In early December 2024, a team of young Indonesian marine biologists from Ocean Gardener, after receiving training from the Italian University of Milano Bicocca’s Map the Giants programme, located and measured what could be the biggest coral colony in the world in Nusa Penida off Bali in Indonesia.

The news comes after a large coral colony, back then believed to be the world’s largest coral, was discovered in the southwest Pacific, in the Three Sisters island group. The ‘mega coral’ measures 34 metres wide, 32 metres long, and 5.5 metres high and has a circumference of 183 metres. 

The newest contender for the title of the world’s largest coral is a colony of Galaxea astreata coral which was recently measured on the north coast of Nusa Penida, off Bali, in a popular diving spot. The colony measures 58 metres wide, 71 metres long, 10 metres high, and covers an area of over 4,000 square metres.

“This discovery has the potential to set a new world record. However, further testing is needed to confirm its status among the world’s giant coral colonies,” Ocean Gardener research and science coordinator Manikmayang explained.

Vincent Chalias, founder of Ocean Gardener, said in an interview with Oceanographic Magazine: “We knew about this coral colony for many years, but it’s only recently that it became mainstream. We partnered with the Map the Giants programme around two months ago to measure the colony and determine that it was, in fact, a single organism. We want to record the colony to put it on the Map the Giants database and, ultimately, get it protected.”

Map the Giants is a project brought to life by Milano Bicocca University and represents a tool for tracing the past and modelling future responses to coral conservation. The project seeks to locate, measure and research giant corals, those larger than 5 metres in any of their lengths, and adding them onto a global map to advance multidisciplinary protection measures.

Chalias explained that to measure the coral a large group of 11 divers was needed: “We had wanted to measure the coral for a good few months but it took a good weather window and a four-week coral restoration course with nine students to make it happen.”

The next step is to better understand the colony’s ecological importance. “These giant corals actually occur often. Each coral species probably has a giant somewhere, and finding the biggest one of all hard coral species is an interesting challenge,” explained Chalias. “Not only are they old and enormous, but they produce billions of offspring that seed coral reefs around the world. That particular colony off Nusa Penida, due to the water flow, could probably seed reefs all the way in the Maldives and maybe even as far as east Africa. While their ecological importance is not yet well understood, it could be as gigantic as their size.”

Nusa Penida, Bali, is located in the Lombok Strait and in the middle of the Indonesian Throughflow current, where the Pacific Ocean flows into the Indian Ocean. It is a major crossroads in the coral world, a central location where corals can grow to gigantic sizes and produce billions of larvae that seed reefs all over the Indian Ocean. For these reasons, Nusa Penida is a critically important location in the centre of the Indo-Pacific coral map.

The giant coral colony off Nusa Penida is already located within a Marine Protected Area. The team at Ocean Gardener now hopes this coral will be a new focal point within the region, supporting further conservation efforts.

The first step in finding out more about the colony is to check its DNA to check whether it is, in fact, the same coral. To do this, Ocean Gardeners is currently looking for funding. “We would like the whole sequencing to be done in Indonesia to give Indonesians control over their natural wonders,” explained Chalias. “Nusa Penida is home to many other giants which we’d also like to test and we want to understand how important these corals are to regions in the Indian Ocean. How are they connected? A lot of genetic work is necessary to find out. Then, the second step is to get local government to understand the immense potential of these assets, not only for tourism and direct financial return, but also for long-term ecological purposes.”

“Indonesia is currently in a race of human development and corals could be the big looser of that race. It’s of the biggest importance of us to put these giant corals on the map, encourage conservation, and get Indonesians to realise that their corals are their real assets,” said Chalias.

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