Biology & Society

What Can Be Done About Invasive Mussels?

It's hard to imagine that shellfish could cause millions of dollars worth of trouble every year. Meet the zebra mussel and the quagga mussel. Both species were carried to the Great Lakes in the mid-1980s from Eastern Europe in ships' ballast waters (water carried inside boats for balance). As adults, these mussels attach to almost any hard surface, including water pipes and boat hulls. After just a few years, both species colonized the entire Great Lakes region. Since then, they have been spread by recreational boaters who unknowingly carry mussels attached to their boats. By 2008, zebra mussels had been reported in 24 states; quagga mussels are already known in 14 states.

Why have these mussels become such pests? In American waterways, they escape whatever environmental factors keep their numbers in check in their native European habitats. As a result, these introduced species have become invasive species whose exponential growth produces huge populations at high densities—over 10,000 mussels per square meter of water in some places! These mussels grow in layers up to 20 centimeters thick, clogging water pipes that supply power plants and water treatment facilities. They also upset aquatic food webs, filtering so much plankton from the water that some native fishes and shellfish starve. What can be done to control such invasive species?

The Viewpoints

Invasive Species Should Be Destroyed A number of groups contend that zebra mussels should be removed completely. Some engineers are developing robotic submarines that can remove mussels from pipes. Some chemists are testing chemicals for the potential to destroy or disrupt the life cycle of zebra mussels. Other scientists are adding chemicals to paints and plastics to prevent mussels from attaching to new surfaces.

Zebra mussels clog water intake pipes.

Invasive Species Management Should Focus on Control and Prevention Others argue that efforts to physically remove or chemically poison invasive mussels offer only temporary control. The population bounces right back. These removal efforts are also incredibly expensive. In the Great Lakes alone, more than $200 million is spent each year in efforts to get rid of zebra and quagga mussels.

Therefore, many scientists believe that there is no way to remove these mussels and other established invasive species. Instead, these scientists attempt to control the growth of populations and prevent transfer of invasive species to new areas. One regulation, for example, could require boaters to filter and chemically clean all ballast water. Meanwhile, the search continues for some kind of control that naturally limits mussel numbers when they rise.

Research and Decide

1. Analyze the Viewpoints Research the current status of invasive mussel populations and the approaches being used to prevent the spread of these and other invasive aquatic species. What trends are zebra mussel populations showing?

2. Form an Opinion What kinds of natural population controls do you think would manage these invasive mussels most effectively? Why?

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