Antarctic trip shows climate change effects
19 March 2007, Hamburg (dpa) - An expedition has revealed the first evidence of biological changes under the sea caused by the collapse of ice shelves in the Antarctic due to global warming, according to German researchers.
19 March 2007
Hamburg (dpa) - An expedition has revealed the first evidence of biological changes under the sea caused by the collapse of ice shelves in the Antarctic due to global warming, according to German researchers.
Scientists searched 10,000 square kilometres of seabed that were covered for millennia by two massive roofs of ice, Larsen A and B.
The ice shelves disintegrated 12 and five years ago respectively, due to higher temperatures that have been linked to man-made global warming.
As the ice broke up, it made the region accessible for the first time, lifting the lid on the unique plants and creatures inhabiting this part of the ocean floor.
A team of 52 international marine scientists aboard the German ice breaker Polarstern have now completed the first comprehensive 10-week survey of the ice shelf ecosystem.
As well as discovering biological oddities and numerous new species, the researchers found signs of rapid and fundamental change.
The disappearing ice had invited newcomers into the area, such as fast-growing, gelatinous sea squirts and slow-growing animals called glass sponges.
Minke whales were found to be colonising the new habitat in 'considerable densities,' and a very rare beaked whale was found near Elephant Island.
In contrast, planktonic algae that grew beneath the ice was being lost. The algae are food for krill, small shrimp-like creatures which form an important link in the food chain sustaining animals such as penguins, whales and seals.
An adult blue whale alone eats about four million individual krill a day.
The future effect of the break up of the ice on food supplies and larger animals was difficult to predict, said the scientists.
But a recent study had confirmed that krill stocks are decreasing significantly around the Antarctic peninsula.
In the relatively shallow waters of the Larsen zone, the researchers were surprised to find abundant numbers of deep sea creatures that normally live at depths of 2,000 metres or so.
The deep sea lilies and their sea cucumber and sea urchin relatives are able to adapt to life where resources are scarce - conditions similar to those under an ice shelf.
Among the hundreds of animal specimens collected were 15 potentially new amphipod or shrimp-like, species. The star attraction was a 10-cm-long crustacean thought to be a new species from the amphipod family Shackletonia.
Four presumed new species of cnidarians, organisms related to coral, jelly fish and sea anemones, were also found. One anemone-like creature lived on the back of a snail, providing protection in return for transport.
The survey, which probed down as far as 850 metres using a camera-equipped unmanned submersible, covered an area about the size of Jamaica.
Dr Julian Gutt, a marine ecologist at Germany's Alfred Wegener Institute for Polar and Marine Research, said: '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.
'The collapse of the Larsen shelves may tell us about impacts of climate-induced changes on marine biodiversity and the functioning of the ecosystem.
'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 a marine ecosystem considered one of the least disturbed by humankind anywhere on the planet.'
The expedition forms part of the Census of Antarctic Marine Life, which is gathering data on Antarctic Ocean life.
Fishery investigations were carried out at islands west and north of the Antarctic peninsular.
The results of 85 hauls over 19 days showed that the biomass of two Antarctic cod species had increased since a survey carried out in 2003. Meanwhile, stocks of Blackfin and Mackerel Icefish had decreased.
Subject: German news