Breeding super coral La génétique peut-elle sauver le corail ?
Élever du "super corail"
La Grande Barrière de corail. C'est l'un des trésors de l'humanité, qui fait le bonheur de milliers de touristes en Australie. Mais pour combien de temps encore ? La hausse des températures menace les récifs coralliens et les espèces qu'ils abritent. Alors pour les sauver, des scientifiques ont décidé de donner un petit coup de pouce à la nature. Direction le fond de l'océan pour comprendre comment...
On the Great Barrier Reef, off Australia — After a plunge beneath the crystal-clear water to inspect a coral reef, Neal Cantin pulled off his mask and shook his head. “All dead,” he said.
2.Yet even as he and his dive team of international scientists lamented the devastation that human recklessness has inflicted on the world’s greatest system of reefs, they also found cause for hope.
3.As they spent days working through a stretch of ocean off the Australian state of Queensland, Cantin and his colleagues surfaced with sample after sample of living coral that had somehow dodged a recent die-off: hardy survivors, clinging to life in a graveyard.
4.“We’re trying to find the super corals, the ones that survived the worst heat stress of their lives,” said Cantin, a researcher with the Australian Institute of Marine Science in Townsville.
5.The goal is to find the ones with the best genes, multiply them in tanks on land and ultimately return them to the ocean where they can continue to breed. The hope is to create tougher reefs — to accelerate evolution, essentially — and slowly build an ecosystem capable of surviving global warming and other humancaused environmental assaults.
GLOBAL WARMING
6.After decades of accumulating damage, followed by a huge die-off in 2015 and 2016, some scientists say they believe half the coral reefs that existed in the early 20th century are gone. Instead of standing around watching the rest of them die, a vanguard of reef experts is determined to act.
7.In Florida, they are pioneering techniques that may allow the rapid re-establishment of reefs killed by heat stress. In the Caribbean, countries are banding together to create a genetic storage bank for corals, a backup plan if today’s reefs all die. Yet this new push to aid
the world’s reefs comes with its own risks, and with many questions.
8.While scientists are trying modest approaches first, the most effective strategy for saving reefs in the long run might be through genetic methods, including selective breeding or transferring heat-resistance genes into corals. That type of thing has been done for crops, but would it be ethical to do it in the wild?
9.“How do you decide what interventions are right and when to intervene?” said Madeleine van Oppen, a professor of marine biology at the University of Melbourne who is leading the experiments in Australia, aiming at what she calls the “assisted evolution” of coral reefs. “There’s a long road ahead; that’s why we’re starting now.”
10.Scientists first warned decades ago that coral reefs were particularly sensitive to heat stress and would be among the earliest victims of global warming if emissions were not brought under control. Most of the heat trapped by those emissions has gone into the oceans, which have now warmed enough that just a bit of additional heat can cause massive coral die-offs. The extra jolt arrives during El Niño weather patterns that warm large parts of the tropics.
11.The first global coral die-off began in 1982, and now they seem to be happening every few years. Along the Great Barrier Reef, the El Niñorelated heat wave of 2015-16 left 35 to 50 percent of the corals dead along a 650-mile stretch of the Queensland coastline. 12.“It’s not too late to be aggressive and make changes to preserve the reef of the future,” Cantin said. But, he added, without a broad effort that includes tackling the emissions causing climate change, reefs could largely die within this century.
SCIENTIFIC INTERVENTION
13.Future generations of corals, the offspring of those Cantin harvested, will be tested for resilience in an artificial environment, with warmer and more acidic water that mimics what scientists are predicting for the years 2050 and 2100.
14.The strongest corals will then become parents again, with some crossbreeding of the same species from different sections of the reef and also crossbreeding of different species to create genetic hybrids.
15.Under normal conditions the animals grow and build their reefs only slowly, one of the factors that is stymying the effort to save them. But at the Mote laboratory in Sarasota, Florida, a researcher named David Vaughan has perfected a technique in which coral samples are broken into tiny fragments; the polyps grow much faster than normal as they attempt to re-establish a colony.
16.“It used to take us six years to produce 600 corals,” Vaughan said “Now we can produce 600 corals in an afternoon.” The Mote lab and other centers have already replanted thousands of small coral colonies.
17.Though the risks remain unclear, the day may come when many of the reefs off Florida and Australia will be ones created by scientific intervention — a human effort, in other words, to repair the damage humans have done. to attempt to tenter de. 16. used to sert à marquer une distinction nette entre le passé et le présent, à indiquer qu'une action passée n'est plus d'actualité (it used to take... cela prenait...). 17. to remain rester, demeurer / in other words en d'autres termes / to repair réparer, compenser.