Status of Coral Reefs of the World 2000
Status of Coral Reefs of the World 2000.pdf
Status of Coral Reefs of the World 2000.pdf
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The 1997-98 Mass <strong>Coral</strong> Bleaching and Mortality Event<br />
Arabian Sea<br />
There was major bleaching around Mirbat, sou<strong>the</strong>rn Oman, in May 1998 with 75 to 95% <strong>of</strong><br />
abundant Stylophora bleached, and 50% <strong>of</strong> large Porites colonies were partially bleached.<br />
No bleaching was observed at Sudh, 40km east <strong>of</strong> Mirbat, nor in <strong>the</strong> Muscat Area, Gulf <strong>of</strong><br />
Oman at temperatures around 30.5°C. Upwelling during <strong>the</strong> sou<strong>the</strong>ast monsoon normally<br />
drops temperatures to 19ºC. No recovery <strong>of</strong> bleached colonies was seen in mid-October<br />
when temperatures increased to 25°C after <strong>the</strong> summer upwelling. There was also extensive<br />
coral bleaching on <strong>the</strong> Socotra Archipelago (see chapter 2).<br />
Indian Ocean<br />
Probably <strong>the</strong> most extensive coral bleaching ever witnessed occurred in <strong>the</strong> central to<br />
nor<strong>the</strong>rn Indian Ocean during <strong>the</strong> first 6 months <strong>of</strong> 1998, with devastation <strong>of</strong> coral reefs<br />
along Eastern Africa, in <strong>the</strong> Seychelles, Chagos Archipelago, <strong>the</strong> Maldives, Sri Lanka and<br />
India and on reefs <strong>of</strong>f Western Australia. The normal monsoon and trade winds stopped<br />
and surface waters warmed during this severe El Niño, and <strong>the</strong> warm water ‘followed’ <strong>the</strong><br />
sun from south to north between January and June. When <strong>the</strong> El Niño switched to an equally<br />
strong La Niña in June 1998, winds and currents started again and bleaching stopped.<br />
Eastern Africa<br />
<strong>Coral</strong> bleaching and mortality were severe on <strong>the</strong> coasts <strong>of</strong> Kenya and Tanzania from March<br />
to May, 1998. In Kenya, bleaching varied from 50% to 90% on most reefs, but less on reefs<br />
below 10 m depth (about 50%). <strong>Coral</strong> cover in many sites has dropped from a mean <strong>of</strong><br />
30% to 5–11%, irrespective <strong>of</strong> whe<strong>the</strong>r or not <strong>the</strong> reefs were protected in a protected area.<br />
New coral recruitment is very low, so recovery will be prolonged. Bleaching was similar or<br />
worse in Tanzania, particularly in <strong>the</strong> nor<strong>the</strong>rn half with 60-90% losses <strong>of</strong> corals at Tutia<br />
(Mafia Island Marine Park) and Misali (west coast <strong>of</strong> Pemba). There was less bleaching on<br />
some reefs e.g. 10% or less on Unguja Island, Zanzibar. <strong>Reefs</strong> in <strong>the</strong> nor<strong>the</strong>rn part <strong>of</strong><br />
Mozambique with up to 99% mortality e.g. on some patch reefs at Inhaca Island. Inshore<br />
areas, which experience greater variations in temperatures experienced less bleaching.<br />
Only a few corals in South Africa were affected, probably because most coral growth is<br />
deeper than 10 m.<br />
Sou<strong>the</strong>rn Indian Ocean<br />
Bleaching impacts were far more severe in <strong>the</strong> north (Comoros and Seychelles) than in <strong>the</strong><br />
south (Madagascar, Mauritius and Reunion) where it was minimal. Mortality on <strong>the</strong> Comoros<br />
reef flats and slopes was approximately 40% to 50%. Most reefs <strong>of</strong> <strong>the</strong> inner Seychelles<br />
have less than 10% coral cover and on some it is as below 1%. On Madagascar, <strong>the</strong>re was<br />
30% bleaching <strong>of</strong> corals at Belo sur Mer (mid-west coast) and similar bleaching at<br />
Antananbe, Toliara, Nosy Bé, and Mitsio archipelago. At Mananara-Nord (nor<strong>the</strong>ast coast,<br />
15 o S), 40-80% <strong>of</strong> corals bleached with high mortality, and 10-40% <strong>of</strong> mixed species corals<br />
bleached in deeper water. A similar pattern was reported on Mayotte, except on <strong>the</strong><br />
exposed sou<strong>the</strong>rn end and <strong>the</strong> lagoon, which receives cooler water from <strong>the</strong> north.<br />
South Asia<br />
The most severely impacted reefs in <strong>the</strong> world during <strong>the</strong> 1998 bleaching event were<br />
probably those <strong>of</strong> Chagos, Sri Lanka, India and <strong>the</strong> Maldives. In this region, and on nearby<br />
reefs <strong>of</strong>f <strong>the</strong> Seychelles and Western Australia (Case Study 3), <strong>the</strong>re were losses <strong>of</strong> 80% <strong>of</strong><br />
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