Science · Giant coral mappingCocos coral colony mapped at 1.56 kilometres as DNA tests probe its identityWritten November 11, 2026 at 4:51 AM UTCWatchTranscript0:00Cocos coral colony mapped at one point five six kilometers as DNA tests probe its0:04identity.0:07A rose coral formation stretches one point five six kilometers along the reef off0:11Cocos.0:12Researchers have mapped one of the largest coral formations ever recorded.0:15Its deeper water growth could help scientists investigate refuges for corals damaged0:19by bleaching and cyclones.0:21They're now testing whether that entire stretch is one genetic individual or many.0:25The coral grows on the outer reef of the Cocos or Keeling islands.0:29This remote Australian territory lies in the Indian Ocean.0:32Local divers knew parts of the expanse for decades before researchers measured how0:36far it continued.0:37The survey puts a number on something diverse couldn't see from a single site.0:41The length is roughly equivalent to one hundred buses laid end to end.0:45Researchers identify the formation as rose coral in the genus Pachiseris.0:49They formally mapped and examined it over recent months.0:52The formation averages thirty six point five meters wide and covers about fifty six0:56nine hundred and forty square meters.0:57It extends through depths of fourteen to sixty five meters.1:00Those dimensions describe coral spreading along a reef slope, with its width and1:05depth varying along the way.1:06Its approximate area has also been compared with three Melbourne cricket grounds,1:10but the discovery that changed researchers' understanding came from following the1:13coral between familiar dive sites.1:15Cocos, base dive operator Dieter Gerhard, had first seen the expanse more than1:19thirty years ago.1:20Gerhard alerted Adelaide University Marine Biologist JP Hobbs after seeing coral at1:24several dive sites.1:25Those sites were around six hundred meters apart.1:28Hobbs wondered whether the patches connected, and the survey found that the1:31formation continued beyond them.1:33Gerhard said people hadn't realized its size or how far it went.1:36His decades of observations gave researchers a starting point.1:39Hobbs and the team then began measuring centimeter by centimeter with tape measures.1:44As they followed the coral, their supply of air became the practical limit.1:47The divers ran out of air before they could reach the coral's end.1:50Hobbs said.1:51The team switched from tape measures to GPS tracking as the scale became clear.1:56It took twelve dives to map the full extent.1:58Researchers from Queensland Museum and James Cook University are collaborating on2:02the investigation.2:03With the length mapped, they're tackling a question the shape alone can't settle.2:07A continuous-looking expanse can leave researchers uncertain about how many2:10genetically distinct individuals it contains.2:13The team collected about fifty samples along the coral for genetic testing.2:16Those samples will help determine whether the expanse represents one individual or2:20many.2:21A single genetic individual could make this a contender for the world's largest2:24single coral.2:25The formation already ranks among the largest recorded coral expanses.2:28It's possible single coral record depends on the DNA result.2:31Meanwhile, the coral's growth in deeper water gives researchers another question to2:36investigate whether depth can help shelter corals from disturbances that damage2:40shallow reefs.2:41Hubbs wants to investigate whether deeper areas can act as refuges when bleaching or2:45cyclones damage shallow water corals.2:47Scientists still need to find out whether depth helps explain why this coral is2:50thriving.2:50Its growth gives them a place to investigate.2:52Gerhard links growing scientific interest to the declaration of marine parks around2:56Cocos and Christmas Island.2:58Hubbs sees the island's isolation as an opportunity to explore questions relevant to3:02reefs elsewhere.3:03The genetic testing is still underway, and the team hasn't given a firm date for the3:07results.Read the articleStory timelineHeyDex
