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Florida's Coral Reefs Quick Topics

Florida is the only state in the continental United States to have extensive shallow coral reef formations near its coasts. Coral reefs create specialized habitats that provide shelter, food and breeding sites for numerous plants and animals, including spiny lobster, snapper and other commercial and recreational species. Coral reefs lay the foundation of a dynamic ecosystem with tremendous biodiversity. The Florida Reef Tract (FRT) stretches 358 miles from the Dry Tortugas National Park off of the Florida Keys to the St. Lucie Inlet in Martin County. Roughly two thirds of the Florida Reef Tract lies within the Florida Keys National Marine Sanctuary (FKNMS), a marine protected area that surrounds the Florida Keys island chain. The reefs stretching north of the FKNMS are managed by the Florida Department of Environmental Protection's (DEP) Coral Reef Conservation Program (CRCP) and the Southeast Florida Coral Reef Initiative (SEFCRI), which is one of several programs administered by the CRCP.

Florida's coral reefs came into existence 5,000 to 7,000 years ago when sea levels rose following the last Ice Age. Reef growth is relatively slow; an individual colony may grow one-half inch to 7 inches a year, depending on the species. All coral reefs are in a constant state of flux. While expanding with new polyps (the living tissue) on the outer surface, they are simultaneously being ground into sand by storms and animals. During long periods of favorable conditions, the reefs may reach awe-inspiring heights and diversity.

Corals are classified as animals, yet microscopic plants live within the animal tissues in a symbiotic relationship. The coral animals benefit from the sugars and oxygen that the plants provide through photosynthesis and the plants gain nutrients from animal waste and are protected within the coral tissues. These tiny plants give the coral much of its color.

Coral reef development occurs only in areas with specific environmental characteristics: a solid structure for attachment, relatively warm water temperatures, clear waters low in phosphate and nitrogen nutrients, and moderate wave action to disperse wastes and bring oxygen and plankton to the reef. Most of Florida's sport fish species and many other marine animals spend significant parts of their lives around coral reefs.

Coral polyps close-up

Close-up detail of coral polyps on a great star coral (Montastrea cavernosa)
Photo: Dave Gilliam, National Coral Reef Institute

Types of Reefs and Corals

The three major types of coral reefs around the world are atolls, fringing reefs and barrier reefs. Florida's coral reef system most closely resembles a barrier reef, however, the reefs are closer to shore and they lack the shallow inshore lagoons found on most barrier reefs so it is more aptly named a bank reef. Florida also has patch reefs, which grow between the reef tract and the land in shallower waters. Patch reefs are typically small (the size of your back yard or a small home).

More than 45 species of stony corals and 37 species of octocorals are found along the Florida Reef Tract. Each kind lives in a separate colony that is shaped differently. The colonies take on the various hues of the algae that live within them. Corals can generally be divided into two main categories: stony corals and octocorals (sea fans and other soft corals). Marine sponges are also very important within the coral reef community and over 70 species can be found along the Florida Reef Tract.

Stony corals are the major reef architects. Polyps, the living portion of corals, extract calcium from seawater and combine it with carbon dioxide to construct the elaborate limestone skeletons that form the reef backbone.

Staghorn coral

A coral reef off Fort Lauderdale, FL with federally threatened staghorn corals (Acropora cervicornis) in the right foreground
Photo: Dave Gilliam, National Coral Reef Institute

Florida's most common reef-building corals are brain, star, elkhorn and staghorn. Brain coral is dome-shaped and has the waves, folds and ridges that resemble those of a human brain. Star coral is also dome-shaped, but has a distinctive star pattern on its surface that is caused by the accordion-like folds within its polyp cups. Elkhorn and staghorn corals are so named because their branchlike projections resemble the antlers of those animals. In recent years, corals have experienced declines due to a combination of factors, including coral disease and damage from hurricanes. In 2006, elkhorn and staghorn coral were listed as threatened species under the Endangered Species Act. To restore these corals that were once so abundant, coral nurseries have become established along Florida's coast and in the Florida Keys. Nurseries are growing new colonies and successfully out-planting them to locations where they had once flourished.

 

Octocorals, some of which are also called gorgonians, look like strange trees and shrubs, although they too are composed of living polyps. Unlike stony corals, octocorals are unable to build thick limestone skeletons, but are supported by an internal structure composed of a horn-like substance called gorgonin.

The most common octocorals in Florida are sea fans and sea whips. Sea fans are pale lavender or green fan-shaped corals. Their fans flutter in the ocean current like lace curtains. Sea whips have long feathery branches that spread in all directions. They can be orange, lilac, purple, yellow, brown or buff.


Along the northern extension of the Florida Reef Tract, the reefs generally occur in a series of one to three discontinuous reef lines (terraces) that parallel the shoreline, extending north from Miami-Dade County to Martin County.

Different reef organisms characterize the type of habitats found along Florida reefs, typically transitioning from a cover of algae and small octocorals nearshore to numerous octocorals and varied hard coral populations at the outer reefs. The various reef architectural and compositional components create an environment that is ecologically diverse and productive, one that supports many other aquatic plants and animals that make southeast Florida reefs their home.

 

Last updated: July 19, 2011

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