Melting
Ice Gives Birth
To A Strange New World
By Steve Connor
28 February 2007
The
Independent
Herds
of sea cucumbers on the move, fields of sea squirts and forests of glass
sponges. These were just some of the fantastic sights scientists captured
on an underwater expedition to a remote region of Antarctica.
Marine biologists made a
unique inventory of lifeforms on a part of the seabed that had been
sealed off for thousands of years by massive ice shelves before they
suddenly broke up. Waves of colonising plants and animals quickly moved
in to exploit the new habitat which had opened up after a region of
ice a third of the size of Belgium had disappeared and let in daylight
and oxygen.
"This is virgin geography,"
said Gauthier Chapelle of the International Polar Foundation in Brussels.
"If we don't find out what this area is like now after the collapse
of the shelf, and what species are there, we won't know in 20 years'
what has changed, and how global warming has altered the marine ecosystem."
More than 50 scientists from
14 countries spent 10 weeks making the first comprehensive biological
survey of the seabed underneath the Larsen A and Larsen B ice shelves,
which disintegrated in 1995 and 2002 respectively.
They collected specimens
of an estimated 1,000 species, including 15 shrimp-like amphipods that
are probably new to science, including one 4-inch specimen that is the
biggest of its kind. They also found four species of coral-like organisms
called cnidarians, one of which was a new type of sea anemone, found
living on the back of a sea snail's shell.
A remotely controlled submersible
took pictures of animals called glass sponges, growing in dense patches
in the Larsen A area. By the Larsen B ice shelf, fast-growing gelatinous
sea squirts moved in.
"These ice shelves collapsed
due to regional warming," said Dr Julian Gutt, who led the expedition
from the Alfred Wegener Institute in Bremen, Germany.
"For the first time,
we have the opportunity to study life in such an area. The break-up
of these ice shelves opened up huge, near-pristine portions of the ocean
floor, sealed off from above for at least 5,000 years and possibly up
to 12,000 years in the case of Larsen B."
Another surprise finding
was the ability of deep-sea lilies - along with their relatives, the
sea cucumbers and sea urchins - to adapt to the relative shallows of
the Larsen seabed. Normally, these lilies are found at depths of 2,000
metres.
The scientists also saw minke
whales and rare beaked whales moving close to the edge of the pack ice
that had been exposed by the lost ice shelves, said Dr Meike Scheidat,
a German scientist on the team.
"It was surprising how
fast such a new habitat was used and colonised by minke whales in considerable
densities. They indicate that the ecosystem in the water column changed
considerably."
One overwhelming conclusion
from the expedition was that the marine ecosystem was in a state of
flux after the changes in the space of just 10 years. "The collapse
of the Larsen shelves may tell us about impacts of climate-induced changes
on marine biodiversity and the functioning of the ecosystem," Dr
Gutt said. "Until now, scientists have glimpsed life under Antarctica's
ice shelves only through drill holes. We were in the unique position
to sample wherever we wanted in the marine ecosystem considered one
of the least disturbed by humankind anywhere on the planet."
The Larsen shelves were attached
to the Antarctic peninsula, one of the fastest-warming regions, with
temperatures 2.5C higher than 60 years ago. Since 1974, some 13,500sq
km of ice shelves, which are attached to the mainland but float on the
sea, have disintegrated in the Antarctic peninsula. Scientists fear
more ice-shelf disintegration could lead to the rapid loss of glaciers
and ice sheets from the continental mainland, and a consequent rise
in global sea levels.
Dr Gutt said one question
the scientists wanted to answer is whether the massive movements of
ice was detrimental to the life-forms on the seabed. "During the
disintegration of the shelves, many icebergs calved, and the question
arises whether grounding icebergs only devastate life at the sea floor
or whether such disturbance contributes to a high biodiversity.
"Iceberg disturbance
was much more obvious north of the Larsen A and B areas where icebergs
typically run aground. At depths of 100 metres, we saw fresh ice scour-marks
everywhere and early stages of marine life recolonisation but no mature
community. At about 200m, we discovered a mosaic of life in different
stages of recolonisation."
The scientists also found
small clusters of dead clamshells littering a dark area of the seabed
which was probably the site of a mineral-rich "cold seep",
spewing methane and sulphide, which had fertilised the region then petered
out and starved the surrounding life-forms.
© 2007 Independent News and Media Limited