Abstract

Twenty years have passed since the mass mortality event of the giant urchin, Diadema antillarum, across all the western region of the Atlantic. Nevertheless, the recovery of the populations of the specie has been extremely limited. In fact, little is known about the actual state of the populations of D. antillarum in Puerto Rico. The objectives of this study were: 1) to document the actual state of the populations in the fringing reefs of Puerto Rico; 2) to document the relationship that exists between the structure of the benthic reef’s communities and the populations of urchins; and 3) to determine if there exists some relationship between the water’s quality, the structure of the reef’s benthic communities and the density of urchins. Twenty-six localities around the island were studied using band transects of 15 x 2 m (n = 312 transects). The method of point-intersect transect was used to characterize the benthic communities in the same transects established to characterize the urchin populations. The horizontal water’s transparency was documented using an oceanographic Secchi disk. Significant differences were observed in the density of the populations of D. antillarum between the localities, and between geographic regions also. The largest densities were documented at Culebra’s region (13.2 individuals/ 30 m2), followed by the Northern region (6.9 individuals/ 30 m2), mainly, at the northwest. The largest densities of urchins were correlated positively with the coral cover percentage, the percentage of incrusting calcareous algae and the water’s transparency. Very low densities or absence of D. antillarum were documented in those localities under severe environmental degradation.

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