What is the sound of microorganisms

Diversity of microbes in the Mariana Trench : The lowest point on earth is full of life

The water pressure is extremely high, nutrients from cadavers or algae residues have to fall eleven kilometers from the sea surface into the abyss. "A sterile, almost desert-like place" is the Mariana Trench in the western Pacific, reported director James Cameron, who in 2012 became the third person to go there in a submarine. That sounded plausible, after all, no more than two percent of the organic material sinks to a depth of 3.7 kilometers. It was unclear how much deeper it would get.

Despite the adverse living conditions, the microorganisms in the deepest depression of the earth's surface are more active than in shallower sea areas, writes an international team of researchers from Denmark, Germany, Japan and Scotland in the journal "Nature Geoscience". The oceanographers couldn't just take samples and analyze them in the laboratory. "Many of the microorganisms would have died because of the changed pressure and temperature," says Ronnie Glud from the University of Southern Denmark. So they constructed an underwater robot weighing 600 kilograms that can insert fine sensors into the ocean floor and measure the distribution of oxygen on site. They then compared the measurements at the Challenger Deep, the deepest point of the Mariana Trench, with those at a six-kilometer-deep point about 60 kilometers south in the Pacific.

“We found a world of microbes,” says Glud about the measurement results and additional videos. Amazingly, the oxygen consumption in Challenger Deep was almost twice as high as in six kilometers. The number of bacteria in the sediment was ten times as large. A lot of organic material must therefore be available in the sea trench. The researchers suspect that it is loosened by earthquakes from shallower areas and sliding into the trench.

The extremely active microorganisms in the Mariana Trench also influence the earth's carbon cycle. Further studies should now show whether they are important for the climate. dpa / yes

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