Bacteria thrive in earth's deepest site

Bacteria thrive in earth's deepest site

Scientists have discovered a large and highly active bacteria community in the world’s deepest oceanic trench on the Pacific sea floor.

The international research team studied one of the most inaccessible places on earth: the bottom of the Mariana Trench located nearly 11 kilometres below sea level in the western Pacific, which makes it the deepest site on earth.

They documented a highly active bacteria community in the sediment of the trench - even though the environment is under extreme pressure almost 1,100 times higher than at sea level.

In fact, the trench sediments house almost 10 times more bacteria than in the sediments of the surrounding abyssal plain at much shallower water depth of 5-6 km water.

Deep sea trenches act as hot spots for microbial activity because they receive an unusually high flux of organic matter, made up of dead animals, algae and other microbes, sourced from the surrounding much shallower sea-bottom.

It is likely that some of this material becomes dislodged from the shallower depths during earthquakes, which are common in the area.

So, even though deep sea trenches like the Mariana Trench only amount to about 2 per cent of the World Ocean area, they have a relatively larger impact on marine carbon balance - and thus on the global carbon cycle, said Professor Ronnie Glud from Nordic Center for Earth Evolution at the University of Southern Denmark.

“We have also made videos from the bottom of the Mariana Trench, and they confirm that there are very few large animals at these depths. Rather, we find a world dominated by microbes that are adapted to function effectively at conditions highly inhospitable to most higher organisms,” said Glud.

The expedition of the Mariana Trench took place in 2010. Since then, the research team has sent their underwater robot to the bottom of the Japan Trench which is approximately 9 km deep.

Later this year they are planning a dive in the world’s second deepest trench, the 10.8 kilometres deep Kermadec-Tonga Trench near Fiji in the Pacific.

“The deep sea trenches are some of the last remaining “white spots” on the world map. We know very little about what is going on down there or which impact the deep sea trenches have on the global carbon cycle as well as climate regulation.” Glud said.
The study was published in the journal Nature Geoscience.

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