EDITOR'S NOTE: This is the last in a four-part series examining invasive mussels and how they could affect Lake Tahoe's ecosystem and economy.
When zebra mussels were found in San Justo Reservoir, about 250 miles away from Lake Tahoe in California, in January the state and local agencies made the decision to close the lake to boating.
"Boating on there is not really heavy," said Alexia Retallack, a spokeswoman for the California Department of Fish and Game who has been working closely with the reservoir. "For their purposes they were more concerned with the spread."
San Justo is one example of how a water body infected with invasive mussels has handled the creatures. Quagga and zebra mussels are cousins in the same species family that have similarly devastating effects. Originally from Europe, they have no natural controls in America and can multiply rapidly, destroying the economy and ecology of a body of water from boating to fishing to beaches. They have never been successfully eradicated from a body of water.
Closing the San Justo was a viable solution because of the reservoir's size and number of access points, Retallack said. But the control method for a body of water once infected is dependent on many variables including size, recreation uses and point in the water system.
"It depends because each water body is in a unique position, there are so many variables," she said.
Beginning the invasion
Quagga and zebra mussels were introduced to North American in the Great Lakes in the 1980s, probably from the ballast water from a boat traveling from Europe. Mussel larvae are microscopic and can travel in boats from water source to another.
Since then, the Great Lakes zebra mussel infestation cost the power industry $3.1 billion from 1993 to 1999, with an economic impact to industries, businesses and communities of more than $5 billion, according to estimates from U.S. Congressional researchers.
"They are still here and we are still dealing with them," said Bob McCann, a spokesman with the Michigan Department of Environmental Quality.
In addition to rebuilding infrastructure to deal with the mussels, there is also a strong effort to educate Michigan boaters about what they could bring to other water bodies.
"One of the biggest things we can do is increase public awareness of how zebra mussels spread," McCann said.
Before 2007, zebra and quagga mussels had proliferated in many places on the East Coast but had not made it past the 100th meridian. But in January 2007 inspectors found quagga mussels in Lake Mead.
Lake Mead was prepared for zebra mussels with a prevention program in place, said Roxanne Day, a spokeswoman for the Lake Mead National Recreation Area. Employees and concession workers were trained to spot the mussels, and sampling areas were in place around the lake.
But in January 2007 a marina employee discovered a quagga mussel while reattaching a cable line to an anchor.
"We tried to do as much research as we could," Day said.
Now the strategy at Lake Mead has shifted from prevention to control, with a focus on the 4,500 slipped and moored boats at Lake Mead. Those boats must be cleaned before entering Lake Mead and after exiting the waters. Boaters are also required to notify the marina manager when they leave the marina.
The Southern Nevada Water Authority is also tasked with keeping its infrastructure safe from the creatures, which could cost $24 million in capital in the long run, said Peg Roofer, a regional water quality program manager with the SNOW.
SNOW is installing a new 3-mile-long intake valve and chlorination line. The temporary solution, chlorinating raw water before it comes into the treatment plant, has a capital cost of $5 million and annual operating cost of $1 million to 4 million, Roefer said.
After quagga mussels were introduced into Lake Mead, they were also introduced into the Colorado River and other locations in Southern California including Lake Havasu and various reservoirs in San Diego County.
Controlling the invasion
It could cost between $10 million to $50 million a year to deal with the quagga infestation in Southern California, according to Ric De Leon the microbiology unit manager for the Metropolitan Water District of Southern California.
"We are in the stage where we are doing control since most of our system is infected," De Leon said.
When quagga or zebra mussels get into a water infrastructure they can clog pipes by growing on each other, eventually creating layers of mussels encasing the walls of pipes and valves, De Leon said.
In response, filters at Lake Havasu are cleaned regularly and additional chlorination facilities are being constructed.
"We have a pretty active maintenance and control program," said Bob Muir, a spokesman for the water district.
There is one case of successful eradication of zebra mussels at the Millbrook Quarry in Prince William County, Va., in May 2006. The water body, an abandoned rock quarry used for recreational and instructional scuba diving, was infected in late August 2002.
To eradicate the zebra population, 174,000 gallons of potassium chloride solution was injected into the water over a three-week period. The process cost more than $400,000. But the same method would not be feasible at Lake Tahoe, said Ted Thayer, Natural Resource and Science Team Leader for TRPA.
"Chemical treatment's not an option in a lake this size," he said.
Researching natural enemies
Zebra and quagga mussels are controlled in their native Europe because of the natural predators in that environment that don't exist in North America.
However, some researchers are looking at biological solutions to quagga mussels, and one has discovered a small part of the solution.
Dan Molloy, director of the Cambridge Field Laboratory of the New York State Museum, and a team of scientists have been researching a biological control for two decades. Recently they discovered a soil bacteria that kills zebra and quagga mussels while not harming other organisms in the ecology.
The product was developed for power plants in lieu of chemicals, but research could be done on how it would fare in reservoirs, Molloy said.
"The U.S. Bureau of Land Reclamation is interested in the potential for this," Molloy said. "Now people are interested if it could be used in the west in open water."