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See the giant, pristine coral reef that explorers found deep in the ocean’s ‘twilight zone’

In deeper water, reefs are more likely to escape human activity and warming waters that are destroying their counterparts nearer the surface.

See the giant, pristine coral reef that explorers found deep in the ocean’s ‘twilight zone’
[Photo: @Alexis.Rosenfeld]

In 2019, a coral bleaching event took place in the waters around French Polynesia, which was estimated to attack 50% to 60% of the coral reefs around the islands of Tahiti and Mo’orea in a matter of days, stripping them of their nutritional algae—the food and habitat for various sea creatures.

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[Photo: @Alexis.Rosenfeld]
But a newly discovered coral reef off the coast of Tahiti appears to have remained completely unharmed by that event. Divers on a research mission found the reef to be pristine, possibly because it’s deeper than many of the reefs we know about and therefore is better equipped to protect itself from warming water and human activity. The finding, aided by technological advances, gives hope that more healthy reefs exist in deep waters. But it’s also a reminder that we need to map more of the world’s oceans in order to produce a sensible framework for sustainable ocean management.

[Photo: @Alexis.Rosenfeld]
A team of divers, led by French explorer and photographer Alexis Rosenfeld, found the “magical” reef to be about 3 kilometers long, consisting of rose-shaped coral structures that are completely intact. The divers spent 200 hours studying and capturing images of the reef, and even witnessing it spawn. “This reef in particular, it’s quite a beautiful piece,” says Julian Barbière, head of marine policy and regional coordination at UNESCO. Unlike many, this one is located deeper, in the ocean’s “twilight zone,” about 30 to 65 meters deep, which is unusual at that size.

[Photo: @Alexis.Rosenfeld]
And it’s in better shape than those closer to the surface, which suggests to scientists that the depth protects it from destructive forces, including human activities like overfishing and pollution, as well as warming waters caused by climate change; about half of all the Earth’s reefs have lost their cover since the 1950s due to frequent bleaching episodes. It’s crucial that reefs stay intact, as they sustain about 25% of all marine species; what’s more, they are key to the livelihoods of coastal communities, they protect against storms and tsunamis, and they are even a source for medicine manufacture.

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[Image: @Alexis.Rosenfeld/Lacaz’a Productions]
Barbière says the finding provides some hope that there might be more thriving reefs out there. For its part, UNESCO, the United Nations agency in charge of oceans, aims to have all the world’s oceans mapped in high resolution by 2030. The stated objective of the agency’s Decade of Ocean Science initiative is to “reverse the cycle of decline in ocean health” between 2021 and 2030. “Before we go out there and raid all the resources,” Barbière says, “it’s important that we have the right science so that we are put on a sustainable path.”

[Photo: @Alexis.Rosenfeld]
So far only 20% of the seabed has been mapped using modern methods. Ocean mapping started in the 19th century, using rudimentary measurements involving lead-weighted ropes, and the first official “bathymetry” chart was published by commission of Prince Albert I of Monaco in 1905. Now more efficient means include radars and echo sounders on research vessels, as well as remotely operated autonomous vehicles for ocean observation.

For this particular dive, UNESCO partnered with French scientific research bodies as well as Rosenfeld’s organization, 1 Ocean, which is using photography as an awareness tool to help adopt the U.N.’s target of conserving at least 30% of the globe’s oceans by 2030; currently, only 7.5% have achieved marine conservation status. “It’s all very nice to find nice ecosystems,” Barbière says, “but we need to protect them.”

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