Zebra mussels in infested areas impact facilities such as locks, dams, and hydroelectric plants. Mussels have blocked pipes, screens, condenser units, and many other small openings through which water passes. They do this by forming druses (clumps of mussels) or simply attaching to available hard substrates with byssal threads.
Once a single mussel is in place, others may settle on or around it and their density increases, filling in and clogging pipes, screens, and trashracks until water flow is impeded and/or equipment shuts down.
Periodic backflushing of pipelines can help eliminate buildups such as this.
Druses of zebra mussels clog and impede water flow through screens such as this these.
Zebra mussels will settle and colonize on any suitable substrate such as this grate.
Even if mussels are killed by a control technique, the shells and any decaying animal material may remain behind, causing additional problems. Thus killing the mussels may be only part of the solution to opening a blockage. A complete solution may require removal of mussel shells.
Dreissena has formed such dense encrustations that entire facilities have been forced to shut down for mechanical cleaning, as demonstrated by these images of the interior of the Detroit Edison Hydroelectric Plant undergoing cleaning.
Note the dense mats of zebra mussels on all exposed surfaces. These shutdowns cost power companies thousands of dollars in maintenance costs and lost revenue.
Lock facilities of the Corps of Engineers are vulnerable to heavy encrustations. In addition to the problems posed by dense mussel encrustations, there is evidence that zebra mussel byssal threads may accelerate corrosion around joints and rivets of metal structures of power plants. Bacteria are present in the area between the substrate and the pad of a byssal thread. Through anaerobic respiration, these bacteria produce an acidic compound that increases the corrosion and pitting of iron and steel surfaces. This increase in turbulence may cause a decrease in head pressure (Claudi and Mackie 1994).
Note the dense zebra mussel encrustation and corrosion around the visible rivet. This is after only 1 year of zebra mussel settlement.
The zebra mussel is also capable of clogging water intake pipes and pumping units in private homes, camps, and cottages located alongside lakes, rivers, and streams. This type of fouling has occurred in areas of the Great Lakes region. O'Neill (1995) placed the number of threatened dwellings in the eastern half of North America at over 100,000 as of 1995. That number was considered to be a conservative estimate at the time. Further information on controlling zebra mussel infestation of private water intakes, such as within homes or camps, may be obtained in a fact sheet produced by the New York Sea Grant Institute called "Control of Zebra Mussels in Residential Water Systems" (O'Neill 1995).
For water treatment plants and private homes where water is drawn directly from infested source water, zebra mussel infestation can impede proper function by altering water chemistry. Zebra mussel pseudofeces can affect the taste of drinking water. As the uneaten particles of ingested matter are expelled from the inhalant siphon, they are bound by mucous. This mucous-wrapped pseudofeces accumulates and creates a foul environment that uses up oxygen. This lack of oxygen, in turn, increases the acidity of the water, giving it a bad taste.
Zebra mussels may colonize fishing nets and navigational buoys where the added weight of zebra mussel colonization can render them useless by dragging them under the water. The cost of retrieving, cleaning, and deploying additional buoys can be a further expense.
Zebra mussels will settle and form druses on virtually any hard substrate such as this net.
Economic Impacts of Zebra Mussel Infestation