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Pacific Ocean's Mariana Trench teeming with bacteria

March 18, 2013|By Geoffrey Mohan
  • The Deepsea Challenger, carrying filmmaker James Cameron, is lowered into the western Pacific Ocean in March 2012.
The Deepsea Challenger, carrying filmmaker James Cameron, is lowered… (Mark Thiessen/National…)

The vastly deep ocean trenches at the edge of continents have been something like the Mars of oceanography — off limits until recently.

Now they are providing information nearly as freaky as that provided by the Mars Rover.

There is abundant life at 36,000 feet below the ocean surface, living under the kind of pressure (more than 1,000 times atmospheric pressure at sea level) that would crush human bones down to liquid, according to the first data from a 2010 robotic exploration of the sediments in the Mariana Trench, in the western Pacific Ocean.

Bacterial communities are 10 times more active at the bottom of that trench than in the plains surrounding the trench, according to the findings, published in Nature Geoscience.

"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,” said lead author Ronnie Glud, a biochemist from Nordic Center for Earth Evolution at the University of Southern Denmark.

Earthquakes may be shaking organic matter — dead animals, algae and other microbes — from these plains into the trenches, providing a feast for the bacteria that thrive there, according to the research team.

This makes the bacterial colonies an important factor in the long-term carbon cycle of the ocean, a process that interests scientists studying such topics as climate change.

Glud was joined by researchers from Germany, Japan, Scotland and Denmark. The team used a massive robot to collect sediment in the trench and measure the distribution of oxygen in them, which can be used to deduce microbial activity.

That measurement was done at the bottom of the trench, not in a laboratory.

"If we retrieve samples from the seabed to investigate them in the laboratory, many of the microorganisms that have adapted to life at these extreme conditions will die, due to the changes in temperature and pressure,” Glud said.

The robot, standing more than 12 feet tall and weighing more than 1,200 pounds, used ultra-thin probes inserted into the sediments to take the measurements.

Video sent back from the depths reveals very little other visible life. “There are very few large animals at these depths,” Glud said. “Rather, we find a world dominated by microbes that are adapted to function effectively at conditions highly inhospitable to most higher organisms.”

Exploration of the Mariana Trench has been this generation’s equivalent of scaling Mt. Everest. Filmmaker James Cameron last year became the first person to reach the depths of the Mariana Trench in a solo submersible craft. The feat was first accomplished by a duo, U.S. Navy Cmdr. Don Walsh and Jacques Piccard in 1960, who descended in a bathyscaph. Several expeditions using remotely operated vehicles followed, in 1996 and 2009.

In 2011, Scientists from the Scripps Institution of Oceanography exploring the depths of the Mariana Trench found sponge-like amoebae, called xenophyophores, that were nearly the size of a human hand.

The Mariana Trench is named for its location off the Mariana Islands, where the Pacific tectonic plate slides under the smaller Marianas plate.

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