Florida is the only state in the continental United States to have extensive shallow coral reef formations near its coasts. These reefs extend from near Stuart in Martin County on the Atlantic coast, to the Dry Tortugas in the Gulf of Mexico. The most prolific reef development occurs seaward of the Florida Keys. The most extensive living coral reef in the United States is adjacent to the island chain of the Florida Keys. The Florida Reef Tract which extends from Soldier Key, located in Biscayne Bay, to the Tortugas Banks possesses coral formations very similar to those found in the Bahamas and Caribbean Sea. The Florida Reef Tract is nearly 150 miles long and about 4 miles wide extending to the edge of the Florida Straits. It is the third largest barrier reef ecosystem in the world. All but the northern-most extent of the reef tract lies within the boundaries of the Florida Keys National Marine Sanctuary. The 2,800 square nautical mile Florida Keys National Marine Sanctuary (FKNMS), designated in 1992, surrounds the entire archipelago of the Florida Keys and includes the productive waters of Florida Bay, the Gulf of Mexico and the Atlantic Ocean. Discontinuous and less biologically diverse coral reef communities continue northward along western Florida shores to the Florida Middle Grounds, a series of submerged pinnacles rising to within 60-80 ft of the surface, about 100 miles northwest of St. Petersburg.In addition to local residents, millions of vacationers come to Florida in order to enjoy scuba diving, snorkeling, and fishing on south Florida’s coral reefs. These activities provide a great source of income for Florida and its coastal communities. It is estimated that coral reef activities in Martin, Palm Beach, Broward and Miami-Dade counties generate $3.4 billion in sales in general and income and support 36,000 jobs in the region each year.

florida-reef-sistemFlorida reef tract

Reef Structure and Physical Features:


The Florida reef tract is the most extensive living coral barrier reef system in North American waters and the third largest system in the world. The reef tract has a distinct profile along most of its length, with depths decreasing seaward of Hawk Channel toward the reef tract. Scattered dead coral outcroppings supporting sparse hardbottom biota are dispersed in seagrass beds, marking the landward edge of the bank reef community. Just seaward is a discontinuous band of offshore patch reefs that parallel the Keys and comprise the first major habitat encountered in a seaward progression toward the reef tract. The topographic relief of patch reefs varies depending on their proximity to the more seaward back reef and bank reef communities. Sediment accumulation landward and behind some bank reefs is rapid, and may have an effect on the relief of offshore patch reefs.

A back reef or reef flat (i.e., a shallow water habitat dominated by turtle grass and manatee grass, with scattered coral heads and small patch reefs) separates the offshore patch reefs from the bank reefs. Bank reefs are considered unique due to the presence of elkhorn coral (Acropora palmata), coral zonation by depth, and seawardly oriented spur-and-groove formations. These formations give the reefs three-dimensional relief and contribute to their complexity. Many of these reefs are found 4.6 to 6 m below the surface.

Seaward of the bank reefs are deeper intermediate reef communities. This habitat, which forms the majority of available reef substrate along the reef tract, begins at an approximate depth of 10 m and extends out to a depth of approximately 19 to 21 m. The slope is gradual, decreasing only about 11 m over 1 km. The reef is composed of a drowned spur-and-groove system exhibiting low-profile coral spurs.

At about 20 m, the intermediate reef begins to slope at a greater angle, and a deep reef habitat is formed descending to about 30 m. At the deepest margin of the deep reef habitat, the reef terminates into soft sand/mud substrate. This extends seaward, gradually sloping until it reaches a deeper reef community approximately 1 km from the base of the deep reef called the outlier reef.


Coral Species and Cover:

A survey at Looe Key, one of the more diverse reefs in the Florida Keys, reported 63 taxa of stony corals, 42 species of octocorals, and two species of fire coral. Stony corals and octocorals dominate offshore patch reef habitat. Massive corals include: Montastrea faveolata, Montastrea cavernosa, Solenastrea bournoni, Dendrogyra cylindrus, and giant brain coral. Millepora complanata, Acropora palmata, boulder corals, head corals, and soft corals are typical on the bank reef. Boulder corals are most prominent on the intermediate reef where colonies of Porites are sometimes over 1 m in diameter. Platelike growth forms of Agaricia agaricites, Montastrea faveolata, Montastrea cavernosa, and Madracis mirabilis and deepwater octocorals such as Ellisella barbadensis and Iciligorgia schrammi are common on the deep and outlier reefs.



 Giant brain coral

Other Fauna and Flora:

Over 500 fish species have been recorded in the sanctuary. Queen and horse conch are found occasionally on seagrass and sand areas. The spiny lobster, snow crab, echinoderms, Caribbean manatee, American crocodile, and leatherback, loggerhead, Kemp’s ridley, and green sea turtles may occur. Seagrass communities surround the offshore patch reefs. Dominant plants of the fore reef include encrusting red algae of the genera Lithothamnium, Goniolithon, and Peyssonellia. Halimeda opuntia and Dictyota species occur on the fore reef and the intermediate reef.



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