Have you ever seen a coral this big?

Amid the doom and gloom of news about the Great Barrier Reef comes a feel-good story: volunteer snorkellers have discovered the widest coral on the reef.

At 5.3 metres in height and 10.4 metres wide, it’s the sixth-tallest and by far the widest coral on the Great Barrier Reef – 2.4 metres broader than the silver medallist, described back in the 1980s.

Snorkeller next to the giant coral
Credit: Woody Spark

It was found off the coast of Goolboodi, also known as Orpheus Island, in Queensland’s Palm Island Group. It is in relatively remote area, in a protected marine national park.

The traditional custodians of the islands, the Manbarra people, have named the coral Muga dhambi (meaning, delightfully, ‘big coral’).

The specimen is of the stony coral genus Porites, and is in good health – 70% of it is composed of live coral, with the rest covered in sponge and algae.

Estimated to be between 421 and 438 years old, it’s one of the oldest-known corals on the reef. It would have started growing well before Europeans turned up, and has survived all sorts of natural events, including about 80 major cyclones.

The discovery was made during a citizen-science survey in March 2021, led by researcher Adam Smith from Reef Ecologic and James Cook University.

“Surprisingly few monitoring programs measure or even estimate the size of coral colonies,” Smith and colleagues write in their paper describing the coral, published in the journal Scientific Reports.

“Its location had not been previously reported and there is no existing database for significant corals in Australia or globally.”

They suggest that constructing a database – similar to the Significant Trees Register – would be beneficial.

“Cataloguing the location of massive and long-lived corals can have multiple benefits. Scientific benefits include geochemical and isotopic analyses in coral skeletal cores which can help understand century-scale changes in oceanographic events and can be used to verify climate models.”

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