The National Oceanic and Atmospheric Administration projects this year’s harmful algal bloom in western Lake Erie to be moderate. 

The agency monitors the lake for potentially hazardous algae growth every spring and summer.

NOAA researcher Rick Stumpf says cyanobacteria thrive in the lake’s warm, shallow environment. He also says they feed on phosphorus, a key ingredient in farm fertilizer.

Stumpf says rain can wash phosphorus from farm fields in northwest Ohio into the Maumee River, which runs through Toledo.

“It is most of the water into the western basin of Lake Erie, where these blooms form,” he says. “It warms up quickly, which these algae like, and it allows the phosphorus to stay at a fairly high concentration, which favors them.”

Early rain provides a clue

Based on the amount of phosphorus already in the lake, Stumpf projects this year’s bloom will range between mild (2.5) and severe (5.5) on a scale of 1 to 10. Last year’s bloom was mild (2.4). At its peak, it covered more than 400 square miles.

Lake Erie has not experienced a severe bloom since 2019.

The key to controlling harmful algal blooms is reducing the amount of phosphorus that feeds them.

Stumpf says injecting the chemical directly into soil instead of spreading it on top could make a big difference.

“Injecting phosphorus into the soil help keeps it on,” he says. “There’s also a big push on testing because if there’s enough phosphorus in the soil, you don’t need to add it.”

Blooms can be toxic

Cyanobacteria can produce microcystin, a toxin capable of sickening people and pets. In 2014, microcystin contaminated Toledo’s municipal water system. That left more than 400,000 people in northwest Ohio and southeast Michigan without drinkable water for several days.

Stumpf says pets are especially susceptible to microcystin poisoning. Many dogs who ingested contaminated water have died.

He advises people to keep their pooches out of the lake if they see a bluish-green scum or something like sawdust floating on the surface.

“Keep in mind its mouth is going to be right in the water, and then they often lick their fur when they’re done,” he says.

Stumpf says if the water looks fine, don’t worry about it.

NOAA updates its harmful algal bloom projections every week.