Breed­ing su­per coral

Can sci­en­tists save threat­ened reefs?

Vocable (All English) - - Édito | Sommaire - DAMIEN CAVE AND JUSTIN GILLIS

The Great Bar­rier Coral Reef is one of the world’s great­est trea­sures, and a must-see lo­ca­tion for many tourists vis­it­ing Aus­tralia. But for how much longer? Threat­ened by ris­ing tem­per­a­tures, coral reefs all around the world are dis­ap­pear­ing, putting many species that live and feed tin them in dan­ger as well. Sci­en­tists are at­tempt­ing to de­velop a “su­per coral” to save these beau­ti­ful habi­tats.

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.

(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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