Coral colony stretching 1.56km found off Cocos Islands, one of the largest on record

The colony of rose coral runs 1.56km off the coast of the Cocos (Keeling) Islands, Australia's most remote inhabited territory. That is roughly the length of 100 buses laid end to end, covering an area about three times the size of the Melbourne Cricket Ground. Researchers formally mapped and examined the formation only in recent months.

Adelaide University marine biologist JP Hobbs said the team started out with measuring tapes before switching to GPS tracking once the scale sank in. He was tipped off by Cocos-based dive operator Dieter Gerhard, who had been seeing the coral at dive sites around 600 metres apart. Gerhard first spotted the expanse more than 30 years ago but had no idea how far it stretched.

It took 12 dives to chart the colony's full extent. Hobbs said it reached beyond Gerhard's dive sites and kept going. Working with Queensland Museum and James Cook University, the team has now collected about 50 samples along the coral and will run genetics to determine whether it is a single individual or many.

Hobbs said the discovery could help other coral species. Understanding why rose coral thrives in deeper water gives insight into whether deep areas can act as a refuge for shallow-water corals hit by bleaching or cyclones. The islands' isolation, he said, lets researchers answer questions that apply worldwide.

Gerhard said interest in the area has grown since both the Cocos Islands and Christmas Island were declared marine parks in 2022, with the scientific community eyeing more research. He believes plenty is still down there to find.