Starry Stonewort Confirmed in Thunder Lake in Cass County

Sample of starry stonewort found in Thunder Lake (Photo credit: DNR)

The Minnesota DNR has confirmed the presence of the aquatic invasive species starry stonewort in Thunder Lake, located near Remer in Cass County.

This discovery brings the number of bodies of water in Minnesota where starry stonewort has been found to 23. It was located by DNR staff conducting a survey of algae in Thunder Lake.

Starry stonewort is an algae that can form dense mats that compete with native aquatic plants and can interfere with recreational uses of lakes. It’s thought to spread when boats, docks, and other water-related equipment are pulled from the water without being properly cleaned and are transferred to another lake.

Follow-up surveys are being conducted to determine the extent of starry stonewort in Thunder Lake. Removal of the algae would be considered if it is found to be in localized areas of the lake.

Starry stonewort has never been eradicated from any U.S. lake or river, but treatment or careful removal can help reduce the risk of spread and relieve associated nuisance impacts on water-related recreational activities. The DNR says early detection is key to effective management.