In the ocean’s twilight zone, this diver is discovering vibrant new species

Editor’s Note: Call to Earth is a CNN initiative in partnership with Rolex. Luiz Rocha is a Rolex Laureate.

CNN
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Hundreds of feet below the ocean’s surface, somewhere between the dark ocean floor and the bright blue shallows, lies the twilight zone.

It’s a world of the unknown, but in some tropical and subtropical waters coral reefs thrive. Very few scientists have ventured to these deep reefs, known technically as mesophotic coral ecosystems, meaning “middle light,” and many assumed that the lack of light and chilly temperatures meant few species could exist there.

But one scientist has been diving into the inky depths to show there’s much more to life there than was first thought.

“When you get up close, it’s a very colorful ecosystem,” says Luiz Rocha, Brazilian ichthyologist (a person who studies fish) and co-director of the Hope for Reefs initiative at the California Academy of Sciences. “There’s many different kinds of fish and many of them are unknown.”

Despite its dimness, the twilight zone is home to fish of a stunning variety of colors, such as the Cirrhilabrus wakanda.

Rocha, whose studies focus on ocean life between 200 and 500 feet deep, was attracted to twilight zone reefs because of their mystery. “Every dive we do to those depths (leads to) a new discovery,” he says.

To date, he has identified around 30 new species – from a purple fairy wrasse named after the mythical nation of Wakanda, to the Tosanoides aphrodite, a pink and yellow reef fish named after the Greek goddess of love. But his deep-sea explorations have also proven that these reefs and the rainbow-hued species that roam them are under threat. His mission is to protect them.

Entering the twilight zone is no easy feat. While it could be reached by submarine, this would be a clumsy way to study fish that flit in and out the shadows, says Rocha, comparing it to studying birds in a rainforest with a helicopter.

Scuba diving scientist shines a light on the world’s deep sea reefs

Instead he scuba dives, but the deeper he descends the more dangerous it becomes. Recreational diving is capped at 130 feet for safety reasons, but Rocha dives as far as 500 feet. To do this requires deep concentration, intense technical training and a strong dose of bravery.

“What really makes this research special is that there’s only a handful of scientists in the world doing this,” he says.

Rocha usually dives in a group with two scientists and one safety officer. They spend hours preparing the kit, ensuring every piece of equipment is functioning well and that they are equipped to deal with underwater emergencies. The divers must use rebreathers, which recycle the gas exhaled by the diver, and a special breathing gas containing helium that is safe for deep dives.

Rocha and a team of divers prepare to explore the twilight zone reefs of the Maldives during a recent expedition.

Getting down takes just 10 to 15 minutes depending on how steep the reef is, says Rocha, but the ascent can take five to six hours to allow the body to decompress.

All that effort gives him just seven to 10 minutes at maximum depth, where he and his team look for fish, collect DNA samples and record the number of organisms in an area. If they think they have found a new species, they usually catch it and carry it up to the surface in a decompression chamber so they can study the specimen back in the lab.

Despite having done it dozens of times, Rocha still feels the pangs of anxiety before each dive. The deeper you go, the darker and colder the water gets, he says. “But when we get there, we know why we’re there. When you see something that nobody has ever seen before … it’s absolutely amazing.”