Southern Minnesota lake reopens after rare outbreak of toxic algae blooms

Toxic algae blooms, and not sewage, were the cause of contamination that kept a southern Minnesota lake off limits for a week until it reopened Friday, state environmental officials said.

Problems on Beaver Lake in Steele County were first detected Aug. 5 by a lake homeowner who reported them to the Sheriff's Office, blaming sewage from a septic tank.

That prompted the closure on Aug. 6 of a county park along the east side of the 98-acre lake, and nearby residents were cautioned to keep themselves and their pets out of the water.

Testing by the Minnesota Pollution Control Agency (MPCA) revealed the blue-green toxic blooms as the culprit, the agency said Thursday.

The park reopened Friday and visitors were allowed back in the lake, thanks to workers who quickly removed a large portion of the toxic blooms — and more than 4 inches of rain Thursday that helped drive the blooms back under water, said county deputy emergency management director Chris Gannon.

Gannon called the development of the toxic blooms "extremely rare" in his county.

Toxins produced by the blooms can be harmful if swallowed, the MPCA said. In extreme cases, dogs and other animals have died after drinking lake water containing such toxins, the agency noted.

"Scientists do not yet know what causes some blooms to produce toxins while others do not, so the safest course of action is to avoid contact with all severe blooms," the MPCA's Cathy Rofshus said in a statement announcing the test results.

Harmful algae often take on the appearance of pea soup or spilled green paint but can take other forms and can be hard to distinguish from other types of algae, Rofshus said.

Rofshus said there's no short-term fix for the aquatic quandary. Significant rainfall, wind shifts or lower temperatures are needed to stymie the algae's growth, she said.

Steele County was posting notices from the MPCA on Friday at various points around the lake explaining the water's condition. That way, Gannon said, "whether or not to enter the lake is a personal decision."

Paul Walsh • 612-673-4482