Smith College
Extending for a distance of 250 km, the Belizean Barrier-Reef Complex is the largest continuous reef system in the western Atlantic. We initiated our study of the south-central province of the barrier reef and nearby backreef patches in January 1999 with a survey of 6 sites. We returned in May 1999 to re-census the same sites and extend our assessment to include 9 sites in the south-central region and 4 sites in the northern province off Ambergris Caye (over 5000 coral colonies were surveyed).
A combination of increasing fishing pressure; two recent coral bleaching events (1995 and 1998); mass die-off of a dominant space occupier, Acropora cervicornis, from white-band disease; and the effects of Hurricane Mitch in late October 1998 have taken a dramatic toll on the Belize reef complex. Snapper and grouper abundances were extremely low except within the Hol Chan Marine Reserve off Ambergris Caye. Very little living A. palmata was observed except in the forereef region; at backreef sites, heavy growth of macroalgae covered standing dead A. palmata colonies. Overall, macroalgal (fleshy) cover ranged from 10-40%; turf algae predominated at all sites. Agaricia tenuifolia, the major species colonizing the A. cervicornis rubble on the steep flanks of distinctive shoals of south-central Belize, experienced nearly 100% mortality associated with the recent bleaching event. The coral rubble on these steep flanks is now becoming covered by sponges. The mound and boulder corals were also strongly affected by the warming event; nearly all Montastrea annularis and Diploria spp. colonies were severely bleached (averaging >80% of the living coral colony). By May 1999, the majority of Diploria spp. and Siderastrea siderea had recovered; however, M. annularis still showed widespread bleaching, with nearly 50% of the colonies censused still bleached 9 months after the warming event. During the same time interval, the percentage of coral colonies showing signs of disease tripled, particularly among the mound species, likely related to the stress of bleaching.
The effects from Hurricane Mitch had the greatest impact on branching corals and gorgonians in the forereef region. Rubble and entire colonies of A. palmata and Diploria spp. littered the area immediately behind the reef crest. Overall, the corals in the forereef region showed significantly lower levels of recent mortality (~5%) and long dead (~25%) when compared with colonies censused in the backreef sites. Full recovery from these back-to-back severe natural disturbances may be difficult and lengthy for this reef system.
For more information contact Paulette Peckol ppeckol@email.smith.edu or Alan Curran acurran@science.smith.edu.
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