An Antarctic octopus (Paraledone turqueti) discovered by scientists on the seafloor in the area formerly covered by the Larsen B ice shelf off the east coast of the Antarctic Peninsula.

Credit: Alfred-Wegener-Institute

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PARIS: The collapse of two ice shelves in Antarctica has exposed an exquisite seabed ecosystem, including previously unknown species of crustacean and marine anemone.

The hidden marine world was revealed by the breakup of the Antarctic Peninsula's Larsen A and B ice shelves, 12 and five years ago respectively. Their collapse laid bare a 10,000-square-kilometre portion of the sea bed - an area almost the size of Jamaica - that had been roofed by ice for millennia.

Part of the area was explored by an unmanned robot, lowered from the German Alfred Wegener Institute's research vessel, the Polarstern (North Star), in a 10-week international expedition that ended on 30 January 2006.

"The breakup 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," said Julian Gutt, the expedition's chief scientist.

"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 team of 52 scientists from 14 countries collected around 1,000 species, some of which are believed to be new to science, and took what they describe as "brilliant" images of unfamiliar creatures.

The newcomers to the book of knowledge about Antarctica include 15 shrimp-like crustaceans called amphipods, one of which was nearly 10 centimetres long, the researchers said.

Four new species of cnidarian - organisms related to coral, jellyfish and sea anemones - were also found. One of them lives on the back of a snail, showing a symbiotic relationship in which the snail provides locomotion for the cnidarian, and the cnidarian, with its stinging cells, provides protection for the snail.

At present, international databases have recorded 5,957 forms of marine life, but scientists believe that many more remain to be discovered.

The ice shelf had covered a highly varied sea floor, ranging from bedrock to pure mud, with flora and fauna that were correspondingly diversified, the researchers said. In shallower waters to depths of about 220 metres, they came across rich patches of deep sea lilies, sea cucumbers and urchins - an intriguing find, as these species usually lurk in deep water of around 2,000 metres.

Antarctic ice shelves such as the Larsen are really the feet of glaciers that reach the coast and then creep out to sea, floating on the water but still attached to land. In 1992, the so-called Larsen A ice shelf disintegrated, and in 2002, the Larsen B followed suit, creating the most massive icebergs ever seen.

The loss of the shelves is giving Antarctica-watchers the chance to see how different species move in to colonise the freshly uncovered seabed, starting with opportunistic gelatinous creatures called sea squirts and glass sponges. Mammals, too, have moved in.

"It was surprising how fast such a new habitat was used and colonised by Minke whales in considerable densities," said German specialist Meike Scheidat. "They indicate that the ecosystem in the water column changed considerably."

The newly-opened vista also provides a barometer for change, for parts of the Antarctic coast are being hit by global warming at a far greater rate than other parts of the world.

"This is virgin geography," said Gauthier Chapelle, a biologist at the International Polar Foundation in Brussels, Belgium. "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."