Research suggests invasive freshwater mussels Could take hold in the Columbia River Basin

In a presentation to the Council today, Portland State University researchers who have been studying the potential for freshwater mussels to take hold in the Columbia River Basin say water chemistry and temperature are sufficient, if not ideal, to support the invasive species that have wrecked havoc in lakes and rivers from the Midwest to the Southwest.

“This appears to confirm our fears that mussels would grow well in the Columbia,” Council Chair Bill Bradbury said. “The results underscore the importance of the boat inspection programs and other efforts in our states to keep mussels out of Northwest waters.”

Dime-size zebra and quagga mussels adhere to boat hulls and submerged structures, including dams and dock pilings, and form thick hard mats of shells that can not only block water passage but also disrupt the environment by depleting nutrients for other species and ruining fish habitat. In the right conditions of water temperature and calcium content, the mussels grow voraciously. They are transported from place to place primarily on infested watercraft.

Mussel infestation is a significant concern for states and dam operators in the Northwest. The Council’s Independent Economic Advisory Board estimates that the potential cost of controlling an infestation and cleaning hydropower and fish-passage facilities if the mussels take hold here would easily be in the tens of millions of dollars per year -- and hundreds of millions in total costs to protect lakes and rivers, inspect and decontaminate infested watercraft, and address other impacts.

“We found that 68 percent of the mussels raised in untreated Columbia River water gained weight -- they grew. This does not bode well for the Columbia,” researcher Brian Adair, a Portland State graduate student, said.

Adair and the Portland State research team focused their research on quagga mussels. They collected mussels from a dock in Lake Mead, Nevada, and submerged them in buckets of untreated Columbia and Willamette river water. Then they gradually adjusted two critical growth factors for mussels -- calcium concentrations and water temperature -- and observed how the mussels reacted.

In the research setting, optimal growth of quagga mussels occurred at calcium concentrations between 35 and 50 milligrams per liter of water, and temperatures of 64-68 degrees Fahrenheit. Calcium concentrations and water temperature in the Columbia River vary throughout the year from about 12-22 milligrams of calcium per liter, and from 37-76 degrees Fahrenheit.

“Our conclusion is that the Columbia appears to be suitable for quagga mussels,” Adair said.

Because of lower calcium levels, primarily, mussels did not grow as well in Willamette River water.

“The Willamette may be marginal habitat, but mussels probably could adapt,” he said.

The Portland State team did not include the Snake River in their research, Adair said, “but we know the Snake has higher calcium than the Columbia.”

The researchers also tested several types of surface coatings to see how well they inhibited mussel growth. Such coatings, painted on submerged surfaces, present a slick surface that can either prevent mussel attachment or be more easily cleaned of mussels and other undesirable organisms with high-pressure water. The coatings are not toxic, but they are expensive -- about $130 per square meter.

Panels of several materials -- treated and untreated concrete, and steel -- were submerged in the Columbia River water. After three months, the results are encouraging: some products performed better than others, depending on the surface material, but quagga mussels could not adhere to any of the surfaces. The experiment will continue until the panels have been submerged 15 months; the researchers then plan to conduct a similar test at the infested San Justo Reservoir, a Bureau of Reclamation project about 90 miles south of San Francisco, and then prepare a cost estimate for treating a Columbia River dam.