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.”
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.
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.
“What really makes this research special is that there’s only a handful of scientists in the world doing this,” he says.
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.”
Human impacts run deep
While the twilight zone has been explored by very few people, the effects of human activity are still apparent.
He has found plastic trash and fishing gear in some of the deepest reefs and has observed the impact of overfishing and climate change. While there is not yet enough data to determine the scale of the damage compared to shallow reefs, he says it is clear that water temperatures are warming in the deeper zones too and causing reefs to bleach.
Rocha believes that technology will soon advance to a point that gives many more people access to the twilight zone and even more species will be discovered. But his main goal is that when they do, the ecosystems will look the same as they do now.
“I don’t think it’s enough just to do the science,” he says. “We take many, many photographs … and we bring those stories back up to the surface and we share it with as many people as possible.”
“For the most part, when people realize that those reefs are there, they move towards protecting them,” he adds.