GRAND RAPIDS, Mich. (WOOD) — A stretch of hot weather has triggered algae blooms all across West Michigan, including on Lake Michigan.

Viewers have been sending News 8 reports of algae blooms all over West Michigan beaches that arrive one day and dissipate the next.

So are they dangerous? Dr. Alan Steinman with Grand Valley State University’s Robert B. Annis Water Resources Institute says there is some good news and some bad news about local blooms.


  • Algae on Lake Michigan is nontoxic.
  • Algae on inland lakes could be either toxic or nontoxic.
  • Algae blooms typically die off fast.
  • Algae blooms can reemerge, especially in areas with a high nutrients.


First and foremost, the algae on Lake Michigan is nontoxic.

“The algae that are forming here along the Michigan shoreline are filamentous green algae and they don’t look very nice — swimming in them you can get tangled — but they are not harmful. They are not toxic. They are just aesthetically a little unpleasing,” Steinman said.

This month, Muskegon saw its longest streak of 90-degree days on record. Grand Rapids has seen its longest streak since the year 2000. The surge of heat has caused the surface of Lake Michigan to jump 10 degrees warmer than average. The big lake is warmer now than the average during its typical temperature peak in late August and early September.

Current Surface Water Temperature of Lake Michigan in 2020 Compared to Average

Algae needs nutrients to form. While the middle of Lake Michigan lacks nutrients, the shores can have more, especially due to the circulation of currents where rivers dump into the lake. This is why you will only see algal blooms on the shoreline and not in open water.

Runoff is a big contributor to increasing nutrient content. In the 1960s, bursts of algae were much more common because there were looser restrictions on water quality.

“…In the ’60s and ’70s before we started to control runoff, filamentous green algal blooms were horrific back in then, so it’s nothing compared to what we saw 50 years ago,” Steinman said.


When it comes to inland lakes, Steinman said the type of algae that can bloom is much more diverse and needs to be approached with more caution.

“If you see a bloom forming on the lake, don’t go near it. Don’t let your pets down there to drink the water,” he said.

Algae is much more complex than many of us would think. Scientists are still working to study and define all the different kinds. Steinman said it is difficult to discern which blooms are harmful or toxic just by looking at them. He also said you can have two similar blooms on the same inland lake that have different levels of toxicity — some could be completely safe while others would be dangerous to ingest.

“We are still trying to figure out why some species trigger the toxins and others don’t,” he said.

This means that even if you have had decent encounters with an algae bloom on a lake, don’t think a similar-looking bloom will have the same toxicity content.


Storms and mixing will signal the death of algal blooms.

Turnover in Lake Michigan mixes nutrients and brings in colder water to the shores, making it hard for algae to survive.

For inland lakes, mixing and cooler temperatures also help in killing off the blooms. But keep in mind any bloom can pop back in again at any time, especially if the conditions are right.



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