Caribbean Staghorn Coral Populations: Pre-Hurricane Allen Conditions in Discovery Bay, Jamaica
Abstract:In August 1980, Hurricane Allen caused damage of catastrophic proportions on the coral reefs of Discovery Bay, Jamaica. The extensive staghorn coral (Acropora cervicornis) beds were flattened and rapid recovery is not evident. This study describes the staghorn populations as they were before the hurricane; work on the present state of the reefs is in progress.
Three areas of Discovery Bay were studied. A. cervicornis was most abundant on the haystacks of the west fore reef between 5 and 20 m depth where up to 11 corals per m2 produced a maximum of 10 m of branches. Here the individual corals were significantly larger than those of the east fore reef or the back reef. Although a significant negative correlation of growth rate with depth (cm·yr−1 = 14.46 − 0.19 [depth, m]) was found on the west fore reef, the shallow corals were not taller but rather showed a higher level of branching; there is an indication that shallow corals branched more frequently. Contacts between adjacent corals were common and showed varying grades of tissue acceptance. The number of between-coral grafts did not correlate significantly with population density but did with water depth. An examination of branch orientation across the fore reef revealed a shift coincident with wave refraction but scatter was very high; frequent breakage disrupts the preferred growth directions.
Most of the staghorns at all sites had been broken at some time but the predominant method of reattachment differed at each site. The numbers of broken branches in corals on the fore reef was a function of coral size; in the back reef they were directly proportional to depth which suggests a lagoonward transport of the corals. An average of one-third of each coral is bare of tissue. The major predators are a sea urchin, damselfish, a snail and a polychaete. Clionid sponges are abundant in the coral skeleton. There is a large contribution by A. cervicornis to the skeletal calcium carbonate of the reef, and thus to vertical reef accumulation; this study estimates 1.4 kg·m−2·yr−1 in the cervicornis zone. There appeared to be a slight down-reef shift of material before it was cemented in place. A. cervicornis dominated the west fore reef community; abundances of massive corals fell where those of the staghorn rose.
The success of A. cervicornis derived primarily from its ability to regenerate from fragments. It exerts a competitive dominance over other space-occupiers by virtue of its high growth rate, a pronounced shading effect, mechanical damage to underlying corals through its breakage, and aseasonal recruitment to available spaces by fragmentation. There does appear to be a limit on its tolerance to disruption; present questions center around the fate of these Jamaican reefs.
Document Type: Research Article
Publication date: 1983-01-01
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