Caribbean Coral Reefs

The term "Caribbean coral reefs" (as used herein) includes reefs of the entire Greater Caribbean region, including Florida, The Bahamas, Bermuda, and the northeastern coast of South America.

While coral reefs throughout the world show many similarities in their basic structure, habitat types, and species interactions, there are some fundamental differences that distinguish Caribbean coral reefs from those of the Indo-Pacific region.

Coral Reef Types Of The Caribbean Region

The Greater Caribbean region is heavily dominated by fringing reefs.

Fringing reef off NW Cuban coast. Courtesy NOAA

In many cases these are quite extensive and well developed, such as those that parallel much of the coast of Cuba (see photo, left), and the the east coasts of Andros Island and Eleuthera in The Bahamas.

Fringing reefs also encircle most of the smaller islands of the Caribbean region, including those off the coasts of Bonaire and the Cayman Islands.

The entire Caribbean region is home to only two true barrier reefs. The largest (the Belize Barrier Reef) is about 220 km in length and runs from the Yucatan (southern Mexico) through Belize to the Gulf of Honduras. A smaller barrier reef lies north of Providencia Island (Colombia) in the southwest Caribbean.

There are also only a few true atolls (between about 10-20) in the Caribbean region. Most of these lie offshore Central America from the Yucatan to Nicaragua, and most (if not all) appear to have developed in ways other than volcanic island subsidence as is typical of Indo-Pacific atolls. The best developed atoll in the Caribbean region is Glover's Reef, which lies about 50 miles off shore the coast of southern Belize.

Distinctive Characteristics of Caribbean Reefs

Along with the overwhelming predominance of fringing reefs as the major reef type, Caribbean coral reefs differ from those of the Indo-Pacific region in a number of other distinctive ways.

One such marked difference is the rarity of a prominent algal ridge on Caribbean reef crests. This feature is a well-developed and prevalent component of Indo-Pacific reefs.

Another distinguishing feature of many shallow Caribbean reefs is that they often support an abundant mixture of sponges and octocorals that grow from the hard coral base of the reef (see photo; left). These additions afford Caribbean coral reef surfaces substantialadded biodiversity and topographic complexity.

Such features are not nearly so common or abundant on most Indo-Pacific reef surfaces, which tend to be mostly composed of hard corals (and microalgae) alone.

Well developed reef systems of the Caribbean region generally contain numerous patch reefs. Usually, the dominat corals of Caribbean patch reefs are Porites porites, Montastrea annularis, and other species of Diploria and Porites.

Northern Caribbean Reefs

The underlying geological structure of the northern portion of the Greater Caribbean region, particulalrly in The Bahamas and Turks and Caicos, differs from that found in almost all other island nations of the Caribbean region.

The Bahama Banks. Courtesy NASA

Nearly all of the islands and coral reefs of these two island nations are found along the rims of a number of large submarine formations called the Bahama Banks.

The Banks are extensive atoll-like structures consisting of shallow sand-topped plateaus rising from the surrounding deep blue ocean depths and ringed by islands and coral reefs.

Despite their appearance however, the Bahama Banks are not true atolls but rather were formed by completely different geological processes.

The large interiors of the Banks consist essentially of vast expanses of shallow (less than about 5 to 7 meters) back reef habitat composed largely of sand plains rimmed in many places by extensive mangrove forests. In some areas, the Banks also contain substantial seagrass meadows, and/or numerous isolated coral heads and patch reefs.

The outer rims of the Banks consist of areas that either simply drop abruptly into much deeper water, or form the floor of island chains and fringing reef systems.

Caicos Bank. Courtesy NASA

Coral reef systems of this northerly part of the Caribbean region are exclusively fringing reefs. There are no true barrier reefs or atolls (as Dawin defined them).

However, the particularly extensive and well-developed fringing reef system off the east coast of Andros Island is now often referred to as a "barrier reef" or "fringing-barrier reef".

In general, the fringing reef systems are best developed along the eastern margins of the Banks, where island coasts and reefs face prevailing trade winds and broad expanses of deep ocean. These conditions provide a clear water, high energy environment well suited for coral reef development.

Biodiversity Of Caribbean Reefs

The Greater Caribbean became completely isolated from the Pacific Ocean some 3-4 million years ago by the closing of the Isthmus of Panama, and has since developed its own unique coral reef biota.

The diversity of Caribbean coral reef life is considerably poorer than that of the Indo-Pacific region. Here, "only" about 65-75 species of hard corals are recognized and perhaps 500-700 reef-associated fish species.

The center of marine biodiversity for the region lies in the west-central Caribbean Sea, in the neighborhood of the Belize Barrier Reef. Reef biodiversity generally decreases with distance from this center.

For example, of the estimated 70 or so hard coral species recorded from the Greater Caribbean region as a whole, varying estimates ranging from 40-50 species have been recorded from The Bahamas. The number of reef-associated fish species likewise is about 480, or about 80% of the total reef fish species recorded in the entire Greater Caribbean.

Current Status of Caribbean Coral Reefs

For many nations within the Caribbean Sea, coral reefs provide vital protection from the rages of frequent summer hurricanes.

Many island and coastal residents are also highly dependent on coral reef fisheries for both their food supplies and livelihoods. Coral reef related tourism, particularly scuba diving, also represents a major source of revenue.

Over the last 30 years, Caribbean coral reefs have suffered enormous declines both in terms of overall coral reef ecosystem "health" and the productivity of reef fisheries.

Caribbean reef damaged by algal overgrowth. Credit: NOAA

Overdevelopment of coastal areas, overuse of particular reefs for recreational diving and snorkeling, and concurrent declines in water quality have in many cases led to large areas of hard coral becoming overgrown with smothering algae, leaving a devastated underwater seascape where once stood thriving hard coral colonies (see photo, above).

While the condition and extent of Bahamian reefs have drastically declined near the more developed and populated islands, they remain in generally good condition on more isolated out islands largely because of low levels of human impacts.

In recognition of the intrinsic value and vulnerability of their coral reef ecosystems, many Caribbean nations are developing more Marine Protected Areas (MPAs) and increasingly stringent regulations aimed at better protecting their coral reefs and associated marine life, and ensuring the continued quality of Caribbean diving for future generations.

Further Reading

Introduction to Caribbean Coral Reefs. This newly released Ebook is packed with color photos throughout. It simply and clearly describes the fascinating interplay - the ecology - of creatures, natural forces, and biological processes of Caribbean coral reefs.

A Field Guide to Coral Reefs: Caribbean and Florida (Peterson Field Guide Series. With more than 500 species described and more than 400 illustrations, this guide provides quick and easy visual identification of coral reef animals of the Caribbean and Florida.