Mike Brittsan thinks back to his teens, when he was diving around Looe Key in the Florida Keys. “I remember elkhorn coral being everywhere back in the early 1970s,” he said. Today, that’s all changed, according to Brittsan, who is chairman of SECORE (SExual COral REproduction) International, a nonprofit coral reef conservation organization, and director of aquatic sciences and the dive and safety officer at the Columbus Zoo and Aquarium in Powell, Ohio, where SECORE is based. “Now when I go down there, the coral is not there,” he said.
Coral—elkhorn (Acropora palmata) and staghorn (Acropora cervicornis) coral, in particular—has been decimated throughout the Caribbean in the last four decades. Both are listed as threatened species under the Endangered Species Act and have suffered declines of more than 90 percent, according to the National Oceanic and Atmospheric Administration (NOAA). The decline began in the early 1980s after Diadema antillarum—a long black spine sea urchin that eats algae off coral reefs—died off, due to a waterborne pathogen. In its absence, young coral struggled against the algae growth. Coupled with other stressors, including pollution, climate change, overfishing, hurricanes, disease and more, the impact has reverberated throughout the ocean and beyond. As coral reefs dwindle, the oceans lose diverse ecosystems that support thousands of species and provide food, shoreline protection, marine habitats and tourism and recreational opportunities throughout the year.
Today, SECORE and the Columbus Zoo and Aquarium, in collaboration with facilities such as Shedd Aquarium in Chicago, Ill., Omaha’s Henry Doorly Zoo and Aquarium in Omaha, Neb., California Academy of Sciences in San Francisco, Calif., and others, are working to better understand—and reverse—the decline in coral. Brittsan said that teamwork among the Association of Zoos and Aquariums (AZA) community is key to future success, as these facilities work to put more coral back in the ocean and help bolster reefs for future generations.
Coral can reproduce in two ways: asexual reproduction (a piece of broken coral may reattach to the reef and grow into a new coral colony) and sexual reproduction (most coral are hermaphrodites and release their sperm and egg once a year).
When Dr. Dirk Petersen got the idea for SECORE in 2002, while researching coral at the Rotterdam Zoo in Rotterdam, Netherlands, one of his goals was to bring both the scientific and aquarium communities together to advance coral conservation through sexual reproduction. While scientists bring knowledge about reproduction and biology of coral, Petersen said they tend to be lacking in one important area: “Most scientists have no idea how to keep these animals alive,” said Bad Camberg, Germany-based Petersen, who is founder and executive director of SECORE. That’s where the aquarists come in. It’s an area where they excel.
At that time, most groups had been relying on asexual reproduction to grow their coral colonies for restoration. That, however, has its own limitations, said Petersen. “All these fragments are genetically identical and are basically clones of the donor colony, so they don’t contribute to genetic diversity,” he said. Genetic diversity is important because it allows a species to adapt to change. With the threats that coral is facing, that adaptation is imperative.
In 2006, SECORE led a workshop in Puerto Rico with the goal of collecting spawn, fertilizing them and growing coral in the labs of participating AZA-accredited facilities. Elkhorn coral is quite precise about when it spawns, and it only happens over a couple of nights each year—usually in early August, a few days after a full moon, between approximately 9:15 pm and 9:45 pm. A team of divers, coordinated by SECORE, planned accordingly. This was the first time that Mitch Carl, a SECORE member who sits on the organization’s Zoo and Aquarium Advisory Board and is curator of aquatics at Omaha’s Henry Doorly Zoo and Aquarium, had been involved in such a project, and he and the other attendees had a steep learning curve from the start.
The first night out, Carl was with another diver when they saw just what they were looking for: an egg sitting on a polyp. “You use your flashlight and you can see these pink little balls—you see them there on the polyp. And then they just release them kind of slowly, one by one,” he said. The divers were hoping to catch the eggs in a large funnel, which was topped with a bottle. Carl said the conditions were challenging. The water was only 10 or 15 feet deep, so the surge was difficult to navigate—especially while holding the large funnel and trying not to smash into the coral. “It was like you were controlling a giant wind sail in all the current,” he said. By the end of the night, they had collected about four eggs.
The team regrouped. They decided the funnels were too unwieldy, and they needed something akin to a net. With no aquaculture stores in sight, and no access to any kind of mesh netting, they had to be creative. “We used ladies’ slips and coat hangers,” said Carl. “We made butterfly nets out of that.”
Over the next two nights, the egg release came more quickly. “During a big spawn, they do start out slowly, but each colony can have hundreds of thousands of eggs (or more), and once they start to release them, it quickly becomes an underwater blizzard,” said Carl. Using their makeshift nets, they caught nearly 1 million egg bundles, which consist of 5 to 15 eggs wrapped in sperm. They took the egg bundles back to shore and shook them gently to help break up the bundles. Then, they placed the eggs from different coral colonies in the same cooler, diversifying the genetic makeup, and the sperm fertilized the eggs. The SECORE team cared for the gametes 24 hours a day, and, in time, representatives from different aquariums took them home to care for them in Omaha, Chicago, Columbus and other zoos and aquariums. Some of the coral are still around at AZA-accredited facilities today. “We were extremely successful,” said Carl.
That workshop informed future SECORE workshops, which have taken place in Puerto Rico, Mexico, Guam and Curaçao.
In 2010, SECORE, along with the Carmabi Marine Research Station in Curaçao; the Columbus Zoo and Aquarium; Omaha’s Henry Doorly Zoo and Aquarium; Shedd Aquarium; and the Pittsburgh Zoo & PPG Aquarium in Pittsburgh, Pa., began building a lab with a flow-through aquarium system at the Curaçao Sea Aquarium on Curaçao.
After collecting the spawn and raising elkhorn corals in the lab for a year, the team planted the thumb-sized corals on a reef in the Caribbean. Three years later, some corals reached the size of a soccer ball, and, to the delight of researchers, spawned.
“This is a real milestone because nobody knew when this coral species would reach maturity,” said Petersen. It’s the first time a critically threatened, lab-bred coral has sexually reproduced in the wild. The next step, said Petersen, is to apply the findings on a larger scale in Curaçao, Mexico and other places throughout the Caribbean.
One of the challenges coral faces when it comes to spawning is reaching other colonies in order to reproduce. If the sperm and egg from the same colony unite, nothing will happen. The sperm from one colony needs to reach the egg of a different colony to fertilize. Because coral populations have diminished, the colonies are now spaced so far apart that the sperm from one colony might not find the egg from another, said Brittsan. By adding more coral to the mix, the odds of successful reproduction increase. “We’re trying to bridge that gap by putting corals in between.”
To that end, asexual reproduction is another important part of the restoration puzzle. Andrew Stamper, science operations manager/clinical veterinarian at Disney's Animals, Science and Environment in Lake Buena Vista, Fla., has been doing just that—growing staghorn and elkhorn coral in nurseries and then transplanting them to reefs at Disney’s Castaway Cay, located in the southern Great Abaco of The Bahamas. Disney recently announced a new initiative called Reverse the Decline to focus on advancing collaborative and strategic conservation efforts to benefit wildlife, including coral reefs in The Bahamas. Disney will direct funding through the Disney Conservation Fund and engage the expertise of its teams to support research, conservation, restoration and education to address the threats facing coral. Stamper said the goal is to provide a framework and momentum to encourage others to get involved to make a difference for marine life and people in The Bahamas. To date, the project has brought together about 30 institutions—including several AZA-accredited facilities—to work throughout The Bahamas.
Stamper said that the coral Disney has transplanted has been resilient, despite the fact that other coral nearby underwent a massive bleaching recently. Coral bleaching occurs when stressed corals react to higher ocean temperatures, expelling the zooaxanthellae—photosynthetic algae—that grow in them and provide them with color, as well as food. “The corals that we put out on that reef actually did fantastic, where the others were not doing so well,” said Stamper. He’s continuing to study why.
Disney’s coral restoration work will, ultimately, help to complement the work that SECORE is doing with sexual coral reproduction. By establishing more reefs, more sexual reproduction will hopefully occur in the wild, helping to reverse the decline of coral reefs.
Of course, the success of coral restoration relies on more than sexual and asexual reproduction. A number of other factors must be addressed in order for coral colonies to thrive once again in the wild. Pollution, climate change, overfishing—the same things that have threatened coral for decades—are all still issues. Mark Schick, collection manager of special exhibits at Shedd Aquarium has worked on coral conservation with SECORE for years and said he’s optimistic about the future but is cautious about oversimplifying any kind of coral solution. “What we don’t want people to think is, ‘Oh there’s a problem; you just grow some [coral] out, throw ‘em out there, and they’ll be fine,” he said. “Well, you have to have the right habitat. You can’t take a coral and stick it in a forest and say it’s going to grow. If it’s full of pollution and improper fishing techniques are being used, or people are just walking on the reef, you can’t just regrow it.” Schick said that AZA-accredited zoos and aquariums have a powerful platform to educate people on the threats to coral in hopes of making a difference before it’s too late.
And there’s reason to be hopeful. SECORE’s success, so far, is inspiring to divers like Brittsan. While he may never see the types of coral forests he saw off the coast of Florida in the 1970s, he remains optimistic that he’ll see a difference in the next 20 or so years.
“When I see us putting these corals back and I see them growing to a soccer ball size, it makes me feel good. And then they spawn, and it makes me feel even better because that’s happening,” said Brittsan. “And I feel like maybe by the time I’m 80, if I’m still diving, I’ll see some cool coral reefs come back.”
Kate Silver is a writer based in Chicago, Ill.