Diadema antillarum Population Status Assessment in Dominican Republic 30 Years after the Mass Mortality Event

Abstract

The long-spined sea urchin Diadema antillarum plays an important role in the coral reef community dynamics and geomorphology of the Caribbean. A dramatic dieoff event in 1983-84 reduced its population by as much as 95-99% throughout the Caribbean resulting in dramatic changes in the benthic community. This study aims to report population density; bathymetric distribution and population size structure of this sea urchin in four localities of Dominican Republic: Bayahibe, Punta Cana, Samana and Sosua. For this study, 15 m2 transects were conducted using a 0.5 x 0.5 (0.25) m2 quadrants at Acropora cervicornis restored reef sites. Transects were laid in and out the restored plots. The benthic cover was also estimated and classified in 5 main categories: macroalgae, coralline algae, corals, sand/rock/rubble and sponges. The mean density of D. antillarum obtained for the entire study was 0.89±0.11 Ind·m-2 (Mean ± SE, n=48). The distribution of this sea urchin was mostly limited to depths comprised from 1-10 m of the sublittoral; no significant differences were observed in the vertical distribution by age. The mean benthic cover found for the four localities was: Coral 6.75%, Macroalgae 22.66%, Coralline Algae 24.99%, Sand/Ruble/Rock 41.75% and Sponges 2.68%; although substrate communities vary significantly at different sites even within same localities, depending on multiple factors affecting the area. A discrete slow patchy recovery of D. antillarum has been observed in Dominican Republic.