- Icebergs crashing against the sea floor
could be the most devastating natural disaster that any living community
on Earth experiences.
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- Scientists from the British Antarctic
Survey have discovered that over 99.5% of all visible sea-bed dwellers
are massacred when the bergs collide with the ocean bottom.
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- Floods, earthquakes and even meteorite
impacts cannot claim such total destruction. The project leader, Professor
Lloyd Peck, told BBC News Online: "In biological terms it is outrageous
- it's almost a sterile environment."
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- Up to 20% of the world's oceans are prone
to catastrophic ice berg impacts. Even ocean floor as deep as 500m is at
risk.
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- The bergs float in and gouge and trample
the communities as they rock back and forth in the tide. It is their immense
weight that causes the damage.
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- "The biggest icebergs are the size
of Oxfordshire and weigh two billion tonnes. The impact force is greater
than that of cruise missiles - it's immense," says Professor Peck.
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- His team, including colleagues from Gent
University, Belgium, set up three underwater test sites near Signy Island,
Antarctica. All were destroyed within 18 months.
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- They dived beneath the sea and used vacuum
pumps to suck up the animals living on the sea bed both before and immediately
after the berg impact.
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- They were shocked by the totality of
the death toll. In some cases, literally everything had been ground to
a fine powder.
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- "For animals bigger than one millimetre,
there were eight really common groups and six disappeared completely,"
explained Professor Peck. "The removal of the other two species was
over 99.5%.
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- "Animals smaller than one millimetre,
like nematodes, went down from two million per square metre to a few hundred."
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- Rising from the ashes
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- For the first time, the scientists also
tracked the recovery of the obliterated sites. It had been thought this
would take years.
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- But the first arrivals re-colonised within
a few days, simply by walking back in. The smaller creatures needed the
assistance of a major storm to be swept back in. This occurred within four
months, with a 150 km/h gale.
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- And this revealed a surprise - the berg
impacts actually revitalise the sea floor communities in the same way that
forest fires clear "dead wood" and allow new trees to flourish.
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- "The icebergs actually help to maintain
the population with a larger number of young animals because it's clearing
areas for settlement," says Professor Peck. "So the ice bergs
do have positive effects as well."
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