Climate Change Threatens Florida's Corals in Water and on Land

On the morning of October 7, 2024, Keri O’Neil’s eyes were locked on National Weather Service updates as Hurricane Milton thundered across the Gulf of Mexico toward Florida. Still two days away from the coast, Milton was exploding in intensity, strengthening within hours from a Category 2 storm to a Category 5 monster with 180 mph winds and predicted to bring more than 12 feet of storm surge to the Tampa Bay area.

Front of mind for O’Neil were the thousands of corals under her team’s care at The Florida Aquarium’s Apollo Beach facilities on the east side of the bay. The facilities were built to withstand hurricane-force winds and are 11 feet above sea level, but they would be vulnerable if Milton’s power and path did not alter.

If O’Neil decided to relocate the corals to safety, it had to be now, before roads deadlocked with millions of Floridians fleeing the coast. She picked up the phone: It was go time.

Many of the corals that needed relocating were adults that had already been rescued from Florida's hot, polluted, and disease-addled waters. They are the broodstock for future reef restoration, and some represent the last of their kind. More Florida corals now live on land and in artificial coastal nurseries than in their natural habitat due to degraded water quality. But as Milton demonstrated, pulling corals from the water isn’t enough to keep them safe.

By the afternoon of the rescue mission ahead of Milton’s landfall, a group of coral scientists from multiple institutions, coordinated with help from NOAA and the Florida Fish and Wildlife Conservation Commission (FWC), was securing corals in baskets and lowering them into four-by-four-foot insulated bins and coolers of salt water. The team loaded more than 4,000 corals onto box trucks, working in shifts so staff could prep their homes for the storm.

“There’s no way we could evacuate every coral,” O’Neil said. “We were focusing on really rare individuals.”

Forty-two endangered pillar and elkhorn corals—species now considered functionally extinct in the wild—headed to the Reef Institute in West Palm Beach while boulder and brain corals found shelter at Atlanta’s Georgia Aquarium. Young corals that The Florida Aquarium had spawned in 2023 for restoration projects underwent an early delivery to collaborators at the University of Miami and the Keys Marine Laboratory.

The rapid-fire operation, executed by coral researchers from government agencies, universities, and nonprofits, is the latest example of how climate change continues to challenge scientists’ efforts to conserve Florida’s corals. The aquarium also evacuated corals ahead of Hurricane Ian in 2022 and served as a safe haven for corals evacuated from the Florida Keys during the unprecedented marine heat wave of 2023 that triggered mass coral bleaching. Some of the survivors of the 2023 crisis were among the Hurricane Milton evacuees. 

A recent study shows that climate change supercharged most Atlantic hurricanes between 2019 and 2023 and every hurricane in 2024, ratcheting up both Ian and Milton to Category 5 disasters.

“As sea surface temperatures go up, the amount of fuel available to these storms goes up,” said Daniel Gilford, lead author of the study and a climate scientist at Climate Central. “We're seeing just more intense hurricanes in general in the North Atlantic Ocean.”

Even in parts of Florida that lay outside Helene and Milton's direct paths—including the Reef Institute, in West Palm Beach—the storms brought rough winds, churning waves, and stronger rip currents that disrupted researchers' fieldwork for weeks. 

“We need to stop pretending that they’re not all going to be major hurricanes from now on,” said Leneita Fix, the institute’s director. The Reef Institute will move into a new 23,000-square-foot building in July 2025, not only to ramp up its coral breeding program and reef restoration efforts but also to have more space for emergency operations similar to the Milton evacuation. 

The Florida Coral Reef is the third-largest barrier reef on the planet, stretching more than 350 nautical miles from the St. Lucie Inlet on the East Coast to the Dry Tortugas in the Gulf of Mexico. Home to more than 60 species of coral, it helps buffer the coastline from waves and serves as a lynchpin for the state’s tourism and fishing industries, attracting divers and snorkelers and sheltering snapper, grouper, lobster, and other commercially important species. A 2020 NOAA report estimated the reef’s value at $8.5 billion. 

“It is probably the single most valuable natural resource in Florida,” said Jason Spadaro, manager of Mote Marine Laboratory’s Coral Reef Restoration Research Program.

But the Florida Coral Reef has been on the decline for decades, crippled by a changing climate, disease, and pollution. Overall, more than 50 percent of the reef’s coral cover has vanished in the last 25 years, with cover in the Keys in particular down by 98 percent. FWC researchers estimate about 50 million colonies of Florida’s five key reef-building species have perished since the first detection of the highly lethal Stony Tissue Coral Loss Disease in state waters in 2014. Then 2023 brought record-high ocean temperatures and the longest marine heat wave documented in 30 years. A sudden influx of broiling water in early July triggered mass coral bleaching and death, including at Mote’s most populous coral nursery—housed in the water off the coast of Looe Key—where researchers were cultivating tens of thousands of coral fragments for reef restoration. “[Almost] every single coral in the nursery bleached within about 48 hours,” Spadaro said. 

As water heats up, corals expel the symbiotic algae that lend them their vivid colors, and provide nutrients they need to survive, leaving behind a stark white skeleton. Spadaro was accustomed to seeing a gradual drain of corals’ deep golden color as they pale, then bleach. In many cases, corals can recover if temperatures cool. In July 2023, however, “This was such a dramatic slug of very hot water in a very short period of time that a lot of the corals did not even have time to bleach,” he says. “The tissue just started sloughing off.”

Mote mobilized staff and six research vessels to evacuate corals immediately from the water, pulling about 12,000 boulder, brain, and star corals from the Looe Key nursery and thousands of corals from other sites. Some coral scientists who witnessed the damage in the Keys, including O’Neil, wept into their dive masks.

“We’re losing the keystone species of the coral reef habitat,” said FWC’s Stephanie Schopmeyer, who assisted with the pre-Milton coral rescue operation after evacuating her St. Petersburg home. 

NOAA's Mission: Iconic Reefs is a collaborative, multi-decade program to restore seven iconic Florida reef sites, and in the program's management strategy scientists accounted for climate change. But "we didn't necessarily anticipate the severity and the duration of the bleaching event that happened [that] summer," said the program's then senior scientist Jennifer Moore in a 2024 interview with Sierra.

Relocating corals to land not only safeguards species from blinking out but gives scientists a chance to preserve, clone, and breed genetically unique individuals in the search for new combinations that can survive the challenges posed by Florida waters. The Florida Aquarium, which pioneered captive breeding in corals, is searching for variants that are more disease-resistant and can withstand thermal stress.

“Our program is really aimed at giving corals a chance to adapt to the changing ocean conditions,” O’Neil said.

In the short term, NOAA and Mote will pivot to focusing on reproducing boulder, brain, and star corals, which proved more resilient to 2023’s bleaching event and recovered more quickly than pillar and elkhorn corals. Researchers are also testing whether corals can be hardened against heat by exposing them to warm temperatures in the lab and experimenting with symbiotic algae that may boost their tolerance.

Florida’s coral scientists have faced criticism from the public and the larger scientific community for continuing to invest time, money, and energy into on-the-ground coral research and restoration. Their opponents argue those resources should be diverted to combating climate change instead.

“My counter to that is the alternative is not acceptable,” Moore said. “If we don't continue to grow and produce corals, there will be no corals around when we fix climate change.”

The Florida Aquarium’s Apollo Beach facilities were largely spared from Milton, which veered south, and it has since welcomed home all but one of its evacuated corals. A pillar coral, the last representative of its colony, succumbed to stress induced by its October journey. O’Neil said scientists will now prioritize cloning genetically unique corals from broken coral fragments, which can grow into new colonies. Storing the pieces in multiple locations is an insurance policy against future losses. Meanwhile, the mounting challenges of the past decade have engendered a new level of cooperation among Florida’s coral conservation community. 

“It's easy to get discouraged when so many difficult things are happening to Florida's coral reef,” said O’Neil. “But one thing that has come out of this is this amazing collaboration between coral scientists and knowing that we are stronger together.”