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Gerald Matisoff, chair of CWRU's department of geological sciences,
was among seven researchers to testify last month during U.S.
Senator George Voinovich's field hearing in Cleveland for the
U.S. Senate Committee on Environment and Public Works.
The researcher briefed the senator on conditions that have led
to a "dead zone" in the Lake Erie that stretches between the islands
off Sandusky to Erie, Pa. This dead zone has the potential to
lead to massive fish kills, foul-smelling and tasting water from
undesirable algae blooms as well as a rise in toxic algae and
water-borne toxins.
Matisoff is director of "Lake Erie Trophic Status," an Environmental
Protection Agency-funded project. This summer 27 investigators
from as many as 18 institutions have surveyed the lake during
several week-long trips on the EPA's RV Lake Guardian, studying
why the colder layer of lake's bottom water has become oxygen-deprived
or anoxic.
Although Matisoff says they do not have complete answers as to
why there is a dead zone, he added that "human activity can and
has exacerbated the development of anoxic bottom waters." He referred
to phosphorus from fertilizers derived from agricultural runoffs
and from sewage discharges that have led to increased algal growth
in the lake.
While the Great Lakes research community established a model-environmental
program during the 1960-70s to turnabout the lake by keeping phosphorous
levels at 11,000 metric tons per year, he posed the research question
of why now anoxic conditions in the lake's central basin.
He offered the three hypotheses as to why this is happening:
- The problem may be climate-related, with variations
in climate leading to longer time periods in which the lake
has a warmer upper layer and a colder, denser bottom layer.
- The second hypothesis is the phosphorous load
might be greater that researchers are aware of.
- The third hypothesis is that zebra mussels,
an exotic species, are changing the carbon transfer system of
the lake from a pelagic food web (sunlight-phytoplankton-zooplankton-fish)
to a benthic system (sunlight-phytoplankton-zebra mussels).
The zebra mussel's filtration of the water possibly has allowed
more sunlight to reach deeper depths, spurring the growth of algae
and rooted plants that eventually die. In their decay, bacteria
grow and derive the bottom of oxygen.
Matisoff told the senator that proposing any solutions to anoxia
problem were "premature." He said first the causes need to be
identified in order to understand the ecosystem's response to
the stress. This summer's survey of Lake Erie might provide that
information.
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