 NOAA NOS Cooperative Oxford Laboratory, 904 South Morris St., Oxford, MD 21654, USA 3 Marine Biological Association, Citadel Hill, Plymouth, PL1 2PB, UK 4 Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH, UK 5 Tetra Tech, Inc., 10306 Eaton Place, Suite 340, Fairfax, VA 22030, USA 6 Coral Reef Conservation Project, Mombasa, Kenya 7 Present address: The Center for Marine Studies, University of Queensland, Brisbane, QLD 4072, Australia (*Author for correspondence: E-mail: tmcclanahan@wcs.org) Key words: Astreopora, Echinopora, coral disease, coral histology, marine fungi, Montipora Abstract In early 2002 coral mortality occurred along 600 km of coastline from Tanzania to Kenya. Astreopora, Echinopora, and Montipora species were severely affected, with Montipora being nearly eliminated from Kenyan reefs. Acropora, Platygyra, Goniopora, and massive Porites were also affected; however, Porites and Goniopora rarely died and often recovered, whereas death for most other species occurred within 2 weeks. In Echinopora and Montipora, a dull ashy tissue color and brittle skeletons characterized the early stages of this event with a mucus layer on the tissue surface in intermediate stages. Mucus and embedded debris then disappeared and surfaces were left covered in a white calcareous dust that sometimes capped a black layer. Astreopora tissues became dull and pale, and seldom produced mucus; eventually the skeleton became bare and white. Either a colorless translucent or brownish thin margin of tissue was visible between living tissue and bare skeleton, depending on species. Scanning electron micrographs of affected corals revealed the presence of fungi. Histology and staining showed that the fungi were mostly in the three genera that died from the syndrome and it may be that fungi invaded and killed corals weakened by another unidentified pathogen. Introduction Coral diseases or syndromes are increasingly being recognized as a major cause of coral mortality (Peters, 1997; Richardson, 1998; Harvell et al., 1999; Porter, 2001). Most investigations are from the Caribbean where diseases have caused large- scale mortalities of corals (Aronson & Precht, 2001; Aronson et al., 2002). Few investigations have been conducted into coral pathologies in the western Indian Ocean, and the extent to which diseases kill coral and change reef ecology there are not known. Many of the common ‘band’ dis- eases have been identified in that region (Antonius, 1988a, b; Korrubel, 2000; Ravindran et al., 2001; Ben-Haim & Rosenberg, 2002; Riegl, 2002); however, the causes and ecology of these diseases are poorly understood. We summarize investiga- tion into a mass coral mortality that occurred along a 600-km stretch of the East African coast- line in 2002. We describe the changes occurring in the corals as they became morbid and often died, and investigate potential causes and consequences to the coral community. Hydrobiologia 530/531: 469–479, 2004. D.G. Fautin, J.A. Westfall, P. Cartwright, M. Daly & C.R. Wyttenbach (eds), Coelenterate Biology 2003: Trends in Research on Cnidaria and Ctenophora. Ó 2004 Kluwer Academic Publishers. Printed in the Netherlands. 469