INCIDENCE OF PARTIAL MORTALITY AND OTHER HEALTH INDICATORS IN HARD-CORAL COMMUNITIES OF FOUR SOUTHWESTERN CARIBBEAN ATOLLS

摘要

Four southwestern Caribbean atolls (Albuquerque, Courtown, Roncador, and Serrana) were visited in 1994-95 to evaluate the status of coral reefs. A study of the health condition of hard corals (Cnidaria: Scleractinia and Milleporina) was performed at 62 stations, covering different reef environments from shore to 20 m depth. The surface of over 2100 colonies of 30 species was carefully examined along haphazardly selected linear transects. Old dead areas were found in a great number of colonies (mean = 78.9% ± 2.5%), but only 23.7% (± 1.7%) of the colonies showed evidence of recent mortality. Other frequent conditions were live tissue invaded by algae (mean = 54.1% ± 3.2%) and Stegastes planifrons (Cuvier in Cuvier and Valenciennes, 1830) territories (mean 11.5% ± 1.8%). Remaining recorded conditions (including diseases, predation, invasion by other organisms, and physical damages) occurred at frequencies < 9%. Mean affected area was < 4% of the colony surface, except for old mortality (mean = 33.2% ± 1.5%). Since the atolls are far away from continental influence and urban impacts, the origin of the high old coral mortality is probably related to degrading agents of regional and global nature occurring during the past 20 yrs (bleaching events, epidemic diseases, Diadema antillarum (Philippi, 1845) mortality).