The Morning Herald (Sydney, Australia), October 14, 2008

GREENHOUSE GAS THREATENS FOOD CHAIN

[Rachel's introduction: Polar life, from tiny seabirds through penguins and seals to whales, depends for food on Antarctic krill, which has a biomass estimated at around 500 million tonnes. A new study suggests that rising levels of greenhouse gases could have a "catastrophic" impact on Antarctic life by harming krill.]

By Andrew Darby

The predicted rise of atmospheric carbon dioxide will wreak havoc on krill, the tiny crustacean at the heart of the Antarctic food web, a study has shown.

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

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

Polar life, from tiny seabirds through penguins and seals to whales, depends for food on Antarctic krill, Euphausia superba, which has a biomass estimated at around 500 million tonnes.

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 about 900 ppm in 2100.

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. Krill rely on calcium for the formation of their shells. In Ms Hale's pilot 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 levels 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. 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."

The Australian Antarctic research ship Aurora Australis departed on Sunday carrying researchers who will investigate ocean acidification's effects on marine microbes.