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
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."
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.
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
mussel is really something else," Greenberg says. "Just about any
science fiction thought you ever had is true with these little devils."
listening, Stephen King? They're coming...No, they're here.