Two miles away,
the Monroe water-treatment plant also came under siege. The plant employs a
30-inch gravity-flow pipeline extending more than a mile out and 20 feet down
in Lake Erie to provide water to 55,000 people. The pipe terminates on land at
a pumping station that sends water through a nine-mile long transmission main
to the treatment plant. By July 1989, mussel buildup inside the pipe had cut
the flow by 12�%. Three months later, the flow was down by 20%. On Dec. 15, the
water stopped, creating what The Monroe Evening News later called "a water
emergency that all but brought the city to a standstill."
restaurants and bars closed, Mercy Memorial Hospital released all the patients
it could and postponed elective surgeries, and residents were told not to bathe
or do dishes or laundry, and to boil any water used for cooking or drinking.
Random clumps of zebra mussels in the pipelines had not only reduced the amount
of water inside the pipe, but had also made the flow erratic along the length
of the pipeline, creating conditions that allowed ice to form. When the
temperature fell to zero on Dec. 15, the ice joined with the mussels and
completely blocked the pipe.
changed the next day," says Greg Allen, the operations supervisor at the
treatment plant. "The sun came out and warmed the water enough for a flow
to come through." Ozone and chlorine have been used on an experimental
basis to kill the mussels, but to keep the bivalves at bay, the city of Monroe
plans to install a new intake system costing more than $6 million. Water rates
have been increased by 18% to help pay for this new equipment.
have been discovered in other Lake Erie intake systems, in three Canadian
water-treatment plants (in Tilbury, Blenheim and West Lorne), and in the
water-treatment plant that serves Cleveland. "They are in all our
intakes," Cleveland's Greenberg said in August, "but they have not yet
decreased our flow capacity. Thank God. We have one crib [a steel structure to
protect pipelines] that's four solid inches of zebra mussels inside and out.
Are they a matter of concern? Absolutely!"
Zebra mussels are
also present in all power-plant intakes in Cleveland, including the Perry
Nuclear Station. They are in three of Detroit Edison's eight plants. They have
threatened production at the huge Ford Canada plant in Windsor, where they have
The city of
Detroit draws its water via three intakes. Two are in the Detroit River and the
third is some 80 miles north, in Lake Huron, where a pipe extends about five
miles into the lake to a depth of more than 100 feet. Mussels are known to have
settled on the mouth of that pipe and on two intake cribs.
ago, mussels were found in the intakes of the Cook Nuclear plant in Bridgman,
Mich., on Lake Michigan some 200 miles from Detroit. They were discovered last
year in Gary, Ind., and Green Bay. In June, zebra mussels were found nearly 700
miles west of Detroit, at the mouth of the St. Louis River near Duluth, Minn.,
at the western end of Lake Superior.
Many people have
the misconception that Lake Erie is "dead." In fact, antipollution
efforts have been effective to the extent that the lake is now the home of a
$900-million a year sports and commercial fishery, including the richest
walleye fishery in the world. Zebra mussels are a distinct threat to the
newfound health of that industry.
obtain nourishment by filtering water for phytoplankton, the microscopic plant
life that is the very foundation of the freshwater food web. Under ideal
conditions, a zebra mussel will filter one liter of water a day to provide
itself with enough phytoplankton to thrive. At present, Dr. Joe Leach, a
research scientist at the Ontario Ministry of Natural Resources in Wheatley,
Ont., estimates that Lake Erie's exploding zebra mussel population is filtering
all the water in the lake's western basin every four days. Even phytoplankton
cannot reproduce fast enough to sustain such an assault.
The mussels do
not devour all the phytoplankton, but consume those less than 50 microns in
size. The problem is that the larger zooplankton, as well as water fleas,
forage on the small phytoplankton, and they in turn constitute a significant
percentage of the diet on which larval and juvenile yellow perch, large-mouth
and smallmouth bass and other fish depend. The eating habits of zebra mussels
could short-circuit a food web that has evolved over thousands of years.