Rare, untouched coral reef discovered off Tahiti near the ocean's 'twilight zone'

A diver swims along a vertiginous drop-off covered with corals on April 27, 2018 in Tubbataha Reef Marine Park off Philippines
A diver swims along a vertiginous drop-off covered with corals on April 27, 2018 in Tubbataha Reef Marine Park off Philippines, Sulu Sea (Image credit: Alexis Rosenfeld/Getty Images)

A new and expansive coral reef system has been discovered off the coast of Tahiti on the border of the ocean's "twilight zone," and shows encouraging signs of resilience against global climate change.

The new reef was found at a depth between 30 and 65 meters beneath the surface of the ocean, with its deepest parts approaching a depth where light struggles to reach. 

The reef stretches roughly three kilometers long and varies between 30 and 65 meters across. Its rose-shaped corals can stretch as wide as two meters.

What makes this reef particularly special is that it is the deepest reef we've ever found, with nearly all known reefs reaching 25 meters at most. It is also one of the healthiest coral reefs on record, according to UNESCO.

Between 200 and 1,000 meters, there is so little light getting through that a kind of twilight condition exists before dropping off into total darkness below 1km. This "twilight zone" is an unexplored borderlands of sorts where all kinds of bizarre marine life live.

You don't have to go that far down to get into unexplored waters, though. Researchers are rarely able to dive below 25 meters even with modern equipment, though new technologies and unmanned marine drones are opening up these unexplored spaces.

Still, 70% of the Earth is covered by oceans, and we've only mapped a small fraction of it, so there is a lot out there that we simply haven't reached yet.

"To date, we know the surface of the moon better than the deep ocean," Audrey Azoulay, UNESCO Director-General, said in a statement

"Only 20% of the entire seabed has been mapped. This remarkable discovery in Tahiti demonstrates the incredible work of scientists who, with the support of UNESCO, further the extent of our knowledge about what lies beneath."

Analysis: new corals bring good news on the climate change front, for once

Most remarkable about the new coral reef is that it appears largely undamaged from the kind of climate-change-induced acidification that is expected to kill up to 90% of all known coral in the next two decades.

While that still means vast amounts of corals will be killed off by human activity – along with the marine life that depends on them – there is at least some resiliency in the ocean against it. How long that holds true is another question though.

"French Polynesia suffered a significant bleaching event back in 2019 however this reef does not appear to have been significantly affected," said Dr. Laetitia Hedouin, of France’s National Center of Scientific Research. 

"The discovery of this reef in such a pristine condition is good news and can inspire future conservation. We think that deeper reefs may be better protected from global warming," added Dr. Hedouin. 

The coral reef isn't entirely immune, and increasing acidification of the ocean could soon do to these deep water coral reefs what it has already done to their shallow-water counterparts. 

In other words, don't take this as a sign that human activity isn't posing a threat to marine ecosystems. Instead, it should be seen as a warning that there is still time to turn things around, but that window is closing. When that will happen isn't known, so the sooner we act, the better off our oceans will be.

John Loeffler
Components Editor

John (He/Him) is the Components Editor here at TechRadar and he is also a programmer, gamer, activist, and Brooklyn College alum currently living in Brooklyn, NY. 

Named by the CTA as a CES 2020 Media Trailblazer for his science and technology reporting, John specializes in all areas of computer science, including industry news, hardware reviews, PC gaming, as well as general science writing and the social impact of the tech industry.

You can find him online on Threads @johnloeffler.

Currently playing: Baldur's Gate 3 (just like everyone else).