Skip to main content
Bridge Michigan
Michigan’s nonpartisan, nonprofit news source

Experts predict moderate Lake Erie toxic algae bloom

Green algae in Lake Erie
Every summer, toxic algae blooms form on Lake Erie, posing a health risk to humans and animals. (Courtesy National Centers for Coastal Ocean Science)
  • Scientists forecast a moderate harmful algae bloom on Lake Erie’s western coast this summer
  • Monroe is already seeing a small bloom forming on its coast, which is unusual the early in the summer
  • If you plan on visiting Lake Erie, experts warn to stay out of green scum or risk illness

Lake Erie’s annual algae bloom has begun to form weeks ahead of schedule off the coast of southeast Michigan, but scientists say they expect only a moderate bloom this year.

“There was scum off Monroe,” said Richard Stumpf, a National Oceanic and Atmospheric Administration oceanographer who leads the federal government’s bloom forecasting effort. “It’s not huge now, about 20 square kilometers, but it has actually started up in that area.”

Two satellites of algal blooms in Lake Erie
On June 24, harmful algal blooms were spotted on the coast of Monroe, an unusual sight this early in the summer. (Courtesy National Centers for Coastal Ocean Science)

Cyanobacteria, known as blue-green algae, fouls hundreds of square miles of western Lake Erie every summer, typically from July to October. The putrid, sometimes toxic blooms pose a risk to human and animal health and the region’s tourism economy.


Under the right conditions, they produce harmful toxins that can sicken humans and kill pets. 

The National Center for Coastal Ocean Science (NCCOS) released this season’s forecast on Thursday, predicting a bloom severity of 5 with a “potential range” of 4.5 to 6, similar to last year’s bloom of 5.3. 

2024 Lake Erie Seasonal Forecast
Scientists forecast a harmful algal bloom severity of 5, with a potential range of 4.5 to 6. (Courtesy National Centers for Coastal Ocean Science)

Moderate blooms have an index of 3 to 5, while an index above 5 indicates a more severe bloom. The highest severity index recorded in western Lake Erie was 10.5 in 2015. 

The green blooms thrive in warm, shallow water that’s overloaded with nutrients like phosphorus, which makes Lake Erie an ideal breeding ground.

Each year, the lake absorbs millions of pounds of fertilizer and manure runoff from farms in Ohio, Michigan, Indiana and Ontario. The problem has persisted despite decades of effort to fix it.

Polluted runoff is worse during heavy rainfall. This spring’s rainfall was average, leading to a moderate bloom severity forecast. 

Scientists said a heavy storm in the next few weeks could increase the forecasted bloom severity to as high as 7, but the chances of that happening are low.


Aside from rainfall, temperature also affects bloom formation. Stumpf said warmer temperatures this spring encouraged the bloom to form unusually early. 

NCCOS has monitored the blooms with satellite data since 2002. 

Although this year’s bloom is starting along Michigan’s coast, it’s not clear how much the algae will affect Michigan beaches this summer. Wind patterns this summer will decide what cities see the most blue-green algae, Stumpf said. 

His message to anyone who notices green scum in the lake: “Keep your kids, yourself, your pets out of the water.”

You can check the NCCOS website for the latest updates on harmful algae blooms, their location and severity. 

How impactful was this article for you?

Michigan Environment Watch

Michigan Environment Watch examines how public policy, industry, and other factors interact with the state’s trove of natural resources.

Michigan Environment Watch is made possible by generous financial support from:

Our generous Environment Watch underwriters encourage Bridge Michigan readers to also support civic journalism by becoming Bridge members. Please consider joining today.

Only donate if we've informed you about important Michigan issues

See what new members are saying about why they donated to Bridge Michigan:

  • “In order for this information to be accurate and unbiased it must be underwritten by its readers, not by special interests.” - Larry S.
  • “Not many other media sources report on the topics Bridge does.” - Susan B.
  • “Your journalism is outstanding and rare these days.” - Mark S.

If you want to ensure the future of nonpartisan, nonprofit Michigan journalism, please become a member today. You, too, will be asked why you donated and maybe we'll feature your quote next time!

Pay with VISA Pay with MasterCard Pay with American Express Pay with PayPal Donate Now