Algae anxiety a false alarm

Duckweed washes up on the north end of Silver Beach in St. Joseph Thursday afternoon. A large patch of it floating in the lake this week had prompted concerns that it might be an algae bloom. Duckweed is not toxic.

ST. JOSEPH — The blue-green mass that has been floating on Lake Michigan near St. Joseph this week – suspected of possibly being harmful algae – wasn’t all it was quacked up to be.

Investigators believe that it is actually non-toxic duckweed, and not an algae bloom that can generate toxins in the water.

Officials from the Berrien County Health Department’s environmental division, the Michigan Department of the Environment, Great Lakes and Energy, St. Joseph and Benton Harbor water inspectors, and others have been busy since residents spotted the growth early this week about a mile off the shore at Lookout Park in St. Joseph.

Concerns were raised because of the potential for pollution from algae that gets out of hand. An algae bloom on Lake Erie has grown to 620 square miles.

Greg Alimenti, director of St. Joseph’s water treatment plant, went out in his boat Wednesday and took samples that he showed to Ann St. Amand, head of PhycoTech in St. Joseph and an expert on water quality.

St. Amand determined that the plant was duckweed, that likely washed into Lake Michigan from the Galien River, Alimenti said.

It’s easy to mistake the plant for something more harmful, Alimenti said. “It does look from a distance like blue-green algae.”

Much of the suspected duckweed had washed up along the shore at the northern end of Silver Beach by Thursday morning.

Gillian Conrad, spokesperson for the health department, also reported that the culprit is likely duckweed.

“From all the preliminary information that we are getting back, this actually looks like duckweed, a plant, not algae at all,” Conrad said in the email.

The good news is that the water is safe, she said. “We should have final results soon, but the lab samples are not suggesting the presence of any toxins at this point.”

St. Amand said that she took samples during a recent workshop, and the dominant algae she found was not toxic.

Harmful algae is more of a risk on inland lakes, St. Amand cautioned. If people see a green sheen on a lake or pond, they should find out what it is before allowing their kids, pets or livestock touch it, she advised.

Alimenti said that the state environmental experts were conducting the final tests for toxins.

Lake Michigan does have blue-green algae, Alimenti said, but in low concentrations.

Once it gets into a water system, it’s difficult to remove, he said. “It’s something we take seriously.”

Contact:, 932-0360, Twitter: @HPMatuszak