In July, scientists outplanted very special elkhorn corals (Acropora palmata) onto a reef in Biscayne Bay. They believe these cross-bred corals, created from a Florida Keys/Honduras pairing, could hold the genetic keys to giving Florida’s elkhorns a fighting chance.
Elkhorn corals are a foundational species on the Florida Reef Tract, which includes the reefs in the Keys. The branching hard corals used to dominate the Caribbean, protecting shorelines from storm surge and providing critical habitat for many species.
Unfortunately, elkhorn populations have declined by more than 99% since the 1980s due to diseases, warming oceans, overuse and other stressors, the University of Miami (UMiami) reports.
As such, and because of how vital these corals are to the entire reef ecosystem, elkhorns have been a key focus of restoration efforts throughout the Florida Reef Tract.
Searching for resilience
“Today there are just 158 genetically unique individual Florida elkhorns in existence,” reports Anthropocene Magazine. “And just 23 of them are found in the wild.”
Genetic diversity gives all species a greater chance to evolve to cope with changing environmental conditions, including warmer water. After the 2023 mass bleaching event that killed off much of Florida’s living coral, scientists agreed our reefs need more diversity.
Given the state of Florida’s reefs, with corals too sparse and distant to meaningfully reproduce, Andrew Baker and his team recognized that they had to look beyond Florida’s waters to truly make a difference. Baker is the director of the Coral Reef Futures Lab at the University of Miami Rosenstiel School of Marine, Atmospheric and Earth Science and the study’s principal investigator.
Their search led them to Tela, Honduras, where over a dozen endangered coral species survive and even thrive — in conditions that normally kill corals. Groves of wild elkhorns stretch further than the eye can see, a site that Conchs in the 1970s and ‘80s recall nostalgically.
Even though they look like the reefs of old, these corals might be future-adapted, having endured over a century of pollution, heat and overuse. Nobody understands exactly what’s going on because so little science has been conducted on this spectacular reef.
Why plant a hybrid coral?
In 2024, Baker visited Tela to gather elkhorns and research their ability to withstand heat. Baker’s initial research shows that Tela’s corals have more thermotolerance than other elkhorns, a key adaptation that could help Florida’s struggling corals.
“The reef in Tela, Honduras, routinely experiences temperatures that are about 1-1/2 to 2 degrees warmer than Florida’s warmest temperatures and those are about the same kind of conditions that we saw in Florida in the 2023 bleaching event,” Baker told NPR.
The Honduran corals were crossed at the Florida Aquarium with corals from the Florida Keys that were rescued ahead of a disease front. The “Flonduran” babies have been growing at the aquarium for a year, awaiting their debut.
“Tela Bay’s reefs have shown us that corals can survive and even thrive in challenging, warm-water environments,” said Antal Borcsok, co-founder of Tela Marine, who coordinated efforts with Baker to get Tela’s corals to Florida. “By sharing this resilience and collaborating across borders, we are giving elkhorn coral a better chance not just in Honduras, but across the Caribbean.”
The ‘Flondurans’ are a first
In July, 35 Flonduran (Florida/Honduras) baby corals were planted next to 35 Florida corals that spawned on the same night. Monitoring will show whether, as scientists hope, the hybrid corals will retain more heat tolerance from their one Honduran parent than their Florida-Florida half-siblings.
“It’s the first time ever in the world that an international cross of corals from different countries have been permitted for outplanting on wild reefs,” Baker told CBS. If successful, the research could represent a fundamental shift in conservation science, which, until now, has been a closed-border endeavor.
The Florida Fish & Wildlife Conservation Commission granted Baker permission to outplant the Flondurans in Florida’s state waters because they recognized that mixing the Honduran and Floridian coral populations “mirrors natural processes in the wild and is critical to the species’ survival,” UMiami reported.
“Because Tela’s corals have had over a century to figure out how to thrive in much hotter conditions with a lot of runoff, which are like those in Florida today, we hope that their resiliency will be transferred to these offspring,” said Juli Berwald, co-founder of Tela Coral, a U.S.-based nonprofit working in Tela to safeguard these unique reefs.
What’s next?
The National Oceanic and Atmospheric Administration noted that Baker has been in talks with NOAA staff at the Florida Keys National Marine Sanctuary to determine if the Flondurans might also be suitable for Mission: Iconic Reefs, the $100-million Florida Keys-specific coral restoration effort that’s been underway since 2019.
If the Flondurans survive better than the control Florida crosses in the next marine heat wave, it paves the way for more international hybrids to be used in coral restoration in Florida and perhaps beyond. As of the last, unofficial reports, the Flondurans are still alive and appear to be larger than their Floridian counterparts.
