The 1997-1998 Mass Bleaching Event Around the World

Southeast and East Asia

Coral bleaching was first observed in Indonesia in January and February, 1998 as warm waters flowed through the Java Sea eastwards towards Lombok where bleaching was seen in March. During April and May, a warm pool of water developed during the northern summer around Cambodia, Thailand and parts of Sabah, Malaysia. Warm water bathed parts of the Philippines, Vietnam, Taiwan, and Japan in June and July, and also spread southwards towards Singapore and the Riau islands off Sumatra in June and July, before cooling in late July. Warm waters continued around Japan until August when the first typhoon in September cooled the waters.

Cambodia

Corals around Sihanoukville, Cambodia were moderately to severely bleached in mid-May. The water was warm (no thermometers available) and very turbid. The predominant corals are massives (poritids, faviids and mussiids), with few Acropora and Pocillopora species, but most species bleached, with approximately 80% in some places.

(Vicki Nelson)

Indonesia

Bleaching was initiated by a warm current from the South China Sea that flowed through the Java Sea from the Riau Islands as far as Lombok. There was no bleaching to the north in Spermonde Archipelago, southwest Sulawesi (near Ujung Pandang), and Manado, Bunaken, nor around Bangka, north Sulawesi where coral cover varied between 25 and 75% depending on location and predominant wind direction.

Coral bleaching of approximately 75-100% of the 25% coral cover was seen around Bali Barat National Park (north-west Bali), and at Tulamben (eastern Bali), with many soft corals seen disintegrating. There was less bleaching at Nusa Penida and Nusa Lembongan. Many anemones to 36 m at Telumban, Bali bleached, but others at 44 m were normal. Bleaching in Pulau Seribu off Jakarta, and Karimunjawa Marine National Park (north of Java) started in January and February, continued through May and corals had either recovered or died by August. Bleaching ranged from zero to 46% at 3 m (mainly Acropora and Galaxea), and 1% to 25% at 10 m (Pachyseries, Hydnopora and Galaxea), with 50-60% mortality of bleached corals. On the Gili Islands (Air, Meno, Trawangan), facing the Lombok Strait, almost 90% of hard corals bleached (especially Acropora) in March 1998, down to 20 m. In August, there was high mortality, but some massive corals, especially Porites, were recovering.

There was significant coral bleaching, up to 60-70% at some depths, in East Kalimantan (Borneo) during January, however, water temperatures were much colder than normal (approximately 23^oC) with extensive plankton blooms.

(Irdez Azhar, Imam Bachtiar Clay Bryce, Alastair Harborne, Taufik Hizbul Haq, Bert Hoeksema, Otty Lalamangkit, Gayatri Lilley, Ghislaine Llewellyn, Suharsono, Yempita)

Japan

Coral bleaching started on Okinawa Island (26^oN) in mid-July 1998, when temperatures increased from 25-28^oC in June to 28-31.5^oC in July. Bleaching increased in August (31^oC), but was less extensive on offshore islands (30^oC), with shallow water corals (Acropora, Pocillopora, Merulina, Montipora, and Porites affected. In September, bleaching continued with all corals, and spread north to the Japanese mainland (33^oN), and down to more than 20 m on Okinawa. By mid-October most bleached Acropora were dead and covered with algae on Okinawa, however, many Acropora colonies in shallow moats of Okinawa and on offshore islands had survived. Many faviids and poritids regained colour by mid-October with temperatures around 28^oC.

Bleaching was conspicuous on Ishigaki Island (24^oN; 50-70% bleached) and Amakusa, Kyushu (32^oN) when water temperatures went over 30^oC in July and August. It was unusual that water temperatures remained high until the first Typhoon in September. Most species were extensively bleached, except for minor bleaching in the blue coral Heliopora. Earlier, a few mushroom corals (Fungia) bleached with water temperatures of 28-29^oC, which is apparently a regular, annual occurrence. No bleaching was seen down to 30 m in September off the southwest of Shikoku Island (33oN), where there is 75% coral cover of plate Acropora down to 10 m. Previous bleaching was in 1980 and 1983.

(Charles Delbeek, Hajime Kayanne, Tadashi Kimura, Keven Reed, Rob van Woesik)

Malaysia (Sabah)

Coral bleaching has been highly localised and not very significant in Sabah. In mid-May, there was bleaching of 30-40 % of all live coral cover in 1-2 m at Pulau Gaya, Sabah (near Kota Kinabalu) with water temperatures of 32^oC. In Pulau Sakar up to 30% of all species bleached with 10% mortality down to 20 m. Acropora colonies were about 90% bleached and also some giant clams with about 20% showing bleaching. Less than 5% of corals were bleached in Pulau Baik down to 15 m, especially large polyp species (Symphyllia, Lobophyllia and Lithophyllon). There was minor to insignificant bleaching on Mamutik Island (Tunku Abdul Rahman Park), Turtle Islands Park, and off Semporna, Sabah during surveys in July and August. Intensive surveys of Darvel Bay (Lahad Datu) east Sabah (4-5^oN, 118^oE) in September showed no significant bleaching at 20 reef sites (Pulau Sakar, Pulau Maganting, Pulau Bohayan, Pulau Tabawan, Pulau Baik, Pulau Laila, Bakapit, Bagahak and Shoal Point).

(Don Baker, Ranjith de Silva, Ridzwan Abdul Rahman)

Philippines

Massive bleaching started in mid-July, and may be still ongoing in western regions where reports are coming in from Bolinao (northwest Luzon), to Puerto Galera and southern Negros Island, central Philippines (Dumaguete, Campomanes Bay, Danjugan Island, El Nido (Bacuit Bay) and Coron Island (Palawan), and Pag-asa Island (Spratleys). Temperatures of 33-34^oC degrees were reported, and bleaching went as deep as 28 m (temperatures of 30-31 ^oC) and completely affected soft corals and some anemones. Bleached hard corals were primarily the plating, branching and foliose forms, with up to 75% of the community bleached in some areas. Massive corals were also affected; faviids were bleached, but large Porites appeared to resist bleaching below 5 m, but not on shallow reef flats of Bolinao and Negros. Black-band disease was observed on a few bleached colonies. Mortality, however, of bleached corals appears to be low. On the well-known Apo Island, some large colonies of Galaxea fasicularlis showed some patchy bleaching. Massive bleaching also reported in Danao Bay, near Baliangao, northwest Mindanao in October 1998, with bleaching mostly affecting branching corals and significant rotting of soft corals, but fire coral (Millepora) not affected.

(Jade Fraser, Fiona Gell, Gillian Goby, Rex Montebon, Laurie Raymundo, David Medio)

Singapore

There was mass bleaching in June and July, 1998 probably due to elevated seawater temperatures (33^oC when they are normally 28 to 30 ^oC). The bleaching affected all species of hard corals and extended throughout the entire depth of coral growth. Soft coral mortality was high. When temperatures dropped in July, some corals started to show recovery. This is the first time bleaching has been seen on this scale.

(Loke-Ming Chou, Jeffrey Low)

Taiwan

Coral bleaching was first observed in June, around Penghu Islands (Pascadores Is) during Reef Check 1998. About 30-40% of corals were bleached in 1-5 m, some corals were dead with water temperature around 30^oC. In August, extensive coral bleaching was observed around Posunotao, an offshore island in southeast Taiwan. Over 80% of corals bleached down to 20 m, with water temperatures of 31^oCat 20 m and 34^oC at 1 m. Posunotao is in the Kuroshio current, and other regions down current (Kenting Reef and HisaoliuChio) bleached afterwards.

(Allen Chen)

Thailand

Warm water temperatures in April 1998 caused widespread coral bleaching in the Gulf of Thailand from Narathivat province (South) and Trat province (far east), up to Chonburi province (the inner part of the Gulf). But there was no bleaching on the other side in the Andaman Sea. Water temperatures in the Gulf increased from the normal of 28-29^oC to above 32^oC, such that on Ko Samui it was 35^oC. It was first noticed in the tourist centres of Chumpon and Surat Thani. Then bleaching spread north to reefs in the inner part of the Gulf (Koh Samet, off Samaesan) and off Pattaya. In some places, bleaching has affected 100% of Acropora, 80% of Pocillopora damicornis, and about 60 to 70% of massive Porites, especially in shallow water. Around Chumporn (Ko Kai, Ko Samet and Ko Tao – 10^o50’N), 30-50 % of corals bleached. Around Sichang Island (inner part of the Gulf) and Mun Islands (Rayong), the impact was 50-60% of corals bleached, with mortality of about half. This is the first report of widespread bleaching in the Gulf of Thailand.

(Tenshi Ayuki, Vipoosit Manthachitra, Suraphol Sudara).

Vietnam

Extensive coral bleaching began in mid-July1998, in the areas off of Nha Trang (south-central Vietnam), with moderate levels of mortality in shallow water, especially Acropora species. Major bleaching was reported further south in Con Dao National Park (200 km south of Ho Chi Minh City –Saigon, and 80 km off the Mekong Delta) with 70% of corals affected at most reefs down to 15m. These were particularly impressive coral reefs, which had been damaged by Typhoon Linda, November 1997. At most sites, 90% of the dominant table Acropora and many other corals were dead by mid-September, with total losses of about 70-80% of the shallow water coral cover (1-2 m). Bleaching was equally bad in deeper water with 90% mortality of the dominant massive Porites and many other large colonies, for example Lobophyllia. Coral cover loss in deeper water was 60-70%, and hundreds of 2-3 m diameter, massive Porites were killed, including 9 m diameter colonies which were several hundred years old. No bleaching was seen at Hon Mun Island (off Nha Trang) where there is frequent cold upwelling, nor was bleaching seen at Halong Bay (far north off Vietnam).

(Gregor Hodgson, Vo Si Tuan, Sue Wells)

web@aims.gov.au
Last updated - 7 December 98

Copyright ©1996-1998 Australian Institute of Marine Science

URL http://www.aims.gov.au