Coral Bleaching

Clive Wilkinson c.wilkinson at
Tue Oct 6 03:17:10 EDT 1998

Coral Listers
If you are not interested in coral bleaching - please delete.

For the others; here is a compiled summary of information gleaned out of
CHAMP pages and in reply to requests.  I have some descriptive summaries to
add to each section.

The intention is to release this as a plain language report on what has
happened, without any analysis of what it may mean with respect to global
climate change or coral evolution or whatever.  Others are preparing
summaries and reviews on that.

Please look at these and send back any more information on areas I missed,
errors in transcription, and updated results on recovery or death. Many of
the early stories of extensive bleaching are now coming back with reports
of significant recovery.  This report as it is may be overly alarmist -
much of the bleached coral may recover.

Please send replies back to <c.wilkinson at> (please do not send
the whole document back - just the bit to change.)

thank you=20

Clive Wilkinson

There has been unprecedented bleaching in coral reefs throughout the Indian
Ocean, the Caribbean and parts of the far eastern and western Pacific
ocean.  This bleaching has been in parallel with a severe El Nino - event
during late-1997 and early-1998, which switched over to a La Nina in=

(More to add)


( 1 paragraph Regional summary to add)
1998 was a very hot year on land, and coral bleaching was first observed in
mid-August when water temperatures went from 34 to 370C in a week, and
stayed that way for a few weeks (up to 390C  in shallow areas).  There was
100% bleaching from Hayr Shutaya (20 miles north of Bahrain) south to Fasht
Al Adhom, and Fasht Al Dibal (all less than 10 m depth). Mortality of coral
was 90% a few weks later.
Bleaching was estimated at 50 % on Abul Thama (about 50 miles north of
Bahrain).  There was major bleaching in summer of 1996 when water
temperatures were 37.30C at Fasht Al Dibal. Most corals on Fasht Al Adhom
bleached then died and half of corals at Abul Thama that bleached later=
(Roger Uwate)

Extensive bleaching was observed, with temperatures between 29.5 and
31.5=B0C, at 8 sites around Mirbat, southern Oman, between 22 and 26-MAY-98
just prior to the south-east monsoon which drops temperatures as low as
18=BAC. Between 75% and 95% of Stylophora (the most abundant coral genus)
bleached, and  50% of large Porites colonies were partially bleached. About
95% of coral were still living despite losing their zooxanthellae.  But no
bleaching was observed at Sudh, 40  km to the east where seawater
temperatures varied between 25 and 25.5=B0C, nor in the Muscat Area, Gulf of
Oman where water temperatures in early June were 30.5=B0C. No bleaching was
also observed on the Hallaniyat islands, just north of the Yemen border, in
an upwelling area from February to April 1998. This was described as a
pristine area with coral cover from 10 to 90% growing down to 35 m where
macroalgae and corals co-exist in waters which vary between very cool to
very warm.=20
(Robert Baldwin, Simon Wilson and Peter Collinson)

Saudi Arabia=20
Widespread coral bleaching was seen on 4 patch reefs (seawater temperature
35 to 360C) in mid August,  1998. There was very high mortality (about 95%)
in Acropora and other species.  Bleaching was minimal at an offshore island
reef with seawater temperature below 340C.
(Reynaldo Lindo)


The extent of bleaching in the Indian Ocean during 1998 is unprecedented in
both the extent and severity.  Warm surface waters have migrated from south
to north during the first 6 months, with considerable coral reef bleaching
occurring in each locality.  The warm pool of water was observed in
satellite images from the National Oceanic and Atmospheric Administration
of USA. This bleaching is similar, but more severe than the1987 El Nino in
the Indian Ocean, which caused some mortality, but the reefs recovered
quite quickly in the Maldives.
The atolls apparently escaped bleaching as none has been reported in the
past 2 years.  No details known.
(Charles Sheppard)

Bleaching at Kavaratti Island, Lakshadweep islands in May appears similar
to what was seen in the Maldives,  perhaps less severe. Some bleaching,
between 10-30%, was seen in the Gulf of Kutch on the northerly Gujarat
coast in early to mid-May.=20
(Arjan  Rajasuriya and Jason Rubens)

Bleaching started north of Lamu (2oS), on 18-MAR-98 when temperatures
reached 32.50C and continued to April. Bleaching around Mombasa started
around 25-MAR and was as low as 50%, but mostly near 100% on almost all
reefs seen, where there had been 20% to 50% coral cover.  Bleaching was
most extreme in shallow water, but was also 50% or more at 20 m.  Coral
mortality is nearly 100%, but some reefs still have 1 to 5% coral cover.=20
(David Obura)


There has been patchy bleaching on the Masoala peninsula (north-east coast,
15oS), which probably started in March, but there were no observers.
Bleaching and mortality of predominantly Acropora corals in shallow water
was 40 to 80%, and 10-40% of mixed species corals in deeper water.=20
(David Obura)

There has been heavy damage to coral reefs in the central tourism region of
the Maldives. Relatively severe, short-term bleaching was reported between
late April to May, and there are now some signs of partial recovery. Around
80% of corals wholly or partially bleached on the back reef, with around
45% at 10m on the reef slope and 30-40% at 20-30m. Bleaching was also seen
at 50m. These observations on North Male Atoll have been effectively
confirmed by sea-plane operators who have seen similar levels throughout
the Maldives. Other reports from North Male and the Ari Atoll were of up to
95% of mostly Acropora communities dead, including soft corals and
anemones. Many massive corals are still under=20
stress and partially bleached.=20

By late May, some recovery is beginning Porites spp. on South Male and
Vaavu Atolls, but Acropora species had suffered major mortality, some times
up to 100%. On South Male Atoll, temperatures were high, being over 30=B0C a=
30 m from April to June 1998. Here 100% of some Sinularia soft corals
bleached (but not Sarcophyton spp.); corals (Acropora, Fungia and Porites
were 60-80% bleached; and even giant clams (Tridacna sp.) were  partially
bleached. Many anemones have since regained their colour. A similar result
was seen in the 70s, with large areas of reefs dead from unknown causes,
but recovery was rapid.
(Jason Rubens, William Allison, Norbert Schmidt, Reto Wyss, Zdenka Vapenik)

There was minor bleaching in Mauritius this year, with some small localised
areas of moderate bleaching. =20
(Loic Charpy)

Corals began to bleach at Mayotte (Comoro Archipelago) in mid April on the
southern end exposed to the tradewinds, and also in the lagoon, which
receives cooler water from the north.
(Bernard Thomassin)

During the last 2 weeks of March, there was significant bleaching on the
reef flats and reef slopes of Reunion, with Acropora, Galaxea and
Pocillopora the genera most affected. were. Water temperatures were high
(but not recorded) and there was very heavy rainfall for most of February.
(Michel  Pichon)=20

Corals at 14 sites in the Seychelles Marine Park system were filmed which
showed that an average of about 75% were recently dead (ranging from 50% to
95%). The dead corals were covered with filamentous algae which were
expanding to cover areas of corals which were dying. Other reports were of
moderate bleaching, which was not exceptional.
 (Loic Charpy and Tom Goreau)

Sri Lanka
Bleaching started about 10-APR-98 in the south-west at the Hikkaduwa Marine
Sanctuary with over 75% bleaching in the beginning. Almost all coral
species between 1 and 8 m, except Montipora spp. were affected when water
temperatures went from the normal 29=B0 to 30=B0 C to about 35.5=B0 C in mid
April and remained above 320 C until late May.   It increased to in excess
of 80% on the reef flat 25-APR-98 and on deeper offshore reefs off Colombo.
 All species appear to have been affected, but soft corals appear to have
resisted the bleaching better. Bleaching was noticeable around down to 42 m
on the south-east coast near Battilacoa in mid-MAY.  No bleaching was
observed 100 km further up on the north-east coast of near Trincolamalee in
early May.

Corals remained bleached up to early June 1998, with most branching and
tabulate Acropora and Pocillopora colonies starting to die off and be
covered by algae.   Some recovery (regaining normal colour) of  about 10%
of bleached corals was observed in mid July.  Bleaching like this has never
been seen in Sri Lanka before; any bleached corals in the past recovered
within 3 to 4 weeks.
(Arjan Rajasuriya and Jason Rubens)

Scott Reef (Australia)
This remote atoll reef (14oS; 121oE) was observed to have extensive
bleaching in May 1998. There was between 70% and 100% bleaching and
mortality of corals between 1 m and 9 m and 40% at 30 m depth. Protected
shallow sites had up to 75% coral cover, which is now down to 15%, with
more corals still dying 3 months after bleaching started.
(Luke Smith)

A serious bleaching episode occurred, which affected principally Acropora
and other branching species.
(J.L. Solandt)


During June, a warm pool of water developed during the northern summer.  It
bathed the Philippines, Vietnam, Thailand, part of Malaysia, Singapore and
northern Indonesia. ( 1 paragraph Regional summary to add)

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)

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.=20

There was significant coral bleaching, up to 60-70% at some depths, in East
Kalimantan (Borneo) during Janaury. However, water temperatures were much
colder than normal (approximately 23oC) with extensive plankton blooms.=20

Up to May 1998, there was no bleaching on the Spermonde Archipelago,
south-west Sulawesi (near Ujung Pandang) and at Bunaken, and around Bangka,
north Sulawesi. Coral cover varied between 25 and 75% depending on location
and predominant wind direction. =20
(Alastair Harborne and Bert Hoeksema)

Many corals bleached in wide area from Okinawa (24oN) to Amakusa (32oN)
when water temperatures went over 30oC in July and August.  Water
temperatures remained high until the first Typhoon in September, which is
very unusual. Earlier, a few mushroom corals (Fungia) bleached with water
temperatures of 28 to 29oC, which is apparently a regular, annual=
(Tadashi Kimura and Keven Reed)  =20

Malaysia (Sabah)
In mid-May, there was bleaching of 30 to 40 % of all live coral cover in 1
to 2 m at  Pulau Gaya, Sabah (near Kota Kinabalu) with water temperatures
of  320C.  Acropora colonies were about 90% bleached and so were some giant
clam populations with about 20% showing bleaching.
(Don Baker)

Massive bleaching started in mid-July, and  may be still ongoing in western
regions where reports are coming in from Bolinao (north-west Luzon),  to
Puerto Galera and southern Negros Island near Dumaguete (central Phils), El
Nido (Bacuit Bay) and Coron Island (Palawan), and Pag-asa Island
(Spratleys). Temperatures of 33 to 34oC degrees were reported. Bleaching
went as deep as 15 m 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 spp.
appear 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
(Fiona Gell, Rex Montebon, Laurie Raymundo and David Medio)

There was mass bleaching in June and July, 1998 probably due to elevated
seawater temperatures.=20
(Jeffrey  Low)

Warm water temperatures in April, 1998 have caused widespread coral
bleaching in the Gulf of Thailand from Trat province (far east) down to
Singapore. The bleaching has affected tourist attractions such as Chang,
Tao and Pha-ngan islands, but not over the other side in the Andaman Sea.
Water temperatures in the Gulf increased from 28 to 290C to 320C. It was
first noticed in the centre (Chumpon and Surat Thani), then off Pattaya,
near Samaesan and Koh Samet, and later at Rayong and Trat. In some places,
bleaching has been 100% of Acropora, 80% of Pocillopora damicornis, and
about 60 to 70% of massive Porites, especially those in shallow water.
Around Chumporn (10.50N), there was 30 - 50 % of corals bleached around Ko
Kai, Ko Samet and Ko Tao.
(Tenshi Ayuki and Suraphol Sudara).

Major bleaching was reported in mid-July, 1998 on reefs of the Con Dao
Islands, 200 km south of Ho Chi Minh City (Saigon)  and 80 km off the
Mekong Delta. Extensive bleaching, estimated at over 70% was observed down
to 15m on particularly impressive coral reefs, which had been damaged by
Typhoon Linda, November 1997. 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 of Vietnam).
(Sue Wells)

Sea surface temperatures warmed considerably off eastern Australia during
early 1998. Extensive bleaching was observed on inner shelf reefs of the
central Great Barrier Reef in late January and February 1998 from Elford
Reef (17oS), to Heron Island (23oS). Over 100 coral species bleached,
including bleaching and partial death of large Porites colonies that were
centuries old.  This bleaching appeared to be a combined effect of raised
temperatures and massive flows of rainwater in January. Soft corals were
extensively bleached on these inner reefs with almost orders bleached. In
the upper 5 m, soft corals are 100% bleached and about 20% bleached at 8 -
12 m depth. Mortality was high, even in the normally resistant Sinularia.
On Orpheus Island, between 84 and 87% of corals bleached, but 5 weeks
later, mortality was between 2.5 and 17%, with the Acropora species being
most affected. Pocillopora species were hardly affected.

In March, bleaching also extended to southern Queensland (Gneering Shoals
(26oS) and northern New South Wales (28=B030'S) on rocky reefs with
populations of corals up to 50% coral cover. Water temperatures were around
28=B0C (maybe as high as 30=B0C), whereas they are normally in the mid 20s.
Pocillopora damicornis and Stylophora pistillata were most affected with
60-70% of these species bleached to 15m depth. No bleaching was observed on
the Flinders Reefs (27oS), between these 2 sites.
 (Andrew Baird, Simon Banks, Daniel Bucher, Katharina Fabricius)


( 1 paragraph Regional summary to add)

No bleaching was seen during the past year over about 180 km on the South
side of the Great and North Astrolabe Reefs (18oS), which have extensive
coral cover.
(Joan Koven)

Johnston Atoll=20
No bleaching was seen, but there was evidence of recovery from a bleaching
event a few years earlier. These reefs have nearly 100% live coral cover in
suitable areas. No elevated water temperatures were observed by satellite.
(Les Kaufman)

Major coral bleaching occurred in Palau in September, 1998 with water
temperatures from 30 to 32oC. About 75% of corals shallower than 15 m
bleached.  The eventual impact not known, but the area looks awful.
(Pat Colin)

Papua New Guinea
Water temperatures below 10 m around Kimbe Bay (New Britain) were 31-31.5
=B0C in February, and on the surface they were 32-33 =B0C. High mortality of
corals was observed with 75% of Acropora affected, and bleaching in many
other genera including Porites, Platygyra and Montipora. Some others were
partially bleached, but effects were observed down to 50 m.  On the
south-west side of Kimbe Bay, water was 29.5 to 30=B0C, and there was only
10% Bleaching of Acropora and only isolated cases of bleaching on other

In March 1998, large areas of reefs south of Normanby Island through to
Cape Vogel, and Tufi (far south-east PNG) showed coral bleaching from
mid-February.  Bleaching extended down to 20 m, but was most=20
extensive in shallow water (almost 100% in some areas, including soft
corals and anemones). Water temps were 29 to 300C from December to
February, the longest period of warm water on record for in Milne Bay.
Reefs to the north Normanby and Fergusson Ids were apparently not affected
by any major bleaching.
 (James Cervino and John Rewald)

Samoa (Western)
Between 60 to 70% of all Acropora on the reef top bleached within 5-6 days
just before 28-FEB-98 at Palolo Deep, National Marine Park near Apia.
Corals in deeper water appeared healthy.=20
(Mike King)


( 1 paragraph Regional summary to add)

Colombia (Pacific Coast)
The first signs of bleaching were in late-May, 1997 with small patches on
Pocillopora sp. when water temperatures were 29oC. More bleaching was
observed in July and August, 1997 with increased signs of bleaching at
similar temperatures. In September 1997, up to 30% of some Pocillopora was
bleached, whereas similar corals nearby appeared normal.
(Fernando Zapata)

The first bleaching reports were in mid-December when water temperatures of
280C were recorded from satellites.  Water was 20C warmer in February and
bleaching continued.  Nearly all corals on the Galapagos were bleached to
some extent by March 1998.  The most strongly affected were Porites and
Pavona. The genera Psammocora, Diaseris and Cycloseris were bleached on
top, but many still had pigment around the bases. Corals bleached down to
30m, but was more extensive shallower than 10 to 15 m depth.  Pocillopora,
which was most impacted during the big El Nino of 1982-83, seems to be
largely resisting this time.=20
(Andrew Baker, Joshua Feingold, Jerry Wellington, Al Strong)

Mexico (Pacific Coast)
Bleaching was first noticed in July, 1997 from the Gulf of California
(25oN) to Jalisco (19oN) and in the remote Revillagigedo Islands (18oN).
Bleaching peaked in August- September, 1997 involving about 25% of total
coral cover (water temperatures were 31 to 34oC). The most extensive
bleaching occurred at Nayarit (20oN), of about 60% of corals mostly
shallower than 4 m. Bleaching was 10% to 15% in  the Revillagigedos, with
some mortality, but had finished in October. The only significant recovery
in the Gulf is from new Pocillopora recruits settloing on the old
skeletons. This the first time that bleaching has been reported on the
Pacific coast.
No bleaching or death was observed at Oaxaca (16oN) nor at Clipperton Atoll
in November, 1997.=20
(Hector Reyes)

Panama (Pacific Coast)
There was significant coral bleaching on 17 September 1997 at Uva Island,
Gulf of Chiriqui. All coral species were affected down to 20 m. Millepora
intricata, the most common species remaining after the 1982-83 El Nino,
bleached and died.  Other species were still alive but bleached.

Almost all coral species in the Gulf of Chiriqui region started bleaching
in mid-April, 1998 with 50% to almost 90% of corals with at least partial
bleaching. This follows the bleaching above, but is much less intense than
1983. Bleaching occurred when water temperatures were 29 to 31oC, more
1.5oC above normal. Corals from nearby Gulf of Panama showed much less
(Andrew Baker, Mark Eakin, Peter Glynn and Juan Mat=E9 )

( 1 paragraph Regional summary to add)

Corals of the central Bahamas showed extensive bleaching in August 1998,
with over 60% of all head corals bleached to 20 m around New Providence
Island.  Extensive bleaching (around 80%) between 15-20 meters depth.
Montastrea cavernosa was not bleached, and Acropora palmata bleached on the
upper sides only of branches in shallow water. Hurricane Bonnie then
dropped water temperatures by 2oC. There was also extensive bleaching at
Walker's Cay in the northern Bahamas, with many types of coral affected.
(Benjamin Mcpherson, Bill Precht)

The entire Belizean coral reef ecosystem experienced massive coral
bleaching in early September 1998. Severe bleaching down to 8 m on the
fore-reef, top-reef and back-reef of: the main barrier reef at Ranguana
Pass; patch reefs at Bird, Crawl, Laughing Bird, Scipio, South Water, and
Cocoplum Cayes; pinnacle reefs between Ranguana Pass and Lighthouse Caye
off Placencia; offshore reefs of Glover's Reef Atoll and Ambergris Caye;
and shallow banks off Rum Point.  No bleaching of this extent has been seen
before. The bleaching is correlated with exceptionally high water
temperatures, and calm weather.  Water temperatures have been consistently
between 30 and 32oC, and on the surface near some of the cayes, it was
between 36 to 38oC. Almost all hard corals and the zooanthid Palythoa
exhibited some bleaching. Total to high bleaching was prevalent in
Millepora, Agaricia, and  Porites.. High to moderate bleaching was
prevalent in Montastrea, Siderastrea, and Diploria. Moderate to low
bleaching occurred in Dendrogyra and Acropora (although A. palmata was only
moderately bleached on the main Barrier Reef, but some totally
bleached colonies were seen lagoon patch reefs.
 (Tom Bright)

Bonaire (Dutch Antilles)
Less than 15% of corals have bleached in August and September 1998, with
partial bleaching in Montastrea  annularis between 10 and 20 m and in
Agaricia below 20 m. Only a few, small corals in shallow water appear to
have bleached.
(Kalli De Meyer)

Cayman Islands
Unprecedented bleaching has occurred during late September 1998 on Little
Cayman and Grand Cayman, with all species affected and possibly 90% of all
corals heavily bleached. There was extensive bleaching of Acropora palmata
and  Montastrea annularis at 1 - 5 m depth, and widespread mortality to the
abundant Millepora. Even previously resilient Montastrea cavernosa partly
bleached. Between 50 and 60% of large colonies of Montastraea faveolata
bleached on the North Side of Grand Cayman, but there was virtually no
bleaching on the West Wall.
(Phil Bush and Jason DeSalvo)

No bleaching has been reported on the south coast of Cuba. =20
(Judy Lang, Peter Sale)
Florida (USA)
Scattered bleaching was observed in inshore waters of the Florida Keys in
early August, 1997, with some  colonies partially bleached and others
extremely mottled or blotched. Small colonies were entirely bleached.=20
Extensive bleaching to large coral heads in the Gulf of Mexico area of the
Keys (Boca Grande Channel, between Boca Grande Key and the Marquesas Keys)
was also reported.

In July and August, 1998 there was bleaching at Coffins Patch Light in the
Florida Keys, with water temperatures of 30 and 31oC.  Minimal bleaching
was observed Millepora colonies, but there was none on nearby Coffins Patch
Special Protected Area (SPA). In late August, 1998 extensive bleaching was
seen in Western Sambo Ecological Reserve, Florida Keys. Surface water
temperatures were between 30 and 31oC, but 26oC at 10 m. Bleaching was seen
in up to 90% of Acropora palmata, with some mortality, 50-80% of Montastrea
annularis and A. cervicornis, and 40-60% of other corals.  There was
moderate bleaching between 10 and 30 m in Dry Tortugas National Park and on
the Tortugas Banks in early September, 1998. Approximately 15 to 25% of
colonies were affected with water temperatures around 30oC. There was also
evidence of bleaching at Ft. Jefferson. In September there was significant
recovery of corals on an inshore patch reef known as the Rocks that had
been severely bleached in June. Very little mortality was evident.
 (Billy Causey, George Garrett, Ben Haskell, Walt Jaap, Alina Szmant)

Some bleaching was reported for the Yucatan coast, but no bleaching was
seen near Cozumel.
(Judy Lang and Peter Sale)

Puerto Rico=09
There was no bleaching in 1997. There was, however, moderate bleaching in
1996 after Hurricane Hortense hit the south coast, and all colonies
recovered well from partial or total bleaching. In 1998, there has been
sporadic, but low frequency bleaching, in several species down to 30 m
deep. The most affected were a zoanthid (Palythoa caribbaeroun), and
Millepora, but most other corals were normal.
(Ernesto Weil)


A large area of the Carribee bank reef at 25 to 30m on the south coast has
bleached, apparently in September,1998.
(Renata Goodridge)


There was mass bleaching on patch reefs off the northern coast of Bahia
State (12oS; 38oW) on 14-APR-98. There was bleaching of: more than 90% of
Mussismilia hispida (endemic coral); 80% of Agaricia agaricites; and 70% of
Siderastrea stellata (endemic). Other corals may have been less affected
when water temperatures reached 29.5oC on the bottom of these reefs at 9to
12 m, the highest temperature measured during the last 3 years.
(Ruy Kenji)

Acknowledgements: Thanks go to all those people mentioned above who
provided reports.  Special thanks go to Al Strong who provides regular
reports on sea surface temperatures from the National Oceanic and
Atmospheric Administration of USA, and Jim Hendee who runs the NOAA coral
e-mail listing, which has compiled many bleaching reports.

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