One day in early April, coral scientists at the Florida Aquarium in Tampa received a surprise when they found a baby coral in one of their tanks. They'd been keeping their eye on a different coral species that was expected to reproduce, but they hadn't seen any results. The larva indicated that one of the other corals had started spawning instead.
Using special larval collector buckets, the scientists decided to observe the ridged cactus coral, a stony coral in shades of blue, green, and red that look almost peacock-like in photos. They placed it in the buckets overnight and awoke the next morning to find hundreds of larvae inside. The event marked the first time ridged cactus coral has ever reproduced while in human care.
In the past year, the aquarium has made several breakthroughs in coral spawning, advances that might have significant implications for reef restoration. Last August, in partnership with the Horniman Museum and Gardens in London, it became the first organization to successfully spawn Atlantic pillar coral using lab-induced techniques — the first time this had ever been done with any Atlantic coral species. The successful spawning of maze coral followed in the fall, then the ridged cactus coral success in one of its greenhouses (called coral arks) in April. Most recently, on May 20, another lab coral, the grooved brain coral, successfully spawned for the first time.
"It's still magical to me how they all know that it's time to go," says Keri O'Neil, a senior coral scientist at the aquarium. "They still know that even when they're not in the ocean and they are being given their environmental cues using technology."
These breakthroughs, while exciting, are just one step toward the much larger goal of the aquarium and its partners: to preserve and restore Florida's reefs.
At the outset, the aquarium's coral conservation program focused mainly on creating an archive of coral species native to Florida.
"When we first started, we were thinking of this project as a way to archive the genetic diversity of corals from Florida," O'Neil recounts. "We were looking to get a variety of different species and different genetic individuals and be able to hold them on land where they are protected from things like hurricanes and disease and climate change. But then, over time, we realized that we can do more than just archive them."
The Florida Reef Tract is the third-largest barrier reef in the world, spanning about 360 miles along the state's southeastern coast. Often nicknamed "America's Great Barrier Reef," it's formed by around 70 to 80 hard and soft coral species that provide a home to a host of sea life. During hurricanes, the reef also helps dissipate wave energy, preventing the full force of the waves from hitting the beach.
"People don't realize that the coral reef is important to our way of life in Florida," O'Neil says. "They protect our beaches, they provide habitat for our seafood, they give snorkelers and divers a reason to come to Florida to see our beautiful reefs. Once they're gone, we'll feel the impacts of that."
The reef faces threats from the impacts of climate change, such as warmer and more acidic water, and the reduction of key species that help maintain the balance of the ecosystem. In 2014, stony coral tissue loss disease began to invade the reef and infect corals. The deadly condition has since affected at least 22 species, spreading across the entire reef except for the remote Dry Tortugas National Park.
In response, the Florida Fish and Wildlife Conservation Commission and NOAA Fisheries spearheaded the Coral Rescue Project, sending scientists to collect members of the coral species that were most highly threatened by the disease, and those that were most important in reef-building. Their goal was to collect 200 healthy individuals from each species.
"The primary point of this project is to preserve the genetic diversity of these species before they're lost to the disease. That way we still have the diversity of genes to use for reproduction and restoration in the future," O'Neil says. The rescued corals are being stored at aquariums across the U.S., including the Florida Aquarium. The ridged cactus and grooved brain corals that recently spawned were both initially collected as part of this project.
In 2017, the aquarium partnered with the Horniman in London to work on reproducing corals in a lab setting, aiming to reintroduce the offspring back into the ocean.
"A lot of corals in the wild are now in such low numbers in Florida that their natural sexual reproduction is very limited or not occurring at all, and that's a problem because you can't adapt if you can't reproduce," O'Neil explains. "We're simply trying to fill that gap in the process by allowing these corals to reproduce and then recruit the offspring successfully and put them back into the population."
To get the corals to spawn, they found success using technology initially developed by coral hobbyists in the marine aquarium community who grow and trade Pacific corals and often have their own elaborate home aquarium systems.
"The knowledge that exists in that industry is really useful. It helps us understand what corals need to be able to thrive. It helps us understand how to best propagate them," O'Neil says. "The process of growing these corals in aquariums has grown so much in the past ten years, and now we are just starting to take that technology and bring it back into science and say, How do we use this to help save corals?"
For its lab-induced spawning systems, the Florida Aquarium uses computers and LED illumination to create temperature, sunset, sunrise, and moon cues to simulate the corals' environmental conditions in the wild. Researchers work to learn the unique needs and patterns of each coral species to best recreate the conditions they need to reproduce. For some corals, there's only a small window each year when reproduction occurs, giving the scientists little room for error. The corals also have different spawning patterns. A brooding species like the ridged cactus releases its sperm into the water, where it then finds its way to the female.
"We didn't know if our filtration systems might filter it out before it even got a chance to fertilize the other coral," O'Neil says.
When the coral reproduces, it releases fully formed babies one at a time over a long period — by the end of May, the coral had produced at least 1,500 larvae, and the scientists didn't know how long it might continue. The grooved brain coral, on the other hand, is known as a broadcast spawner.
"That one is this highly synchronized event, and all these bundles come out into the water within a few seconds of each other — it's like a snow globe," O'Neil says. The eight reproducing corals released almost half a million larvae between them.
To date, the aquarium has released three coral species back into the ocean, in partnership with the Coral Restoration Foundation on Key Largo. They've since been monitoring the young corals to see how they adapt, and O'Neil reports that they are doing well in the wild, with a survival rate of more than 90 percent.
"That's really exciting, and it kind of changes the way we think about restoration," she says. "When we return them to the ocean, these offspring now represent a much larger genetic diversity than what was in the original population, and hopefully, some of them are now able to withstand the stressors that are happening."
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While the aquarium's progress marks a significant step forward, O'Neil cautions that there's still a lot of work to be done to have a healthy, thriving Florida Reef Tract again.
"We would be extremely naive to say that breeding one coral species will save coral reefs — that's not the way it works," she says. "But I do look at it as buying time and securing the future of our coral reefs. We now have the ability to keep these corals healthy, keep them in a safe place, and produce hundreds of thousands of offspring when we know that they can survive back out on the reef."
Perhaps most exciting of all is the possibility that these discoveries can be replicated and further explored across the scientific community.
"Each individual spawning event is amazing and is a breakthrough and a milestone, but the bigger thing that gives me hope is the fact that this technology is working," O'Neil says. "This is now a tool that can be used by scientists around the world to do any number of research projects with corals that will help save coral reefs."