Wednesday, April 30, 2008

World's largest lake warming rapidly: Scientists

Siberia's Lake Baikal has warmed faster than global air temperatures over the past 60 years, which could put animals unique to the world's largest lake in jeopardy, US and Russian scientists said.

The lake has warmed 1.21 degrees Celsius since 1946 due to climate change, almost three times faster than global air temperatures, according to a paper by the scientists to be published next month in the journal Global Change Biology.

"The whole food web could shift," Marianne Moore, a biology professor at Wellesley College in Massachusetts and one of the authors of the paper, said in an interview. The frigid lake, which holds 20 per cent of the world's freshwater, boasts 2,500 species with most of them, such as the world's only freshwater seal, found nowhere else.

In potentially bad news for that animal, the paper found that the lake's annual days of ice cover had fallen an average of 18 days over the last 100 years and could drop a further two weeks to two months by the end of the century.

The findings could foreshadow the vulnerability of smaller lakes to global warming because Baikal's great volume of water had been thought to protect it from rising temperatures, the paper said.

Moore said Baikal's seal, which raises its pups on the ice, could suffer because the animal has several onshore predators. If ice caves the pups are raised in melt, Asian crows could also eat the pups, she said.

Changes in the food cycle have already been seen. Numbers of multicellular zooplankton, which normally live in warmer waters, have increased 335 per cent since 1946, while numbers of chlorophyll have risen 300 per cent since 1979, it said.

In addition, the number of diatoms, which live under the ice and later die and become food for tiny organisms living in the lake's depths, could fall, Moore said. "Ice recession may have a greater effect than the rising temperatures," she said.

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