As South Florida braces for what experts predict could be another record-breaking hot summer, coral scientists are racing against time to protect one of the planet’s most fragile ecosystems.
With ocean temperatures already surging, researchers fear another devastating mass bleaching event could further cripple Florida’s struggling reefs.
On a sweltering summer morning, volunteers from Rock the Ocean joined scientists from the University of Miami’s Rescue a Reef program on a coral restoration mission off the coast of Key Biscayne.
Their work has become increasingly urgent after recent data revealed sea surface temperatures in parts of Florida Bay reached an alarming 97 degrees.
“Miami has been feeling that heat stress for actually three years straight,” said Dalton Hesley, a coral restoration ecologist at the University of Miami’s Rosenstiel School.
The extreme conditions are reminiscent of the historic summer of 2023, when South Florida experienced the worst coral bleaching event ever recorded. During that crisis, NOAA scientists documented near-total bleaching across many reef systems.
“We’re seeing 100% bleaching. That’s crazy. It’s absolutely crazy,” NOAA coral program lead Ian Enochs said during the event.
While NOAA has not yet reported widespread bleaching in the Florida Keys this season, early warning signs are already appearing closer to Miami. Colin Foord, of Coral Morphologic, who operates the Coral City Camera at Government Cut, recently observed bleaching in roughly 25% of corals near PortMiami.
“We’re ground zero for the coral crisis,” Hesley said.
Florida’s reefs have already suffered catastrophic losses over the past several decades. Since the 1970s, more than 90% of the state’s coral cover has disappeared due to warming oceans, disease outbreaks, hurricanes, and pollution.
“There’s been a suite of stressors that have really decimated our reefs to the point that they’re on the brink,” Hesley explained.
Growing Corals Underwater
About three miles offshore lies Paradise Reef, home to Rescue a Reef’s underwater coral nursery. The site functions like an ocean farm where scientists grow young corals before transplanting them onto damaged reefs.
Critically endangered staghorn corals hang from metal “trees” suspended underwater. Volunteers regularly clean the structures to remove algae, barnacles, and sponges that can smother the growing corals.
“If we’re not there to actually clean them, they’re going to get overgrown,” Hesley said. “We want these to be healthy habitats for the corals themselves.”
Once mature enough, the corals are harvested by clipping fragments from the nursery trees. Those fragments are then carefully planted onto nearby wild reefs.
“We easily planted over 150 staghorn corals, a threatened species today, back onto the reef to really fill in this restoration site,” Hesley said.
Over the past decade, Rescue a Reef has restored approximately 2,000 corals at the local site alone. But scientists acknowledge restoration alone will not fully reverse decades of reef decline.
Building “Super Corals”
Researchers are now turning to science and selective breeding in hopes of creating more heat-tolerant corals capable of surviving warmer oceans.
Just weeks before the latest restoration mission, scientists launched a groundbreaking pilot project aimed at reviving Florida’s endangered elkhorn coral using heat-resistant coral strains from Honduras.
“It’s the first time ever that it’s been permitted and we’ve gone ahead and outplanted,” said Dr. Andrew Baker, a marine biologist at the University of Miami Rosenstiel School.
Last year, University of Miami scientists traveled to Tela Bay, Honduras, where they collected fragments from unusually resilient elkhorn corals. Those corals were later crossbred with Florida elkhorn coral in partnership with the Florida Aquarium.
The resulting juvenile corals — now planted on a Miami reef — could represent a critical step toward building reefs better adapted to climate change.
“We’re going to see how well these do over the next few months, particularly over the course of a warm summer, to see if they are more thermally tolerant, as we hope, and better able to deal with the changing conditions in Florida’s corals reef,” Baker said.
Combined with Miami’s own resilient urban corals, scientists believe these so-called “super corals” may help shape the future of reef restoration.
“They are tough, so they are special,” Hesley said. “We’re trying to better understand why, so we can integrate that into gardening and restoration. So we’re building that super coral reef.”
Still, scientists stress that even the most resilient corals cannot survive indefinitely without broader action on climate change.
No matter how resilient we make our reefs, unless we address the root cause behind the coral crisis — climate change, greenhouse gas emissions, pollution — our coral reefs don’t stand a chance.
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