With South Florida facing what could become another summer of blistering ocean heat, scientists are bracing for a disastrous coral bleaching season.
Groups across the state that tend to nurseries growing coral to restore Florida’s ailing reef have started making plans for a worse case scenario. In the Florida Keys, one nursery has begun labeling and preparing to move fragile elkhorn and staghorn coral to cooler, deeper water. Off Key Largo, elkhorn specially bred to be more heat tolerant will remain on reefs to test their durability.
The University of Miami Rosensteil School is leading responses, but each organization will determine its own plan of action.
Each “will have a different equation based on the number of people and funding they have,” said UM professor Andrew Baker, the program’s lead. “So everybody will have a different solution to that equation.”
READ MORE: Florida promised to restore a quarter of the state's reef by 2050. So where's the funding?
Chief on some lists: protecting the last remaining wild elkhorn coral declared functionally extinct last year.
In 2023, despite frantic efforts to move coral to deeper water and land-based facilities, a marine heat wave fueled by climate change blasted the nurseries and wilted the few remaining wild stands of reef-building elkhorn and staghorn. Few patches of native “Founders” elkhorn remain, with the largest collection now housed in an offshore nursery in Key Largo operated by Reef Renewal USA.
“I t's really important to maintain the Founders because all of your genetic diversity is wrapped up in those Founders,” said Ken Nedimyer, Reef Renewal’s technical director. “So keeping those alive is the primary focus of what we're trying to do right now.”
Since early June, waters around Florida have been steadily climbing, becoming hotter faster than in 2023, when reef after reef sizzled in the Florida Keys and parts of Miami-Dade County. On Monday, the National Oceanic and Atmospheric Administration upped its bleaching alert, with conditions now possible for significant bleaching. But Nedimyer said the reef is already showing signs of paling, fueling concerns that fragile elkhorn and staghorn being grown in offshore nurseries to help restore reefs could again be decimated.
”In 2023, the water temperature in the Middle and Lower Keys got so hot, it literally went to 94 degrees in a week,” Nedimyer said. “Those corals didn't even bleach, they just died.”
In the wake of the heat wave, nursery restoration efforts pivoted. Different groups operating nurseries in the Florida Keys began coordinating efforts. NOAA awarded UM’s Rosenstiel School a four-year, $16 million grant to oversee efforts by 10 groups. But with an El Nino expected to quiet this hurricane season, producing fewer storms to help cool water, the group’s weekly meetings have focused more often on what to do if another heat wave strikes, Baker said.
“The issue is not just that coral are going to accumulate more thermal stress but they’re experiencing high stress earlier, when they’re not ready,” he said. “It’s like getting caught with their pants down.”
For Baker, the heat could be the first real-world test for elkhorn coral specially cross-bred with elkhorn from Honduras that regularly endure hotter waters. The “Floridan” coral were planted off Key Largo in July 2025 and weathered that bleaching season in fine shape.
“But it wasn’t really a hard test,” he said. “They’ve got a hard test coming their way.”
At Reef Renewal, Nedimyer said he’s focused on preserving wild elkhorn he’s collected in his nursery and distributed to other groups to maintain genetic diversity. Reef Renewal’s offshore nursery near Key Largo now holds 100 different genotypes and the largest collection of native elkhorn, he said, with others kept at Mote Marine Laboratory and Coral Reef Foundation nurseries.
On Wednesday, Reef Renewal staff labelled and organized elkhorn to be moved in coolers to a deepwater nursery and possibly other land-based facilities. Corals expected to spawn in early August will remain until after they reproduce, Nedimyer said.
”These corals are 30, 40 inches across. They're really big,” he said. “Even if you had a big truck, you could only do 20 or so at a time. So it's logistically very, very difficult, and they're fragile, and they're sensitive to everything.”
Also, moving them now could disrupt their once-a-year fling.
“It’s a calculated gamble,” he said.
This year’s heat also comes at a time when the state has eliminated promised funding intended to help expand coral restoration programs. In 2023, Gov. Ron DeSantis set a state goal of restoring 25% of the reef by 2050, with $28.5 million budget to get a “coral pipeline” up and running and then $25 million a year starting in 2027 to maintain the work. Instead, programs have been left scrambling for money.
