Florida Reefs

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Location on Continental Shelf
Mid-Shelf Bank
Area of Coverage
3035.00km2

From: NOAA, 2002; Porter and Porter, 2002
The Florida Keys, a chain of islands running in a southwesterly arc off the coast of South Florida, are home to the Florida reefs, the third largest shallow water coral reefs in the world. They have the only emergent coral reefs off the continental United States. The reef tract has been described as a bank reef system comprised of an almost continuous reef community with elongated reef habitats paralleling one another. In addition to the bank reefs, over 6000 circular to oval patch reefs lie along the Florida Reef Tract in 2 to 9 m of water. Arching southwest 356 km from South of Miami to the Dry Tortugas, the Florida reef tract comprises one of the largest reef communities in the world. It is almost continuous except between Rebecca Shoal and the Dry Tortugas. An outer reef tract lies 4.8 to 11.3 km east and south of the keys.

The majority of the reef tract lies within the boundaries of the Florida Keys National Marine Sanctuary. Two additional marine protected areas encompass reefs: the Biscayne and the Dry Tortugas National Parks. This sub-tropical region sustains many other interdependent habitats including fringing mangroves, seagrass meadows, hard bottom regions, patch reefs and bank reefs. This complex marine ecosystem is the foundation for the commercial fishing and tourism-based economies that are vital to south Florida. Major issues facing the sanctuary include declines in healthy corals brought on by an increase in coral disease and coral bleaching, invasion of algae in seagrass beds and coral reefs, overfishing, reduced freshwater inflow from Florida Bay, and damage to coral from careless boaters, snorkelers, divers and occasional large ship groundings.

Community Structure

The reef ecosystem of the Florida Keys consist of distinct habitat types: nearshore patch reefs, mid-channel reefs, offshore patch reefs, seagrass beds, back reefs, reef flats, bank or transitional reefs, intermediate reefs, deep reefs, outlier reefs and sand/soft bottom areas. Primary corals found in the outer reef tract include the star corals, massive starlet coral and fire corals.

Geological Characterization
The region consists of a series of carbonate banks, Holocene corals and several sandy islands, which define a roughly circular pattern. The seaward facing spur and groove formations of the Florida Reef Tract are constructional features formed partly by wave energy. They extend 1 – 2 km off the main reef, from 1 to 10 m. Historically, the top of the spurs were composed mainly of elkhorn coral, especially at depths less than 5 m, while grooves contained carbonate sands and reef rubble. These features are typically no more than 200 m long from offshore to onshore. Florida Bay islands (west of the Keys) are made mainly of modern sediment, carbonate mud, sand and mangrove peat, while the elevated Keys are made of limestone. The main stratigraphical units of the elevated Keys are the Key Largo Limestone and the Miami Limestone. The Key Largo Limestone is a raised coral reef, with thickness greater than 60 m, comprised of hermatypic corals with intra- and interbedded calcarenites. The Miami Limestone, which has a maximum thickness of 15 m, is comprised of a bryozoan facies and an oolitic facies.
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