Lake Erie harmful algal bloom likely to be mild this year, researchers say

A dock at Lake Erie
(Farm and Dairy file photo)

Researchers are expecting a relatively mild harmful algal bloom in Lake Erie this summer. This follows a similarly mild bloom in 2020.

“For the first time in a decade, we’re actually looking at two consecutive years with a relatively mild bloom,” said Rick Stumpf, the National Oceanic and Atmospheric Administration’s lead scientist for the seasonal Lake Erie bloom forecast, in a June 30 forecast.

That’s mostly attributed to a fairly dry spring. Harmful algal blooms are caused by nutrient runoff from farmland, mostly. Less water going into the lake means less nutrients, too. But the concentration of nutrients in that water isn’t lower this year. Still, as water quality efforts in Ohio continue, researchers are hoping to see improvements for Lake Erie.


This year’s bloom is forecast to be at a 3 on the severity index, a scale of 1-10 where anything over 5 is considered a more severe bloom, but could range anywhere from 2-4.5, depending on other factors.

“Most of the lake will be fine most of the time, even though there will be some bloom in the lake,” Stumpf said.

Last year, the forecast predicted a severity of 4.5, but the actual bloom was only at a 3. Researchers made adjustments to several models after the 2020 season to try to improve the accuracy of this year’s forecast.

The index predicts the size of the bloom, but not how toxic it will be. Larger blooms aren’t necessarily more toxic — while phosphorus runoff affects bloom size, nitrogen runoff influences the toxicity. Researchers are still working on tools to predict how toxic a bloom will be.

Wind has a big impact on where the blooms end up and how long they stay. On calm days, Stumpf said, some areas may see scum in the water. People and dogs should avoid swimming in scum, he said.


The amount of phosphorus going into the lake this year should be close to target, based on the Great Lakes Water Quality Agreement goal of reducing the phosphorus going into the lake by 40% by 2025. But phosphorus concentrations in water flowing into Lake Erie are still well above targets.

“We’re meeting the target mostly just because it’s a dry year,” explained Laura Johnson, director of the National Center for Water Quality Research, at Heidelberg University.

The last couple of years suggest a trend towards hitting water quality targets. But Johnson urged people to keep context in mind. This year and 2020 both were relatively dry.

And even though 2019 was a very wet year, many farmers were unable to get into their fields to apply fertilizer and plant in the spring. That year, the water flow was well above average, but phosphorus concentrations were lower, since there was less farming activity.

It’s possible that we’re headed into a drier period now, after a period of several wet years, Stumpf said. But though the area cycles back and forth between dry and wet periods, the wet periods seem to be getting longer over time — consistent with climate change patterns in the area.

Unless phosphorus concentrations also go down, the area will see larger harmful algal blooms again the next time there is a year with heavier rainfall, he said. And even though there’s already a smaller bloom forecast for this year, if concentrations were also on target, there may be almost nothing this year.

“We would have a clearer, cleaner lake overall if we were able to reduce that target,” Stumpf said.


Still, the last few years have taught researchers a lot. The bloom in 2019 was fairly severe, but if phosphorus concentrations had been average that year, instead of lower, due to less farming activity, it would have likely been one of the worst blooms the lake has seen.

That means more farmers adopting conservation practices, like soil testing, cover crops and applying fertilizer below the surface instead of on top, could have a fairly quick impact.

“If we do those 4R practices … 2019 showed us that if those practices are happening, you can see a pretty quick reduction,” said Christopher Winslow, director of Ohio Sea Grant and Stone Laboratory.

Many seem to be hanging their hopes on H2Ohio, the state’s water quality initiative, which includes funding to help farmers in the Western Lake Erie Basin adopt nutrient management plans and best management practices to reduce phosphorus runoff into the lake. Farmers have enrolled a million acres in the voluntary program — nearly 44% of Maumee River Watershed cropland.

It’s likely still too early to really see the full impact of H2Ohio programs, since many farmers in the program are just getting started on implementing practices, Johnson said. But she and other researchers said the 2019 season suggests programs like H2Ohio could have a significant impact on Lake Erie’s water quality in the near future.

“That nutrient management, I think, is going to be really key,” she said.


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