Assessing population structure of Diadema antillarum in a shallow reef of the southeastern coast of the Dominican Republic

The sea urchin Diadema antillarum is an herbivore that plays an important ecological role in controlling benthic community structure in Caribbean reefs. After the mass mortality documented between 1982-1983, their populations were reduced by 94-99% triggering a phase shift from coral to macroalgae-dominated benthic communities across the Caribbean. Almost 4 decades after its regional collapse, it is not clear weather D. antillarum populations are recovering, thus local surveys are valuable to track the fate of this herbivore. This study aims to determine the population structure of this sea urchin in a shallow reef located southeast of the Dominican Republic. We conducted a visual survey in three haphazardly selected sites of the reef studying a total surface of 90 m2 in which test size and D. antillarum densities were measured. Overall, the mean density of D. antillarum was 1.77 ± 1.07 ind/ m2 (Mean ± SD) with an average test size of 67.3 ± 22.7 mm (Mean ± SD) a median of 70 mm and a mode of 80 mm. Test diameter had a platykurtic distribution (kurtosis = 2.53) slightly skewed to the left (skewness = -0.1). This information is valuable to establish a local baseline to follow up the population dynamics of this key species.