The Larsen A shelf collapsed twelve years ago while Larsen B disintegrated in February 2002.
"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 of the Alfred Wegener Institute for Polar and Marine Research, who was chief scientist on the Polarstern expedition. "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 Wegener Institute's research ship Polarstern conducted the first comprehensive biological survey of the area that was once underneath the ice shelves from November 2006 to January 2007. The vessel travelled to the northwest Weddell Sea off the Antarctic Peninsula.
"The collapse of the Larsen shelves may tell us about impacts of climate-induced changes on marine biodiversity and the functioning of the ecosystem," said Gutt.
Scientists on Polarstern found abundant deep-sea sea lilies (crinoids), sea cucumbers such as Elpidia glacialis, and sea urchins in the Larsen zone. These species generally live at a depth of around 2000 m, where resources are scarce. The researchers say that conditions are likely to be similar under an ice shelf.
"Our measurements of environmental parameters of the sediment and the water column will contribute to answer the question why there are such similarities between habitat use of the deep-sea and below the former ice shelf," said Enrique Isla of the Marine Sciences Institute in Barcelona, Spain.
The seafloor of the Larsen zone ranged from bedrock to pure mud. The researchers say that, as a result, animals living on the sediment were also highly varied, though far less abundant than in the sea beds in the eastern Weddell Sea, away from the Larsen zone.
The team also found dense patches of sea squirts, which they believe were probably only able to colonize the Larsen B area after the ice shelf broke up in 2002. Glass sponges, a slow-growing species, were seen in the highest densities in the Larsen A area, which was available for re-colonization 7 years earlier than the Larsen B zone.
In total, the researchers collected around 1,000 species. They believe several of these may be new discoveries - including 15 amphipod (shrimp-like) species and four cnidarians (animals related to jellyfish). One of the amphipod species, at around 10 cm long, is one of Antarctica's biggest amphipods and is larger than many similar species found in temperate climates. Among the new cnidarians is a sea anemone that lives on the back of a snail in a symbiotic relationship - the snail provides the anemone with transport while the anemone protects the snail.
"This knowledge of biodiversity is fundamental to understanding ecosystem functioning," said Gutt. "The results of our efforts will advance our ability to predict the future of our biosphere in a changing environment."
The researchers will meet again at a workshop in the autumn to synthesize their results - the information will feed into the Census of Antarctic Marine Life. An additional 13 expeditions undertaken as part of International Polar Year, which is due to launch on March 1st, will also provide data for the census.
Around 13,500 sq. km of ice shelf have disintegrated in the Antarctic Peninsula since 1974.