Caribbean coral: Scientists make major breakthrough in revitalization

Scientists at the Florida Aquarium have made a breakthrough in the race to save Caribbean coral: For the first time, marine biologists have succeeded in breeding critical elkhorn coral using the technology of the aquarium.

It’s a historic step forward, and they hope it could help revitalize Caribbean ecosystems and could repay humans by providing additional protection from the fury of hurricanes.

Elkhorn coral once dominated the Caribbean. But, just as other vital coral ecosystems are being degraded around the world, elkhorns are now rarely seen alive in the wild. This species – so important as it provides the building blocks for reef development – has until now been notoriously difficult to cultivate in aquariums.

That’s why scientists were thrilled when they saw that their breeding experiment was a success.

“When it finally happened, the first feeling is just pure relief.” said Keri O’Neil, the senior scientist who oversees the Tampa Aquarium’s spawning lab. “This is a crucial step in preventing the extinction of elkhorn coral in the state of Florida.”

O’Neil’s colleagues call her the “coral whisperer” because she has managed to spawn so many varieties of coral. Elkhorn marks the 14th species in the aquarium spawned inside the Apollo Beach lab, but the team ranks it as the largest to date.

O’Neil estimates that there are only about 300 elkhorn corals left in the Florida Keys Reef Tract — but the spawning experience has produced thousands of baby corals. She expects up to 100 of them to survive to adulthood.

Named for its resemblance to elk antlers, the coral grows atop reefs, typically growing in water depths less than 20 feet. This makes their colonies crucial for breaking large waves. During peak hurricane season, the reefs are a silent but powerful ally that protects Florida’s shores from storm surges, which grow larger as sea levels rise.

“As these reefs die, they start to erode and we lose that coastal protection and all the habitat that these reefs provide for fish and other species,” O’Neil said. “Now there are so few left, just a few scattered colonies left. But we are really focused on restoring the elkhorn coral population for coastal protection.”

The Florida Aquarium news comes after scientists reported in early August that the Great Barrier Reef had the largest extent of coral cover in 36 years. But the outlook for coral around the world is bleak – studies have shown that the climate crisis could wipe out all of Earth’s coral reefs by the end of the century.

Elkhorn coral was listed as federally threatened under the US Endangered Species Act in 2006 after scientists found the disease had reduced the population by 97% since the 1980s. And global warming of the oceans is its greatest threat. As the temperature of the ocean rises, the coral expels the symbiotic algae that live there and produce nutrients. This is the process of coral bleaching, and it usually ends with the death of the coral.

“They’re dying all over the world,” O’Neil told CNN. “We’re at a point now where they may never be the same again. You can’t have ocean fever every summer and not expect there to be impacts.”


The Elkhorn coral seems to have something analogous to a fertility problem. Its reproduction is sporadic in nature, making it difficult to maintain a much-needed population increase. Due to their low reproductive rate, genetic diversity can also be very low, making them more susceptible to disease.

“You could say they have successful sex, but fail to make babies. [in the wild]“, O’Neil said. “Terrestrial animals do this all the time. When you have an endangered panda or chimpanzee, the first thing you do is start a breeding program, but coral breeding is super weird.”

The hardest part for O’Neil’s team was doing what was unprecedented: getting the coral to spawn in a lab. O’Neil said other researchers doubted they could pull it off.

“We faced a lot of criticism from people,” she said. They would say “”you can’t keep them in an aquarium. You know it’s impossible! “”

They were right. First.

The Elkhorn coral only spawns once a year. In the lab’s experiment in 2021, the environment was strictly controlled to mimic natural conditions. Using LED lights, they accurately mimicked the cycles of sunrise, sunset, and the moon. But the coral did not spawn.

We “realized that the timing of the moonrise was off by about three hours,” O’Neil said.

After that frustrating failure, aquarium scientists knew they had a much better chance this year. And, with support from the National Oceanic and Atmospheric Administration Restoration Center and the National Fish and Wildlife Foundation, the Florida Aquarium achieved in August what some peers thought was impossible.

Spawning could be a game-changer, according to Thomas Frazer, the dean of the College of Marine Science at the University of South Florida, and it could lead to a future where coral is more resilient to the dramatic changes brought about by the climate crisis. .

“This type of work really matters,” Frazer told CNN. “Corals selected for restoration could, for example, be more resistant to warmer ocean temperatures and bleaching, exhibit skeletal properties capable of withstanding more intense wave energy, or traits that could make them more resistant to disease. or other environmental stressors.”

Margeret W. Miller is a coral ecologist who has focused on restoration research for over two decades. Miller co-authored a study in 2020 that found the reproductive rate of elkhorns in the Upper Florida Keys was so low, it would indicate the species was already “functionally extinct” and could be wiped out in six to 12 years.

Miller said the Florida Aquarium’s breakthrough will open new doors to tackle the larger restoration effort.

“Because this species is an important restoration target, the ability to spawn under human care opens up many research opportunities to develop interventions that could make restoration efforts more resilient to climate change and other environmental threats.” , Miller told CNN.

Miller said more research needs to be done to ensure that lab-spawning elkhorn coral is reasonably safe and effective for use in species conservation.

“This type of captive spawning is not a tool that directly addresses widespread coral restoration on a global scale that would match the scale of the need. Indeed, no current coral restoration effort reaches this scale. , and none will truly succeed unless we can take serious action to ensure that coral reef habitats can remain in a viable state where corals can thrive,” Miller told CNN.

The climate crisis is the ultimate problem that must be solved, Miller said. The rapid increase in ocean temperature must be taken into account, as well as the threats to water quality. Still, she said, the ability to grow elk horn in a lab is an important tool in the restoration effort.

“Research on coral propagation and interventions that may be enabled by captive spawning efforts, however, may buy us time to make such changes effectively before corals completely disappear from our reefs,” said Miller.


Elkhorn branches can grow up to five inches per year, making it one of the fastest growing coral species, according to NOAA. And based on observations by Florida Aquarium scientists, their new baby Elkhorn corals will take three to five years to become sexually mature.

Within the next year or two, scientists plan to replant these lab-grown corals in the Florida Keys National Marine Sanctuary.

In the race to restore reefs, scientists agree that this breakthrough is just the first step.

“We’re really buying time,” O’Neil said. “We’re buying time for the reef. We’re buying time for the corals.”

The ultimate goal is a breeding program where scientists could select for genetic diversity and breed more resilient corals that can withstand threats such as pollution, warming ocean waters, and disease.

Then nature can take the wheel.

“There is hope for coral reefs,” O’Neil said. “Don’t lose hope. All is not lost. However, we need to make serious changes in our behavior to save this planet.”