Monday, October 13, 2008

The krilling fields: study fears catastrophe in Antarctic food chain

Andrew Darby, Hobart 
The Age, October 14, 2008

THE first evidence suggests that a predicted rise of atmospheric carbon dioxide will wreak havoc on krill, the tiny crustacean at the heart of the Antarctic food web.

Although public sympathy for the crustacean is undetectable, polar life such as penguins, seals and whales would wither without it.

Captive-bred krill at the Australian Antarctic Division developed deformities and lost energy when they were exposed to the greenhouse gas at levels predicted globally for the year 2100.

The damage meant that the krill were unlikely ever to breed, a University of Tasmania investigator, Lilli Hale, said yesterday.

Polar life, from tiny seabirds through penguins and seals to whales, depend for food on Antarctic krill, Euphasia superba.

A loss of krill suggested there would be a catastrophic impact on these other species, Ms Hale said.

The level of atmospheric carbon dioxide now stands at 384 parts per million (up 100 ppm since 1832), according to the Intergovernmental Panel on Climate Change. At a worst case it could reach around 900 ppm in 2100, IPCC models show.

Carbon dioxide is absorbed by the sea most easily in the colder Southern Ocean, which becomes more acidic, interfering with the formation of calcium carbonate.

Organisms, including krill, rely on calcium for the formation of their shells.

In Ms Hale's study, the division's world-first krill breeding research facility near Hobart was used to hatch 200 larvae in jars with an artificial atmospheric carbon dioxide level increased to the worst-case 2100 level. "Their anatomy wasn't quite right," Ms Hale said. "They were a bit deformed, and they were listless. It's unlikely they would have survived through to adulthood."

When carbon dioxide levels were raised even further, fertilised eggs did not hatch at all.

The Antarctic Division's program leader, Steve Nicol, said ocean acidification from rising carbon dioxide was real, and there was an urgent need to find out what effect it was going to have on sea life.

"At the microbial level some species might have time to evolve," Dr Nicol said. "But longer-lived animals like krill won't have time to adapt to higher levels of carbon dioxide.

"The next step is for us to conduct longer studies at lower carbon dioxide levels to see what krill can cope with."

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