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You have been hearing about Aquatic Invasive Species (AIS) for years but what are they actually doing to our lakes? Populations of AIS can rapidly grow and reproduce, and change the habitat of a lake. According to the MN DNR, female zebra mussels can produce 100,000 to 500,000 eggs per year! They filter algae and zooplankton out of the water for food, reducing the amount of food available for native animals and disrupting the food chain from the bottom up. Zebra mussels hurt people as well, damaging boat motors and slicing swimmers feet. And since AIS have evolved in other ecosystems, they do not have any natural predators to keep their population in check and their populations can increase quickly.

Aquatic invasives also have many other unseen effects on our lakes. When plants such as curly leaf pondweed and Eurasian water milfoil grow in thick mats, they can clog waterways. This reduces habitat for native plants, and may impact water recreation. However, just as we cannot know exactly how an invasive species will affect a lake, we cannot know how they will affect property values or recreation. It is extremely important that our lake ecosystems are as healthy as possible in order to minimize the negative impacts of AIS. This means that we all need to work together to reduce watershed and shoreline disturbance and conversion, and protect lake water quality.

With the effects AIS are having, what is being done to try to reduce and remove them from our lakes? You may have heard of Christmas Lake west of Minneapolis being treated in 2014 with Zequanox along with 2 other substances, copper sulfate and potassium chloride. Zequanox contains a bacterium that has been shown to kill the mussels in laboratory experiments by dissolving their digestive tracts; it only affects quagga and zebra mussels. This is a very expensive treatment, and was found to kill the zebra mussels treated within a barrier in the lake. However, other zebra mussels were found outside of the barrier and it was determined that the population was too widespread for an effective Zequanox treatment.

Other control methods are being researched including natural lethal parasites that would infect and reproduce inside zebra mussel shells, ultimately killing them. It may take another five to 10 years of research before this type of treatment could begin to be tested.

Other types of methods to reduce aquatic invasives are being used, including biological controls and manual removal. In 1992 the first biological control agents were released to reduce purple loosestrife, a flowering invasive plant that grows in wetlands in Minnesota. Since 1992, four different types of beetles, specifically weevils, have been introduced onto purple loosestrife plants in an effort to reduce the population. These weevils eat specific parts of the plant targeting either the leaves, flowers, or roots. The introduced beetles are now reproducing on their own and reducing the amount of purple loosestrife found in wetlands to which they were released. Biologists are finding that the weevils are now dispersing to other populations of loosestrife.

Where can I learn more about research being done on reducing and removing aquatic invasive species?

• National Wildlife Federation

• Aquatic Nuisance Species Task Force

• MN DNR

• University of MN Aquatic Invasive Species Research Center

For more information about aquatic invasive species in Cass County lakes, contact Rima Smith-Keprios at 218-547-7324 or [email protected].

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