Deep in the South Pacific, scientists have explored a rare patch of pristine rose-shaped coral off the coast of Tahiti. The reef is considered to be one of the largest found at such depths and appears untouched by climate change or human activities.
Laetitia Hédouin said she first saw the corals months earlier during a recreational dive with a local diving club.
“When I first went there, I thought, ‘Wow – we need to study that reef. There’s something special about that reef,” said Hédouin, a researcher at the French National Center for Scientific Research in Moorea, French Polynesia.
What Hédouin noticed was that the corals looked healthy and were unaffected by a bleaching event in 2019. Corals are small animals that grow and form reefs in oceans around the world.
Worldwide, coral reefs are depleted due to overfishing and pollution. Climate change is also harming delicate corals — including those in areas adjacent to the newly discovered reef — with severe bleaching caused by warmer waters. According to a 2020 report by the Global Coral Reef Monitoring Project, 14% of the world’s corals were killed between 2009 and 2018.
The newly discovered reef, which is 3 kilometers long, was studied late last year during a diving expedition supported by UNESCO. Unlike most of the world’s charted corals, which are found in relatively shallow waters, this one was deeper — between 115 feet (35 meters) to 230 feet (70 meters).
Exploring such depths presented a challenge: the deeper a diver goes underwater, the shorter the time that can be safely spent at any depth. Equipped with special tanks, the team spent 200 hours studying the reef, including taking photos, measurements and samples of the coral.
The reef is in a place where many researchers haven’t spent much time, said former National Oceanic and Atmospheric Administration oceanographer Mark Eakin.
“We’ll see more of these discoveries as the technology is applied to these sites,” Eakin says. “Maybe we’ll find bigger ones somewhere, but I think this will always be an unusual reef.”
The recent volcanic eruption in Tonga that triggered tsunami waves across the Pacific has not affected the reef off Tahiti, Hédouin said.
Hédouin hopes the research can help experts understand how the reef is resilient to climate change and human pressure, and what role these deeper corals can play in the ocean ecosystem. More dives are planned in the coming months.
“We know very little about the ocean, and so much remains to be recorded and measured,” said Julian Barbière, UNESCO’s head of marine policy and regional coordination.