SPATIAL VARIATION OF DIADEMA ANTILLARUM SETTLEMENT IN LA PARGUERA, PUERTO RICO

Settlement of Diadema antillarum (Philippi, 1845) was studied at monthly intervals with artificial turf plates at six reefs along an inshore-offshore gradient in La Parguera, Puerto Rico, from February to April 2008, and from July to September 2008. Plates were placed at various depths on individual mooring lines. From a total. of 220 D. antillarum settlers, 217 were collected from the shelf-edge reefs (Old Buoy and El Hoyo). The remaining three settlers were collected at Media Luna, a mid-shelf reef. The optimal depth for D. antillarum settlement at the shelf-edge was or. the 9 m plates, with lowest settlement found on the shallower plates. Fouling of settlement substrate was shown not to be a major factor influencing settlement of D. antillarum on plates at inshore and mid-shelf reefs. Inner and mid-shelf reefs had higher abundances of microinvertebrates, particularly lobsters. The inverse relationship between settlement by D. antillarum and other microinvertebrates warrants further analysis. Post-settlement mortality may be regulating populations of D. antillarum at the shelf-edge, while settler mortality and/or low larval supply are two factors that may limit rapid recovery of D. antillarum populations at the inshore and mid-shelf reefs.