In the twilight zone of the ocean, this diver discovers new vivid views

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

But one scientist plunged into the inky depths to show that there is much more life out there than first thought.

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

Rocha, whose research focuses on ocean life at depths of 200 to 500 feet, was drawn to the reefs of the twilight zone because of their mystique. “Every dive we make into these depths leads to a new discovery,” he says.

To date, he has identified about 30 new species – from purple fairy wrasse named after the mythical people of Wakanda, the Tosanoid aphrodite, a pink and yellow reef fish named after the Greek goddess of love. But his deep sea research has also proven that these reefs and the colorful species that roam them are under threat. His mission is to protect them.

Dive into

Entering the twilight zone is not easy. Although you can get there by submarine, it would be a clumsy way to study the fish that flit in and out of the shadows, Rocha says, comparing it to studying birds in a rainforest with a helicopter.

Instead, he scuba dives, but the deeper he goes, the more dangerous it becomes. Recreational diving limited 130 feet for safety reasons, but Rocha dives up to 500 feet. This requires deep concentration, intense technical training and a large dose of courage.

“What really makes this study special is that there are only a few scientists in the world doing this,” he says.

Rocha usually dives in a group with two scientists and one security officer. They spend hours preparing the kit, making sure every piece of equipment works well and is ready for emergencies underwater. Divers must use rebreatherswhich process the gas exhaled by the diver and a special breathing gas containing helium that is safe for deep diving.

The descent takes only 10 to 15 minutes depending on how steep the reef is, according to Rocha, but the ascent can take five to six hours for the body to relax.

All this effort gives him just seven to ten minutes at maximum depth, where he and his team search for fish, collect DNA samples and record the number of organisms in the area. If they think they’ve found a new species, they usually catch it and bring it to the surface in a decompression chamber to study the specimen in the lab.

Despite having done this dozens of times, Rocha still experiences anxiety attacks before each dive. According to him, the deeper you go, the darker and colder the water becomes. “But when we get there, we know why we are here. When you see something that no one has ever seen before…it’s just amazing.”

The human impact is deep

Although very few people have explored the twilight zone, the consequences of human activity are still evident.

It was previously thought that coral reefs in deeper waters could serve as a refuge because they were less affected by human development and climate change. But Rocha proved it wrong: “One of our first discoveries is that these deeper reefs are not really a haven for shallow reef organisms. They are almost as affected as the shallow reefs,” he says.

He found plastic debris and fishing tackle on some of the deepest reefs and observed the effects of overfishing and climate change. While there is not yet enough data to determine the extent of the damage compared to shallower reefs, he says it is clear that water temperatures are rising in deeper areas as well, leading to reef bleaching.

This year, Luis Rocha identified Cirrhilabrus finifenmaa, or the pink-covered fairy wrasse.
Rocha hopes his research will help educate people about the Twilight Zone and inspire action to protect it. He works with politicians to advocate for the marine protected areas where these deep reefs lie. In 2019, the Hope for the Reefs initiative aimed to protect coral reef habitat on Marikaban Island in the Philippinesand a year before their research served as the basis for the creation two protected areas in Brazil.
Rocha also works closely with local communities, collaborating with local researchers and giving local names to newly discovered species. For example, earlier this year he and Maldivian biologist Ahmed Najib discovered rainbow fish which they named Cirrhilabrus finifenmaa or pink-covered fairy wrasse, after the national flower of the Maldives, a pink rose called Finifenmaa. Rocha hopes this will “transfer ownership to the locals.”
Ahmed Najib (left) and Luis Rocha inspect fish specimens during a recent expedition to the Maldives.

Rocha believes technology will soon advance to the point where many more people will have access to the twilight zone and even more species will be discovered. But his main goal is that when they do, ecosystems will look the same as they do now.

“I don’t think it’s enough just to do science,” he says. “We take lots and lots of photos… and we bring those stories back to the surface and share them with as many people as possible.”

“For the most part, when people realize these pitfalls exist, they move on to protecting them,” he adds.

Leave a Reply

Your email address will not be published. Required fields are marked *