In just over a decade, two major ice shelves have collapsed on the eastern side of the Antarctic peninsula, uncovering a part of the sea floor that had not seen sunlight for several thousand years. A ten-week expedition that ended in late January has shed light on the biology of these waters, and has recovered samples of some 1,000 species from the region, several of which may be new to science.

Sea squirts colonizing the site of the Larsen A ice collapse are a sign of increasing biodiversity, while this male sea spider clutching its mate's eggs (inset) is a newly discovered species. Credit: J. GUTT / P.J.LOPEZ, CLIMANT-ECOANTHA / ALFRED WEGENER INST

“This is one of the first opportunities to see what will happen when climate change alters the conditions in the polar seas,” says Jesse Ausubel, programme director at the Alfred P. Sloan Foundation in New York. The foundation is funding the Census of Antarctic Marine Life, an initiative for International Polar Year that has 13 voyages scheduled.

From the German research vessel Polarstern, around 50 marine biologists from 14 countries used various approaches, including a remotely operated vehicle equipped with a camera, to scour the depths and trawl for samples. They surveyed an area of seabed roughly the size of Jamaica beneath what used to be the Larsen A and B ice shelves, to a depth of 850 metres.

The biologists had two main aims: to discover what kinds of creatures live beneath ice shelves, and to track what happens to those communities once the ice disappears. Unexpected inhabitants of the relatively shallow waters were species more commonly found at greater depth.

“We found a species of sea urchin that has previously been found only at depths of 2,000 to 3,000 metres off Peru,” says Gauthier Chappelle, the expedition's outreach officer and a biologist at the Brussels-based International Polar Foundation. Presumably, such species are better able to adapt to conditions where resources are scarce, as they would have been under the ice.

Another find was juvenile forms of glass sponges in the Larsen A region; the Larsen A ice shelf collapsed 12 years ago, whereas the Larsen B region opened up only 5 years ago. Glass sponges take hundreds of years to mature into adults, but are key members of Antarctic marine ecosystems, as they provide habitats for other species. “It seems like the system is shifting towards supporting the rich communities found in other parts of the Antarctic,” says Julian Gutt, a marine ecologist at the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany, and chief scientist on the Polarstern expedition.

It would probably take between 1,000 and 5,000 years for the region to mature into the kind of community typical of Antarctic coastal regions, says Gutt. And future climate change could result in soils from the coast degrading the crystal-clear waters and potentially blocking any further succession to a rich community of Antarctic filter-feeders.