Starry Stonewort causing disturbances in Minnesota-Wisconsin lakes

A submerged green algae is causing some problems in lakes in Wisconsin and Minnesota, according to an article on

An announcement from the Minnesota Department of Natural Resources on Friday says the state’s lakes are being invaded by the algae, known as Starry Stonewort.  The same algae has already been reported by the Wisconsin Department of Natural Resources as being present in five of 23 lakes in the southern part of the state.

The Wisconsin agency says it plans to survey 35 more lakes, checking for infestations there.

Starry Stonewort is a macroalgae, with a main stem with whorls that have from four to six leaves with dull edges.   It usually lives in slow-moving water or relatively shallow lakes.  It is commonly found in lakes near the sea, which leads researchers to believe the species prefers salty environments.

It also thrives in areas that are dark and shady, with a minimal light supply.

First identified in the United States in 1978 at the St. Lawrence River, the species has spread across the lakes of the US northeast.  The first confirmed occurrence in Wisconsin was noted in 2014.

The Starry Stonewort has a tendency to overwhelm other native vegetation and form its own stands, causing harm to natural fish breeding areas.  It can also cause damage to power boat equipment and other types of watercraft, used by fishermen and as recreational water enthusiasts.  This type of nuisance has already been noted in the states of Michigan, New York and Indiana.

Property owners have reported seeing large amounts of vegetation in lakes, which prompted the state agencies to investigate.

The Minnesota agency confirmed that the Starry Stonewort has infested about 53 acres of Lake Koronis and Mud Lake, found in Stearns and Meeker counties respectively, in Minnesota.



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