New research reveals new threat to Lake Tahoe

Sunday, July 11, 1999 | 9:09 a.m.

Charles Goldman, director of the Tahoe Research Group of the University of California, Davis, said oxygen plays a key role in breaking down algae that dies and descends to the bottom.

Algae growth is believed to be the primary cause of the lake's declining clarity.

"If we ever lose the oxygen in the deep waters of Lake Tahoe, the battle will be lost," said Goldman, who has studied the lake for 41 years.

A combination of nitrogen and phosphorous from nutrients such as fertilizers, erosion and vehicle exhaust - byproducts of the Tahoe Basin's development - is promoting the algae growth.

A layer of nutrients that could harm the Sierra lake's clarity is locked in the ground at its bottom. Holding in the layer is an oxidized layer of sediment just above it.

But if oxygen levels continue to drop, the top layer could give way to a nutrient-filled layer, promoting algae growth, Goldman warned.

The solution to stopping the oxygen depletion is the same as that of stopping algae growth: keeping phosphorous from Lake Tahoe, Goldman said.

That can be achieved by controlling storm water runoff, stopping erosion, acquiring sensitive lands and restoring wetlands, he said.

The lake's clarity suffered the second-worst year on record in 1998, according to Goldman's research group.

A white disc dropped into the lake could be seen at an average depth of 66 feet in 1998.

In 1967, the disc was visible as far as 100 feet down.

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