Spatial Variation of <i>Diadema Antillarum</i> Settlement in La Parguera, Puerto Rico

Abstract

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 on 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.