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A snail fish in the Canada Basin at roughly 6000 feet water depth. Credit: Bodil Bluhm, University of Alaska Fairbanks (UAF) and Ian MacDonald, Texas A&M University, Corpus Christi
More than five miles below the surface of the Pacific Ocean, the temperature is near freezing, there’s no sunlight, and the pressure is more than five tons per square inch. Yet that forbidding zone is home to the deepest fish yet seen — a tadpole-shaped creature known as a snailfish.
It was found in late 2014 in the Mariana Trench, the deepest spot in all the oceans. It bottoms out at a depth of seven miles. It’s one of more than a score of ocean trenches. They form where one of the plates that make up Earth’s crust plunges below another, forming a deep “wrinkle” in the ocean floor.
When scientists first discovered marine trenches, it seemed impossible for anything to live in such a hostile environment. Yet biologists have cataloged thousands of species of life in the trenches, many of which were previously unknown.
A recent study says that because of the great pressure, fish probably can’t live at depths much greater than five miles — right where the new snailfish was discovered. But expeditions have found other forms of life at greater depths, including some shrimp-like creatures in the Mariana Trench.
And one expedition found that the sediments at the bottom of the trench are teeming with microscopic life. In fact, there are more bacteria in the sediments there than in the much shallower waters around the Mariana. That may be because the steep slopes of the trench funnel food into the depths — supporting an amazing diversity of life in the most difficult of environments.
