A sparse community of microbes can persist for eons in the clay beneath the deep blue sea. When scientists drilled into the Pacific Ocean bottom and pulled up a long core of clay, they also pulled up microbes living on so little that it was hard for the scientists to tell if they were alive in the first place. |
The microbes are still being precisely identified but they are not like the other deep-sea extremophiles that scientists have found everywhere from hydrothermal vents to more than a kilometer beneath some parts of the ocean floor. These microbes, like those closer to the surface, rely on oxygen to live - unlike other denizens of the deep sea muck that find the reactive element inimical to their lifestyle and were driven to the dark, secret places of the planet when photosynthetic organisms like plankton began to fill the atmosphere with oxygen more than 2 billion years ago.
The site where these microbes were found is beneath the North Pole Gyre, a massive whirl of current north of Hawaii. Since there is hardly any land nearby, precious little dead plankton and other nutritious detritus falls to the seafloor - only 0.2 millimeters accumulates every thousand years - and what does mostly gets consumed by quicker-living microbes on the surface of the seafloor. But, when scientists drilled a core during a cruise of the Woods Hole Oceanographic Institution’s Knorr research vessel, they found roughly 1,000 cells of these bacteria and archaea living in extreme slow-motion per cubic centimeter’s worth of mud core from 20 meters below the bottom of the ocean.
That depth suggests these microbes have persisted for 86 million years and haven’t seen fresh food since dinosaurs roamed the Earth. To cope, these newly-found microbes use oxygen to respire - or convert food into energy and release the waste byproducts - 10,000 times slower than microbes on the surface of the seafloor, leading the scientists who conducted the research, and published it in the journal Science on Friday, May 18, to write that “these microbial communities may be living at the minimum energy flux needed for prokaryotic cells to subsist.”