Valérie Chamberland swims like a dolphin, quickly and fluidly, and for most of the past hour she has been darting through the warm, shallow water off the Caribbean island of Curaçao. Now, she is dangling upside down, hovering above a pillow-sized brain coral. Her rubber fins twitch steadily overhead, and as she sips air from the aluminum tank on her back, a stream of bubbles rises from her regulator’s mouthpiece.
The reef spread below Chamberland isn’t one of those flashy, fluorescent gardens seen in calendar photos and nature documentaries. Only a few dozen yards from shore, it lies almost literally in the shadows of a stone jetty, a busy casino, and a Denny’s restaurant. The waters that surround it are murky, and most of its corals are brown and lumpy, sparsely accessorized with bright-purple vase sponges and waving, rusty-red sea fans.
But as anyone who studies coral reefs will tell you, beauty doesn’t necessarily equal health, and this reef has good vital signs. It retains plenty of what reef scientists call “structure”—meaning that it’s three-dimensional, not flattened into rubble or sand—and most of its unlovely lumps are formed by brain coral, one of the sturdiest types of coral in the Caribbean. The reef is lively with fish, and it lies on the outer edge of Curaçao’s wing-shaped coastline, where fast-moving currents sweep out at least some of the island’s pollution and slow the growth of coral-suffocating green algae. It’s also sheltered from major storm damage: Curaçao, which is only 40 miles north of Venezuela, rarely experiences hurricanes.
Chamberland flicks away an agitated crowd of silvery butterflyfish, then descends slightly for a closer look at the mound of brain coral. She inspects the meandering grooves on its surface, looking for the tiny white bumps that appear immediately before its annual spawning. For the butterflyfish, the pinhead-sized bundles of sperm and eggs released during a spawning event are a calorie-rich feast; for Chamberland, they’re the raw materials she needs to further a long-running mission.
Over the past two decades, Chamberland and other scientists throughout the Caribbean—many of them now associated with a research and conservation group called SECORE, which stands for Sexual Coral Reproduction—have stubbornly advanced the art and science of raising coral babies. Through trial and error, these researchers have learned to better predict the quiet, hidden phenomenon of coral spawning, to fertilize coral eggs in the lab, and to foster young corals until they’re ready to grow in the open sea, on a living reef.
Newborn corals are, in their way, as high-maintenance and idiosyncratic as their human counterparts, and the process of raising and releasing them, formally known as “assisted recruitment,” is full of frustrations and disappointments. Thanks to some recent successes and to rising interest from conservationists, however, the job is becoming easier and cheaper. The progress is such that on Curaçao this past June, Chamberland and her colleagues hosted an intensive workshop in assisted recruitment for 10 park rangers, conservationists, biologists, and others from a half-dozen Caribbean islands, intending to both share the techniques they’ve developed and, in time, learn from the experiences of new practitioners.
Chamberland, who moved to Curaçao from Québec nearly a decade ago, sometimes feels as if she’s counting down to a rocket launch: After years of careful preparation, assisted recruitment is nearly ready to blast off into new territory.
On the reef, Chamberland finishes her inspection of the brain coral and leaves the butterflyfish to their vigil. She surfaces and takes off her mask, freeing its rubber strap from her dark hair. The setting sun pinkens her often serious face, and she grins. “Tomorrow night,” she says, her consonants softened by her native French. “It’ll happen tomorrow night.”
Once these cultivated colonies reach a certain size, they can be relocated and used to supplement the structure of reefs damaged by hurricanes, disease, or human activity. But Virdis and the other workshop participants know that coral gardening isn’t a wonder tool, either. To survive long-term, corals need not only structure but also genetic diversity, which is enhanced through sexual reproduction—the chance combination of sperm and eggs, or gametes, from different colonies. In most coral species, this cross-fertilization takes place during periodic spawning events, when colonies simultaneously release a brief blizzard of eggs and sperm into the open water. While colonies cultivated from fragments can eventually spawn and cross-fertilize, it takes years for any coral colony to reach maturity; the SECORE scientists believe that by cross-fertilizing coral at the beginning of the restoration process, they can bolster the variation corals need to evolve new defenses against changing conditions.
In the CARMABI classroom, Chamberland explains the protocol for gamete collection, laying out the cone-shaped nets that will be draped over the coral colonies and the plastic collection tubes that will catch gametes from Diploria labyrinthiformis, the species of brain coral affectionately known as D. lab. The nets are made from tarps, and none of the gear is high-tech—in fact, it’s deliberately designed to be low-tech, accessible to conservationists with even fewer resources than those at this modest field station.
Chamberland describes how gametes are handled back in the lab, long after dark, and how researchers sometimes keep watch on the embryos until the next morning. When she asks if there are any questions, Houtepen raises his hand. “So,” he says hesitantly, “do you sleep during this process?”
Chamberland laughs, but doesn’t answer. “Let’s do this,” she says.
The conservationists in Curaçao are thoroughly infected with the drama of spawning, partly because at some point in their lives, each has been infected with a passion for coral reefs. Every coral enthusiast remembers when he or she discovered the hidden world of reefs, whether it was through Jacques Cousteau television specials (a surprisingly common route, even for younger reef conservationists), with a borrowed mask and snorkel on an idle childhood afternoon, or during a college course taken on a whim. Some were struck first by the colorful beauty of the reefs, or by the abundance and weird variety of its life forms; some were enchanted by scuba diving, which allows even the clumsiest human to float gracefully through an alien world. Some consider the coral life cycle as beautiful and complex as great art. “I find it elegant,” says Vermeij.
Working in pairs, the group takes its cue from the swarms of butterflyfish that have again gathered in hopes of a gamete meal. The divers drape nets over the most popular mounds of D. lab, check the time on the dive computers on their wrists, and wait. Fifteen minutes pass, then 30. One pair of divers points excitedly to the tube at the top of one net: pinkish-gray spheres are floating into the tip. It’s happening! Another pair spots gametes rising out of a net, and then another. As the sun sets and the water starts to darken, the divers cap and detach the collection tubes and gather up the nets, making their way back to shore by the beams of their dive lights.
At the surface, the mood is subdued. The spawn wasn’t as big as everyone hoped it would be; this team has only a few vials of gametes, and none is full. Maybe the other team got more; maybe there will be more tomorrow evening. Maybe it’s just a bad month.
Back in the CARMABI lab, though, spirits rise. The divers argue good-naturedly over which team, and which pair, returned with the most gametes, and when all the tubes are lined up on the lab bench, it turns out that there are more eggs and sperm than the equipment on hand can handle. “A lot of dribbles adds up to a pretty good catch,” says Chamberland. Even more important than volume is variety, and the group has managed to collect gametes from a lot of different colonies. “We have 18 parents!” Chamberland exclaims to Vermeij, who raises his eyebrows comically. “I’m … jealous?” he says. The variation among the gametes is obvious, even to the untrained eye; the batches of egg and sperm bundles range in color from purplish-gray to pink to beige.
The SECORE researchers and workshop participants, who are crowded into the small lab, are still wet from the dive; some are in their swimsuits, with lingering pressure marks from their masks on their faces. But everyone is carefully obeying the laboratory rules: no touching or even leaning over the vials, since sweat and sunscreen can disrupt fertilization. No mosquito repellent anywhere near the lab. The room is closed and muggy—83 degrees Fahrenheit, to be exact, the current surface temperature of the ocean—and as Chamberland uncaps the vials and mixes the bundles into laboratory pitchers filled with seawater, the group is almost reverently quiet. “You’re making me nervous,” Chamberland jokes. In the pitchers, the bundles are already breaking up, and the sperm and eggs are floating freely.
Assisted recruitment is, in some ways, as much art as science, and some of its steps can’t be precisely expressed in a lab protocol. The SECORE researchers have learned, for instance, to dilute the concentration of sperm in the pitchers so that the resulting larvae have the room—and oxygen—they need to develop. “The water in the pitchers should look like fogged-up glasses,” Vermeij says. When Chamberland says, “I think of it as looking like weak lemonade,” Vermeij, who was her PhD adviser and has worked alongside her for years, looks genuinely puzzled. No two people handle coral gametes in exactly the same way.
“Anybody thinking of trying this at home, so to speak?” Vermeij asks the group. Rita Sellares, of FUNDEMAR, says that one of her graduate students recently made a bare-bones attempt at assisted recruitment, turning Sellares’s office into a makeshift lab and filtering seawater through a swimsuit. To everyone’s astonishment, the larvae survived. “Hey, if it works, it works,” says Vermeij. Coral gametes are frustratingly finicky, but once in a while, they’re not; during a trip to Mexico a few years ago, Vermeij collected a few gamete bundles in a coffee cup, and the resulting larvae did just fine.
Chamberland stands back from the lab bench, satisfied with her weak lemonade. “This is pretty much where we wait for the magic to happen,” she says. Over the next few hours, the gametes will combine to form embryos, and overnight, the embryos will develop into larvae. The spectators wish the gametes luck and adjourn to a late dinner, which they eat at a row of surfside picnic tables and wash down with bottles of Venezuelan pilsner. On the balcony above, cleaned and drying collection nets hang over the railing like so many gray ghosts.
Late that night, restoration technician Kelly Latijnhouwers pours about half of the brand-new embryos—about 100,000 nearly invisible specks—into a plastic water jug and, with a number of workshop participants in tow, drives them across town to the Curaçao Seaquarium. There, in a quiet channel not far from the dolphin show and the shark tank, SECORE has set up a floating coral nursery, an experimental design that looks something like a very sturdy, highly engineered kiddie pool. If it works, it could eventually eliminate the need for a temperature-controlled laboratory, making assisted recruitment more affordable and accessible for small conservation groups.
Latijnhouwers lies belly down on the dock next to the nursery, hoists up the jug of embryos, and carefully tips it in. The workshop participants, seated on the seawall nearby, applaud, and Latijnhouwers scrambles to her feet with a smile, mockingly acknowledging the cheers. It’s close to midnight, and there’s still work to do.
Such a large and willing crew of helpers was unimaginable in 2002, when SECORE was founded by German coral researcher Dirk Petersen. Petersen, then working at the Rotterdam Zoo, initially focused on helping zoos and aquariums boost the genetic diversity of their coral collections, but he soon began to consider how assisted recruitment could be used to restore reefs in the open ocean, on a large scale.
Petersen knew that any such large-scale undertaking was a long way off, not only because of the technical challenges but also because at the time, the notion of active restoration was viewed with suspicion, even hostility, by many conservationists. Some thought it just wouldn’t work; some feared it would distract from the more immediate job of protecting reefs; and more than a few disliked the idea of tinkering with a natural process, especially the elegant intricacy of coral reproduction.
In Australia, where the reefs were relatively healthy, restoration was “a dirty word,” says marine biologist and workshop co-organizer Joe Pollock, who spent several years studying corals on the Great Barrier Reef before moving to the Caribbean. “The attitude was, ‘That’s something they do in the Caribbean, because they’re really messed up and don’t have any other options.’” Australian conservationists talked instead about “managing for resilience”—protecting reefs so that corals could, on their own, evolve defenses against new stresses.
In Florida, where the reefs were already desperately degraded, conservationists wondered if any kind of reef restoration was worth pursuing; in an academic journal in 2005, managers of several marine protected areas published an opinion piece called “The Folly of Coral Restoration Programs Following Natural Disturbances in the Florida Keys National Marine Sanctuary.”
Today, the conversation is different. “The paradigm has changed blindingly fast because the decline has happened blindingly fast,” says Miller. “Now, everything is on the table.” In the wake of the 2016 bleaching event, Australian conservationists began asking Caribbean researchers for help with assisted recruitment, and SECORE and other coral reproduction researchers received funding from sources including The Nature Conservancy, the California Academy of Sciences, and Microsoft founder Paul Allen.
“We’re trying to figure out how this fits within the solutions we have at our disposal,” says Pollock, who now heads The Nature Conservancy’s Caribbean coral conservation program. “We’re working on regional issues, trying to increase protection, getting involved with work that’s happening on a local scale, and at the same time trying to develop and disseminate these promising technologies that—I’ll be the first to tell you—are not the solution right now, but could be part of the solution down the line.”
Although discussions of the risks of “tinkering” with reefs continue, resistance has begun to fade. While managers and conservation groups alike continue to manage for resilience, they are seriously considering interventions once considered heretical, from assisted recruitment to the transplantation of corals into new ecosystems to the inoculation of coral polyps with symbiotic algae known to be heat-resistant.
In a quieter but perhaps even more significant departure from conservation tradition, SECORE has expanded its focus beyond critically threatened corals, and its researchers are now developing assisted recruitment techniques for a dozen different species, many of them still common.
“Most of the funds for this kind of work go to endangered species, and that’s a pity, because over and over and over again people are failing with the same species,” says Chamberland. “It’s just not feasible to bring everything back everywhere—some reefs are too degraded.”
The primary goal of reef conservation, these days, isn’t to preserve pristine reefs—most of those are gone—but to preserve at least some reef structure, some habitat for fish and other marine species, some ability to evolve. It’s to help protect Caribbean shorelines from strengthening Atlantic hurricanes, and to beat back the toxic bacteria and reef-suffocating green algae that thrive on degraded reefs. It’s to prevent wholesale coral loss as global temperatures rise, in the hopes of having some diversity left if and when climate stability is restored.
“If we want anything that resembles a coral reef in the future, we’re going to have to put our thumbs in the dike for the next 10 or 20 or 30 years,” says Miller. “We’re going to have to be very actively engaged for decades just to maintain the puzzle pieces, just so we have something to work with when the environment gets fixed.”
While interest in assisted recruitment swells, SECORE researchers are still trying to perfect their techniques—and in the humid warmth of the CARMABI lab, the young D. lab corals are about to enter the riskiest phase of their development.
So, like fretful parents of picky children, the SECORE researchers keep presenting their lab-raised larvae with choices, hoping to hit on the ideal menu. Ritson-Williams has found that while larvae like to settle near some species of coralline algae, other species inhibit larval growth. Unfortunately, the helpful and unhelpful species of algae look exactly alike—unless you happen to be a coral larva, or a coral scientist with a microscope and a lot of algal expertise.
Early SECORE experiments used hand-cut clay tiles as a surface for settlement, but soon found that clay tetrapods gave the larvae additional surfaces on which to settle and a better shot at survival. Chamberland and other SECORE scientists are now working with the design-software company Autodesk to develop 3D-printed settlement tiles in a variety of textures and fantastical shapes.
In the CARMABI lab, the D. lab swimming pools have been furnished with an array of clay settlement tiles, and the larvae are starting to make their choices. Though they’re still almost too small to see, Chamberland uses an ultraviolet flashlight to illuminate the corals’ fluorescent pigments, and finds that several glowing green dots have come to rest on the submerged tiles—the first of what she hopes will eventually be thousands of settlers.
The odds are daunting, and so are the number of variables. No matter how carefully and thoroughly the SECORE researchers tweak the conditions in these swimming pools, it sometimes seems impossible that one of these pinhead-sized dots could survive to adulthood—much less multiply into a thriving colony. Robert Steneck is a marine biologist at the University of Maine who has helped the Caribbean island of Bonaire improve the resilience of its reefs by protecting the fish species that control algae growth. He cautions that lab-raised corals may never be able to make a cost-effective contribution to reef resilience. “You have to be mindful of natural mortality rates, and of what small fraction of a lot of effort is going to be successful 10 or 20 years down the road,” he says. “And you have to be mindful of the scale at which you’re going to be able to implement these very money- and time- intensive activities.”
But in the shallow ocean near the Seaquarium, just a few hundred yards from the floating coral nursery where Latijnhouwers deposited the rest of the D. lab larvae, is a bright-yellow elkhorn coral colony, a broad, scallop-edged funnel about a meter (3 feet) across. Seven years ago, this colony was a lone dot on a tetrapod in the CARMABI lab; just four years after the tetrapod was planted on the reef, Latijnhouwers was finishing a routine spawning dive when she checked the young colony and saw that it was releasing gametes.
For the first time, she realized, a SECORE-raised colony had completed the coral life cycle, and was contributing to the genetic stock of a living reef. Latijnhouwers, elated, surfaced into the warm night air, tossed aside her regulator, and called out to Chamberland, who was waiting on shore.
“Val!!” she yelled. “Your babies are spawning!!”