| OSLO, March 17
OSLO, March 17 Microbes are thriving in
surprising numbers at the deepest spot in the oceans, the
11,000-metre (36,000 ft) Mariana Trench in the Pacific, despite
crushing pressures in sunless waters, scientists said.
Dead plants and fish were falling as food for microscopic
bugs even to the little-known hadal depths, parts of the seabed
deeper than 6,000 metres and named after Hades, the god of the
underworld in Greek mythology, they said.
The presence of life in the trench also shows how the
greenhouse gas carbon dioxide, vital for the growth of tiny
marine plants at the ocean surface, can eventually get buried in
the depths in a natural process that slows climate change.
A Danish-led team of scientists, using a robot to take
samples, found double the amount of bacteria and other microbes
munching away on debris at the bottom of the Mariana Trench in
the western Pacific than at a nearby site 6,000 metres deep.
"It's surprising there was so much bacterial activity," said
Ronnie Glud, of the University of Southern Denmark and lead
author of the study in Monday's edition of the journal Nature
"Normally life gets scarcer the deeper you go. But when you
go very deep, more things start happening again," he told
Reuters of the report that also involved research institutes in
Scotland, Greenland, Germany and Japan.
The finding backed up a theory that dead plants and fish
falling onto the steep sides of the Mariana Trench often slide
to the bottom to form a "hot spot" for microbes. Earthquakes
also trigger mudslides that carry debris down.
The Mariana Trench is five times longer than the Grand
Canyon and could easily swallow the world's highest mountain
Mount Everest, which stands 8,848 metres tall.
Life has been detected at the bottom before, but its extent
is little known. The scientists' video cameras also spotted a
few shrimp-like crustaceans at the bottom of the trench.
"It's most likely that more carbon is deposited" in the
hadal depths than previously believed, Glud said.
"We have a small exotic piece of the puzzle which has never
been studied before," Glud said of the way that the oceans
recycle or bury carbon.
Only about 2 percent of the world's oceans are deeper than
Until now, scientists had suspected that life in most of the
ocean depths, where waters are just above freezing, was severely
limited by a lack of food.
Only about one or two percent of living material in the
upper waters is expected to sink even to the average ocean floor
depth of 3,700 metres, the study said. Most food gets scavenged
and carried up towards the surface before it falls so deep.
And water pressure at the bottom of the trench is about
16,000 lbs per square inch (1,125 kg per sq cm), about the same
as being stepped on by an elephant wearing high-heeled shoes.
The scientists were also studying the genetic makeup of the
microbes, living in temperatures just above freezing.
The ability to survive crushing depths may mean they have
enzymes that could be used by industries that use high
pressures, ranging from fermentation to oil and gas.
The bottom of the Mariana Trench was first reached by
scientists in a submarine in 1960. Film director James Cameron
also descended in 2012 and reported few signs of life.
(Reporting By Alister Doyle; Editing by Sophie Hares)