How Do Zebra Mussels Affect Humans?

Look around at any beach, pier, lighthouse, dock, boat launch or campground and you are likely to see a sign describing the dangers of zebra mussels to the boat you're launching, the fish you want to catch and even the pier you're standing on. The zebra mussel contamination of North American lakes and rivers is a threat to native species, industrial production and the weekend trip to the beach. The cost of removing the animal is high and the cost of not removing them is even higher.

What is a Zebra Mussel?

• The zebra mussel (Dreissena polymorpha) is a freshwater mollusk that has invaded North American waterways. It is named for the striped pattern found on the mussel's shell. It is thought that the species was first transported to North America in 1988, trapped in the ballast of a ship coming from Europe. Release of the mussel-contaminated ballast into the Canadian waters of Lake St. Claire introduced the species to the continent.

The Problem

• During adolescence, zebra mussels are able to swim and can be carried far into the inland waterways by currents in lakes and rivers, expediting the spread of the species. As they reach adulthood the mussels attach to hard surfaces with a multi-threaded organ called a byssus. Zebra mussels attach themselves to both man-made and organic objects, causing damage to the objects and negatively affecting the ecosystem they are invading.

Industry

• Man-made objects disrupted by the attachment of zebra mussels range from water intake pipes leading to plants and factories where they narrow the passage and restrict water flow, to boats hauling cargo through lakes and rivers where they create drag on their haul or motor, leading to overheated engines and similar problems.
  Zebra mussels have been known to increase safety hazards. They colonize on navigational buoys in numbers great enough to sink them as well as other water-based structures like docks and piers. The attachment of zebra mussels deteriorates materials as strong as wood, steel and concrete.

Recreation

• The effect of zebra mussels on recreational fishing has been negative. Changes in fish population have been recorded as a result of the increased competition for food in the ecosystem.
  Beaches as a recreational outlet are also at risk, as mussels pile up on swimming areas, creating a blanket of sharp-edged shells.

Native Species

• The zebra mussels' invasion is a threat to the native species populations of lakes and rivers. The mussel attaches itself to other animals' shells in life-threatening numbers. Colonization on clams can be so great that the native mussel cannot open for feeding. Other species that are threatened in this way include crayfish and turtles.
  The rate of filter feeding by the zebra mussel also threatens the lives of native species that rely on the sediments floating in the water.

The Financial Cost

• Removing zebra mussels from a structure or intake pipes is nearly impossible with current technology. The most common cost incurred by plants and other affected facilities are from retrofitting the affected areas of the plant. Nuclear plants incur the highest cost as their need for fresh water in producing energy is the greatest, followed by industrial plants, fossil fuel power plants and water purification facilities.