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Musseling In
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# : |
20656 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
10 / 1992 |
1,786 Words |
| Author
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Dwight G. Smith
Dwight G. Smith is professor and chairman of the biology
department at Southern Connecticut State University in New
Haven. His latest book, Plants, was released this summer by
Pearson Publishing Company of Boston. |
Introduced just a few years ago in Lake St. Clair, the black-and-white striped zebra mussel has already proven to be one of the most successful--and most troublesome--invaders of North American aquatic habitats during this century. Its rapid spread across the Great Lakes and into inland lakes and water ways has exceeded all expectations, and scientists are predicting that the zebra mussel will soon become the dominant freshwater mollusk in North America.
Zebra mussels apparently arrived in North America in 1985 or '86, carried in the ballast water of a European freighter that was emptied into Lake St. Clair. They were first detected in June of 1988 near the headwaters of the Detroit River. In the following December, zebra mussel populations were found throughout the southern half of Lake St. Clair and in the western half of the Lake Erie. By 1991, zebra mussels had spread eastward into several New York waterways including the Finger Lakes, the Erie Canal, and the upper Hudson, Mohawk, and Susquehanna rivers. Southward, they had reached as far as several of the major rivers of the upper Mississippi River Basin, including the Illinois, Ohio, Tennessee, and Kentucky rivers. Their recent appearance in the Mississippi watershed promises major economic problems for all of the hydroelectric plants and water treatment plants within the jurisdiction of the Tennessee Valley Authority. They also threaten the river's important commercial shellfish beds.
An Ecological Menace
Ecologically, zebra mussels can devastate whole aquatic systems by disrupting food chains and altering patterns of energy production and flow. They are filter feeders that strain minute phytoplankton algae from the water. Highly efficient, a single individual can process a quart of water each day. A whole colony of zebra mussels can quickly transform murky green but organically rich waters into clear but sterile blue waters as a result of their filtering activities. Zebra mussels not only consume the phytoplankton but also retain in their bodies the minerals in the water; which are bound in insoluble iron compounds, thus depriving higher plants and animals of food and mineral resources. The ecological pyramid of plants and animals native to the aquatic ecosystem collapses, and once diverse and thriving aquatic communities may be transformed into simple, single-species habitats. Of more direct concern to humans, game fish and other desirable animals and plants are lost and with them the commercial and recreational sport fishing industries.
Zebra mussels also affect native
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