A giant boulder coral standing more than five metres tall has been discovered off the North Queensland coast.
At 10 metres wide, the single Porites coral is 2.4 metres wider than the largest coral previously measured on the Great Barrier Reef.
James Cook University professor and reef expert Adam Smith was diving near Orpheus Island in the Palm Island group in March when he and a group of citizen scientists made the discovery.
"Out of the corner of our eye we saw something huge," Dr Smith said.
"We went back to the lab and realised we'd found something very special," Dr Smith said.
After consulting other scientists and doing a literature review, Dr Smith found it to be the "largest diameter Porites coral measured by scientists and the sixth-highest coral measured in the Great Barrier Reef".
The coral was estimated to be up to 438 years old and a survivor of 80 major cyclones, numerous bleaching events and centuries of exposure to invasive species.
"Which is pretty mind-blowing," Dr Smith said.
He said corals were similar to giant trees because they had growth rings.
He said numerous marine experts from JCU and the Australian Institute of Marine Science were able to tell the age of the coral, based on its height, location and average sea surface temperatures.
The discovery has been documented in a new scientific paper, Nature.com which has been co-authored with traditional owners.
The coral has been named Muga dhambi, big coral, by the Manbarra people, the traditional custodians of the Palm Islands.
