A deep dive on Lake Erie’s algae blooms

blue-green algae, cyanobacteria by the shore mivod/Shutterstock

If you’re spending any time swimming, boating, or fishing on Lake Erie in the summer and fall, you need to be aware of algae blooms. According to the National Ocean and Atmospheric Foundation (NOAA), harmful algal blooms, or HAB, can release toxins that impact drinking water quality and cause health problems for both people and pets.

NOAA and partner agencies release an annual forecast in July, the Lake Erie Harmful Algal Bloom (HAB) Forecast, to help community members prepare for potential harmful blooms.

The Lake Erie HAB Forecast consists of a measurement on a severity index that ranges from one to ten. A press release from the Ohio Sea Grant on the 2020 forecast states that the severity index is based on the bloom’s biomass, or the amount of algae, over a sustained period. Anything over a five is considered a severe bloom.

But the numbers on the severity index aren’t an area measurement. The severity index compares each year’s bloom relative to the last two decades of blooms, says Dr. Christopher Winslow, Director of the Ohio Sea Grant College Program, in a phone call with Cottage Life. 

The bloom that occurred in 2011 has the honour of representing ten on the severity index. “2011 was a very, very bad bloom,” Winslow says. “2011 was like, oh god, it can’t get any worse than 2011. Every bloom is now gauged relative to that.” 

The forecast, which NOAA releases annually on the second Thursday of July, is to prepare people for what the summer might look like, says Winslow. The number tells you, relative to the last two decades, is it going to be a good year or a bad year, he says. It can help cottagers plan how much time to spend on the lake, and indicate whether grocery store owners should stock up on bottled water.

After the early forecast is released, NOAA provides a bulletin every Tuesday and Thursday with an actual satellite image indicating bloom size and position. People are encouraged to subscribe to the bulletin and use it for day to day decisions regarding their time on the water, says Winslow.

In a presentation during the Stone Laboratory Lake Erie Summit in October, Winslow reported that the 2020 bloom severity was slightly lower than what was forecasted. The bloom was projected to range between a 4.0 and 5.5 on the forecast’s severity index, but ended up a milder 3.0 as reported by NOAA’s Western Lake Erie HAB Seasonal Assessment.

Generating the annual forecast is a team effort. “For us to be able to accurately estimate how big these blooms might be in the summer, we need to know how many nutrients made it into the lake,” says Winslow. The primary driver for nutrients entering the lake is the Maumee River on the far west of Lake Erie. This nutrient-rich river is the largest tributary not only of Lake Erie, but of all the Great Lakes, says Winslow. 

“One of the things that needs to occur for us to do this forecast is to know the amount of water coming out of that river,” says Winslow. That information is provided by Heidelberg University in Tiffin, Ohio, home of the National Center for Water Quality Research. Gauges placed throughout the river tell researchers at the university the amount of nutrients, primarily phosphorus, that enter Lake Erie from the first of March to the end of July. This information is sent to NOAA and other university partners, who use forecast models to develop the annual severity index. 

The majority of nutrient flow into Lake Erie comes from agricultural land. But cottagers can do their part to reduce nutrient run-off into the water. To start, cottage owners with septic tanks need to keep an eye out and make sure their systems are running ship-shape. “Not all of those are functioning the way they should,” says Winslow. “Make sure your septic system isn’t leaching nutrients into the lake.”

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Gardeners should avoid purchasing and applying fertilizers with phosphorus. “All you need is nitrogen and potassium,” says Winslow. “There’s already enough phosphorus in the soil already.”

If you need further convincing, certain design changes that reduce the flow of nutrients into the lake can save a cottage-owner money and improve the property’s aesthetics. Install gutters to divert water from a cottage roof into a rain barrel, and you’ll reduce the chance of flooding and have a fresh supply of water for the garden. If your property has a natural depression in the soil where water pools, you can plant a rain garden. Planting native shrubs and flowers will absorb and hold water like a sponge, and be beautiful to boot. 

“You can have nutrients in your soil or in your farmer’s field, but if nothing carries it from the field to the lake you don’t have a problem,” says Winslow. “It’s the movement of water off the landscape that drives those nutrients from the soil into the lake.” 

Read more: Environmental groups call on province, feds to fight Lake Erie algae blooms

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