Patterns of reef community structure, North Jamaica

Reef communities were quantitatively surveyed over the range of 0.5 to 56 m in the vicinity of Discovery Bay, Jamaica, at intervals spanning 1977–1982. This study provides data on reef communities which were subsequently altered by major disturbance events (e.g., Hurricane Allen in 1980 and the mass mortality of the urchin, Diadema in 1982). Living cover by the sessile epibiota is typically high, between 82–95%, at the census sites. Corals occupy from 28–60% of the reef surface with no clear depth-related trends in cover. The most striking bathymetric trends are displayed by the algae and sponges. Cover by macro- and filamentous algae (8–32%) and fleshy sponges (2–15%) is positively correlated with increasing depth on the fore reef while cover by coralline algae (4–37%) and boring sponges (0–32%) is negatively correlated with increasing depth.Coral species diversity (H′, loge) increases from 0.13 on the seaward portion of the reef crest at 0.5 m to 2.12 at 22 m on the fore reef escarpment. This highest value at 22 m may represent an edge effect. Despite the lowered rates of physical and biotic disturbance on the fore reef slope (30–56 m), diversity values fluctuate between 1.49–1.76 and are similar to, or higher than, values from the shallower (0.5–15 m) reef crest and fore reef terrace.Q-mode cluster analyses of eight reef sites resulted in the delineation of the following five reef zones (listed from onshore to offshore): the Rear Zone (1 m depth), Reef Crest (approximately 0.5–5 m), Lower Fore Reef Terrace (approximately 10–25 m), Upper Fore Reef Slope (approximately 30–45 m) and Lower Fore Reef Slope (approximately 45–60+ m). Similar zonations were produced regardless of whether the distribution of coral species or larger, operational taxonomic units (e.g., corals, coralline algae, macro- and filamentous algae, boring sponges and fleshy or erect sponges) were employed. Both biotic and abiotic factors contribute to this zonation