What Is The Florida Reef?

Stretching nearly 350 miles and forming a major part of both Biscayne and Dry Tortugas national parks, the Florida Reef is the only coral barrier bank reef in the continental United States and the third-largest in the world.  

This dynamic underwater ecosystem, with biodiversity rivaling that of tropical rainforests, supports more than 1,400 species of plants and animals. Among them are a third of Florida’s threatened and endangered species, including elkhorn and staghorn corals, green sea turtles, Nassau grouper, and humphead wrasse.

The reef is approximately 10,000 years old, having developed when sea levels rose following the last ice age. But its building blocks date back some 200,000 years to when sandbars in what are now the lower Florida Keys were shaped by tidal currents flowing between Florida Bay and the Atlantic Ocean. Coral reefs that dated to the same time period died when water levels dropped around 100,000 years ago. After sea levels stabilized following the ice age, corals began to grow on the former reefs.

Today the Florida Reef hosts more than 45 species of stony corals and 35 species of octocorals, along with marine species ranging from sea turtles and sponges to anemones, rays, lobsters and seabirds.

Reef Under Stress

But coral reefs are highly fragile ecosystems, vulnerable to shifts like water temperature changes and nutrient influx, and the Florida Reef has suffered dramatic degradation in recent years. Twelve reef species have been overfished to unsustainability, studies have shown. Only 2 percent coral cover remains at some monitored sites, according to the federal Office of National Marine Sanctuaries. The historic norm for healthy reefs in the Florida Keys was live coral cover of around 30 percent.

The reef-building corals — brain, star, and elkhorn corals — all now are in decline as warmer ocean temperatures lead to more frequent coral bleaching events, Among other stressors weighing in, stony coral tissue loss disease and other maladies degrade the reef. Pollution from sources including Florida’s drainage canal system taints the water. Marine debris and commercial and recreational fishing have diminished marine life.

In 2006, elkhorn and staghorn coral were listed as threatened species under the Endangered Species Act, and in 2014 the boulder star coral, mountainous star coral, lobed star coral, rough cactus coral and pillar coral were added..

The reef, which according to a 2016–2017 study funded by NOAA's Coral Reef Conservation Program generates $1.1 billion a year for the local economy and supports 71,000 South Florida jobs, is slow-growing, with coral colonies adding only one-half inch to seven inches a year. The living tissue known as coral polyps grows on the outer surface while its skeletons erode, producing the white sand that's prized on tourist beaches.

But coral growth can only occur on a solid structure for attachment, in water temperatures between 75°F and 85°F and clear waters low in phosphate and nitrogen nutrients, and with moderate wave action to disperse waste and bring oxygen and plankton to the reef. 

Florida Reef Parks

The reef is a dominant feature of Biscayne and Dry Tortugas national parks, which together draw around 600,000 visitors a year. It is closer to shore and lacks the shallow inshore lagoons found on most barrier reefs. Scientists therefore refer to the Florida Reef as a barrier bank reef. Particularly in nearshore reef areas like those in Biscayne National Park, changes in freshwater can affect salinity nutrient levels, and sediment, all factors in coral reef health.

Coral reef coverage at Biscayne is estimated at about 50 percent of the park. About 99 percent of Dry Tortugas is underwater, and approximately 37 percent of that area is covered by coral reef habitat.

Because the reefs are so central to the parks, both National Park Service staff at Biscayne and Dry Tortugas are working to protect and restore their corals. Initiatives aim to enhance knowledge of park reefs; improve or maintain the reefs’ ecological condition; and protect them from stressors and threats.

As part of their reef protection efforts, the parks conduct out-plantings of nursery-reared corals to increase abundance and diversity. They restore storm damaged corals and remove derelict fishing gear and other marine debris. They also conduct programs to manage invasive species such as the Indo-Pacific lionfish.

Everglades National Park, which borders but does not overlap with the reef, has developed a Comprehensive Everglades Restoration Plan (CERP) that benefits the reef. The plan is a collection of long-term projects to store, clean, and deliver freshwater more naturally across South Florida with the goal of restoring the natural flow of freshwater from the Kissimmee River south through the Greater Everglades ecosystem. Freshwater flows from the Everglades eventually enter Florida Bay and Biscayne Bay, which influence coastal ocean waters, including the Florida Reef Tract. 

In order to increase reef protections, Looe Key and Key Largo National Marine sanctuaries were created and then expanded in 1990 to form the sprawling Florida Keys National Marine Sanctuary. It encompasses approximately 3,427 square nautical miles of coastal, ocean, and Gulf of Mexico waters around the Florida Keys. The sanctuary is adjacent to Biscayne National Park and includes a zoned management system to reduce user conflicts. To protect the reef ecosystem, some reefs are off-limits with fishing restricted.