Yahoo – AFP,
Mariƫtte Le Roux, February 13, 2017
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| A Nature picture of a Hirondellea gigas, known to consume almost any organic material that descends from the surface waters, including any pollutants (AFP Photo/Dr. Alan JAMIESON) |
Paris (AFP)
- Banned chemicals are tainting tiny crustaceans that inhabit the deepest
ocean, a study said Monday -- the first evidence that humans are polluting even
the farthest reaches of our planet.
Even at
depths of nearly 11 kilometres (seven miles) these scavengers could not escape
"extraordinary" levels of contamination with chemicals used in
coolants and insulating fluids, researchers said.
The
pollutants likely came from plastic waste and dead animals sinking to the ocean
floor, they wrote in the journal Nature Ecology & Evolution.
"We
still think of the deep ocean as being this remote and pristine realm, safe
from human impact, but our research shows that, sadly, this could not be
further from the truth," said study co-author Alan Jamieson of Newcastle
University.
Jamieson
and a team used specially-built underwater craft to collect bottom-dwellers
called amphipods from the Pacific Ocean's Mariana and Kermadec trenches.
These are
some of the deepest, darkest places on Earth, less well-known to mankind than
the surface of the Moon.
Amphipods
are among the few creatures that can survive in this inhospitable zone of
extreme pressure.
The researchers
used mackerel-baited traps to catch the shrimp-like carrion-feeders, then
analysed them for traces of chemicals.
The tests
revealed high levels of pollutants, including polychlorinated biphenyls (PCBs)
banned almost 40 years ago for causing cancer and wreaking havoc with hormones.
"The
fact that we found such extraordinary levels of these pollutants in one of the
most remote and inaccessible habitats on Earth really brings home the
long-term, devastating impact that mankind is having on the planet," said
Jamieson.
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Hirondellea
gigas inhabit depths of 6000 to nearly 11,000m below sea level (AFP Photo/
Dr.
Alan JAMIESON)
|
Last
frontier
The
research was carried out in the ocean's hadal zone, between six and 11 km deep,
and comprised of deep trenches in the sea floor caused by tectonic plate
activity.
It is the
least-explored ecosystem on Earth, "and the last major marine ecological
frontier," the team wrote.
The Mariana
trench is deeper than Mount Everest is high.
It is
believed that some 1.3 million tonnes of PCBs -- which can persist in the
environment for decades -- were produced from the 1930s to 1970s.
About 65
percent of the total is thought to be in landfills or still in electrical
equipment today, and the other 35 percent in coastal sediment and the open
ocean.
The
scientists also found traces in the amphipods of another long-lived pollutant
-- polybrominated diphenyl ethers (PBDEs) used in flame retardants.
"PCBs
and PBDEs were present in all samples across all species at all depths in both
trenches," the researchers wrote.
In the
Mariana trench, the world's deepest, the highest PCB levels in samples were 50
times higher than in crabs from paddy fields fed by the Liaohe River, one of
China's most polluted.
The team
inferred that pollutants must be pervasive "across the world's oceans and
to full ocean depth."
"What
we don't yet know is what this means for the wider ecosystem", the animals
that feed on amphipods and the food chain higher up, Jamieson said in a
statement.





