June 14, 2002 at 5:44 PM EST - Updated July 28 at 4:00 PM
CLEVELAND (AP) - A dead zone, an oxygen-deprived area devoid of life, is expected to form again this summer on Lake Erie and scientists plan to find out why.
The worst dead zone since the early 1980s formed offshore between Ohio and Ontario last summer, a sign that the lake's environmental progress is shifting into reverse.
With a larger dead zone expected to form this summer in the central basin, ships loaded with scientists and monitoring equipment will try to determine what is threatening to undo years of environmental improvement.
"I don't want to sound alarmist, but we have no idea, really, what is going on," Murray Charlton, a scientist at Canada's National Water Research Institute told The Plain Dealer.
Already this spring, an Environmental Protection Agency boat has found water samples heavily clouded with algae and other forms of floating plant life.
Too much algae is a sign that nutrients such as phosphorus and nitrogen are overabundant -- a combination that eventually creates a barren region beneath the surface. In effect, the nutrients enrich the lake to death.
A lake can die when its bottom becomes covered with too much decomposing plant matter, which consumes more and more oxygen as it rots. When the oxygen is gone, the suffocating swath becomes lifeless.
Gerald Matisoff, a Case Western Reserve University geo-chemist heading the U.S. side of the Lake Erie investigation, said an eight-boat flotilla of research vessels will crisscross the central basin in search of answers.
Scientists will gather thousands of water samples to more precisely measure the dead zone's boundaries, depths and development in June, July and August. By midsummer, the United States and Canada will have about 40 researchers from 17 universities studying the area, The Plain Dealer reported Friday.
"Back in the 1960s and 1970s, the lake had the same problems. We thought they were solved, and for the last 10 years we've been patting ourselves on the back," Matisoff said. "All of a sudden we've got a disturbing trend of degrading water quality. The question is: How come?"
Many scientists suspect that zebra mussels and other exotic species such as round gobies are starting to reshape Lake Erie's ecosystem in ways that scientists have yet to fathom, Matisoff said. Others theorize that the lake may be suffering from the effects of climate changes linked to global warming.
Another theory is that sewage treatment plants could be dumping excess wastes, Charlton said.
The lake should not be in decline after nearly $8 billion was spent on new sewage treatment plants since the 1970s. Laws were passed to restrict the use of phosphate laundry detergents. Farmers even changed tillage practices to reduce fertilizer runoff.
Those moves cut the flow of phosphates into the lake by more than half -- from 24,000 tons a year to less than 11,000 tons.
By all prior calculations, Lake Erie should still be growing cleaner, Charlton said.
(Copyright 2002 by The Associated Press. All Rights Reserved.)