Is coral's best hope good breeding?

The Great Barrier Reef is almost dead, and all the world's coral may be killed by the oceans' rising temperature and acidity. But one scientists believes they be fed and bred to be more resilient

Ruth Gates hops off the launch and gestures toward a mass of submerged coral shimmering darkly in the crystalline waters a few feet offshore. “That whitish coral and the one covered with algae over there are dead,” she says. “The brown coral that you see growing in the gaps is still alive.”

We have arrived at Moku o Lo’e (Coconut Island), the site of the University of Hawaii’s state-of-the-art marine laboratory, where Gates and her team are attempting to learn why some coral animals survive bleaching—when an environmental trigger like warm water causes corals to turn completely white and stop growing—while others, often just inches away, perish.

It is not just an academic question. Gates intends to use the results to breed—and eventually introduce—climate-adapted “super coral” to the ocean to help bring the world’s ailing reefs back to life. “So much of our field has been simply watching the demise of reefs,” she says. “It’s time to think about solutions. We don’t have a lot of time.”

This urgency led Gates to team up with marine ecologist Madeleine van Oppen in Australia on a five-year project, funded by Microsoft co-founder Paul Allen (whose company Vulcan supports endeavours to promote ocean health and conservation), to engage in “human-assisted evolution.” It is not so different from what people have done for millennia with food crops, crossbreeding the best performers to create the fruits, grains and vegetables that we eat today. However, the idea of breeding coral, as one would wheat or tomatoes, has sparked controversy.

“This is not [genetically modified organisms], people!” Gates assures a well-heeled audience at the Punahou School in Honolulu, to a smattering of chuckles. She was there to garner public support for an approach that alarms those who believe humans should never interfere with nature, especially when that manipulation involves genes, the very building blocks of life. The coral biologist counters that our carbon-spewing civilisation has already interfered big-time, so why not use our best science to help repair the damage? “Should we act now? I say yes,” Gates exclaims as she paces the stage. “The pace of environmental change is faster than the organism’s capacity to adapt. It’s as simple as that!”

Yet there is nothing simple about the Noah-like ambition of re-seeding the globe’s imperiled reefs, where things have just gone from bad to much worse. In only the past few months, 93 percent of Australia’s vast Great Barrier Reef has been damaged by coral bleaching, according to researchers at Australia’s James Cook University. In some areas, the destruction is perhaps irreparable. The culprit is the current El Niño weather system, which has generated a peripatetic mass of warm water—nicknamed “the blob”—that has advanced steadily across the Pacific, slow-cooking untold billions of delicate coral animals as it passes.

Coral has been in decline for a long time due to shoreline development, industrial pollution and even the suntan lotion swimmers slather on their bodies. Gates had her road to Damascus moment in 1985, when a reef she was studying in Jamaica was run over by a ship. It was an “emotionally horrific experience” she recalls, “a vibrant and spectacularly beautiful cathedral-like structure created over thousands of years reduced to rubble.” She resolved then and there to find a way to rescue reefs.

Gates’s testing grounds is Kane’ohe Bay, where Coconut Island is located. Encircled by the corrugated green cliffs of Oahu’s Ko’olau Mountain Range and the seaward sweep of the Mokapu Peninsula to the north, the waters of the bay are a postcard-perfect turquoise. But the coral colonies, which cover 70 percent of the bay’s shallows, are reeling from a series of successive bleaching events in each of the past three years.

That coral still lives in Kane’ohe Bay is nearly miraculous. For decades, the community on its shores allowed sewage and storm runoff to foul the ocean, triggering the growth of bubble algae that all but smothered colonies under stinky green mats. When a public outcry ended this destructive practice in the late 1970s, the coral gradually came back, illustrating Gates’s core idea that reefs can recover, if they are given half a chance. “There is this incredible diversity in coral, how they feed, how they reproduce, how they respond to water temperature and acidity,” says Gates. “I hate it when this enormously complex story gets translated as ‘all coral will be dead in 50 years.’ There is so much that we don’t yet understand about their capacity for resilience.”

The challenge is to discover the biological mechanisms that allow some corals to fare better than others. The University of Hawaii team will be sequencing the genomes of the five main coral species in the bay to pinpoint the genes that best equip corals for the rigours of climate change. But another big factor, Gates says, is the nature of the symbiosis between the wormlike coral polyp and the photosynthesising algae that the polyps depend on for food.

Corals bleach when the algae, called dinoflagellates, are flushed from the tissue cells that make up the coral polyp. This happens when water temperatures rise beyond a certain point—though exactly why is unclear. “We don’t yet know if the plants choose to leave,” says Gates, “or the animals are kicking them out.” Either way, once the expulsion is complete, the corals starve.

In a University of Hawaii lab, molecular biologist Amy Eggers turns the lenses of a laser scanning confocal microscope, which allows for three-dimensional reconstructions of complex objects—such as, in this case, a slice of living coral sitting in a tiny pool of seawater on the microscope’s stage. The supersized image of a coral polyp on her screen appears like a sea monster with a gaping mouth and flailing tentacles.

The coral appears garishly multicoloured under ultraviolet light. “Those bright red dots that you see are the algae in the coral,” Eggers says. A flurry of red particles stream slowly away from the polyps. “You are seeing bleaching actually taking place,” Eggers coolly explains, adding that bleaching is a gradual process: Not all of the dinoflagellates leave at once. And this accounts for the fact that, in some cases, a reef can “bleach” but still bounce back. So long as a few algae linger on in the cells, the coral can recover.

There are hundreds of species of algae within the cells of different species of coral, says Gates. Inconveniently, those that excel at making the sugars that coral feeds on tend to be the poorest at withstanding high water temperatures and high acidity, and vice versa. However, achieving the right mix of algae and polyp can give the coral a real shot at survival, Gates says. So her team will be matchmakers, injecting coral polyps with new partner species of algae to discover which ones enhance the animal’s capacity to survive.

On the principle that “what doesn’t kill you makes you stronger”, they are also exposing coral to successive episodes of warmer and more acidic water in experimental tanks. Carbon dioxide is bubbled into seawater that circulates between palm-sized chunks of living coral to simulate future ocean conditions. Gates, a self-described jock and a martial arts teacher, compares this to athletic training: “It’s like running the marathon. When you train for the first time, it is agony, it is completely outside your comfort zone. But the second time you train, you are back in marathon-ready form really quickly. You have a muscle memory; it’s not nearly as gruelling.”

The coral that has undergone this training will then be transplanted back onto the natural reef to see whether it performs better in the wild after it has been toughened up in the lab. The team is also testing to see if the advantages of this “training” can be passed down to the coral’s children. Research assistant Hollie Putnam has been investigating the revolutionary new science of epigenetics: how experience gets transmitted across generations outside the usual channels of genetic inheritance. “We’ve already found that the offspring of coral that have been exposed to stress do better when faced with harsh conditions than the offspring of those that were not exposed,” says Putnam.

“We don’t yet know how long these epigenetic instructions can be passed down,” Putnam continues. “It may be one generation or multiple generations.” Either way, she hopes that by mimicking the ocean conditions that are expected as climate change advances, researchers can induce epigenetic changes in coral in the lab that will enable their offspring to better survive in the warmer, more acidic waters of the future.

Ultimately, the goal is to speed up coral’s natural processes of adaptation to equal today’s unprecedented rate of environmental change. “The critical question is: how fast can they do it?” says Paul Jokiel, the reef ecologist who discovered the phenomenon of bleaching in 1970, while studying coral exposed to heated power plant outflows near Pearl Harbour. “Corals adapt over hundreds and thousands of years. But most reefs today are within a 2-degrees Celsius rise in water temperature of dying out. If we don’t change our ways fast, we’ll shoot past that lethal limit in no time.”

Can human intervention help? “Perhaps on some reefs in the short term,” says Jokiel. “But just look at the projected temperature in 2030, 2040. No matter what you do, your work will eventually be lost.” And then there is the problem of scale. While Jokiel applauds Gates’s cutting-edge science, he says that producing enough lab-adapted seed coral to make a difference for the hundreds of threatened species across the globe would be mind-bogglingly difficult. “Let’s put our energy and resources into something that we know will make a difference—cutting carbon,” says Jokiel, who fears that focusing on rescuing reefs could divert attention from the real work of tackling global warming.

Gates agrees that putting the brakes on climate change is the only way to save the world’s reefs, but she says we also need to help coral tide over during the tough years that lie ahead. “The risk of doing nothing,” she says, “is the obliteration of coral reefs worldwide.”

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