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[Radio Australia] Marianas Trench Has ‘Surprisingly Active’ Microbial Community

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Scientists unexpectedly find large number of single-celled organisms

MELBOURNE, Australia (Radio Australia, March 18, 2013) – Scientists say they have discovered an unexpectedly large and active community of single-cell organisms living on the Pacific sea floor at the deepest site on Earth.

The “surprisingly active” community of microbes exists about 11 kilometres below sea level in the Mariana Trench.

The Mariana Trench is one of the world’s most inaccessible places, around 200 kilometres south-west of Guam.

Many scientists had thought that the deeper the floor below sea level, the more deprived it would be of food – which has to float all the way from the oxygen-rich surface to the bottom of the ocean.

But researchers found the trench houses almost 10 times more bacteria than a nearby six-kilometre deep site.

Ronnie Glud, of the University of Southern Denmark, says the bacteria were living on organic waste from dead sea animals, algae and other microbes which settle on the ocean floor.

“It’s surprising there was so much bacterial activity,” he said.

“Normally life gets scarcer the deeper you go – but when you go very deep, more things start happening again.

“We find a world dominated by microbes that are adapted to function effectively at conditions highly inhospitable to most higher organisms.”

For the latest study, an international research team used a specially designed underwater robot with ultrathin sensors to probe the seabed for oxygen consumption.

Scientists cannot remove samples to study in the laboratory as many of the microorganisms specially adapted to life at these extreme conditions will die due to changes in temperature and pressure.

The team also made videos of the bottom of the trench and confirmed there were very few large animals at these depths.

“We have a small exotic piece of the puzzle which has never been studied before,” Mr Glud said.

Only about 2 percent of the world’s oceans are deeper than 6,000 metres.

Mariana Trench made headlines a year ago when Hollywood director James Cameron made history’s first solo trip by submarine to the bottom.

He described a “desolate” and “alien” environment.

Before Mr Cameron, the trench had been visited only once before, and briefly, by a two-man crew in 1960.

Because of its extreme depth, the Mariana Trench is cloaked in perpetual darkness with temperatures just a few degrees above freezing.

The water pressure at the bottom is a crushing 1,125 kg per square centimetre – described as being the same as being stepped on by an elephant wearing high-heeled shoes.

Mariana Trench is a crescent-shaped scar in the Earth’s crust, more than 2,550 kilometres long and 69 kilometres wide on average.

Radio Australia: www.abc.net.au/ra
Copyright © 2013 Radio Australia. All Rights Reserved

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