They’re back.

Algae are growing in western Lake Erie as they do every year, posing a potential health threat to people and pets.

The National Oceanic and Atmospheric Administration monitors Lake Erie for harmful algal blooms. Each spring, it estimates how large and toxic they might become.

NOAA oceanographer Rick Stumpf tells WDET on a scale of 1 to 10 — with 10 being the worst — this year’s bloom should be relatively mild.

“Right now, we’re estimating between 2.5 and 4.5,” he said.

What is a harmful algal bloom?

According to NOAA, harmful algal blooms form when colonies of microscopic algae called cyanobacteria grow out of control, creating a bluish green scum on the surface of the lake.

“It looks quite green, almost like a green sawdust,” Stumpf said.

Under the right conditions, the algae produce a toxin that can make people sick if they swallow it. In 2014, a toxic algal bloom contaminated Toledo’s drinking water, shutting the system down for several days.

When it rains, it pours

Stumpf says the size and severity of a bloom depends on how much phosphorus the algae can feed on. The main source of phosphorus is farm fertilizer that runs off into the Maumee River when it rains. Stumpf says scientists take water samples from the river, which empties into the lake.

“We look at what comes down the Maumee River from the beginning of March through July,” he said.

The samples they’ve collected so far indicate a mild bloom this summer. But that could change depending on how much rain falls.

Click here to see the latest Harmful Algal Bloom forecast

“We’ll update this weekly until we come up with what we consider the official forecast in July,” Stumpf said.

Budget cuts threaten the lab’s work

NOAA and the Great Lakes Environmental Research Laboratory have been doing this work for decades. But the Trump administration has slashed jobs and funding at the agency, which also runs the National Weather Service. A ProPublica investigation found GLERL has lost a third of its staff since February 2025 and is struggling to buy testing equipment.

Stumpf says harmful algal bloom research is vital.

“Our goal is to protect health so that people are aware there are blooms and that there’s a risk,” he said.

But it’s not just people. Stumpf says toxic blooms can be fatal to pets.

“It does, unfortunately, kill several dogs each summer somewhere in the U.S.,” he says. “So, I can’t emphasize enough, if you see scum in a pond or the lake, please keep your dog out of the water.”

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