A voyage to explore the marine life beneath a vast sheet of Antarctic sea ice has enjoyed great success, uncovering new species and terrain ranging from barren to teeming with fast-growing life.
The barely known ecosystems below Antarctic ice sheets are described as "the last marine frontier" by researchers. The Polarstern expedition found a new species of giant crustacean and sea-cucumbers that had previously only been seen in the deep sea in any number.
View a gallery of the incredible creatures revealed.
The investigation was made possible by the collapse of the Larsen ice-sheet in northeast Antarctica, which disintegrated in two stages. First, Larsen A fell apart in 1995. Then, in 2002, a massive chunk of ice, 3250 square kilometres in area and 220 metres thick, broke off.
New realm
The disintegration of Larsen B made headlines worldwide and was seen as a sign of the dramatic consequences of global warming (see Giant Antarctic ice sheet breaks off). For biologists, it opened a realm that had been virtually inaccessible. The area under Larsen B has been capped by ice since the last ice age.
"The break-up of these ice shelves opened up huge, near pristine portions of the ocean floor, sealed off from above for at least 5000 years, and possibly up to 12,000 years in the case of Larsen B," says Julian Gutt, a marine ecologist at Germany's Alfred Wegener Institute for Polar and Marine Research and chief scientist on the Polarstern expedition. "Until now, scientists have glimpsed life under Antarctica's ice shelves only through drill holes."
As part of a new Census of Antarctic Marine Life (CAML), Gutt led a 10-week voyage to the area which used to lie under Larsen A and B. The seabed varied in depth, between 100 metres and 850 m beneath the surface. In order to explore, the researchers sent down a remotely-operated submarine which captured video footage and collected samples.
Teeming with life
The researchers discovered extremely varied environments in their explorations, which concluded on 30 January. In shallower areas, where the several-hundred metre thick ice shelf had scraped along the bottom, the seabed was barren and carved with parallel grooves left by the glaciers as they moved out to sea. In other areas, the seabed teamed with life.
Gutt believes some of these animals and plants have moved into the area since the collapse of the ice shelves. He mentions the great number and density of fast-growing sea-squirts – transparent tube-like animals that attach themselves to the seafloor. Under Larsen B, the sea-squirts are about five years old, which corresponds closely with when the shelf collapsed.
He was also stunned to find a great number of sea cucumbers, normally found 2000 m beneath the surface. The researchers are uncertain why these species were found in such shallow waters, but note that both the deep sea and the underside of ice shelves have very poor resources in common. "The sea cucumbers belong to that fauna which I believe were found originally under the ice shelf," says Gutt.
Roll of honour
Small clusters of dead clamshells on the ocean floor suggested the past presence of a very rare "cold seep" – a seabed vent which would have spewed methane and sulphides. Such vents can create temporary habitats for life in otherwise barren environments. But when such seeps run dry, the communities that rely on them starve.
Among the potential new species found during the trip were:
• 15 new shrimp-like amphipod species, including one that was 10 centimetres long, making it one of largest ever seen in Antarctica
• Four new species of cnidarians – organisms related to coral, jelly fish and sea anemones
• Two new species of octopus
The researchers have brought specimens back and will now compare them to known species to see if they are indeed new.
CAML is run by the Census of Marine Life. It has 13 expeditions planned during the International Polar Year, which launches on 1 March 2007. The Polarstern expedition brought together 52 researchers from 14 countries.
