Study: Warming to impact Lake Tahoe

March 25, 2008 9:18:43 AM PDT
A recently released University of California, Davis study predicts that climate change will reduce the frequency of water circulation of Lake Tahoe and jeopardize the lake's plant and fish life.

According to the study, a likely affect of climate change would be a warmer lake with fewer cold-water native fish and more invasive species.

"What we expect is that deep mixing of Lake Tahoe's water layers will become less frequent, even non-existent, depleting the bottom waters of oxygen," said Geoffrey Schladow, director of the Tahoe Environmental Research Center at UC Davis, in a prepared statement. "This will result in major, permanent disruption to the entire lake food web."

John Reuter, associate director of the research center, explained that deep mixing occurs when upper lake waters cool to the temperature of lower waters and the wind physically mixes the water. He said the lake is approximately 1,600 feet deep and that the lake mixes all the way to the bottom about once every four years.

Deep mixing moves nutrients from the lake bottom to the water surface, stimulating the growth of algae, according to researchers. It also takes oxygen from the surface and distributes it throughout the lake to support aquatic life.

The study indicates that the lake will continue to mix, but not all the way to the bottom, according to Reuter.

Mixing could become less frequent and less deep within the next 10 years, the study suggests.

"While we expected that the lake would mix less in the future, learning that we may be only a decade or two from the complete shutdown of deep mixing was very surprising," Schladow said. "If mixing shuts down, then no new oxygen gets to the bottom of the lake, and creatures that need it, such as lake trout, will have a large part of their range excluded."

Schladow also said that a lack of oxygen will release phosphorus locked up in lake-floor sediments, which will fuel algal growth, clouding the lakes clarity and creating unpleasant odors and bad-tasting drinking water.

He said researchers are continuing to investigate whether lowered global greenhouse gas emissions would slow down or prevent the lake's decline.

The new findings were announced by Tahoe Environmental Research Center researchers at a conference March 18.


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