The Florida Reef (also known as the Great Florida Reef, Florida reefs, Florida Reef Tract and Florida Keys Reef Tract) is the only living coral barrier reef in the continental United States.The biggest coral reef in the continental U.S. is dissolving into the ocean Accessed May 6, 2016 It lies a few miles seaward of the Florida Keys, is about 4 miles (6 to 7 km) wide and extends along the depth contour from Fowey Rocks just east of Soldier Key to just south of the Marquesas Keys. The system encompasses more than 6,000 individual reefs. Florida waters are home to over 500 marine fish and mammal species along with more than 45 species of stony corals and 35 species of octocorals.
Geography The barrier reef tract forms a great arc, concentric with the Florida Keys, with the northern end, in Biscayne National Park, oriented north-south and the western end, south of the Marquesas Keys, oriented east-west. The rest of the reef outside Biscayne National Park lies within John Pennekamp Coral Reef State Park and the Florida Keys National Marine Sanctuary. Coral reefs are also found in Dry Tortugas National Park west of the Marquesas Keys. The reefs are 5,000 to 7,000 years old, having developed since sea levels rose following the Wisconsinan glaciation.Florida's Coral Reefs Florida Department of Environmental Protection Accessed December 14, 2010.Florida Keys Conservation: National Marine Sanctuary Ichthyology at the Florida Museum of Natural History Accessed December 14, 2010Precht and Miller:243Marszalek et alia:224
Isolated coral patch reefs occur northward from Biscayne National Park as far north as Stuart, in Martin County. In 2024, Florida created the Kristin Jacob Coral Aquatic Preserve to protect the reefs north of Biscayne National Park. The reefs north of Fowey Rocks are non-accreting relicts, with three reef lines. The outer reef line grew from about 10,200 BP until about 8,000 BP. The middle reef line grew from about 6,000 BP until about 3,700 BP. The inner reef line ceased growing about 6,000 BP.
The densest and most spectacular reefs, along with the highest water clarity, are found to the seaward of Key Largo (in and beyond John Pennekamp Coral Reef State Park) and Elliott Key (the northernmost 'true' Florida Key) where the two long keys help protect the reefs from the effects of water exchange with Florida Bay, Biscayne Bay, Card Sound and Barnes Sound. The bays and sounds (all between the Florida Keys and the mainland) tend to have lower salinity, higher turbidity and wider temperature variations than the water in the open ocean. Channels between the Keys allow brackish water from the bays to flow onto the reefs (especially in the middle Keys), limiting their growth.U.S. Geological Survey Circular 1134 - Florida Reef Tract Accessed December 16, 2010Precht and Miller:243Marszalek et alia:228 Microstructural abnormalities in large benthic foraminifera from the Florida Keys indicate carbonate chemistry stress that is also consistent with long-term environmental decline on the reef tract A 2024 study found that the best habitat for Acropora palmata restoration occurs in areas with low chlorophyll‑a levels, moderate wave exposure, and stable salinity, including Biscayne Bay, the Upper Keys, western‑lower Keys, and Dry Tortugas, while conditions in the middle Keys are generally less suitable.
Reef structure and communities The Florida Reef consists of two ridges separated from the Florida Keys by the Hawk Channel. Closest to the Keys is a sand ridge called White Bank, covered by large beds of sea grass, with patch reefs scattered across it. Further out to sea on the edge of the Florida Straits is the second ridge forming the outer reefs, covered by reefs and hard banks composed of coral rubble and sand.U.S. Geological Survey Circular 1134 - Florida Reef Tract Accessed December 16, 2010
Almost 1,400 species of marine plants and animals, including more than 40 species of stony corals and 500 species of fish, live on the Florida Reef. The Florida Reef lies close to the northern limit for tropical corals, but the species diversity on the reef is comparable to that of reef systems in the Caribbean Sea.
The Florida Museum of Natural History defines three communities on the Florida reefs. The hardbottom community lies closest to the Florida Keys and consists primarily of algae, sea fans (gorgonians) and stony corals growing on limestone rock that has a thin covering of sand. The stony corals in hardbottom communities include smooth starlet coral (Siderastrea radians), mustard hill coral (Porites astreoides), golfball coral (Favia fragum), elliptical star coral (Dichocoenia stokesii) and common brain coral (Diploria strigosa). Hardbottom provides habitat for sea anemones, molluscs, crabs, spiny lobsters, sea stars, sea cucumbers, tunicates and various fish, including grunts (Haemulon spp.), snappers (Lutjanus spp.), groupers (Epinephelus spp.), Atlantic blue tang (Acanthurus coeruleus), Ocean surgeon (Acanthurus bahianus) and Great barracuda (Spyraena barracuda).Hardbottom Community Ichthyology at the Florida Museum of Natural History Accessed December 15, 2010
Second is the patch reef community. Patch reefs form in shallow water (three to six meters deep), some in Hawk Channel and some on the outer reef, but mainly on White Bank between Hawk Channel and the outer reefs. Patch reefs start from corals growing on a hard bottom, but grow upward as new corals establish themselves on the skeletons of dead corals. Most of the structure of patch reefs is formed from star (Montastraea annularis, Siderastrea siderea) and brain corals (Diploria spp.). Other corals attach wherever there is an opening. Patch reefs may grow up to the surface of the water, and spread outwards. Dome-type patch reefs (such as Hen and Chickens), found in Hawk Channel and on White Bank, are round or elliptical, and are generally less than three meters high, but may reach up to nine meters high. Dome-type patch reefs are surrounded by sand which is kept clear due to browsing by long-spined sea urchins and grass-eating fish. Linear-type patch reefs are found on the outer reefs, and are linear or curved. They occur in single or multiple rows, trending the same direction as the bank reefs on the outer reefs. Linear-type patch reefs often include elkhorn coral, which is rare on the dome-type patch reefs. As dead coral skeletons age and are weakened by the activities of boring sponges, worms, and mollusks and by wave action, parts of a patch reef may collapse. Patch reefs provide habitat for spiny lobsters and for many species of fish, including Bluehead wrasse (Thalassoma bifasciatum), damselfish (Chromis spp.), Ocean surgeon, French and queen angelfish (Pomacanthus spp.), white, caesar and spanish grunts (Haemulon ssp.), yellowtail and other snappers, redband and stoplight parrotfish (Sparisoma ssp.), sergeant major (Abudefduf saxatilis), tomtate (Haemulon aurolineatum), trumpetfish (Aulostomus maculatus), filefish, groupers, snappers, bar jack (Caranx ruber), great barracuda, pufferfish, squirrelfish, cardinalfish, and green morays (Gymnothorax funebris).Patch Reef Community Ichthyology at the Florida Museum of Natural History Accessed December 15, 2010Marszalek et alia:224, 227
Third is the bank reef community. Bank reefs are larger than patch reefs and are found on the outer reefs. Bank reefs consist of three zones. The reef flat is closest to the keys, and consists of coralline algae growing on fragments of coral skeletons. Further out to sea are the spur and groove formations, low ridges of coral (the spurs) separated by channels with sand bottoms (the grooves). The shallowest parts of the spurs support fire corals and zoanthids. Starting at five or six feet deep, Elkhorn, star, and brain corals are the most important members of the community. Various types of gorgonians are also common. Beyond the spur and groove zone is the forereef, which slopes down to the deeps. The upper forereef is dominated by star coral. At greater depths plate-like corals dominate, and then as the available light fades, sponges and non-reef building corals become common. Bank reefs provide habitat for various fishes, including French angelfish, blue and queen parrotfish, Queen triggerfish (Balistes vetula), rock beauties (Holacanthus tricolor), Goatfish (Parupeneus cyclostomus), porkfish (Anisotremus virginicus) and snappers. The sand found around and in the Florida Reef is composed of shell, coral skeleton and limestone fragments.Bank Reef Community Ichthyology at the Florida Museum of Natural History Accessed December 15, 2010
In 2025, large‑scale planting of nursery‑grown corals began in the Florida Keys, aiming to expand restoration.These efforts involve growing corals in protected nursery environments until they are strong enough to be transplanted into degraded reef areas. Sediment analyses over time show a shift on the Florida Reef Tract, with coral debris tripling in the Middle Keys over a 37-year period, indicating major changes in reef framework production.
Other common species of hard coral found on the Florida Reef include Ivory Bush Coral (Oculina diffusa), which is the dominant coral in the patch reefs along the Florida coast north of the Florida Keys, staghorn coral (Acropora cervicornis), lettuce coral (Agaricia agaricites), grooved brain coral (Diploria labyrinthiformis), boulder star coral (Monstastrea annularis), great star coral (M. cavernosa), clubbed finger coral (Porites porites) and massive starlet coral (Siderastrea siderea).Common Corals of Florida Ichthyology at the Florida Museum of Natural History Accessed December 15, 2010Coral Reefs Geographical Distribution Ichthyology at the Florida Museum of Natural History Accessed December 15, 2010
Individual reefs Notable individual reefs in the Florida reef system include:
9-foot Stake (reef) Alligator Reef Ajax Reef Carysfort Reef Cheeca Rocks (reef) Coffins Patch (reef) Conch Reef Crocker Reef Davis Reef Dry Rocks (reef) Eastern Dry Rocks (reef) Eastern Sambo (reef) French Reef Grecian Rocks (reef) Hen and Chickens (reef) Looe Key Marker 32 (reef) Molasses Reef Newfound Harbor Key (reef) Pacific Reef Pickles Reef Rock Key (reef) Sand Key (reef) Snapper Ledge (reef) Sombrero Key Tennessee Reef The Elbow (reef) Turtle Reef Western Sambo (reef)
Threats to the reefs