Steve Stoler reports
COLLIN COUNTY - A small army of biologists converged on Lake Lavon Tuesday looking for zebra mussels.
The size of a thumbnail, these aquatic creatures can cause millions of dollars in damage to lakes and public water systems.
As News 8 first reported last week, the Texas Parks and Wildlife Deparment discovered the adult mussels in Sister Grove Creek, which flows into Lavon, the major water supply for 61 North Texas cities.
The zebra mussels are most likely to appear in the northern waters of Lake Lavon near the creek's outlet, about 30 miles south of the original discovery.
"Tthe zebra mussel is known as an invasive species," said Texas Parks and Wildlife fisheries biologist Bruce Hysmith. "In other words, we don't want them."
Two boats carrying state and federal biologists set sail from a Caddo Park boat ramp near U.S. Highway 380. They collected water samples from here to a North Texas Municipal Water District pipeline 30 miles north in Grayson County. That's where scientists believe zebra mussels moved from Lake Texoma into Sister Grove Creek.
The biologists didn't expect to find adult mussels in Lavon; they believe it's too early. They're looking instead for microscopic larvae.
Each zebra mussel can produce one million larvae a year.
"We don't know a solution right now," Hysmith said. "In the Great Lakes they haven't found a solution."
The experts first thought the mussels couldn't survive in water warmer than 60 degrees. Now they believe the mussels are adapting to warmer water.
The biggest concern remains the threat to the water supply.
"They block water pipes. They filter water," Hysmith explained. "And the bad thing is, they filter out plankton. Plankton is the basis for the food chain for fish."
Army Corps of Engineers biologists checked a device known as a "portland sampler" -a foot-long section of PVC pipe hanging on a rope. The samplers have been placed at the north end of the lake.
"If you come back in two or three months, if they had grown in and established, you'd actually see little fingernail-shaped zebra mussels attached inside the pipe.," said Army Corps of Engineers biologist Brandon Mobley.
The biologists say there is one thing in Lake Lavon's favor: the lakebed is filled with mud and silt. Zebra mussels need something hard to latch on to.,p> it could be two to four weeks before the results of this week's samplings are released.