A few years ago, film director James Cameron spent hours scouring the world’s deepest ocean canyon for any sign of life. He found a few bizarre animals, but it turns out the real action in the Mariana Trench happens beyond the reach of a submersible’s camera.
Researchers from Japan discovered microscopic bacteria thrive in the canyon called Challenger Deep, which is the lowest point on Earth’s surface and the deepest part of the Mariana Trench, the team reports today (Feb. 23) in the journal Proceedings of the National Academy of Sciences. In particular, they found an unusual community of bacteria there called heterotrophs, or microbes that cannot produce their own food and must eat what they find in the water.
Cameron found that larger life forms were scarce compared to shallow ocean waters. However, the heterotrophic life in Challenger Deep’s waters was relatively abundant, similar to that in untreated well water, said lead study author Takuro Nunoura, a microbiologist with the Japan Agency for Marine-Earth Science and Technology (JAMSTEC).
The average depth of the ocean floor is about 13,120 feet (4,000 meters); its deepest point is in the western Pacific’s Mariana Trench, where the Challenger Deep canyon bottoms out at more than 36,000 feet (nearly 11,000 m) below sea level. All kinds of microscopic life are found in the seafloor at this depth, from bacteria and archaea to yeast and viruses, according to this and other studies. [Infographic: Tallest Mountain to Deepest Ocean Trench]
The heterotrophs in the Challenger Deep likely derive food from sinking particles, such as dissolved fecal pellets or dust, or possibly from geologic processes such as earthquake-triggered landslides, which could send organic-rich sediments tumbling into the canyon’s depths, the researchers said.