World's largest lake 'too hot'
2008-05-01 12:44
New York - 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% of the world's freshwater, boasts 2 500
species, most of them found nowhere else, such as the world's
only exclusively freshwater seal.
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 two weeks to
two months more 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, then 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% since 1946, while numbers of
chlorophyll have risen 300% 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.