This story was originally published in our September/October 2022 issue as “Deep Coral.” Press here subscribe to read more stories like this.
It’s hard to find encouraging news about corals these days. That’s part of the reason images of this extraordinary reef in French Polynesia made the media rounds earlier this year. Located off the coast of Tahiti, its rose-shaped colonies stretch continuously over nearly 2 miles of seabed. But at a depth of about 150 feet in the South Pacific, the reef remained largely unexplored until last year, when coral biologist Letitia Hedwin visited after a tip from a local dive shop. The combination of its size, depth and premium quality was astonishing.
“It’s like a treasure,” says Hedwen, describing the mature coral as almost untouched by climate change. “The question is, how long will it survive?” Studies show that global coral cover halved between the 1950s and the early 2000s, and about 14 percent of the world’s corals disappeared between 2009 and 2018, to largely due to warming seas and ongoing bleaching.
Hédouin partnered with UNESCO to document and study this thriving reef in Tahiti in late 2021. In particular, the team of researchers and photographers documented some of the same species that are threatened in the shallower reefs, suggesting those on -little-studied, mesophotic reefs—those deeper than 100 feet where sunlight is limited—may play a vital role in coral preservation. And scientists don’t really know how many healthy mesophotic reefs are hiding in the depths of our oceans.
Advances in diving technology are changing this. Hédouin says the rebreathing equipment on this latest expedition allowed the divers to recycle their air and extend their time at depth four times longer than conventional diving. Changes in the availability and safety of such instruments are expanding opportunities for ocean exploration.