What Is Happening to Florida's Coral Reefs? Status and Threats

Florida’s Coral Reef at a glance

Florida’s Coral Reef is the only coral barrier reef in the continental United States and is often described as the third-largest barrier reef system in the world. It stretches for more than 500 km (over 300 miles), from the Dry Tortugas west of Key West, along the Florida Keys and the coast of Miami, to the St. Lucie Inlet north of Palm Beach. The main reef tract lies a few miles offshore of the Keys and contains thousands of individual reefs, home to more than 45 species of stony coral.

The reef is also a pillar of the local economy, supporting fishing and tourism and protecting coasts from storm waves. Most of it lies inside protected areas, including John Pennekamp Coral Reef State Park, Biscayne National Park, Dry Tortugas National Park and Florida Keys National Marine Sanctuary.

How much coral has Florida lost?

Until the late 1970s, shallow reefs in the Keys were dominated by thickets of staghorn coral and forests of elkhorn coral. Then the losses began. At Molasses Reef, staghorn coral declined by 96 percent between 1981 and 1986, and at Looe Key, elkhorn coral fell by 93 percent and staghorn by 98 percent between 1983 and 2000.

By the late 2010s, NOAA scientists estimated that only about 2 percent of the reef’s original coral cover remained. Much of the reef is now covered by algae, sponges and soft corals such as sea fans, which are not reef builders. Few young stony corals manage to settle and survive, so natural recovery has been very slow.

Disease: from white band to stony coral tissue loss disease

The first great blow came from white band disease, which swept through elkhorn and staghorn corals across the Caribbean from the late 1970s and killed most of them.

The second came in 2014, when a new disease was found on corals off Virginia Key, Miami. Stony coral tissue loss disease spreads quickly from coral to coral and strips the living tissue from more than 20 species, including brain, star, pillar and maze corals. Infected colonies often die within weeks or months, and death rates in susceptible species range from about two-thirds to nearly all colonies. By the early 2020s it had spread along the entire Florida reef and to many Caribbean islands. Florida’s population of pillar coral is now considered functionally extinct in the wild.

In response, divers have treated thousands of diseased colonies, and since the late 2010s a rescue program led by Florida and federal agencies, together with zoos and aquariums, has collected thousands of healthy corals from the reef. They are kept in tanks in Florida and other states as a living gene bank for future restoration.

The 2023 marine heatwave

In the summer of 2023, the waters around South Florida became hotter than ever recorded. From July, sea temperatures over much of the reef stayed well above the threshold for coral bleaching for weeks. A buoy in Manatee Bay, a shallow bay near the upper Keys, recorded about 38.4 °C (101.1 °F), though that site is not on the reef itself.

The heat caused bleaching from the Dry Tortugas to southeast Florida, and many corals died. A study published in 2025 found that 98–100 percent of the surveyed elkhorn and staghorn colonies in the Florida Keys and Dry Tortugas had died, leaving both species functionally extinct on Florida’s reef. Restoration teams raced to move nursery corals to deeper, cooler water and to tanks on land, which saved many genetic lines. How heat causes bleaching is explained in what is coral bleaching?

Other pressures on the reef

Heat and disease act on reefs that were already weakened by many other problems:

• Water quality. Runoff, wastewater and nutrients from land feed algae and fuel disease, and changes to freshwater flows through Florida Bay affect the reefs behind it.
• Loss of grazers. More than 97 percent of the long-spined sea urchins, important algae eaters, died across the Caribbean in 1983, and another die-off struck in 2022. Without them, seaweed can smother corals and young recruits.
• Storms and cold. Hurricanes such as Irma in 2017 broke and buried corals, and an unusual cold snap in January 2010 killed many shallow colonies.
• Physical damage. Boat groundings, anchors and careless contact break fragile coral.

Mission: Iconic Reefs and other restoration

In December 2019, NOAA and its partners launched Mission: Iconic Reefs, one of the largest coral restoration plans ever attempted. It focuses on seven reef sites in Florida Keys National Marine Sanctuary: Carysfort Reef, Horseshoe Reef, Cheeca Rocks, Newfound Harbor, Eastern Dry Rocks, Sombrero Reef and Looe Key.

The plan is designed to run for about 20 years. After clearing away competing algae, teams plant nursery-grown corals, starting with fast-growing elkhorn coral, which resists stony coral tissue loss disease, and adding star, brain, pillar and staghorn corals. They also release grazers such as long-spined sea urchins and Caribbean king crabs. The goal is to raise average coral cover at the seven sites to 15 percent in the first phase and 25 percent in the second, the level generally considered necessary for a healthy reef.

After the 2023 heatwave, the program adjusted its methods, outplanting fewer corals, timing planting around heat risk and focusing on healthy nurseries and heat-tolerant colonies. Other projects grow corals from spawn collected on the reef, which adds genetic variety; the methods are described in how do corals reproduce?

Is there hope for Florida’s reefs?

Florida’s reefs will not return to their 1970s state, but they are not lost. Some colonies survived the 2023 heat, and scientists are identifying and breeding the most heat-tolerant ones. Rescued corals in tanks preserve genetic diversity, restoration methods keep improving, and many fish, turtles, sponges and soft corals still make the reef a rich place to visit.

The long-term future depends on slowing ocean warming, while cleaner water, protected grazers and careful restoration buy time. Visitors can help by using mooring buoys instead of anchors, never touching or standing on coral, and following sanctuary rules.