Recent changes in Lake Erie have created a dead zone that stretches from the Lake Erie Islands north of Sandusky, Ohio, to Erie, Pennsylvania. After witnessing a rebounding lake from polluted conditions two decades ago, the turnabout in has sent the U.S. Environmental Protection Agency and a score of scientists out on the lake this summer to find out why the dead zone exists.

photo by Susan Griffith Gerald Matisoff, professor of geological sciences; research assistant Britt Hanson; and Tom Neeson, CWRU undergraduate, prepare to board the R/V Lake Guardian, an EPA research vessel preparing to sail Lake Erie.

Gerald Matisoff, CWRU professor of geological sciences, will head the EPA's two-year, $2 million study that began in June, which includes other scientists from CWRU and from some 20 other universities and agencies in the United States and Canada.

Matisoff, along with research assistant Britt Hanson and Tom Neeson, CWRU undergraduate, were among the first team of scientists to board the EPA's research vessel R/V Lake Guardian to conduct research.

Beverly Saylor, CWRU assistant professor of geology, is also participating in the project. She will study the historic conditions, which have created the deep basin in Lake Erie 4,000 years ago that has the possibility for anoxic or oxygen-starved conditions. She will examine the naturally occurring events over time that have produced these oxygen-starved conditions in order to understand how human-induced factors also influence and contribute to the anoxic conditions.

The Lake Guardian which regularly visits the various Great Lakes will spend an extra 35 days on Lake Erie for intensive study this summer. The ship left the Federal Marine Terminal in Cleveland for three, weeklong trips this summer to more than 20 research sites throughout the lake to take water and sediment samples to find out why chlorophyll levels are historically low, why phosphorous levels have increased when the amount entering the lake has decreased and why the "dead zone" is devoid of oxygen in the summer.

"We have tracked Lake Erie for decades and thought we had a good historical understanding of what to expect now and in the future," said Thomas Skinner, EPA Region 5 administrator and manager of the Great Lakes National Program that has the mission to preserve the integrity of the Great Lakes. "But recent discovery of long-term effects on the ecosystem prompted this all-out investigation."

Matisoff said the EPA has worked to decrease phosphorous loads from 26,000 metric tons per year parts to 11,000.

"The lake had gotten better, but over the past few years anoxia in the bottom waters has reappeared," he said.

The hypothesis is that zebra mussels have created havoc with the lake's ecosystem. The zebra mussel is an exotic species from the Caspian Sea and other European waters that entered the Great Lakes in 1989 when sea vessels dump their ballast waters into the Great Lakes.

The waters of Lake Erie have two strata—a top layer of warmer water and a deeper cold layer where many of the lake's salmon, walleye and other fish live and that support the multi-million dollar fishing industry and recreation fishing.

Matisoff speculates that biota, sediment and water samples will show that the zebra mussel is robbing the colder layer of important oxygen for the fish's survival.

He explains that the zebra mussel has shifted the lake's food chain from a pelagic system in the warmer waters to a benthic system in the cold waters. In the warmer, upper and oxygen-rich layer, the food chain supports algae, which blooms during warmer months, with growth spurred by phosphorus from fertilizers and from detergents in sewage. Zooplankton feed on the algae and the fish in turn eat the zooplankton.

With shift to the benthic system, the food chain is shifted to the colder layers of water with the zebra mussel feeding on algae and excreting debris to the sediment, causing an increase in oxygen consumption and depriving fish of the oxygen that sustains their growth. Plants and fish die. Some toxic algae proliferate and produce neurotoxins, which corrupt the water, making it harmful for humans to drink it or swim in it.

Lake Erie's savior may come in the form of another exotic species, the round gobie, introduced by freighters in 1993.

"The round gobie, which feds on the zebra mussels, may eventually turn around the current problem as it eontrols the zebra mussel population," Matisoff said.

Until that might happen, scientists will explore the dead zone for clues to reverse the current situation.

–CWRU–