mussels get second billing to quagga in Lake Erie
8/6/02 6:25 AM
-- A cousin to the better-known zebra mussel may be the
main reason oxygen levels are dropping in Lake Erie.
the quagga -- thumbnail-size clams -- and zebra mussels
are causing high phosphorus levels that are creating a
low-oxygen "dead zone" in the center of the lake. Both
mussels release phosphorus as a waste, but the quagga
Just nine years
ago, the zebra mussel outnumbered the quagga 100 to 1.
the lake have found that the quagga, which arrived in
Lake Erie about a decade ago, outnumbered the zebra mussel
10 to 1 in samples taken last week off South Bass Island
us," said David A. Culver, a professor at Ohio State University
who is part of a research team trying to figure out why
low oxygen levels in Lake Erie's central basin have returned.
Monday at a hearing held by U.S. Sen. George Voinovich
to investigate Lake Erie's low-oxgyen "dead zone."
the lake remains healthy, but they are seeing high levels
"We thought we
had it all figured out," Culver said. "But to have phosphorus
and algae increase, that makes us concerned we'll lose
all the progress we have made."
During the 1970s
and 1980s, state and local governments spent billions
of dollars to improve sewage treatment plants and reduce
phosphorus releases in the Great Lakes.
Culver said the
quagga, a cousin to the zebra mussel, may be a leading
culprit for the dead zone, a term scientists have used
to describe an area between Erie, Pa., and Lorain, Ohio.
fresh water serves a nutrient for the growth of algae.
Decomposition of algae or any other organic material,
such as matter released from sewage-treatment plants,
sucks oxygen from the water.
If oxygen is
used up, fish will not go there or will die.
"If the central
basin were deeper, there wouldn't be a problem," said
Jeffrey M. Reutter, director of the Ohio Sea Grant College
not know why the quagga has replaced the zebra mussel.
However, the quagga survives at deeper depths and spawns
in colder weather.
a team of 27 researchers from 18 institutions is studying
the dead zone for the U.S. Environmental Protection Agency.
which helped sewage-treatment plants make improvements,
will not be easy to come by, Voinovich said.
"From the testimony
submitted for today's hearing, I am very concerned we
may be on the edge of sliding behind rather than moving
ahead," he said.