Mariana Trench hosts hydrocarbon-munching microbes

In the western Pacific Ocean, where the Pacific plate meets the Mariana plate, you’ll find the deepest place on Earth, the Mariana Trench. The trench runs for 2,550 km along the ocean floor and its deepest spot, evocatively named Challenger Deep, is about 11 km deep. To get down there, you need specialized equipment that can survive the crushing pressures. But once at the bottom, there is still a lot to discover.

In 2016, researchers lowered special water-sampling bottles from a surface ship down to Challenger Deep. Using DNA sequencing to characterize bacteria collected in these bottles, researchers in China, Russia, and the UK have found that the Mariana Trench is rich in hydrocarbon-munching bacteria (Microbiome 2019, DOI: 10.1186/s40168-019-0652-3). They confirmed their findings by isolating some of the bacteria and showing that the microbes could metabolize C₁₈–C₂₀ alkanes in the lab.

Scientists don’t know a lot about life in these very deep areas, but they do know the trenches are biological hot spots, says Ronnie N. Glud at the University of Southern Denmark, who was not involved in the study. “Why is it,” he asks, “when we move into the trenches that we have a much higher biological activity than we have elsewhere in the deep ocean?” Perhaps, he says, the hydrocarbons that accumulate in the trenches can be an energy source to sustain life.

“We know more about Mars than the deepest part of the ocean,” said Xiao-Hua Zhang of the Ocean University in China, who led the study, in a statement. More research is needed to understand life in this unique environment as well as the role these bacteria could play in cleaning up oil in the ocean, as do similar microbes found in the Gulf of Mexico.