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