Western Lake Erie algal bloom grows to 620 square miles, largest this summer

The western Lake Erie algal bloom is now the largest it’s been this summer, covering 620 square miles.

And it’s unclear if it’s reached its annual peak yet.

Blooms can linger into October. One nearly lasted until Thanksgiving a few years ago.

The National Oceanic and Atmospheric Administration predicted a moderate bloom when the summer began.

But large mats of cyanobacteria — the scientific word for harmful blue-green algae capable of producing toxins that can make humans and animals sick — are seen via satellite from Monroe to Huron, Ohio.

The densest concentrations are in the lake’s open water between Monroe and Toledo, with patches of high-intensity blooms along the shoreline near Maumee Bay State Park and halfway between Toledo and Port Clinton.

Sandusky Bay has a local bloom of mixed cyanobacteria, NOAA said.

Toxin levels are above safe recreational levels in many areas, according to the agency. It reminded people to keep themselves and their pets out of scum.

A new contact advisory for Maumee Bay State Park’s Lake Erie beach was issued Monday morning by the Ohio Department of Natural Resources.

Rick Stumpf, an oceanographer in NOAA’s National Centers for Coastal Ocean Science, which leads bloom-tracking efforts, said this year’s bloom is actually producing less toxin than other years with similar concentrations.

It’s drawing more attention now that it has expanded to 620 square miles.

Less than a week ago, it was 130 square miles.

“There have certainly been larger amounts in other years, but anything above 100 square miles will draw attention,” Mr. Stumpf said.

Justin Chaffin, Ohio Sea Grant and Ohio State University Stone Laboratory research director, said the bloom “has intensified throughout August.”

South Bass Island State Park is another spot where toxins have been found, he said.

“The north winds today and tomorrow will concentrate bloom biomass and microcystins [algal toxins] on the Ohio coast,” Mr. Chaffin said.

Little, if any, of the bloom has been spotted along the Ontario shoreline or Canada’s open Lake Erie water for much of the summer. Nearly all problem areas have been in U.S. water.

George Bullerjahn, a Bowling Green State University emeritus professor with a research focus on Lake Erie’s Sandusky Bay, said the mixed bloom inside the bay has low toxicity.

The bay’s water is green, but it has no dominant species of cyanobacteria, he said.

Tom Bridgeman, University of Toledo Lake Erie Center director, could not be reached for comment.