Biologists search area lakes for signs of zebra mussels
10/22/2012 12:57 PM
10/22/2012 1:34 PM
EAGLE MOUNTAIN LAKE -- Under a boat slip at one end of the Eagle Mountain Lake Marina sits an early-warning detector to an unwanted invader.
Floating under the marina are a scouring pad and temperature sensor to detect an invasive species that first showed up in the Great Lakes in the 1980s and has been slowly moving across the U.S.
Zebra mussels, which can push out native mussels, clog intake valves and litter shorelines with their shells, have already been found in Lake Texoma and Lake Ray Roberts in Denton County.
And there is fear that it's just a matter of time before they show up in Lake Lewisville and other North Texas lakes.
"Lake Lewisville is under the gun since it's just downstream from Ray Roberts," said UTA professor emeritus of biology Robert McMahon. "But with the population, water transfers and boater movement in the Metroplex, all of the lakes in North Texas are vulnerable."
That makes McMahon's job even more important as he is responsible for monitoring 14 lakes in North and East Texas.
Over the next two weeks, McMahon will work the region to check those lakes monitoring sites.
Last week, he and his wife, Colette, not only checked out Eagle Mountain Lake, but Lake Bridgeport and Lake Arrowhead near Wichita Falls as well.
McMahon's initial inspection at Eagle Mountain Lake didn't find anything to worry about.
In the marina parking lot, he put a microscope on the bed of his Dodge pickup and examined the scouring pad and water samples.
He found signs of life but nothing that looked like the invasive species.
"No signs of zebra mussels," he pronounced after a quick scan.
But his work has only begun.
When he gets back to the lab after his field work, there will be a far more extensive analysis and then samples will be sent off to a Colorado lab for further testing. So it may be another six weeks to two months before everybody learns whether zebra mussels have arrived at Eagle Mountain or any of the other North Texas lakes.
"We'll do far more work back in the laboratory," McMahon said. "You really don't expect to see anything out here but you do a quick look just in case so you can alert people as soon as possible."
Educating boaters important
Zebra mussels, which are named for their distinctive striped pattern, first showed up in Texas at Lake Texoma in April 2009, where they quickly filled bays with shells. The 2011 drought killed off a number of zebras when Lake Texoma's water level dropped but they were still found in large numbers in the lake.
Last fall, low levels of DNA larvae from zebras were found in Eagle Mountain and Lake Bridgeport, but McMahon's testing last spring found no sign of actual mussels.
While many believe it is inevitable that zebras will eventually be in every North Texas lake, McMahon isn't one of them.
"With the education of boaters and more overall awareness, I think they can be stopped or at least slowed down," McMahon said. "There's still a lot we don't know but I think we've learned it takes a lot to get a colony established, more than just a few of them."
There are clearly costs associated with zebra mussels.
The Tarrant Regional Water District, which provides raw water to 98 percent of Tarrant County, has already budgeted $683,100 to control zebra mussels in the $2.3 billion pipeline it is building with Dallas to bring more water from the Richland-Chambers Reservoir and Cedar Creek Lake. The first phase of the pipeline isn't expected to be completed until at least 2020.
Found in 23 states
Other North Texas water providers are already seeing the impacts.
The North Texas Municipal Water District, which provides water to Dallas suburbs, including Frisco, Plano and Richardson, is rushing to complete a $270 million pipeline to safely transport water from Lake Texoma to its water treatment plant so it can bypass Lake Lavon.
The pipeline was needed after water transfers were halted from Lake Texoma to Lake Lavon when zebras were found in Sister Grove Creek, which was the method for moving water between the lakes.
It is believed the mussels came to the U.S. from the release of ballast water from ships that came from the Black Sea, according to the U.S. Geological Service.
They have been discovered in 23 states, including the Mississippi River basin. Oklahoma has found them in 10 lakes.
It was once thought they couldn't survive the hot temperatures in Texas lakes but McMahon's research has shown that isn't a case.
"They have been able to adapt so it doesn't look like the heat is going to stop them," McMahon said.
Bill Hanna, (817)390-7698
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