Grazing by the Echinoid <i>Diadema antillarum</i> Philippi: Formation of Halos around West Indian Patch Reefs

Between patch reefs and marine grass communities there is normally a zone or "halo" of heavily grazed grass 2 to 10 meters wide. Grazing by the echinoid Diadema antillarum Philippi during nocturnal migrations off the reefs is found to be the major factor in the formation of halos.