Mini Monsters "Musseling" into Missouri
after hatching, they settle and will attach to any hard surface, including rock, wood, concrete, plastic, crayfish shells and other mussel shells.
If the tiny - about the size of a grain of sand, at this point - zebra mussels don't land on a suitable surface, they have a single foot to help them swim or crawl in search of one.
Zebra mussels attach themselves to objects with small elastic threads, called byssal threads. Because they can also attach to one another they can quickly form thick living layers.
At a Detroit Edison power plant off Lake Erie, for example, zebra mussels built up like heavy cholesterol in a cooling water intake pipe. According to a plant official they went from nondetectable levels in 1988 to 700,000 per square meter in 1989.
A simultaneous infestation of the water intake pipe of a nearby municipal water treatment plant virtually shut off the faucets of the entire town of Monroe, Mich.
Water pipes are an ideal habitat for zebra mussels because they provide a hard surface and a steady stream of food. Zebra mussels feed on plankton, which they filter from the water. They pump water in, strain it of algae and microscopic animals, then pump it out, along with their wastes.
Billions of these flow-through filter pumps working full -time can have a dramatic effect on the water. Lake Erie, just over a decade ago labeled a eutrophic dead sea, now is known for water clear as a gin bottle.
Filtering sounds like a good thing, except that it threatens established ecosystems.
In any water, big fish feed on smaller fish that have eaten smaller organisms. The chain goes all the way down to the microscopic plankton. Uncountable numbers of zebra mussels successfully competing for this plankton, however, could collapse the chain, devastating sport and commercial fisheries.
The mussels affect ecosystems in other ways. For example, in the Illinois River, the respiration of huge accumulations of zebra mussels is being blamed for low oxygen levels that have caused fish kills. Zebra mussel filtering also allows the sun to penetrate deeper into the water, allowing weeds to multiply.
Zebra mussels directly threaten native mussel populations by blanketing them and preventing them from getting nutrients. In 1986, Lake St. Clair contained 18 different species of mussels. Researchers estimate that in a few years there will be no more native species of mussels living there.
We hesitate to make value judgments about any species, but