DNR steps up chemical treatment of MN lake to halt growth of 'destructive' algae


The main public access to Lake Koronis is closing as DNR teams take steps to fight the spread of the invasive species known as starry stonewort.

The algae was found in Koronis and the adjoining Mud Lake, in Stearns and Meeker counties, last month, and has been described as "destructive" to lakes.

The DNR has said in a press release it has started additional chemical treatment to battle stonewort – which has spread to 250 of Lake Koronis's 3,000 acres – by treating the water at the main public access of Highway 55, which will remain closed until the lake is ice-covered.

Fortunately, the algae has not spread to other lakes in the area, but the City of Paynesville, Paynesville Township, and Stearns and Meeker counties will be coordinating boat inspections at the four other accesses to the lake, which will remain open while treatment is ongoing.

"The goal of this treatment is to knock back the starry stonewort from the DNR access area, in order to reduce the risk of spread when boats leave the access," DNR section manager Ann Pierce said.

Since the algae was discovered, the DNR increased inspection hours at the lake to 10-hours a day, seven days a week.

It is the first case of the species being found in Minnesota waters, having first been discovered in the U.S. in the St. Lawrence River in 1978. It is believed to have been brought to the state by boaters who had previously been on an infected body of water.

The grass-like algae produces “dense mats” that could interfere with recreational use of the lake, and can “choke out” native plants, alter the habitat for young fish, and impede the movement of aquatic life.

When the first case was reported in Wisconsin last year, it was described by a local lake association president as "the start of the death of a lake," according to FOX 6.

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