scientific article | Bull Mar Sci
Kobluk DR, Lysenko MA
Within an interval of 18 h, beginning the afternoon of 25 June 1992, the water temperature at a site on the leeward fringing reef of Bonaire, N.A., declined from its normal value of 27.5°–28°C to 25°C. From 26 June 1992 to 2 July 1992, the water temperature remained low, at one point reaching 24.4°C. This was probably the result of the upward movement of a deep water thermocline to the sea surface. Coincident with this, Agaricia lamarcki, Agaricia fragilis, Eusmilia fastigiata, Diploria labyrinthiformis, Dichocoenia stokesi, Porites astreoides, Meandrina meandrites, Colpophyllia natans, and Siderastrea siderea showed minor bleaching of their tissue. Colonies of Montastrea annularis and Agaricia agaricites (both possibly species complexes) were greatly affected, with up to 84% of A. agaricites colonies at one point in the 7-day interval showing bleaching. The bleaching of A. agariciles was unusual because it appeared as thick white rings scattered over the colonies. In some cases the overlapping rings became so numerous that the colonies were fully bleached. The bleaching of corals in Bonaire (June 26–July 2, 1992) probably resulted from thermal shock caused by the rapidity of cooling combined with the reduction of water temperature to below the normal thermal tolerance of these corals. A comparison with the reefs and coral bleaching in the typically cooler northern waters of Bermuda suggests that in many cases it may not be the absolute water temperature (whether warm or cool) in itself that precipitates a bleaching reaction, but rather the rapidity of temperature change in combination with the deviation from the normal temperatures to which corals in a region are adapted.
Scleractinia (Hard Corals)
SCUBA (open-circuit or unspecified)