By PETER GEIGEN-MILLER
London Free Press
Thursday, July 18, 2002
A dead zone, an oxygen-deprived area
unable to support life, is developing this summer in Lake
Erie and a large-scale scientific effort is underway to
find out why.
After rebounding from being declared dead in the 1960s,
Lake Erie is again a growing concern as puzzling changes
threaten decades of improving water quality.
The U.S. Environmental Protection Agency
is investing $500,000 US in a two-year study involving
25 Canadian and American scientists.
Scientists in eight vessels will criss-cross the lake's
central basin this summer, collecting thousands of water
samples to map the extent of the problem.
Some scientists are declaring it the start of the second
environmental war to save Lake Erie.
The first was waged after plant-nurturing pollutants,
mainly phosphorus and nitrogen from agricultural runoff
and inadequate sew-age treatment, caused huge algae blooms
in the 1950s and 1960s.
This plant matter absorbed oxygen from the water as it
decayed, creating large lifeless zones.
But a massive cleanup effort that saw hundreds of millions
of dollars spent on improved sewage treatment and other
pollution controls returned the lake to what appeared
to be robust health.
Now, scientists are seeing an increase in anoxia, or lack
of oxygen, said Tim Johnson, a Ministry of Natural Resources
researcher in Wheatley.
Important fish species such as walleye may be at risk.
Scientists are concerned because the change can't be explained
by increases in nutrients or algae, said Johnson, one
of the scientists involved in the study.
"So it's puzzling to us what is causing the low oxygen,"
One top theory is zebra mussels, invaders introduced in
the 1980s, have changed Erie's ecosystem, said Gerald
Matisoff of Case Western Reserve University in Cleveland.
"Zebra mussels have . . . taken the algae and organic
matter that used to be up in the water column and put
it down at the bottom of the lake," said Matisoff, who
heads the U.S. side of the study. "When that stuff decomposes
during the summer, the bottom water oxygen gets used up."
The changes brought by such invaders make scientists aware
the lake's ecosystem is more complex than it seemed 15
years ago, said Murray Charlton of the National Water
Research Institute in Burlington.
"There needs to be more effort put into understanding
it and whether further changes are needed in managing
fisheries and nutrient sources."
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