Thu, Mar 01, 2007 page9

• Climate change uncovers Antarctic's secrets

  As scientists research a world sealed off for 12,000 years, they are discovering marine life transformed by rapid climate change

  • By Alok Jha / THE GUARDIAN
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  The seas around the Antarctic peninsula are among the most mysterious places on Earth -- what life there is has remained largely a mystery, thanks to a thick cover of ice for the past few millennia. But the collapse of some of these ice sheets has given scientists a rare opportunity for access, and on Sunday they revealed that they had found a thriving underwater world that is being transformed by climate change.

  As well as new species, the Census of Marine Antarctic Life (CMAL) project found more common ones that were able to survive in the Antarctic because the temperature of the sea is rising. Minke whales were discovered in large numbers.

  The scientists also spotted a rare beaked whale off the coast of Elephant Island -- the famous refuge of Ernest Shackleton's 21-man crew after a doomed attempt to cross Antarctica in 1916.

  

  Parts of the sea here were uncovered for the first time in recorded history when the Larsen A and B ice shelves collapsed, 12 and five years ago respectively, because of the higher temperatures linked to human-induced climate change. Scientists said the new survey would help to predict what will happen to biodiversity as the world warms up.

  Julian Gutt, a marine ecologist at Germany's Alfred Wegener Institute for Polar and Marine Research, who led the expedition, said the area under the Larsen ice shelf was the least known ecosystem on Earth.

  "So far, we did not have access to such areas, with the few exceptions of drill holes or cracks where people could deploy some remote video cameras," Gutt said.

  The break-up of the Larsen ice shelves opened up a pristine area of sea floor the size of Jamaica -- a habitat that has been sealed off from above for several thousand years. Researchers spent 10 weeks scouring the 10,000km2 sea floor for animal life.

  By probing as far as 850m under water, using a remote camera, they collected around 1,000 specimens, including 15 shrimp-like species, known as amphipods, thought to be new to science.

  The star attraction is a 10cm long crustacean from the amphipod family Shackletonia. Gutt said the new biodiversity information would be fundamental in understanding the functioning of the ecosystem.

  "The results of our efforts will advance our ability to predict the future of our biosphere in a changing environment," Gutt said.

  The scientists also found four new species of cnidarians, creatures that are related to coral, jellyfish and sea anemones.

  One anemone-like creature was found living on the back of a snail, providing protection in return for transport.

  In the relatively shallow waters of the Larsen zone, abundant numbers of deep sea creatures that normally live at depths of 2,000m or so were found. These included deep sea lilies, sea cucumbers and sea urchins. The scientists found dense patches of sea squirts and said they were probably able to colonize the Larsen B area only after the ice shelf broke in 2002.

  "We counted a surprisingly high number of Minke whales," Gutt said. "This means the ecosystem in the open water adapts very fast to the new conditions, because the algae grow. Krill feeds on the algae and whales feed on the krill."

  This pattern may not be repeated in future, however. Michael Stoddart, the leader of the CMAL project, said one consequence of the rising global temperatures was a fall in plankton such as algae that grow underneath sea ice, which would have knock-on effects to animals higher up the food chain, all the way up to whales.

  "Algae is a source of abundant, high-quality winter food and is central to the health of the whole ecosystem," he said.

  Other finds in the CMAL expedition included clusters of dead clamshells littering an area of the ocean floor near a suspected "cold seep."

  This is a sea floor vent that spews methane and sulphide. Such vents can create a temporary habitat for animal life in otherwise barren, inhospitable terrain for several years before extinguishing and abruptly starving off a community.

  The expedition team also investigated fish populations in the islands north and west of the Antarctic peninsula. The results of 85 hauls over 19 days show that the biomass of two Antarctic cod species has increased since a survey in 2003, while stocks of Blackfin and Mackerel Icefish have decreased.

  Gauthier Chapelle, a biologist at the Brussels-based International Polar Foundation, said: "This is virgin geography. If we don't find out what this area is like now, following the collapse of the ice shelf, and what species are there, we won't have any basis to know in 20 years' time what has changed, and how global warming has altered the marine ecosystem."

  Backstory
  

  The Larsen shelf is a fringe of ice in the northwest of the Weddel Sea, extending along the east coast of the Antarctic peninsula. In 2002, scientists watched in shock as 3,250km2 of 220m-thick ice -- the Larsen B shelf -- fell into the sea. It had been stable for at least 12,000 years. Larsen A, a smaller ice sheet, had collapsed seven years earlier, but this was around 4,000 years old. Global warming was undoubtedly to blame. Since 1974, 13,500km2 of ice shelf has disintegrated in the peninsula. Even so, the Larsen disintegrations were unusual in their scale. Normally, ice sheets lose mass gradually as icebergs cleave away.
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