NOAA: The 2021 algal bloom is taking hold along western Lake Erie shoreline

Aug. 4—Barely noticeable a few days ago, western Lake Erie's 2021 algal bloom has grown in intensity and is hugging the shoreline from Toledo almost out to Sandusky.

In its latest bulletin, the National Oceanic and Atmospheric Administration said Wednesday the bloom "has intensified along and near the Ohio coast east of Maumee Bay to near Catawba Island."

The observations are based on satellite imagery provided by the National Aeronautics and Space Administration.

While the bloom in general is not believed to be highly toxic, people are urged to keep themselves and their pets away from it because toxins can become concentrated in various high-density patches, which NOAA calls scums.

"If you see scum, keep your pets and yourself out of the water," the agency said.

Conditions can change rapidly based on wind strength, direction, and mixing. But for now, the only toxins detected in field samples have been below the recreational threshold for body contact with the water, NOAA said.

The bloom has fanned out to an area of about 180 square miles.

Lower concentrations of algae are also visible east of Sandusky, past Huron, Ohio.

Lake Erie's open water and the lake's Sandusky Bay usually have two different species of cyanobacteria, or blue-green algae, called microcystis and planktothrix, respectively. But both produce the same toxin, microcystin.

Planktothrix usually arrives earlier and stays longer in Sandusky Bay, and it is not as dependent on phosphorus as is microcystis. For reasons unknown, relatively little planktothrix was seen until recently.

NOAA said in its latest bulletin that "traces of cyanobacteria are detectable in Sandusky Bay" now.

Tim Davis, a Bowling Green State University scientist whose research focus includes Sandusky Bay, said there's still surprisingly little algae there.

"There has been some cyanobacterial biomass just outside the mouth of the bay, which has also been seen via remote sensing. But, for now, the bay is still bloomless, which is overall a good thing."

Toxin-producing cyanobacteria, such as microcystis and planktothrix, form what is commonly referred to as "harmful algal blooms," or HABs.

On June 30, NOAA — in collaboration with scientists from several universities and research groups — released its official forecast for the Summer 2021 algal bloom.

It said this year's bloom is expected to be as small as last year's and relatively mild overall. If that prediction holds true, it would mark the first time in more than a dozen years that relatively mild blooms have occurred in consecutive summers.

This year's forecast is for a bloom with a severity index of only 3 on a scale of 1 to 10, with 10 being the highest.

The forecast was based largely on a dearth of precipitation in March and April. But it's unclear now if it will have to be revised upward because of recent searing, persistent heat and an unusually wet July.

Rick Stumpf, a NOAA oceanographer who oversees the forecasts, said July's heavy rain has "made a slight, and non-significant increase in potential severity, within the margin of error of the original and current forecasts, so we are staying with the June 30 forecast."

The window of time scientists focus on when predicting algal blooms is March 1 through July 31. There is usually a greater emphasis on the spring because of the planting, fertilization, and other activity on farms then.

"Heavy rain in July produces less discharge than the same rain in April or May, because of increased evapo-transpiration from corn (and soybeans), which can remove the equivalent of several inches of water from the soil," Mr. Stumpf explained. "If June had been especially wet, leading to already sodden soil, July rains would have had a bigger impact on discharge and load."

He also noted that rainfall was scattered across northwest Ohio, with some areas wetter than others.

Agricultural runoff is still considered the primary source of nutrients for growing algae in western Lake Erie and its tributaries, even with revelations that Maumee for years illegally discharged its excess sewage into the Maumee River, and several public officials now questioning if others have, too.

Blooms have started earlier in recent years because of changing weather patterns that have warmed up the lake earlier than in years past, Mr. Stumpf said.

"But we have had previous years where it developed mostly in August," he said. "The slightly cooler water temperatures this year probably caused this somewhat later start. In the past, that has not affected the final size."

Tom Bridgeman, director of the University of Toledo's Lake Erie Center, said the summer bloom still has a ways to go before it peaks.

"This year is reminiscent of 2015, when July rains flushed water out of Maumee Bay and pushed the early bloom out toward the islands. The new water in Maumee Bay eventually bloomed as well, a week or two later," Mr. Bridgeman said.

Even though 2015 ended up being the largest bloom since NASA satellite surveillance began in 2002, Mr. Bridgeman said he too doesn't expect this year's to get that large.

"I don't expect anything like the 2015 bloom, but I think the bloom will be at the upper end of the NOAA prediction or a little higher," he said. "If my lawn likes these conditions, so will the microcystis."