Reports Coral Bleaching and Mortality on Arti®cial and Natural Reefs in Maldives in 1998, Sea Surface Temperature Anomalies and Initial Recovery ALASDAIR J. EDWARDS *, SUSAN CLARK , HUSSEIN ZAHIRà, ARJAN RAJASURIYA§, ABDULLA NASEERà and JASON RUBENS    Department of Marine Sciences and Coastal Management, University of Newcastle, Newcastle Upon Tyne NE1 7RU, UK àMarine Research Centre, Ministry of Fisheries, Agriculture and Marine Resources, Male', Maldives §Coral Reef Research Programme, National Aquatic Resources Research & Development Agency, Crow Island, Mattakkuliya, Colombo 15, Sri Lanka   GCRMN Regional Co-ordinator, South Asia, 48 Vajira Road, Colombo 5, Sri Lanka The bleaching and subsequent mortality of branching and massive corals on arti®cial and natural reefs in the central atolls of Maldives in 1998 are examined with respect to sea surface temperature (SST) anomalies. SST normally peaks in April±May in Maldives. The UK Meteorological Oce's Global sea-Ice and SST data set version 2.3b shows that in 1998 monthly mean SST was 1.2±4 S.D. above the 1950±1999 average during the warmest months (March±June), with the greatest anomaly in May of 2:1°C. Bleaching was ®rst reported in mid-April and was severe from late April to mid-May with some recovery evident by late-May. At least 98% of branching corals (Acroporidae, Pocilloporidae) on arti®cial structures de- ployed on a reef ¯at in 1990 died whereas the majority of massive corals (Poritidae, Faviidae, Agariciidae) survived the bleaching. The pre-bleaching coral community on the arti®cial reefs in 1994 was 95% branching corals and 5% massives (n  1589); the post-bleaching community was 3% branching corals and 97% massives (n  248). Sig- ni®cant reductions in live coral cover were seen at all natural reefs surveyed in the central atolls, with average live coral cover decreasing from about 42% to 2%, a 20- fold reduction from pre-bleaching levels. A survey of re- cruitment of juvenile corals to the arti®cial structures 10 months after the bleaching event showed that 67% of re- cruits ( > 0.5 cm diameter) were acroporids and pocillo- porids and 33% were from massive families (n  202) compared to 94% and 6%, respectively, in 1990±1994 (n  3136). Similar post-bleaching dominance of recruit- ment by branching corals was seen on nearby natural reef (78% acroporids and pocilloporids; 22% massives). A linear regression of April mean monthly SST against year was highly signi®cant (p < 0:001) and suggests a rise of 0:16°C per decade. If this trend continues, by 2030 mean April SST in the central atolls will normally exceed the anomaly level at which corals appear there are susceptible to mass bleaching. Ó 2001 Elsevier Science Ltd. All rights reserved. Keywords: bleaching; community structure; coral recruit- ment; sea surface temperatures. Introduction In 1997±1998 there was unprecedented bleaching and subsequent mortality of corals reported from many ar- eas around the world (e.g., Wilkinson, 1998; Berkelmans and Oliver, 1999; Hoegh-Guldberg, 1999) with particu- larly severe bleaching and high mortality reported from the Indian Ocean (Lind en and Sporrong, 1999; McCl- anahan, 2000; Sheppard, 1999; Wilkinson et al., 1999). The Maldives were among sites severely impacted in the Indian Ocean (Rajasuriya et al., 1999) and, being com- posed entirely of low-lying coral cays, are particularly vulnerable to loss of the protection aorded by healthy, Marine Pollution Bulletin Vol. 42, No. 1, pp. 7±15, 2001 Ó 2001 Elsevier Science Ltd. All rights reserved Printed in Great Britain 0025-326X/01 $ - see front matter PII: S0025-326X(00)00200-9 *Corresponding author. Tel.: +44-191-222-6663; fax: +44-191-222- 7891. E-mail address: a.j.edwards@ncl.ac.uk (A.J. Edwards). 7