Now that another western Lake Erie’s algae season is finally over, scientists will spend the next several months taking heed of what just happened in hopes of making the region more resilient to climate change impacts they believe are here now.

This year’s bloom looked for a while like it might be the second consecutive year in which thick clumps of green scum lingered well into November, something that’s never happened, at least not in modern times.

Alas, it fell just short.

Although this year’s bloom started to fade by mid-October, the National Oceanic and Atmospheric Administration said in its weekly bulletins it was difficult to tell how much was still out there because of cloud cover that obscured satellite images.

Strong winds promoted mixing, but the agency didn’t rule out the presence of cyanobacteria, the scientific name for what people commonly refer to blue-green algae, until it issued an Oct. 30 email that stated the 2023 bloom season was finally over.

But even Rick Stumpf, an oceanographer in NOAA’s National Centers for Coastal Ocean Science in Silver Spring, Md., hesitated slightly this past Monday afternoon when asked if there was any algae still out there when Nov. 1 rolled around. Mr. Stumpf runs NOAA’s Lake Erie program from that office.

“Were there cyanobacteria cells? Yes,” he replied.

But he later made the point that the threat had long vanished.

Toxin strength always diminishes near the end of a bloom, though the public is advised to stay away from, and keep their pets out of, anything that looks like algal clumps no matter when they see it.

Fall winds across the lake are usually so strong that remaining parts of the bloom don’t hang together. It’s possible, though unlikely, that could change if the winds die down and the temperatures rise, Mr. Stumpf said.

He said in a follow-up email there were just traces of this year’s bloom left by Oct. 17.

Last year was a different story, though.

The 2022 bloom was still going as of Nov. 19 that year.

For the first time in modern history, it hung around longer than NOAA’s funding for surveillance. The federal agency said on Nov. 19, 2022 it knew enough about that year’s bloom to rank it as a 6.8 on its 10-point severity scale, which is considered moderately severe. It then suspended monitoring it until it formed again this past summer.

In a 47-minute interview with The Blade, Mr. Stumpf said that NOAA sees signs of climate change in how blooms have been forming and reacting in recent years. One of the biggest differences is that, on average, they form sooner now than they did a decade ago, he said.

“The blooms are changing,” Mr. Stumpf said.

Various theories are being explored, including the rate in which zooplankton gobble up the so-called “good algae” particles known as diatoms. Both diatoms and zooplankton are part of the aquatic food chain that makes its way up to Lake Erie fish.

With the heat-dependent, summertime “bad” algae known as microcystis forming earlier, that can pave the way for a longer bloom season when it peters out and gives way to another form of bad algae.

This year’s bloom ended up being ranked as a 5.3 on the 10-point severity index, which made it a somewhat average-sized bloom yet still worse than the 3.0 ranking it was expected to get when the summer began.

The lesson from that, Mr. Stumpf said, is there is a continued need to keep tweaking the summer forecasting system that NOAA does with several universities, including Ohio State University, Heidelberg University, and some as far away as Stanford University in California.

The severity index is based on bloom biomass and intensity over the worst 30 days.

One key difference now is that blooms appear to be reaching some sort of elongated and lingering plateau, instead of a more rapid peak and fall, Mr. Stumpf said.

“The blooms used to be more peaked. Now, they’re more plateaued,” he said.

The earlier arrival is as puzzling as the late exit, Mr. Stumpf said.

“It’s reasonable to say these factors are caused by climate change,” he said.

Another puzzling aspect of the blooms is where they go.

Though they’re always more likely to be found in the warmest, shallowest water near Toledo, they’ve been hugging the Monroe-to-Port Clinton shoreline.

Mike McKay, a former Bowling Green State University researcher now running the University of Windsor’s Great Lakes Institute for Environmental Research, jokingly quipped, “Wait, there was a bloom this year?”

That’s because Canada experienced relatively little of it.

Mr. McKay’s longtime colleague at BGSU, George Bullerjahn, said there was a minor presence of a toxin-producing algae in Sandusky Bay this summer. But, once again, he’s baffled why so little of it, compared to other species.

Planktothrix for years dominated Sandusky Bay, but has been largely absent for about four years now, Mr. Bullerjahn said.

NOAA satellite imagery did show a separate bloom of mixed species in the bay for much of the summer, though.

Justin Chaffin, research coordinator for Ohio Sea Grant and OSU’s Stone Laboratory, said moderate-sized blooms such as this year’s seem to be “the hardest to forecast accurately.”

“There are a lot of factors that play out in the lake, but the models do not account for these yet,” Mr. Chaffin said, citing nitrogen, light and water clarity, and competition with other algae as factors beyond the usual focus on phosphorus runoff.

Gregory Dick said that a researcher who works for him at the University of Michigan’s Cooperative Institute for Great Lakes Research told him the timing of phosphorus runoff to the Maumee River this year was “particularly unusual” because of dry or near-drought conditions from April to June.

“While that’s not unprecedented within the period or record, it likely affected the seasonal progression of the bloom and would not match expectations based on more ‘typical’ years,” Mr. Dick said.

University of Toledo Lake Erie Center Director Tom Bridgeman agreed it “was a pretty typical bloom year overall,” yet “denser than usual” in Maumee Bay.”

First Published November 8, 2023, 12:37 a.m.