In Shock Over Shells

Zebra mussels are fanning out from the Great Lakes. They are known to be in the St. Lawrence River at Kingston, Ont., and Massena, N.Y. They are in New York's Erie Canal, which is linked to the Hudson River. Dr. David Strayer, a mussel specialist at the Institute of Ecosystem Studies in Millbrook, N.Y., expects the zebra mussel to establish itself in the Hudson by 1992, and he predicts that the zebra mussel population in the 90-mile stretch between Troy and West Point will build to 150 billion by 2002, enough mussels to filter all the river water every six days. The proximity of the Hudson to the New York City reservoir system and its 6,000 miles of century-old and largely buried pipeline puts that city's system at risk.

Arrival of the mussels in the Mississippi, connected to Lake Michigan by the Chicago Diversion and the Illinois River, probably has already occurred. "I believe they're already in the Mississippi," Schloesser says, "but they haven't grown to a size that makes people ask, 'What's this?' They were in Lake St. Clair for almost three years before 12 people knew about it."

From the Mississippi, zebra mussels will have access to water systems from Minnesota south to Louisiana, west to Montana and cast to Pennsylvania. Neither mountain ranges nor lack of connecting waterways will stop them from spreading. An angler who takes a boat out of Lake Erie to go fishing in, say, Dale Hollow Lake in Tennessee could cause big trouble for the TVA. Thousands of nearly invisible veligers can be transported to new territory in a single bucket of bait taken from an infested lake or river.

In May, the Michigan Department of Natural Resources (DNR) advised boat owners to inspect both boats and trailers for mussels before transporting. That's not easy. "Pass your hand across the boat's bottom," reads the Michigan DNR brochure. "If it feels grainy, it's probably mussels. Don't take a chance; clean them off by scraping or blasting." Other advice from the same pamphlet: "On wood, aluminum or steel boats, attached zebra mussels may take off the first layer of paint when removed. Be careful not to damage the gelcoat on fiberglass hulls. Repaint if necessary...." In addition to recommending that boat owners scrape the hulls and reapply bottom paint after returning from fishing or waterskiing, the DNR also says: "Zebra mussels can...clog the cooling system of your boat's engine, and they are difficult to remove once they do. The best alternative is to replace the pipes."

So what can be done? The only animals known to feed heavily on zebra mussels are freshwater drum (a fish) and diving ducks, particularly the greater and lesser scaup. In the last two years, the number of scaup gathering at Point Pelee ( Ont.) National Park on the northwestern shore of Lake Erie has increased from 100 to 20,000, probably because of the proliferation of mussels. Although one scaup can cat 50,000 zebra mussels in the course of a year, there are nowhere near enough scaup in the world to control even the mussels in Lake Erie. Based on experiments that monitor the growth of zebra mussels in shallow depths, Leach estimates the mussel population in parts of Lake Erie to be on the order of 900,000 mussels per square meter of water.

"Natural predation has never been known to control populations this dense," says toxicologist Leif Marking of the U.S. Fish and Wildlife Service Research Center in La Crosse, Wis. "Some people are still taking this mussel sort of ho-hum, but I'm not. It can cause dramatic impacts."

In Europe no means of permanently eradicating zebra mussels has been found. The elaborate filtering systems and periodic poisoning and scraping seem to be the only way to contain them. Economically, the control of the mussel in the U.S. is going to require a multibillion-dollar effort; environmentally, the cost could be equally stupendous. The use of such non-selective poisons as chlorine in the amounts required to kill the mussels in large bodies of water could be devastating to entire ecosystems. What is needed is either development of a poison that won't be environmentally destructive or a means to block the maturing of veligers. "We need to try to prevent the veligers from settling and attaching to anything," says Marking. He and others are experimenting with sonic pulses and ultraslippery pipe coatings to thwart the immature mussels.

"This zebra mussel is really something else," Greenberg says. "Just about any science fiction thought you ever had is true with these little devils."

Are you listening, Stephen King? They're coming...No, they're here.