Citizen scientists report potential record-breaking coral colony on Great Barrier Reef

Citizen scientists surveying the Great Barrier Reef say they have identified what could be the largest single coral colony ever documented.

The giant colony of Pavona clavus (sometimes called shoulder blade coral) was discovered by Sophie Kalkowski-Pope, Marine Operations Coordinator of the conservation group Citizens of the Reef, and her mother, Jan Pope, while conducting surveys from the family boat.

The pair were carrying out the surveys as part of the Great Reef Census, a large-scale citizen science programme coordinated by Citizens of the Reef, in which photographs taken by visitors are gathered for analysis by artificial intelligence to determine the overall health of the reef.

Preliminary measurements of the discovery indicate the colony is approximately 111 metres in length and covers an estimated 3,973 square metres – just over half the size of a standard UK football (soccer) pitch.

If verified, the structure would be significantly larger than the last record-breaking coral colony, discovered in 2024 in the Solomon Islands and measuring around 34m x 32m, making the area of the Great Barrier Reef discovery about five times larger.

‘I knew right from the minute we dropped in that it was something special,’ said Kalkowski-Pope in a statement announcing the discovery.

‘When I got in the water, I’d never seen coral growing like this before,’ she said. ‘It looked like a meadow of coral. It just went on and on.’

The site was mapped using manual underwater measurements and high-resolution imagery to create a three-dimensional photogrammetric model of the colony in collaboration with the Queensland University of Technology Centre for Robotics.

‘The benefit of this kind of spatial data is that we can take measurements at very high resolution,’ said Serena Mou, a Research Engineer at the Centre for Robotics.

‘It also means we can return in future months and years and make direct, one-to-one comparisons to understand how the coral changes over time.’

The location of the colony is being kept secret and reef management authorities have been informed of the discovery.

It is thought that the colony has remained previously undiscovered because the area in which it is located is prone to strong tidal currents, making it difficult to dive there.

The Australian Institute of Marine Science (AIMS), which has been studying the Great Barrier Reef since 1985, has welcomed the find, saying that the colony is likely several hundred years old, and good for raising the profile of the reef.

‘Kudos to them for going out and measuring it and getting pretty detailed measurements,’ AIMS research scientist Mike Emslie told the ABC.

‘If it’s not the same coral [as one we’ve already surveyed], that’s even better news that there’s another vast Pavona colony out there,’ he said.

‘It indicates that these large, long corals are still standing up in the face of repeated acute disturbances like mass coral bleaching, cyclones and crown-of-thorns starfish.’

It’s too early to say if the coral is one single colony, as this requires extensive genetic testing over a very large area of the reef to ensure that it is a single, genetically identical organism rather than a number of colonies that have simply grown together over the years.

Nevertheless, the discovery has been widely praised, with scientists noting that citizen science is an important method of measuring the health of a reef.

‘Reef systems on the Great Barrier Reef and around the world are under significant pressure from climate change and local threats,’ said Roger Beeden, Chief Scientist at the Great Barrier Reef Marine Park Authority.

‘Protecting these extraordinary places can’t sit with the government alone. The role of communities, and the people within them, is becoming increasingly critical, not just in Australia, but globally.’

‘Discoveries like this are significant because the reef still holds so many unknowns, and we don’t know what we stand to lose,’ said Sophie Kalkowski-Pope.

‘I think this shows why reef conservation efforts like the Great Reef Census matter now more than ever.’

For more information about the Great Reef Census, head to www.greatreefcensus.org, or follow the team on Instagram @citizensofthereef and Facebook @citizensGBR

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