Enlarged environmental 'dead zone'
ripples across Lake Erie
By Dan Vergano
Cleanup efforts starting in the 1970s rebuilt the quality
of the lake water, polluted for decades by industries
lining the Great Lakes. But within the past decade, monitors
have witnessed an increasingly large region of low-oxygen
water - dubbed the "dead zone" by the Environmental
Protection Agency - in the lake's central basin every
year during the late summer.
Last month, environmental officials and scientists from
a consortium of universities sampled lake water and sediments,
part of a two-year, $2 million study aimed at unraveling
the mystery behind the growing zone.
The zone - a 10-foot-thick layer of cold water at the
bottom, 55 feet deep in this area - stretches 100 miles
across the lake's center and now lasts the entire month
of August, up from two weeks a decade ago. The oxygen-poor
water kills fish and microscopic creatures that support
the lake's food chain.
"It was tremendously surprising" when the enlarged
dead zone appeared a decade ago, EPA scientist Paul Bertram
says, because pollution controls were improving water
quality. "We're trying very hard to understand what
In addition to triggering foul-smelling water and killing
fish that wash up and litter beaches, the zone could create
problems that include decreased sports fishing and higher
water and sewer rates.
"Bad for people, bad for fish and even bad for birds,"
says geologist Gerald Matisoff of Case Western Reserve
University in Cleveland.
It is thought to have multiple causes. Among them:
Zebra mussels, an unwanted foreign species carpeting
the bottom of the lake, may be a key culprit, Matisoff
and others suggest. Efficient lake-water filters, mussels
may be sucking up oxygen in the water and triggering algae
blooms. Algae blooms pull even more oxygen out of the
Undetected phosphates from fertilizers may be making
their way into the lake, says scientist Dave Culver of
Ohio State University. Storm sewers could be depositing
phosphates into the lake as well as some smaller, unmonitored
rivers. Phospates also trigger algae blooms.
"A naturally occurring cycle could be at work, one
somehow worsened by still-undetermined climate changes
or other lake rhythms, although core water samples show
past dead zones were much smaller," Culver says.
"Nature has a way of dealing with imbalances,"
Help could come from another invasive species, the round
gobie fish, which like to dine on zebra mussels.
"It's not like this is the end of Lake Erie,"
Culver says. Lowering phosphates, whether triggered by
pollution or zebra mussels or both, should reduce the
dead zone's severity, he says. "If we don't, it's
definitely going back to the way it was in the 1970s."