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Scientists rolling out mats to greet unwelcome clams

SOUTH LAKE TAHOE, Calif. – Scuba-diving scientists are unrolling long rubber mats across the bottom of Lake Tahoe coves in an attempt to quell a clam invasion that could cloud the world-renowned cobalt waters.

The half-acre mats are designed to smother dime-size nonnative Asian clams that can reach populations of 5,000 per square yard.

Geoffrey Schladow, director of the Tahoe Environmental Research Center run by the University of California, Davis, said the clams promote so much algae growth that they can turn some coves from blue to green.

“They suck in the water and they filter out the algae. Their excretions are highly concentrated packages of nutrients,” he said.

The scientists carpeted one South Shore bay with the rubber mats on Friday. They plan to cover another half-acre soon.

The bottom coverings will remain in place all summer, then will be removed to see if the clams return.

The clams were first found in 2002 in the Sierra Nevada lake that straddles the California-Nevada border, after they were likely inadvertently brought in by boaters. Scientists fear the clams could change the lake’s chemistry, opening the door to other invasive species.