They discover a gigantic coral reef off French Polynesia 1:25
(CNN) --
Deep in the ocean off the coast of Tahiti, scientists made an incredible discovery in November: acres of giant, pristine, rose-shaped corals blooming from the seafloor in what's known as the "twilight zone" of the ocean.
The fact that such a large and beautiful coral reef has yet to be discovered highlights how little we still know about the world's oceans, scientists say.
And its pristine condition, with no evidence that the reef has been harmed by the climate crisis, suggests the need for urgent action to protect the remaining healthy reefs in the ocean.
Alexis Rosenfeld, the photojournalist who led the team of international divers, said the reef, which stretched "as far as the eye can see", was "magical to witness".
"It was like a work of art," he said.
A diver swims over a coral reef found off the coast of Tahiti in November.
A detailed view of the coral reef.
The research mission, led by UNESCO, found that the reef stretches for almost three kilometers and exists at depths of up to 70 meters.
This is the "twilight zone" or "twilight" of the ocean, where there is enough light to support life, and below which the ocean becomes a dark abyss.
"For a change, it's a positive coral reef story in the news, which is quite rare these days," Julian Barbiere, UNESCO's head of Marine Policy, told CNN.
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Ocean warming and acidification caused by the climate crisis have led to widespread coral bleaching.
Last year, scientists found that the global extent of living coral has halved since 1950 due to climate change, overfishing and pollution.
The outlook is just as bleak, with scientists predicting that between 70% and 90% of all living coral will be gone in the next 20 years.
According to UNESCO, so far only 20% of the seabed has been mapped.
And until its latest discovery, the vast majority of the planet's known coral ecosystems were believed to extend to a depth of only 25 meters, illustrating just how much of the oceans, which cover more than 70% of the Earth's surface , still need to be explored.
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"The discovery suggests that there are in fact many more large reefs in our ocean at depths of more than 30 meters that have not been mapped," said Barbiere.
"It's a pretty puzzling finding."
The team of divers were able to spend some 200 hours studying the reef using specialized diving equipment called a "rebreather," or closed-circuit respirator.
Coral reefs are an important source of food and habitat for a wide range of marine organisms, including the fish seen here.
"At a time when we are witnessing a huge investment in space exploration, there is not enough in studying our own home and the ocean in particular," said Barbiere.
"And I think this is where we really want to put our emphasis in the next 10 years: generating the knowledge we need to put the planet on a sustainable path through marine protected areas."
Despite its depth, the researchers say the newly discovered reef still receives enough sunlight for corals to grow and reproduce.
Some of the divers even witnessed coral spawning.
The researchers undertook the mission in November of last year with little knowledge of existing reefs in the region, and came away with an incredible understanding of how extensive, unique and pristine the coral is there.
A researcher swims above the reef, which stretches almost three kilometers.
Despite its depth, the reef still receives enough sunlight for corals to grow and reproduce.
Using rebreathers, which filter carbon dioxide from exhaled air and recycle much of the unused oxygen, the dive team was able to spend some 200 hours studying the reef.
Rebreathers allow divers to go deeper into the ocean floor and stay longer.
These closed-circuit respirators contain a special helium-based gas mixture that prevents narcosis or a drowsy state.
Barbiere said the researchers were surprised to learn that the coral was completely intact and healthy, a sign that it has survived for decades, since large reefs take 25 to 30 years to expand and flourish.
The UNESCO team plans to study the reef further to learn how the coral has thrived for so long in the face of increasingly hostile ocean conditions, in the hope that it may hold the secret to saving endangered reefs.
"We believe that deeper reefs may be better protected from global warming," says Laetitia Hédouin, a marine biologist at the French National Center for Scientific Research and the CRIOBE environmental research center.
"So the discovery of this reef in such a pristine state is good news and may incentivize future conservation."
The reef exists in what is known as the "twilight zone" of the ocean.
Coral reefs under threat
Coral reefs are crucial to Earth's biodiversity.
They are an important food source, as well as a habitat, for a wide range of marine organisms.
But man-made climate change threatens these ecosystems around the world.
About 6,400 kilometers west of Tahiti, off the coast of Australia, the Great Barrier Reef, the world's largest reef system, has suffered several episodes of large-scale coral bleaching in the last two decades due to extreme warming. of the ocean.
A 2021 study found that 98% of the reef had been affected by bleaching since 1998. And despite having adapted to higher heat thresholds, the study found that corals now have less time to recover between bleaching events. more frequent whitening.
The Great Barrier Reef has lost half of its corals in 3 decades
Although the Tahiti reef appears healthy right now, there remains concern that the effects of climate change will catch up with it, said Steven Mana'oakamai Johnson, a postdoctoral researcher and marine scientist at Arizona State University.
"Just because the reef doesn't currently show any impact from climate change, doesn't mean that's going to hold up in the future," Johnson told CNN.
"And so we can't assume that because no one knew it was there, and when we found it it was in good shape, that it will continue to dodge the inescapable weather bullets."
Rose-shaped corals flourish on the seafloor off the coast of Tahiti.
Fish swim in the reef off the coast of Tahiti.
Johnson's recent research found that between 60% and 87% of the world's oceans are expected to experience devastating biological and chemical changes, including higher levels of acidity and changes in oxygen levels by 2060, which would drastically damage the planet's vast coral reefs.
In a special report on the oceans in 2019, the United Nations Intergovernmental Panel on Climate Change concluded with a high degree of confidence that the impact on marine ecosystems will worsen if fossil fuel emissions continue apace.
Even if global warming is limited to 1.5 degrees Celsius, the ideal goal of the Paris Agreement, "coral reefs are projected to suffer significant area losses and local extinctions," the scientists reported, noting that efforts to restore them they'll probably be useless by that point, given the enormous stress they're already under.
Enter the strange world of the twilight zone of the ocean
"The big takeaway is that [the UNESCO team] found this reef road which is in good condition, which definitely speaks to how little we've done to really map the ocean," said Johnson, who is not involved in the survey. research.
"This underscores the importance of passing meaningful climate policy that includes finding ways to support the traditional stewards of these oceanscapes."
A group of researchers examines the reef.
The corals on the reef were found to be healthy, with no signs that they had been affected by the increasing stress of the climate crisis.
Barbiere said more expeditions are planned in the coming months to investigate the reef, primarily to study how it has thrived around the ocean's twilight zone.
An international network of governments, ocean scientists and volunteers is on a mission to map the world's seabed by 2030 to better understand not only the effects of the climate crisis, but also to improve tsunami warning systems.
The study of the ocean, according to Barbiere, could lead to similar discoveries at greater depths that would require broader protection.
"You can only protect what can be measured," Barbiere said.
"And as we're trying to set goals for global ocean conservation around the world, this is the basic information we need to start establishing marine protected areas."
Coral reef