A spectacular coral reef has been found between 35 and 70 metres below sea level near Tahiti, and it seems to be in good health despite the global biodiversity crisis
20 January 2022
This spectacular rose-shaped coral has been found off the coast of Tahiti in the Pacific Ocean, at depths of between 35 and 70 metres. It forms part of a reef that stretches for more than 3 kilometres and measures 70 metres across at its widest. It may be one of the largest found at such depths.
Laetitia Hédouin at France’s National Centre for Scientific Research and her colleagues undertook a diving expedition off the peninsula of Tahiti, where they first discovered the reef. It is primarily composed of two coral species: from 30 to 45 metres deep, Porites rus dominates. Going deeper, Pachyseris speciosa emerges and eventually becomes dominant at depths of 50 to 55 metres.
“It looks like a giant rose garden going as far as the eye can see,” says Julian Barbière at UNESCO’s Intergovernmental Oceanographic Commission.
One of the most remarkable things about this reef is its pristine condition.
“It’s a very healthy reef, like a dream come true,” says Hédouin. “In the middle of the biodiversity crisis, this is very good news.”
Read more: Giant coral is the widest ever found in the Great Barrier Reef
Coral reefs around the world are vulnerable in the face of increasing human-driven pressures, such as climate change, and natural disasters, such as tsunamis and cyclones. Whether the tsunami triggered by the recent Hunga Tonga-Hunga Ha’apai volcano has affected the reef is unknown yet.
This reef is also one of very few we have found at such depths, in what is known as the twilight zone of the ocean, says Barbière.
“There might be many more large reefs in our ocean at such depth that require more investigation,” he says. “This could be one of the largest coral reefs at this depth as far as we know, but the fact is that we haven’t really looked for coral reefs at this depth.”
As it stands, only 20 per cent of the seafloor has been mapped, says Barbière. By mapping more of the ocean, at even greater depths, researchers hope to understand the best ways to protect and manage these rich ecosystems.
“Until now, we see reefs in two dimensions and we rarely include the depth as a critical dimension. [But it] is important for protection, management and conservation targets,” says Hédouin.
Millions of people rely on the so-called ecosystem services provided by coral reefs for their livelihoods. “We need coral reefs for fisheries, for tourism, even for coastal protection,” she says.
“There are also benefits to coral reefs which are not always that obvious,” says Barbière. “We are finding more and more potential medical solutions through some of the marine organisms that lived in those ecosystems. Those could help develop drugs to treat cancer or arthritis for example.”
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