PUT-IN-BAY, Ohio — For the third year in a row, Lake Erie is expecting a below average algal bloom this summer, due largely to less heavy rainfall.
This is the third consecutive year the National Oceanic and Atmospheric Administration has forecasted a lower than average bloom. In 2021, the bloom was more severe than forecasted, suggesting that July rainfall may play a role in Lake Erie’s algal blooms.
Because algal blooms can be caused by phosphorus runoff from farm fields, the amount of rain plays a part in what the bloom looks like each year.
“When the flow is really high, we have very high loads. When the flow is low, we have low loads,” said Laura Johnson, director of the National Center for Water Quality Research at Heidelberg University, at the June 30 forecast.
Researchers at the forecast, hosted by Ohio State University’s Stone Laboratory and Ohio Sea Grant, at Put-In-Bay, said they are not seeing the impacts of conservation programs like H2Ohio in stream monitoring or in the lake yet. But even though the impacts aren’t clear yet, farmers are making progress with getting better nutrient management practices on the ground.
“There’s phosphorus running off [that was] not applied in that year,” Johnson said. “Which means that that’s where that patience has to come in.”
NOAA is expecting an algal bloom with a severity of 3.5, though it could range from 2 to 4. Anything over a 5 on the severity index, which is a scale of 1 to 10, is considered a more severe bloom.
That forecast is based partly on the forecast for rain in July. Right now, July rain is expected to be about average.
In 2021, researchers forecasted a bloom severity of 3, but the bloom wound up being a 6 on the severity index. That may have been because there was more rain than originally expected in July, though because the spring was not also extremely wet, the bloom was not as severe as some years.
The forecast relies partly on looking at rainfall in the spring and early summer, but now, “we think … that July matters a bit more,” said Rick Stumpf, of NOAA’s National Centers for Coastal Ocean Science.
NOAA is planning to release a forecast update at the end of July, based on the rainfall in the area that month. The amount of wind later in the year will also affect how long the algal bloom sticks around, and where exactly it ends up in the lake.
Part of the algal bloom issue in the last few decades comes from heavier and more intense rainfall in Ohio.
“There’s some evidence now coming out, we’re getting heavier rainfall events, and this is very likely a climate impact,” Stumpf said. “And when you have heavier rainfall, the soil cannot absorb it as well.”
The phosphorus load is the amount of phosphorus going into the lake. That is affected by the amount of rainfall. But the concentration of phosphorus in the water running into the lake also matters.
Ohio should be about on target for the phosphorus load based on the Great Lakes Water Quality Agreement goal of reducing the phosphorus running into the lake by 40% by 2025. But to keep hitting that target, especially in years with more rain, the concentration of phosphorus needs to be lower, Johnson said.
That’s partly what the H2Ohio program, and a few other conservation efforts, are trying to address. By changing practices around fertilizer management and water management, farmers can help reduce runoff. Restoring wetlands, another part of the program, can also help by filtering some of the water running into the lake.
Researchers said while they can’t yet detect a true downward trend in phosphorus runoff, they do expect to see the benefits of programs like H2Ohio and other agriculture conservation efforts in the future. They just don’t know yet when that will be.
Johnson said in 2019, most farmers did not get to apply fertilizer because of all of the rain. That year, they saw about a 30% decrease in the phosphorus load going into Lake Erie.
That wasn’t a typical year. But it suggests they might be able to see the impact of conservation efforts sooner than they originally thought.
But it also means about 70% of the phosphorus load is not from fertilizer applied in the same year. So it could be a while before researchers see a decrease in the amount of chronic phosphorus runoff from some fields.
Though the numbers this year don’t necessarily reflect changes on fields yet, that doesn’t mean the changes aren’t happening. In a June 30 release, the Ohio Farm Bureau Federation cited data from The Fertilizer Institute showing the amount of soil tests done in Ohio increased from about 69,000 in 2001 to about 274,000 in 2020.
About 3,000 farmers have enrolled in the H2Ohio program, with almost 2 million acres. That is about 40% of the Western Lake Erie Basin.
“Detecting those decreases that are going to be happening because of agricultural practices, you know, we have to have patience,” Johnson said. “That can take a crop rotation or more.”
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