A number of life forms found by researchers in the trench, including a clam bed and tube-dwelling polychaetes. Nature

An underwater voyage has revealed a network of creatures thriving at the bottom of deep-sea ocean trenches, researchers said in a newly published paper.

The deep-sea trenches, also called Hadal trenches, are "some of the Earth's least explored and understood environments," the researchers wrote. In these extreme environments, the crushing pressure, scant food and lack of sunlight can make it hard to survive. Scientists know that tiny microbes prosper there, but less is known about evidence of larger marine life.

Researchers traveling along the Kuril–Kamchatka and Aleutian trenches in the northwest Pacific Ocean used a manned submersible to find tubeworms and mollusks flourishing at over 31,000 feet deep. The deepest part of the ocean goes down to about 36,000 feet.

Scientists had surveyed this area before and had hints that larger creatures might live at such depths. The new discovery confirms those suspicions and shows just how extensive the communities are, said Julie Huber, a deep sea microbiologist with Woods Hole Oceanographic Institution.

"Look how many there are, look how deep they are," said Huber, who was not involved with the research. "They don't all look the same and they're in a place that we haven't had good access to before."

In the absence of light to make their own food, many trench-dwellers big and small survive on key elements like carbon that trickle down from higher in the ocean.

Scientists think microbes in this new network may instead be capitalizing on carbon that's accumulated in the trench over time, processing it to create chemicals that seep through cracks in the ocean floor. The tubeworms and mollusks may survive by eating those tiny creatures or living with them and snacking on the products of their labor, scientists said.

"These findings challenge current models of life at extreme limits and carbon cycling in the deep ocean," the study's authors wrote. The researchers said that trench-dwelling life forms "may be more widespread than previously anticipated."

With this discovery, future studies will focus on how these deep-sea creatures adapted to survive in such extreme conditions and how exactly they harness chemical reactions for food, study authors Mengran Du with the Chinese Academy of Sciences and Vladimir Mordukhovich with the Russian Academy of Sciences said in a statement.

Their existence challenges "long-standing assumptions about life's potential at extreme depths," the authors said.

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