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The underwater mountains of the Nazca and Salas y Gómez ridges are a world unto themselves. Running for 1,800 miles off the coast of Peru, they are isolated by a vast low-oxygen zone, the depths of the Atacama Trench, and the powerful Humboldt Current—an isolation that allowed evolution to follow its own trajectory.
“Almost half of the species living there live only there,” says Javier Sellanes, a marine ecologist at Chile’s Universidad Católica del Norte.
Until recently, however, researchers had only surveyed the upper reaches of the region’s seamounts. The creatures and communities living farther down their slopes were almost entirely unstudied.
To learn more, Sellanes and a team of scientists set out earlier this year aboard the Schmidt Ocean Institute’s Falkor (too) research vessel, equipped with a remotely operated submersible and all the instrumentation they would need to explore the depths. In the course of mapping more than 20,000 square miles of seafloor and discovering four seamounts, the researchers found a veritable deep-sea wonderland: millennia-old corals, watermelon-sized urchins, fish adapted for walking, and more than 100 species thought to be new to science.
All this was only a glimpse of what Sellanes calls “one of the least-explored areas of the ocean”—but it was enough to see that the region is as extraordinary at depth as it is near the surface.
Though the extraordinary communities the researchers observed are thousands of feet below the ocean’s surface, their lives are intimately connected to—and threatened by—what happens above.
Lost or discarded fishing gear eventually falls to the seafloor. Trawling can destroy in a few hours habitats that took millennia to form. Seabed mining may bring not only localized destruction but long-distance pollution by noise and sediment. Climate change alters the temperature and composition of even deep-sea waters.
Sellanes hopes the information gathered on his expedition will ultimately be used to better manage and protect the seamounts of the southeast Pacific. Doing so can be a matter of human self-interest, notes Sellanes: Commercially important fisheries may depend on species whose life cycles are tied to those seamount communities. But of course the argument is not only about utility.
“A lot of these species have small ranges. They’re endemic to the region,” Easton says. “If you lose them, how will they be replaced?” 
Lead photo: Several different kinds of corals are illuminated by the submersible’s beams. Their bodies provide habitat and protection for many other creatures, including these cactus urchins, and their colonies are the foundation of entire seamount assemblages. Credit: ROV SuBastian / Schmidt Ocean Institute.
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