Zebra Mussels (republished from nationalatlas.gov)
Zebra
Mussel Threats Removal and Control of the Zebra Mussel |
Zebra mussels upset ecosystems, threaten native wildlife, damage structures, and cause other serious problems. Millions of dollars are spent each year in attempting to control these small but numerous mollusks. |
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Zebra Mussel Threats |
Threat to Other SpeciesZebra mussels are filter feeders. An adult zebra mussel filters up to a quart of water per day, which multiplied by millions of mussels means that the mussels may be filtering all the water in a lake or stream in a day. The animals and algae that are the food of zebra mussels are also the food for larval fish and other native species, so a large zebra mussel population may cause a decline in other animals, including native fish, mollusks, and birds. The filter-feeding activity of zebra mussels causes a related and frequently dramatic increase in water clarity in infested lakes and rivers. Zebra mussels can severely effect native mussels and clams by interfering with their feeding, growth, movement, respiration, and reproduction. For example, zebra mussels can colonize a clam shell to such an extent that the clam cannot open its shell to eat. Some native mussels have been found with more than 10,000 zebra mussels attached to them. In addition to colonizing native mussels and clams, zebra mussels may attach to slow-moving species such as crayfish and turtles.
Zebra mussels do have a positive impact on some native species. Many native fish, birds, and other animals eat young and adult zebra mussels. Migratory ducks have changed their flight patterns in response to zebra mussel colonies. Lake sturgeon feed heavily on zebra mussels, as do yellow perch, freshwater drum, catfish, and sunfish. The increase in aquatic plants due to increased water clarity provides excellent nursery areas for young fish and other animals, leading to increases in smallmouth bass populations in Lake St. Clair and the Huron River. However, these native species do not feed heavily enough on zebra mussels to keep the populations under control. Threat to Navigation, Boating, and IndustryIn addition to the impact on wildlife, zebra mussels cause many problems for people. They may colonize water intake pipes, severely restricting the water flow to power plants or other municipal or private facilities that rely on fresh water. Impacts include damage to the facilities as well as the cost of removing or controlling the mussels. Zebra mussels may also foul beaches and create boating and navigation hazards. Increased plant growth provides an additional hazard to navigation. Zebra mussels will attach to almost any hard surface, either natural or manmade. On boats, they may attach to the hull, motor, or any item immersed in the water. Both large and small boats can be severely impacted by increased drag caused by thousands of mussels. Small zebra mussels may get into engine cooling systems, causing overheating and other damage. In addition to threatening boats, zebra mussels pose a threat to navigational buoys, piers, docks, and other structures in the water. Navigational buoys have been sunk under the weight of attached zebra mussels. Wood, steel, and concrete are all damaged by prolonged attachment of the mussels. Threat to Outdoor RecreationShells of zebra mussels foul beaches and near-shore swimming areas. Bare feet are at risk from the sharp shells, and clean up costs are high. Due to changes in fish populations, zebra mussels also adversely impact recreational fishing. |
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Removal and Control of the Zebra Mussel |
Cost of Removal and ControlOnce zebra mussels become established in a water body, they are impossible to eradicate with the technology currently available. Many chemicals kill zebra mussels, but these exotics are so tolerant and tough that everything in the water would have to be poisoned to destroy the mussel. Most commercial water users rely on chemicals such as chlorine, filters, or mechanical scraping to remove mussels from their intake pipes and facilities.
Methods of Removal and ControlZebra mussels are controlled with a wide variety of methods. Many plants install equipment to preoxidize water at the point of intake, while others rely on different chemical treatments, mechanical controls, or filtration. Physical barriers and chemical coatings are used to prevent zebra mussels from attaching to structures. Removal is accomplished with mechanical scrapers, hot water, air, chemicals, and sound; new methods are constantly under investigation. There is no single, ideal solution for all affected facilities. |
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