WELCOME TO AMERICA - The New Wild: Why Invasive Species will be Natures Salvation - page 39

Mussels, clams, and the shrimp-like Diporeia have declined because the lake's plankton are being
consumed by the zebra mussels. And there are fouling problems on the lake floor from their excretion.
But it has to be said that since zebra mussels became established, the clarity of the once-murky water in
Lake Erie has increased dramatically. You can see down for thirty feet in some areas, compared to less
than six inches half a century ago. As light has penetrated the lake, some aquatic plants have revived.
They in turn have become nurseries for fish such as the yellow perch.
The zebra mussel is also itself a food source for important species. The smallmouth bass ( Micr-
opterus dolomieu ) and, most dramatically, the previously endangered lake sturgeon ( Acipenser fulves-
cens )—a giant shark-like beast that has barely evolved for one hundred million years—munch them and
have revived their populations as a result. Lake Erie is now reportedly the world's premier smallmouth
bass fishery. Meanwhile, migrating ducks that once avoided the fetid waters now make detours to feast
on the new mussels. 27
If you are of a gloomy persuasion, you might sympathize with the complaint of invasion biologist
Daniel Simberloff that all this clearing of Erie waters “favors invasion by large-leaved aquatic plants
such as Eurasian water milfoil.” 28 That seems perverse. A new ecological environment is rapidly emer-
ging in the lake, with its own checks and balances. We cannot tell quite how it will work out. The revival
of the ancient sturgeon may limit and perhaps even reverse the proliferation of zebra mussels. Some fish
ecologists say that if humans hadn't hunted the sturgeon almost to extinction, the zebra mussels would
never have got such a grip. So the battle for supremacy between the two species might now get interest-
ing. 29 But surely all this is better than the “dead” lake.
None of this denies that the mussels can be a physical menace for human activity. They cling onto
any hard surface they can find, congregating in dense masses many layers thick. They cover jetties and
clog water intake pipes. The extent of the problem emerged when the Lake Erie port town of Monroe lost
water for three days. But we should be wary of some cost estimates floating around. One widely quoted
statistic puts the cost to utilities and others in the Great Lakes alone at half a billion dollars a year. It is
often referenced to the Center for Invasive Species Research at the University of California-Riverside.
But when I checked it out, the center's director, Mark Hoddle, said they had been quoting someone else,
but he couldn't tell me where they got it. Maybe it would be better to believe the figure put forth by
Nancy Connelly at Cornell University. She found, after interviewing corporations, that the zebra mussel
had cost just a quarter billion dollars over fifteen years. That is still substantial, but only one-thirtieth as
much as Hoddle's annual figure. 30
What happens in Lake Erie does not necessarily stay in Lake Erie. Success breeds success. In less
than a decade, zebra mussels have spread to all five Great Lakes and on into connecting rivers, includ-
ing, via Chicago's canal system, the giant Mississippi and its tributaries. They are now in twenty-seven
US states. In places, this has been good news. “Zebra mussels have had positive impacts on parts of the
Great Lakes ecosystems,” says the USGS's Great Lakes Science Center. 31
As it bobs down the Mississippi, the zebra mussel will probably pass one of the various species of
Asian carp swimming the other way. Asian carp ( Catla catla and others) can grow over three feet long
and eat 40 percent of their own weight in plankton daily. Imported from China in the 1970s to eat algae
in catfish ponds and sewage works, they escaped and spread up the Mississippi. There are fears that this
infidel may soon find its way along the canals linking the river through Chicago to Lake Michigan and
the other Great Lakes.
All manner of ruses are being tested to keep them out, including chemical lures, a high-voltage elec-
trical barrier, an acoustic gun that acts like an aquatic bird scarer, and simply blocking the canals. The
Army Corps of Engineers is advising the White House. A more enterprising option is to treat the carp