Great Bar­rier Reef: sci­en­tists iden­tify po­ten­tial life sup­port sys­tem

The Guardian Australia - - News - He­len Davidson

A group of “source” reefs have been iden­ti­fied that could form the ba­sis of a life sup­port sys­tem for the Great Bar­rier Reef, help­ing re­pair dam­age by bleach­ing, starfish and other dis­tur­bances.

Re­searchers from the Univer­sity of Queens­land, CSIRO, Aus­tralian In­sti­tute of Marine Sci­ence and the Univer­sity of Sh­effield searched the Great Bar­rier Reef for ideal ar­eas that could po­ten­tially pro­duce lar­vae and sup­port the re­cov­ery of other dam­aged reefs.

The Great Bar­rier Reef is the world’s largest liv­ing struc­ture and is made up of more than 3800 in­di­vid­ual reefs, stretch­ing 2300km down Aus­tralia’s east­ern coast­line.

The study found 112 “ro­bust source reefs” – just 3% of the en­tire sys­tem – which had “ideal prop­er­ties to fa­cil­i­tate re­cov­ery” of oth­ers by spread­ing fer­tilised eggs to re­plen­ish other ar­eas.

“Find­ing th­ese 100 reefs is a lit­tle like re­veal­ing the car­dio­vas­cu­lar sys­tem of the Great Bar­rier Reef,” said Prof Peter Mumby, from the Univer­sity of Queens­land’s school of bi­o­log­i­cal sciences and ARC Cen­tre of Ex­cel­lence in Co­ral Reef Stud­ies.

Re­searchers had strict cri­te­ria – the reefs must be con­sis­tently well con­nected to other reefs through the con­stantly shift­ing cur­rents, be less likely to die in a co­ral bleach­ing event and be less sus­cep­ti­ble to crown-of-thorn starfish out­breaks.

Th­ese reefs were more likely to still be stand­ing in the event of bleach­ing in­ci­dents, for ex­am­ple, and were in the right lo­ca­tion to send fer­tilised eggs to the reefs that need them dur­ing the an­nual re­pro­duc­tion, Mumby said.

“It gives us a bit more hope that the ca­pac­ity for the bar­rier reef to heal it­self is greater than we ex­pected.”

There have been four sig­nif­i­cant bleach­ing events on the Aus­tralian reef, in­clud­ing one this year. The long­est and worst for the Great Bar­rier Reef was in 2016, when bleach­ing caused by cli­mate change killed al­most 25% of the reef.

Sci­en­tists have only re­cently been able to un­der­stand how con­nected the reefs are by ocean cur­rents, Mumby said.

“The Great Bar­rier Reef is about the size of Italy and at any given time there are patches that have been dam­aged and patches that are pretty good, so it has an abil­ity to heal it­self if you like.”

The re­searchers used ocean cir­cu­la­tion sim­u­la­tions to model the con­nec­tiv­ity of the reef lar­vae across the Great Bar­rier Reef and gen­er­ated 208 net­works, through which the 112 strong reefs could reach al­most half of all reefs through their “amaz­ing ca­pac­ity to con­nect the wider sys­tem”.

“It’s not per­fect,” Mumby said. “There are ar­eas in the north­ern bar­rier reefs where there are rel­a­tively few of th­ese reefs iden­ti­fied.

“So some next steps are to re­lax the cri­te­ria and look at plan B and plan C.”

As­so­ciate pro­fes­sor John Al­roy, from Mac­quarie Univer­sity’s depart­ment of bi­o­log­i­cal sciences, also noted the lack of the ro­bust reefs in the north, say­ing the re­search pa­per was “thor­ough and in­ter­est­ing” but op­ti­mistic.

“That makes me won­der whether reefs in the far north can really be kept alive by be­ing re­plen­ished from the south.”

Al­roy also sug­gested many of the Great Bar­rier Reef’s an­i­mals would be ab­sent from those reefs and sug­gested the pa­per did not fully ac­knowl­edge the wors­en­ing na­ture of cli­mate change, which would prob­a­bly also kill the ro­bust reefs any­way.

Dr Andrew Len­ton, prin­ci­pal re­search sci­en­tist at CSIRO Oceans and At­mos­phere, said the re­port iden­ti­fied what was needed to max­imise the ca­pac­ity of co­ral to re­cover, in­clud­ing the pro­tec­tion of the ro­bust reefs.

“It also recog­nises that this alone is not likely to be suf­fi­cient to en­sure the longer-term vi­a­bil­ity of the Great Bar­rier as a whole and will need to be cou­pled with cli­mate mit­i­ga­tion, lo­cal man­age­ment and ac­tive man­age­ment such as co­ral re-seed­ing.”

Mumby said new in­for­ma­tion about the reef and the way it func­tioned and re­paired it­self was read­ily adopted by the marine park au­thor­i­ties into its man­age­ment plans, and re­ceived sup­port from the fed­eral gov­ern­ment.

“This list of around 100 reefs is both a tan­gi­ble and fea­si­ble set of in­ter­ven­tion points to form part of a strat­egy for main­tain­ing the sys­temic re­silience of an ecosys­tem that is thousands of kilo­me­tres in scale,” the re­port said.

Tourism gen­er­ated by the 2 mil­lion an­nual vis­i­tors to the reef con­trib­utes al­most $6bn to the Aus­tralian econ­omy.

The “life sup­port” reefs iden­ti­fied in the study were good news, Mumby said, but more needed to be done to en­sure the sur­vival of the Great Bar­rier Reef.

In May sci­en­tists warned that the cen­tral goal of the gov­ern­ment’s pro­tec­tion plan was no longer fea­si­ble be­cause of the dra­matic im­pact of cli­mate change.

“It’s very clear that in or­der to main­tain a beau­ti­ful reef into the fu­ture, we ab­so­lutely need to be much more ag­gres­sive in our re­sponse to cli­mate change,” Mumby said. “We need co­her­ent poli­cies in gov­ern­ment about what gov­ern­ment is try­ing to achieve in our ac­tions to­wards cli­mate change and we need to con­tinue to in­vig­o­rate the lo­cal pro­tec­tions.”

A Great Bar­rier Reef study found 112 ‘ro­bust source reefs’ that could help re­pair dam­age from bleach­ing. Pho­to­graph: Daniela Dirscherl/Getty Images/WaterFrame RM

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