reefs are well developed in the leeward islands but poorly developed in the windward group; coral communities common but no structural reefs have been observed. the zonation with respect to depth, distance from shore and conformation to the bottom resembles that of other Caribbean reefs. density of living coral cover ranges from nearly zero to almost 100%. below 20-25 m on the forereef slope the corals are areally less abundant than crustose coralline algae. generic diversity of hermatypic corals is comparable in both groups of the dutch islands with 24 and 23 genera present. the number of species in the windward group is relatively low. zones: shore zone - Acropora palmata zone - barren zone - lower terrace (coral cover increases) - drop off zone (25-30% surface light, high coral cover) - upper slope (15-30 m depth, diverse but less cover) - lower slope (number of species and cover decreases). the morphology (form) of the reef afffects the zonation.