WASHINGTON — With no natural predators and a high reproductive rate, the quagga mussel has become a growing worry throughout the United States, clogging municipal water pipes, taking food from native species and possibly stimulating the growth of the deadly bacteria that cause botulism.
On Tuesday, researchers told Congress they may have found ways to combat the invasive mollusk, which last year have cost U.S. power plants $1 billion by clogging their water processing pipes, according to Department of Energy estimates,
The thumbnail-sized mussel is no small threat. It's a big and growing worry in the Great Lakes, the Colorado River, Lake Havasu and Lake Mead. More recently, quagga mussels have turned up in the water systems of the Metropolitan Water District of Southern California and the San Diego County Water Authority.
The quagga — which is even hardier than its better-known cousin, the zebra mussel — started out in the Caspian or Black Sea, reached the Great Lakes in the ballast of ships, and in early 2007 hitched its way West on industrial and recreational boat hulls.
The mussels, in densities of up to thousands per square yard, cling to boats, docks and even other shellfish by tendrils called byssal threads. Repellants that have been semi-effective against them in the Great Lakes have failed elsewhere.
Denise Mayer, a scientist at the New York State Museum's Field Research Laboratory in Cambridge, N.Y., told the House Subcommittee on Water and Power that a strain of the rod-shaped, naturally occurring bacteria Pseudomonas fluorescens can kill the quagga mussel within hours. The powerful strain, called Pf-CL145A, is an even more impressive killer because it can poison the quagga without infecting other organisms even when it's dead itself, Mayer said.
Eric Obert, an associate director of the Pennsylvania State University's Pennsylvania Sea Grant program, said that while the bacteria may work, it could be too costly for many uses.
"It sounds really promising, but it's probably more promising for hydro plants, because it's really expensive," he said.
The U.S. Interior Department's Bureau of Reclamation also proposed a solution for the quagga problem. Since January, researchers in Colorado have been testing 19 different coatings on metal panels in the lower Colorado River.
In particular, they're looking at a copper-based coating and a fluorine- and silicone-based coating. The copper is an effective killer of the quaggas, but the Environmental Protection Agency limits copper's use in water because it's toxic to many species. The State of California also has curbed copper's use as a biocide.
The fluorine and silicone coating is less toxic, but it would make it harder for mussels to attach to the hard surfaces.
Allen Skaja, a scientist for the Bureau of Reclamation, said in an interview that even if the copper can kill the quaggas, it might cause ecological damage.
"Well, that's going to be something we have to look at," he said, responding to a question about copper's toxicity. "There's not a good solution — that's the problem."
In southwestern and California waterways, the quagga can reproduce six times faster than it can in the Great Lakes. After they were first spotted in January 2007 in the lower Colorado River, the new visitors quickly became a problem.
"The biologists group had been monitoring for them," Skaja said. "It all of a sudden showed up, and they didn't expect it."
Scientists are especially concerned with the quagga's potential ability to invigorate toxic botulinum bacteria. The quagga mussels deplete oxygen from the water, creating ideal conditions for the bacterial spore, which exists naturally in the water, to vegetate and become dangerous.
Quagga ingest the bacteria without being harmed. Fish and birds, however, may not be so lucky.
The Great Lakes have seen a spike in the deaths of loons, piping plovers and other birds. Though scientists haven't made a definitive link, they're pointing to the quagga as the culprit.