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Water weed taking over Tahoe marinas

Erika Ekman

Lake Tahoe marinas are being choked by an aquatic weed and little is being done to stop its costly, invasive spread.

That’s the assessment of experts studying the growth of Eurasian watermilfoil in Lake Tahoe.

Despite predictions of huge financial loss, a drastic change in the biological makeup of the lake and imminent mass spread of the hardy plant, the local water quality agency has placed a non-priority label on the issue.

The Lahontan division of the California Water Quality Control Board, which oversees the lake’s quality control, has for several months studied the obvious effects of the exotic Eurasian watermilfoil on Lake Tahoe. In the meantime, the weed has more than quadrupled in size in some places and cost property owners, boaters and marinas hundreds of thousands of dollars in control and corrective measures.

All eyes are now on Lahontan to take action.

“We don’t care what they (Lahontan) do, just so long as it’s not nothing,” said Rod Mier, chief administrative officer for the Tahoe Resource Conservation District.

But Ossian Butterfield, director of Lahontan’s board, said that while the agency was made aware of the potential effects of the fast-spreading weed about two years ago, no urgency has been placed on removing it from the lake.

“(The weed) has been very carefully analyzed, but it doesn’t seem to be a real priority at the moment. Maybe in the future it will be, but not right now,” Butterfield said.

The future is too far off for a non-native weed that can reach heights of six to eight feet in a month, warns Dr. Lars Anderson, research leader of the Aquatic Weed Control Laboratory at the U.S.D.A. Agricultural Research Service’s center in Davis, Calif.

“If it can grow to four times its size in one year, it could spread 10-fold to 100-fold in four or five years,” Anderson said. “From a commercial and recreation standpoint, it’s costing thousands of dollars to control in the Tahoe Keys. Biologically, it’s displacing populations of native plants. The longer Lahontan waits, the worse and more expensive it gets.”

Eurasian watermilfoil, known scientifically as Myriophyllum spicatum, was probably introduced in Lake Tahoe during the late 1960s, right about the time the man-made Tahoe Keys was constructed, and was likely brought in on boat props and trailers.

It has since spread to all four corners of Lake Tahoe including Crystal Shores, Homewood Marina, Meek’s Bay Resort, Elks Point, Logan Shoals and Obexer’s Marina and, most recently, has made its way to the headwaters of the Truckee River.

Watermilfoil looks and feels like most other aquatic plants. It’s green, viny and seemingly harmless. But the long vines are being sucked into boat cooling system intakes and causing overheating. The plant winds itself around propellers and requires constant harvesting during summer months. Its effects are widespread.

“Would you want to swim in it? Just think of the loss to the tourism industry,” Mier said.

Of the 200 acres of watermilfoil in Lake Tahoe, 170 are at the Tahoe Keys, Anderson said.

The Tahoe Keys Property Owner’s Association has taken its own eradication measures over the years by use of aquatic weed harvesters, which cut the weed six feet below the water’s surface and remove it. The plants are then hauled to a refuse dump, all at a cost of more than $150,000 each year. Property owners pay for removal through annual dues. They await a better solution.

Lahontan’s chief of planning and toxics, Dr. Ranjit Gill, said the agency last year formed a panel of about eight scientists to study the oceanology, physiology and control potential of the plant.

“The board wanted a second opinion,” to compare with the findings and recommendations for removal made last year by Anderson, Ranjit said.

What the panel came up with was a Catch-22 situation.

The group decided to divide its study into two components. First, they would look at a management strategy.

“That would be based on what you’re trying to achieve,” Gill explained. He said Lahontan has yet to set goals in that regard.

Second, the panel would do a scientific survey of the locations and dynamics of the weed in the lake, then determine if watermilfoil is a water quality issue or not.

But that cannot be done until Lahontan agrees to fund the study, and so far, Dr. Gill’s group has been given “no clear direction from the (Lahontan) board on that,” he said.

Priority must be placed on the issue before a study is funded. But priority cannot be set until studies indicate the weed is a water quality issue requiring attention. Meanwhile, the plant continues to grow and spread.

Dr. Anderson will submit to Lahontan this month a third report in two years on the weed. He’ll make a number of recommendations for eradicating the plant, including use of the herbicide Sonar, which has been used effectively in other lakes against watermilfoil, he said.

Butterfield said Lahontan is not ready to begin using chemicals in the lake without information on potential effects on people and other life in the lake.

“We’ll keep watching the market to see what the industry comes up with. Maybe someone will come up with a better solution, but for now there seems no better solution than to keep doing what we’ve been doing for 10 years – cutting it and hauling it away,” Butterfield said.


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