U.S. Water News Online
CLEVELAND -- A "cousin" to the better-known zebra mussel
may be the main reason oxygen levels are dropping in Lake Erie.
Researchers said the quagga -- thumbnail-size clams -- and zebra
mussels are causing high phosphorus levels that are creating a
low-oxygen ``dead zone'' in the center of the lake. Both mussels
release phosphorus as a waste, but the quagga releases more.
Just nine years ago, the zebra mussel outnumbered the quagga 100
Scientists studying the lake have found that the quagga, which
arrived in Lake Erie about a decade ago, outnumbered the zebra mussel
10 to 1 in samples taken near South Bass Island near Sandusky.
``This astounded us,'' said David A. Culver, a professor at Ohio
State University who is part of a research team trying to figure out
why low oxygen levels in Lake Erie's central basin have returned.
Culver spoke at a hearing held by U.S. Sen. George Voinovich to
investigate Lake Erie's low-oxygen ``dead zone.''
Scientists said the lake remains healthy, but they are seeing high
levels of phosphorus.
``We thought we had it all figured out,'' Culver said. ``But to
have phosphorus and algae increase, that makes us concerned we'll
lose all the progress we have made.''
During the 1970s and 1980s, state and local governments spent
billions of dollars to improve sewage treatment plants and reduce
phosphorus releases in the Great Lakes.
Culver said the quagga, a cousin to the zebra mussel, may be a
leading culprit for the dead zone, a term scientists have used to
describe an area between Erie, Pa., and Lorain, Ohio.
Phosphorus in fresh water serves as a nutrient for the growth of
algae. Decomposition of algae or any other organic material, such as
matter released from sewage-treatment plants, sucks oxygen from the
If oxygen is used up, fish will not go there or will die.
``If the central basin were deeper, there wouldn't be a problem,''
said Jeffrey M. Reutter, director of the Ohio Sea Grant College
Scientists do not know why the quagga has replaced the zebra
mussel. However, the quagga survives at deeper depths and spawns in
This summer, a team of 27 researchers from 18 institutions is
studying the dead zone for the U.S. Environmental Protection Agency.
Federal funding, which helped sewage-treatment plants make
improvements, will not be easy to come by, Voinovich said.
``From the testimony submitted for today's hearing, I am very
concerned we may be on the edge of sliding behind rather than moving
ahead,'' he said.
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