Bleaching and hurricane disturbances to populations of coral recruits in Belize

Abstract

In 1998, coral populations in Belize were disturbed simultaneously by a severe coral bleaching event and Hurricane Mitch. The impact of these disturbances was assessed for naturally occurring populations of coral recruits (2 to 20 mm diameter), at a depth of 8 to 10 m on the forereef of Glovers Atoll. Bleaching took place at all 4 study sites but the hurricane only affected 2 sites, enabling the effects of bleaching to be compared to those arising from bleaching plus hurricane damage. Predisturbance recruit density, size-frequency distribution, and community structure were similar between sites (at kilometre scales). The bleaching event lasted ca 3.5 mo. From 70 to 90 % of adult colonies bleached and at least 25 % of recruits exhibited signs of bleaching. A month after adult colonies had regained usual colouration, only 1 % of recruits showed even partial bleaching. Surprisingly, coral bleaching alone had no measurable effect on either recruit density or community structure. The combination of bleaching and hurricane disturbance reduced total recruit densities to 20 % of pre-disturbance levels. Effects of bleaching/hurricane disturbance on community structure were spatially patchy, and I suggest that such patchiness may arise from variable cover of protective microhabitat and/or different storm conditions mediated by proximity to reef cuts (breaks in the reef crest).