The idea that Holocene-late Neogene reef building in the Caribbean has been generally limited by cold climate is well-embodied in the literature. The recent Caribbean reef summaries by Milliman and Glynn were both directed to showing that reef growth is not as limited as previously thought. Yet, Milliman (14) attributes a list of differences between Pacific and Caribbean reefs as primarily due to direct temperature limiting, and Glynn (8) refers to the possibility of Pleistocene refugia for reef fauna on the Brazilian coast. CLIMAP studies now indicate that there has been little change (1-3^o C) between the present 25-5~0"C water temperatures of most of the Caribbean and those of the last glacial maximum at 18,000 y B.P. In addition, it has been discovered that an extensive early Holocene barrier reef existed along much of the east Florida shelf and around the south side of the St. Croix shelf. Both of thesm areas now lack major shelf edge reefs. Also, the numerous reef borings taken in recent years in both the eastern and western Caribbean generally point to rich reef development. The Indo-Pacific is an enormous area with a considerable geologic diversity. Geologically, the much smaller Caribbean is probably best compared with the Philippine-Marianas region. Yet, while having a difference in coraldiversity that is about proportional to the difference in area, the Indo-Pacific and Caribbean would appear quite comparable in terms of Holocene bioherm construction.
The major framework elements in shallow (20 m) Caribbean reefs have been the scleractinian Acroporidae, Millepora and the coralline algae Porolithon and sometimes Lithophyllum. Porites, Diploria and Montastraea are important in quiet areas, back reefs, patches, and deep water, but are probably rarely critical elements in exposed, shallow water, elongate biohermal structures). As has generally been recognized in the Indo-Pacific, algal ridge frameworks characterize areas with consistently rough seas. In the Caribbean they are especially well-developed in the exposed Lesser Antilles, though in the unusually rough southwestern Caribbean , some algal ridges are also known. In reef crest areas of 2-3 m depth, there is an energy-related gradient of framework types of Acropora palmata/Millepora/Porolithon.
Acropora palmata, although a turbulent water species, is sensitive to breakage by wave action. Breakage in intensive surf, along with restricted grazing by fish and invertebrates on the relatively slow-growing corallines, are apparently the major factors that result in replacement of A. palmata by corallines in algal ridge structures.