Bree­ding su­per co­ral La gé­né­tique peut-elle sau­ver le co­rail ?

Éle­ver du "su­per co­rail"

Vocable (Anglais) - - Édito Sommaire -

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.

(Cha­me­leons Eye/Shut­ters/SIPA)

Great Bar­rier Reef, Queens­land, Aus­tra­lia

(D. Mau­rice Smith/The New York Times)

“We’re trying to find the su­per co­rals, the ones that sur­vi­ved the worst heat stress of their lives,” Neal Can­tin said.

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