1998 Coral bleaching. Statement by ACOR

Michel PICHON pichon at univ-perp.fr
Fri Nov 20 03:32:23 EST 1998

 Would you please find below the text of the statement on the 1998 coral
bleaching episode observed in the reefs of the French overseas territories,
released by ACOR               (the French Coral Reef Society)

 Claude Payri, President





A bleaching episode which has affected many coral reefs in the world in
1998 has been experienced in a number of reefs in the French overseas
territories. However, although the phenomenon was geographically
widespread, there was considerable variation in its intensity from one
locality to the next. For instance, no bleaching at all was recorded in
1998 in New Caledonia and dependencies (where the last bleaching episode
occurred in 1995/96). In French Polynesia, no bleaching was reported from
the Society Islands, while a rather severe bleaching episode has affected
the atolls of the Tuamotus during the same period. (but even there, the
occurrence remained patchy).
As is usually the case during moderate to severe episodes, bleaching was
reported not only for scleractinian corals , but for other Cnidarians as
well, in particular hydrocorals (Millepora), alcyonaceans, actinians and
zoanthids. Among Indo Pacific scleractinian corals, the genera Pocillopora
and Acropora (especially tabular Acropora) were most bleached and showed
highest mortality.
Lagoon reefs and reefs in protected waters were generally affected, but
significant and sometimes severe bleaching was recorded on the outer
(oceanic) reef slopes down to 30 m.
As in many coral reefs world wide, bleaching is correlated with
higher-than-normal SSTs at the end of the summer season, but there is some
evidence that at least in some locations (Guadeloupe and Martinique, La
Réunion) freshwater runoff following periods of very heavy rainfall might
have acted as a triggering mechanism for the onset of bleaching.

In most localities, the situation is monitored with respect to recovery of
corals after bleaching.


® French West Indies (C. Bouchon):
*	No significant bleaching reported (< 1% colonies bleached) until
early October. Affected genera were: Diploria, Montastrea, Meandrina
(scleractinians), Millepora (hydrocoral), Condylactis (actinian), Palythoa
*	Maximum SST 29° C in September
*	Important bleaching, following cyclone "George" in early October.

® Mayotte (B. Thomassin)
*	Severe bleaching of corals and other cnidarians on the outer  reef
slope. Up to 80% of the colonies bleached on the upper outer slope. Most
affected genera were Pocillopora  and Acropora (tabular Acropora, e.g. A.
hyacinthus  seem to be most sensitive to bleaching).
*	Significant bleaching noted in the lagoon in May, most often
followed by recovery except for tabular Acropora , which had  high
mortality rates.
*	Maximum SST in late April-early May above 31°C in oceanic  waters.

® La Réunion (M. Pichon)
*	Significant bleaching was first observed in March, following heavy
rainfall throughout February. Bleaching was mostly recorded on the fringing
reef flats, with some occurrence on the outer slopes. Most affected genera
include Acropora,  Pocillopora  and Galaxea.

® New Caledonia (C. Chauvet, P. Joannot, L. Wantiez)
*	Only a handfull of small bleached tabular Acropora were recorded.
The whole of New Caledonia (both east coast and west coast reefs) and the
Loyalty Islands spared by the phenomenon which, so far, remains uncommon in
New Caledonia (Only one noteworthy episode in 1995/96).

® French Polynesia (Y. Chancerelle, B. Salvat)
*	No bleaching in the Society Islands (where the last severe episode
occured in 1990, with a less severe bleaching in 1994). Coral cover on the
outer slopes is still 30-50% i.e. normal for such communities in the area.
*	Severe but patchy bleaching in at least some of the Tuamotu atolls,
with significant coral mortality, for instance at Rangiroa and Manihi.
Bleaching affecting not only lagoon reefs but also outer slopes down to at
least 20 m. Percentage substratum cover by live corals at Takapoto has
dropped from 20% in 1994 to 12% after the 1998 bleaching event.
*	Maximum SST above 30° C.

	Michel  PICHON
	Laboratoire de Biologie Marine et Malacologie
	Ecole Pratique des Hautes Etudes
	Université de Perpignan   66860  PERPIGNAN Cedex. FRANCE
	Ph: 33 4 68 66 20 55   Fax: 33 4 68 50 36 86
	Email :  pichon at univ-perp.fr

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