Algal blooms in Lake Erie are expected to be smaller than average this summer, according to the National Oceanic and Atmospheric Administration’s Harmful Algal Bloom Forecast published Thursday.
Blooms in 2023 are forecast to measure three on the severity index with a possible range of two to 4.5. The number is a bit lower than the predicted 3.5 measure in 2022 with a range of two to four.
“We’re really good at predicting low versus high bloom, which is great for advance warning,” NOAA Chief Scientist Sarah Kapnick said. “The forecasts have accurately provided early warning of major blooms like those in 2015, 2017 and 2019, and forecasted smaller blooms in years like 2012 and 2020.”
The index is based on the number of algae in the bloom during its peak 30 days, according to the news release.
“An index above 5 indicates more severe blooms. Blooms over 7 are particularly severe, with extensive scum formation and coverage affecting the lake,” the release states. “The largest blooms occurred in 2011, with a severity index of 10, and 2015, with a severity index of 10.5.”
The forecast is based on phosphorus discharge from the Maumee River and satellite image analysis, Kapnick said. The forecast allows local officials, lake users and water treatment facilities to make informed decisions about water quality and bloom severity.
“Having this type of information is really critical to be able to deal with the challenges that we have of extreme weather events in our ... communities, and being able to have this information in advance allows us to build up operational plans when we have a severe HAB,” which is a harmful algal bloom. “This type of science, this information, these seasonal forecasts are really useful for reducing the impacts of these types of events.”
Algal blooms are created by excessive amounts of phosphorus that enter waterways, and they can produce toxins like microcystin, a known liver toxin, which decreases water quality and presents danger to humans and animals. In 2014, half-a-million Toledo residents were left without water to drink and cook with due to toxins from algal blooms in Lake Erie.
Size vs. toxicity
The size of the algal blooms doesn’t determine the toxicity, said Tom Zimnicki, agriculture and restoration policy director with Alliance for the Great Lakes.
“Even small blooms or mild blooms still impact tourism, they still impact recreation, and bloom size is not necessarily correlated with toxicity of the bloom,” he said. “You could have a smaller bloom that is highly toxic, and so that obviously has all sorts of human health impacts that … large blooms might not necessarily have.”
The forecast is a helpful prediction for the extent of algal blooms in the lake, but Zimnicki said conditions can still change.
“We have seen in previous years where blooms were predicted to be mild to moderate (and) they ended up being considerably higher or more substantial than what was predicted. We've seen blooms be mild and moderate, but have … extended through the calendar year much longer than what we had previously seen,” he said. “So, the number is a good initial indication of where we're at or what we can expect, but it is not something that I think people should … necessarily take to the bank.”
Though the 2022 HAB Forecast predicted blooms at a 3.5 severity level, Rick Stumpf, an oceanographer with NOAA’s National Centers for Coastal Ocean Science, said the predictions were a “bit of an underestimate” largely due to phosphorus loads in July. Last year's blooms reached a severity of 6.8, according to the 2023 forecast.
“What we're seeing is not too surprising ecologically. The blooms are developing in July and where you get a pulse of nutrients in and all of that is potentially available to them, perhaps more so than the spring blooms -- the spring load,” Stumpf said. “We do have to pay more attention to these July loads coming into this, and so we think that's one of the key factors.”
Ohio experienced a fairly dry season in May with few severe rain events and two to three fewer cumulative inches of rain water overall. Rainfall in July would increase the likelihood of moderate blooms measuring four to 4.5 on the severity index.
Blooms are common in Lake Erie’s Western Basin due to water temperature and the amounts of nutrients flowing into the lake from the surrounding area. Phosphorus enters Lake Erie and other waterways when it rains, and excess fertilizer and manure on farms forms phosphorus-rich runoff.
Though conditions in the central and eastern basins of the lake make algal blooms less prevalent when compared to the eastern basin, bloom size and location can vary due to wind, the forecast states.
“The areas with high bloom concentration have the greatest risk of scum,” Stumpf said. “Keep yourself, your kids and your dogs out of the water to see scum or if the water looks green. It is dangerous.”
Ohio is unlikely to reach phosphorus reduction goals
Phosphorus runoff from agriculture contributes upwards of 89% of the annual total phosphorus load in the Western Basin, according to a report by Alliance for the Great Lakes and Ohio Environmental Council.
In 2015, Ohio Lt. Gov. Mary Taylor, Michigan Gov. Rick Snyder and Kathleen Wynne, the premier of Ontario, signed a collaborative agreement committing to reduce the levels of phosphorus entering the western basin of Lake Erie by 40% over a 10-year period.
But conservation practices are not being widely adopted in the agricultural industry, Zimnicki said. Because of this, Ohio and Michigan are not on track to meet those goals.
“I don't think anybody at this point is under the illusion that we are going to hit that target,” he said. “Certainly, now here in 2023, we have no shot of moving that from … the non-point source community within the basin.”
Regardless of severity, Zimnicki said algal blooms of any kind can affect those who rely on the lake for water, recreation and more.
“Even in mild and moderate years, this still impacts communities,” he said. “This is still an issue for folks that rely on the lake for any number of reasons.
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