The Return of Diadema antillarum to Discovery Bay: Patterns of Distribution and Abundance

Abstract

By 1999, populations of the sea urchin Diadema antillarum had begun a dramatic resurgence on the north coast of Jamaica after 23 years of stasis at very low levels. This increase in D. antillarum, from population levels near zero in 1984 to densities as high as 16 m2 in 2000, is associated with increases in abundance of the sympatric echinoids Echinometra viridis and Eucidaris tribuloides. In contrast, Tripneustes ventricosus was abundant on the fore reef in 1999 (unusual in that T. ventricosus generally inhabits back reef environments) but declined dramatically by 2000. Geographical Information Systems (GIS) analysis showed that D. antillarum rarely occurred alone: in 1999 and 2000, D. antillarum co-occurred with a second urchin species in 89.95% and 65.47% of the area surveyed respectively. Findings suggest that interactions between members of the echinoid complex are potentially important for reef recovery. Recent research conducted on the recovery of the D. antillarum population suggest that the presence of T. ventricosus on the fore reef may have created a disturbance large enough to facilitate a phase transition from algal to coral dominated substratum (Woodley et al. 1999). Our results are consistent with the findings of Woodley et al. (1999). We propose that recruitment of D. antillarum is facilitated by the presence of sympatric echinoids and is not dependent upon food availability. Sizes of D. antillarum populations at five sites were normally distributed, indicating strong, continued recruitment and suggesting that conditions conducive to reef recovery on the north coast of Jamaica have begun.This article was originally published at http://www.reefbase.org/download/download.aspx?type=1&docid=1231