Évolution récente des récifs coralliens des îles de la Guadeloupe et de Saint-Barthélemy

Recent evolution of the coral reefs of Guadeloupe and Saint-Barthélemy Islands.– The Guadeloupe Archipelago (with Guadeloupe, La Désirade, Marie-Galante, Les Saintes and Petite-Terre Islands), St. Barthélemy and St. Martin are located in the Lesser Antilles between 15° 50’ and 18° 00’ N. Guadeloupe possesses a barrier reef on its northern part, fringing reefs on the windward coast and highly diversifi ed non-reef building coral communities on the leeward coast. The other islands shelter fringing reefs and non-reef building coral communities. The coral reefs of the French West Indies are faced with a common set of threats : high rate of sedimentation, due to deforestation and bad land management, and algal proliferation due to an overload of nutrients in the coastal waters coming from excessive use of fertilizers and poor waste waters treatment. Their coral communities have exhibited a low progressive decline since the beginning of the eighties. Long-term monitoring sites have been implemented in Guadeloupe and St. Barthélemy since 2001. Results indicated the existence of a signifi cant tendency of the coral community to degrade over the study period. Moreover, a severe bleaching event appeared in 2005, when the sea temperature overshoot 29° C from mid May to mid November, with maximum values reaching 31° C. In 2006, in spite of normal seawater temperature conditions, an important delayed mortality affected the corals previously weakened by bleaching. As a fi nal result of the 2005 bleaching event, coral coverage on the reefs of Guadeloupe and St. Barthélemy dropped from 30 to 50 % according to the sites. Fish communities did not exhibit immediate impact of the bleaching event.