Toxic levels of algae detected in Edina’s Lake Cornelia

The city of Edina and the Nine Mile Creek Watershed District have detected high microcystin toxin levels in Lake Cornelia and are urging residents to avoid contact with the water due to public health concerns.

High blue-green algae levels were measured in recent samples by the Nine Mile Creek Watershed District.

High microcystin levels are typical with excess growth of blue-green algae. Follow-up toxicity monitoring was done to evaluate public health risk. The latest data indicates current microcystin levels present a public health risk. High microcystin toxin levels were also detected in the lake last September.

Exposure to microcystins may harm the liver and be harmful to kidneys and, in extreme cases, death.

Symptoms of poisoning include jaundice, shock, abdominal pain/distention, weakness, nausea and vomiting, severe thirst and rapid or weak pulse. If you begin to notice symptoms in you or another person, contact your health care provider; in animals, contact your veterinarian. People and pets should not come into contact with the water until they are notified that it is safe.

Blue-green algae are a type of cyanobacteria present at low levels in many Minnesota lakes and ponds. When water is stagnant, warm and rich in nutrients – especially phosphorus – cyanobacteria can grow quickly, forming “blooms.” These blooms typically look like pea soup or bright green paint. They can produce a strong, swampy odor as the cyanobacteria breaks down.

“The city is working to minimize invasive aquatic plants in Lake Cornelia and promote the growth of a healthy native aquatic plant population to ‘tie-up’ phosphorus, making less of it available for cyanobacteria and other algae to grow,” said City of Edina Water Resources Coordinator Jessica Vanderwerff Wilson.

According to Nine Mile Creek Watershed District Education and Outreach Program Manager Erica Sniegowski, this is a common urban water quality issue.

“Our infrastructure was designed to collect runoff from streets,” Sniegowski said. “This runoff flows untreated to local bodies of water. Pollutants gather in these areas and often create high levels of phosphorus, which can lead to harmful algal blooms.”

Lake Cornelia is treated for algae up to twice per year by lake management companies. Even after algae treatments, residents should exercise caution. When cyanobacteria cells die, the toxins present in the cells are released into surrounding waters. Some toxins are very stable and can remain in the water for days or weeks after the bloom has disappeared, according to watershed district officials.

Once a toxin is in the water, it is generally not feasible to remove the toxin from the lake and, hence, the toxin remains in the lake until it disappears naturally. Algal toxins disappear naturally when they are broken down by bacteria and light. The time period of the breakdown varies from a few days to several months.

The watershed district will continue to monitor the lake until toxin levels drop.

For more information, contact Wilson at 952-826-0445 or Sniegowski at 952-358-2276.