The Coral Nursery

Story Highlights
  • Staghorn and elkhorn coral populations in the Florida Keys, the Dry Tortugas and the U.S. Virgin Islands have declined by more than 97 percent.
  • The Nature Conservancy and its partners are cultivating underwater nurseries to revive degraded coral reefs.
  • Can reseeding reefs and building new nurseries help corals face new threats like the Gulf oil spill and climate change?
"If we see the reef systems collapse, we're going to see these fisheries collapse too."

Tom Moore, NOAA habitat specialist and coral-restoration coordinator

By Matt Jenkins

Five miles off the Florida Keys, on a day straight off the front of a wish-you-were-here postcard, Nature Conservancy scientist Meaghan Johnson stands on the back of a small research boat and pulls on her wetsuit. Erich Bartels and Cory Walter, scientists from the Mote Marine Laboratory, shimmy into their dive gear and stuff an odd assortment of tools and supplies — surgical bone cutters, taxidermy epoxy and the kind of plastic ear tags normally used by sheep ranchers — into the pockets of their dive vests. The three divers do a quick buddy check and then plop backward off the boat.

In the world below, the edges of the horizon race away to a deep, primeval blue that seems to emanate straight from the heart of the wild cosmos. Wreathed in fat champagne sparkles of bubbles, the trio descends toward what looks like a gigantic chess competition laid out on the ocean floor. Row after row of concrete blocks await, each block topped with two rows of small pedestals. A stony, pinkie-size “doodad” — as one diver calls it — is epoxied to the top of each pedestal like a chess piece.

These doodads are Acropora cervicornus, also known as staghorn coral. Along with its broad-fronded cousin, elkhorn coral, staghorn is now listed as threatened on the federal Endangered Species List. Across the entire Caribbean, populations of the two coral species are in steep decline. The National Marine Fisheries Service estimates that coral populations in the Florida Keys, the Dry Tortugas and the U.S. Virgin Islands have declined by more than 97 percent.

The underwater nursery here is part of a far-reaching program to staunch that decline. The corals have been gathered from wild colonies nearby and are being multiplied and grown out in the nursery. Soon, they will be “outplanted” — moved to shrinking reefs in the Florida Keys National Marine Sanctuary to bulk up the reproductive population.

Thirty feet down, with the sun-dappled ceiling of the surface high overhead, Johnson, Bartels and Walter wiggle toothbrushes out of their dive vests and start gently scrubbing each pedestal to remove algae that would otherwise begin overgrowing the coral. This is a fastidious sort of gardening intended to keep the juvenile corals one step ahead of the algae and a host of other threats. Bartels secures several of the blocks to the ocean floor, replacing rebar and zip ties that have worked their way loose. Johnson and Walter search for coral fragments, which are sometimes broken off by passing turtles and sharks. They use epoxy to mount the pieces they find on new blocks.

The divers’ pace is deliberate, and the work can be trance-like. Shop talk happens in an improvised dialect of scuba sign language: An upward-turned palm, fingers splayed, means staghorn; a kneading motion is a call for epoxy; and a thumbs up is the sign that it’s time to head back to the boat.

After more than an hour underwater, the divers take one last look around for dropped gear while a trio of bottle-nose dolphins gambol by. Walter does a slo-mo, one-finger, upside-down pirouette over the last row of blocks, then leads the way toward the light.

Frolicking dolphins aside, the work is a lot less glamorous than it might seem. Boat food, more often than not, is PB&J and pretzels. When the scientists aren’t underwater, they are frequently negotiating the stacks of permits required to work on an endangered species — or fielding concerned calls from the accountants at the Conservancy’s headquarters in Virginia, where credit-card charges for cattle tags, rebar and taxidermy epoxy set off suspicious-activity alarms.

“You have to be creative to do this work,” says Johnson. And there is a lot of work to do. A recent infusion of job-creating federal stimulus funding is helping to transform what started as a home-cooked experiment into a $3.3 million effort that spans from Miami and Fort Lauderdale to the Keys and the Virgin Islands. The project is bringing together a network of local organizations and university groups to carry out the largest coral-restoration project in the world and has created or retained 46 jobs in the process.

But even today, nearly a decade after the project started, improvisation is often the order of the day. Climate change is amplifying all of the threats that corals face, sometimes in surprising ways. In past winters, many of the corals were bleached by cold snaps that also damage Florida’s citrus crops. And other threats still loom in the waters; especially worrisome are the rogue plumes of oil released by the disastrous spill in the Gulf. “We’re still learning as we go, because we have to,” Johnson says. “Things are changing quickly.”

The clock is ticking for coral. Diego Lirman, a professor at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science, has spent his career researching the ability of corals to bounce back from catastrophic events. With oil slicks and climate change looming, the stakes are high. “If we can’t recover them right now,” he says, “the prospects for recovery are getting dimmer and dimmer.”

What does it take to restore a reef? Find out in our photo slideshow.

Reefs in Trouble

Staghorn and elkhorn are the main reef-building corals in the Caribbean, laying the foundation of the complex, protective habitat at the heart of reefs’ famous biological diversity. As they grow, corals take up calcium carbonate from the water and constantly secrete it to form a hard skeleton that can keep pace with the erosive effects of currents, storms and time. 

Corals reproduce and form new colonies two ways: either when pieces of a coral are broken off and drift to a new location to take hold or through sexual reproduction. And when corals reproduce sexually, they tend to go big.

Typically three to five days after a full moon in August, the corals release great blooms of eggs and sperm that erupt like a wave and form massive slicks on the surface. Fertilized embryos develop into larvae that can float on the currents for weeks. When the larvae settle onto rocky structures on the seafloor, they are colonized by algae called zooxanthellae, which photosynthesize and provide the metabolic fuel that corals use to generate the calcium carbonate skeleton that becomes a reef.

As the coral grows, new polyps bud from existing ones, forming the branching structure that makes the corals so important for creating good habitat for other species. The corals provide protective cover for invertebrates and reef-dependent fish such as grouper, snapper, parrotfish, squirrelfish and wrasse. They also help dissipate the energy of incoming waves so sea grass beds, which grow nearer to the shore and provide refuge for young fish, can thrive.

Starting in the early 1980s, however, populations of staghorn and elkhorn began a dramatic decline. Many corals were overrun by algae after populations of long-spined sea urchins, which normally feed on the algae and keep it in check, were decimated by disease. A series of strong hurricanes further damaged and stressed coral, and increasing ocean temperatures have taken a toll as well. Slight shifts beyond the normal seasonal maximum or minimum temperatures — as little as 1.8 degrees Fahrenheit — can stress the corals and cause them to expel their algae fuel sources, leaving the corals bleached and barely alive.

During the past century, the average surface temperature of the planet’s oceans has increased by about one-half degree Fahrenheit, pushing corals closer to the danger line. Bleaching has become more widespread and more frequent.

The combination of these stresses — which has also made the two species more susceptible to disease — has had a devastating effect on corals. Without new growth, reef building stalls out, and “standing dead” coral skeletons crumble like broken concrete.

Were coral populations to completely collapse, it would be not only an ecological disaster but an economic one as well. “These reefs are huge economic drivers,” says Tom Moore, a habitat specialist and coral-restoration coordinator for the National Oceanic and Atmospheric Administration’s Restoration Center. Snorkeling, diving and sport fishing may be the most visible businesses that depend on reefs, but commercial fishing for snapper, grouper and other species of fish is even bigger. “These are billion-dollar industries,” Moore says. “If we see the reef systems collapse, we’re going to see these fisheries collapse too.”

In 2006, the federal government declared that both species of Acropora were threatened under the Endangered Species Act. Yet in recent years, some small pockets of corals have rebounded. That has led scientists to believe that with a focused effort to re-establish corals in key areas, the two species may be able to gain a new foothold throughout the region and begin building reefs again.

“You could re-create that structure with rebar and plaster, but that would eventually break down,” says Chris Bergh, who oversees the Conservancy’s Florida Reef Resilience Program. “The foundation of the reef ecosystem is this ability of the corals to grow and outpace the erosion that’s going on at the same time.”

Since the mid-1990s, a tropical fish collector named Ken Nedimyer has been experimenting with growing corals in an underwater nursery off Key Largo. Nedimyer had been working with the Conservancy to restore long-spined sea urchins, and he was so successful growing corals in the nursery that he began thinking about the possibility of returning them to the reefs. In 2004, he approached the Conservancy about launching a coral-restoration program.

The restoration began as an effort to farm different strains of coral. Nedimyer, Johnson and other researchers snipped cuttings from wild populations and separated them into different genetic subpopulations, or genotypes. The cuttings were then glued to pedestals in underwater nurseries like the one near Big Pine Shoal, and grown out. After a year, they were fragmented, and each of the fragments grown out again, to rapidly multiply the number of corals available for outplanting. After the corals were returned to the reefs, the team made weekly visits to tend to them.

The scientists hoped to find “super corals”—the most hardy and resilient varieties of staghorn. But as the effort progressed, the team had to retool its strategy. “We were hoping we’d find some really strong genotypes that [were] more resilient to disease, or whatever’s coming next with climate change,” says Johnson. But while certain genotypes thrived in the nursery, many of them withered when they were planted out on reefs.

“They were all over the map,” says Chris Bergh. “It was totally unpredictable.”

Today, the restoration project is no longer concerned with the quest for a super coral. Scientists are now focused on re-establishing a genetically diverse family of corals on the reefs in the Keys. Rather than picking a winner, they’re trying to ensure as wide a range of genotypes as possible for natural selection to act upon in the wild.

Propagating multiple genotypes in the nursery will also help coral populations in the Keys and the wider Caribbean break through a genetic bottleneck. Iliana Baums, a coral researcher at Pennsylvania State University, says that for coral to form viable offspring, “it takes two to tango.” A coral from a given genotype can’t self-fertilize; it must cross-breed with another.

The past 30 years of coral die-off has the surviving patches of Acropora corals isolated from one another. With coral colonies fewer and farther between, the lack of opportunities for different genotypes of the same species to interbreed means that sexual reproduction is being stymied. If unchecked, that trend could wipe out the Acroporas altogether. A federal assessment of the two species, completed in 2005, noted that “once a threshold level of population decline has been reached…the chances for recovery are low.”

Interbreeding of the genotypes will shuffle the genetic deck and create new strains that should increase both species’ chances of success in surviving rising ocean temperatures and other threats. But there’s another, perhaps more practical, motivation for outplanting a diverse range of corals that can breed on their own.

“We just don’t have enough manpower to recover these species through fragmentation,” says Lirman, the University of Miami researcher. But by setting up pockets of genetic diversity that will spawn and cross-breed, “we’ll jump-start the sexual reproduction that’s going to be needed for any sort of regional recovery.”

In fact, for the scientists involved in the recovery effort, the one thing they’d most like to see is a sign that their efforts 30 feet down in the nurseries are no longer needed.

“One good, strong sexual reproductive pulse will dwarf anything we can do,” says Lirman. “That is going to make us look puny in comparison.”

What does it take to restore a reef? Find out in our photo slideshow.

Underwater Nurseries

Ken Nedimyer is a man whose engines seem perpetually set to full speed ahead. It is a clear, bright day, and Nedimyer has the throttles on his boat jammed all the way forward as he blazes seaward from Key Largo, discoursing on the nuances of coral restoration. 

“We’re developing the technology as we go,” he shouts over the roar of the outboards. “Technology” might be a bit of an overstatement: One of the most notable characteristics of the coral-restoration field is that it is, for the most part, charmingly low-tech. Much of the infrastructure consists of concrete blocks you can pick up at The Home Depot, coral pedestals made from plaster poured into Dixie cup molds — and lots of All Fix-brand epoxy.

“Oh, man, I love that stuff,” Nedimyer says, laughing. The search for the perfect epoxy led him from the local hardware stores to The Home Depot and then eBay, and left him with shelves full of unsatisfactory candidates that stuck well to dive masks and wet suits but not to corals or rock.

That sort of homegrown experimentation has been a hallmark of the Coral Restoration Foundation, the nonprofit that Nedimyer runs as hard as his boat. “We’re a nimble little organization that doesn’t have a lot of baggage,” he says. “All the money we get goes into gas [for the boat] or air [for diving], and we’re back out here working. We’re a lean, mean, coral-planting machine.”

In the mid-1990s, Nedimyer discovered a couple of staghorn fragments that had landed in the nursery he’d developed for his aquarium-supply business. He and one of his daughters began futzing around with the idea of making a 4-H project out of growing corals — and maybe making a dollar or two by selling the corals to aquariums.

But Nedimyer had a first-hand view of the corals’ decline in the wild, and somewhere along the way, “I started thinking, maybe I don’t want to sell these corals,” he says. “I started getting this whole different vision of what I wanted to do.”

Luck works in mysterious ways in the Keys. In 1984, a freighter full of chicken feed plowed into Molasses Reef, crushing a huge swath of corals. After 12 days, the wayward freighter was towed off the reef. The damage to the corals there was considerable, but the grounding site — the swath of devastation left by the hull, which divers refer to as “the parking lot” — would provide the opportunity that Nedimyer needed. In 2003, the National Marine Fisheries Service gave Nedimyer permission to plant some of his nursery-raised corals on Molasses, and they took to the reef like ducks to water.

The following year, the fisheries service gave Nedimyer permission to collect wild coral fragments and to propagate them in his nursery for an expanded outplanting program in the Keys. “For what you get back in terms of benefit, the little harm that you get from these initial collections is pretty low,” says Moore, the National Oceanic and Atmospheric Administration (NOAA) restoration coordinator. “When you do the numbers, you end up with thousands of percent increases in the amount of coral tissue in a small period of time.”

At the same time, Nedimyer teamed up with the Conservancy, which helped secure a grant from NOAA to fund his nursery and outplanting program. With that, the endeavor transformed from a small-scale project intended to patch up grounding sites into a bona fide restoration effort.

“When we first started this project, we had no idea what we were getting into,” says the Conservancy’s Meaghan Johnson. “We really were learning as we went.”

As they learned, new opportunities to expand the program opened up. In 2007, the partnership grew significantly when Mote Marine Laboratory opened its nursery in the Middle Keys and Nova Southeastern University and the Rosenstiel School of Marine and Atmospheric Science opened nurseries farther north.

For his part, Nedimyer decided to get out of the aquarium and fish-collecting business; three years ago, he began devoting his energy solely to saving corals. He formed the Coral Restoration Foundation, using a second-hand boat from a Boy Scout camp, the scuba power of dozens of Keys high schoolers and an adopt-a-coral fundraising program.

Nedimyer’s nursery, shimmering below the surface three miles offshore, has become a sort of coral supercenter: row after row of blocks, some 4,000 corals in all, plus an experimental “line nursery” where corals grow attached to lines strung between a pair of buoys that hover like balloons near the surface.

The nursery is impressive, but there’s no better place to see what the future might look like than nearby Molasses Reef, where Nedimyer and his compatriots have planted more than 800 corals. The restored coral forest is teeming with life — rafts of barracuda holding fast in the current, clouds of parrotfish, Nassau grouper, lane snapper, sergeant majors and blue chromises, and the occasional nurse shark that comes lazing by.

It was here that something happened that stunned Nedimyer. Two years earlier, he had planted a group of corals, hoping that — with a lot of luck — they would spawn in four or five years. But in August 2009, two days after the full moon, the corals spawned.

Nedimyer was ecstatic. “It’s not an experiment anymore,” he says. “It’s like, ‘OK, any questions?’ It will work.”

What does it take to restore a reef? Find out in our photo slideshow.

Climate Complications

Even as the corals on Molasses Reef were spawning, the Conservancy was ramping up the restoration effort on a much larger scale. Last year, the Conservancy received a $3.3 million, three-year grant through the American Recovery and Reinvestment Act. Using funding from the grant, the Conservancy and its partners have expanded the four existing nurseries and opened new ones at four other sites: on Marathon Key (run by the Florida Fish and Wildlife Conservation Commission), on the Dry Tortugas (in partnership with the National Park Service), and on St. Croix and St. Thomas. Together, the eight nurseries will form a production pipeline to grow corals for outplanting on a much bigger scale.

That effort has helped bring together an otherwise-scattered collection of groups. “The scale of the issue is so overwhelming that it goes beyond a single institution,” says Lirman, the University of Miami researcher.

The effort is, in fact, the largest coral-restoration project in the world. “There are groups doing this throughout the Caribbean,” says James Byrne, the Conservancy’s marine science program manager. “But this is a huge jump up in scale from what anyone’s done.”

Taking on the entire Florida reef tract, plus the Virgin Islands, is a huge step forward. But, Lirman points out, it will be important to cast an even wider net in the future. “Even though most of the work is done within U.S. waters, it’s key to highlight the fact that we’re talking about a small percentage of the regional population of these species,” he says. “To be able to recover these species regionally, we really do need to expand beyond U.S. waters and jurisdictions.”

There are already plenty of challenges. “In 2004 and 2005, we got whacked by four different hurricanes, so we were kind of back to square one,” says Nedimyer. “We lost a lot of corals, [but] you live and learn. You take your hits, and come up with a better plan the next time.”

Now, Nedimyer, Johnson and the others spend a lot of time in the nurseries before the onset of each summer’s storm season, making sure that the corals are secured. Through trial and error, they have devised a way to allow the blocks in the nurseries to swing with the force of storms, like weather vanes.

But behind that season-to-season work lies a stark reality: Coral reefs around the world are facing large-scale, long-term threats like never before. For the scientists working on the program, an ongoing concern — possibly even bigger than the horrendous threat of the Gulf oil spill — is that climate change will amplify not only hurricanes and cyclones but also other threats like disease and bleaching that have been harming staghorn, elkhorn and nearly every other coral species for the past 30 years. “Are we going to see corals adapt to that,” asks Johnson, “or is it going to happen too fast for them to be able to survive?”

Increasing temperature extremes will likely cause more frequent bleaching episodes. As atmospheric concentrations of carbon dioxide dissolve in greater quantities into the oceans, seawater will become more acidic and reduce the availability of carbonate that corals need to build their skeletons. In fact, new research indicates that when carbon dioxide reaches atmospheric concentrations of about 550 parts per million — something that is predicted to happen by the middle of the century if drastic action isn’t taken to slow climate change — reefs begin to actually dissolve.

What does it take to restore a reef? Find out in our photo slideshow.

Farming for Coral

In the face of such a seemingly hopeless situation, coral scientists still believe that the corals are tough enough to survive. “They’re more resistant and resilient than most people give them credit for,” says Lirman. 

For the scientists working with the project, a key focus is finding ways to keep corals one step ahead of the threats. “The guys in the Keys are real survivors,” says Baums, the Penn State researcher. “The more we can slow down the rate of change, the more generations you get in, and the higher the chances are that these species are going to make it.”

The trick will be to stack the deck enough that corals can take on the threats one at a time. “It’s very obvious that corals cannot survive multiple impacts. So if we get to a point where acidification is an issue, temperature is an issue, with corals that also have to contend with overexploitation and all of these other local and regional factors, then there’s no hope,” Lirman says. “But if we’re able to hold things together in the short term, I think we can gain enough time to adapt to climate change.”

And, he adds, “through some of these local activities and actions, you may be able to buy enough time for these other large-scale [climate] processes to either slow down or reverse.”

But there’s the rub: Unless people around the world finally get serious about tackling climate change, efforts to restore coral will be hopeless in the end. “You can propagate and restore as much as you want,” says Lirman, “but if you don’t take care of the reasons why these corals have been declining for the past 30 years, you’re propagating things and then putting them in places [where] they’re going to die anyway.”

And when buying time for corals is so critical, the partners in the project are keeping a wary eye on the year 2012, when the economic-stimulus funding will run out. Even with as far-reaching a restoration program as this one, the coral decline won’t be reversed in just three years. And the Caribbean is already littered with the remains of projects that failed to secure long-term funding. “There are tons of orphan projects sitting out there, overgrown by algae,” says Lirman. “If nobody picks up this project, then we have these 30,000 little corals that are just hanging out there, and somebody’s got to take care of them.”

Hard realities like that have forced everyone on the restoration team to adopt a pragmatic outlook on the future of corals. But, as Baums takes pains to point out, it is still a hopeful view. “We may not have coral reefs the way we have them now. We may have a lot more algae and a whole lot less fish,” she says. “But some corals are going to make it. If we play our cards right, I think we have a good chance of keeping this one from the brink.”

That pragmatism has kept everyone on the water. Gunning his boat on the trip back from Molasses Reef, Nedimyer is talking about how the restoration effort grew from the 4-H project a decade ago to the effort that now spans the Keys, the Dry Tortugas and the Virgin Islands. “We want to duplicate that, and we want to take it throughout the Caribbean,” he says. “I want to share it with as many people as possible: Train ’em, get ’em the tools they need, and get ’em going — train farmers how to farm.”

“If we’re all doing it,” he adds, “we’re gonna get something done.” 

What does it take to restore a reef? Find out in our photo slideshow.