Editorial: Get control of mussels

Friday, Jan. 12, 2007 | 6:57 a.m.

Lake Mead, already under enormous stress from drought and increasing demand for its water, now must contend with a new threat. Zebra mussels were discovered in the lake last week by workers fixing a breakwater.

The discovery triggered immediate responses from agencies that manage Lake Mead, which is the source of 90 percent of the Las Vegas Valley's drinking water.

"This is almost heartbreaking news that the mussels are here," Kent Turner told Las Vegas Sun reporter Launce Rake. Turner is head of resource management for the National Park Service's Lake Mead National Recreation Area.

Heartbreaking is not an overstatement by any means.

Zebra mussels, so called because of the striping on their shells, first appeared in North America in 1988. Native to the Caspian and Black seas that border Turkey, Russia and Iran, they spread throughout Western European water bodies in the 19th century by attaching themselves to boats or boating equipment. That is how they arrived on this side of the Atlantic. By 1990 they had spread throughout the Great Lakes, and are a major menace in much of the East and South.

Zebra mussels can clog water systems and become the dominant consumer of plankton, meaning they are a threat to break a water body's food chain. If that happens at Lake Mead, the numbers of its fish and other forms of wildlife would drastically decline.

The thumbnail-sized mussels can lay and fertilize millions of eggs, which quickly turn to larvae that spread wherever the current takes them. Mature mussels mass together, and as many as 700,000 per square yard have been found at some intake valves in the Great Lakes.

The mussels are also a threat to navigational buoys and docks, and can corrode steel and concrete if not removed.

When it built a second intake pipe four years ago, the Southern Nevada Water Authority installed a system that pumps a chemical (potassium permanganate) into the water around the intake, which will keep mussels from massing there. But the other, older intake valve has no such protection.

Water authorities throughout the Southwest are discussing how to control the mussels. Turner said it is going to be very expensive. We hope money does not become an issue. Our only chance of keeping this invader under control is to employ the best-known methods of fighting it.