Lake Erie's 2021 algal bloom is finally gone and was worse than expected

TOLEDO — Finally, it's over. Western Lake Erie's 2021 algal bloom wasn't the most serious, but it ended up being worse than expected and — thanks to an unusually warm October — was so resilient it threatened to last into November. Rick Stumpf, a National Oceanic and Atmospheric Administration oceanographer who coordinates and oversees bloom research from NOAA's National Centers for Coastal Ocean Science in Silver Spring, Md., told The Blade that Sunday's satellite imagery was the first time there wasn't enough bloom left to be seen from outer space since the algae began matting up in July. In its seasonal wrap-up issued Monday, NOAA said it has calculated the 2021 bloom as "moderately severe" and gave it a ranking of 6.0 on a scale of 10. That leaves it tied with the 2010 bloom as the eighth most severe since such calculations began in 2002. But it was worse than expected, too, fanning out across 530 square miles at its peak. "The bloom was less concentrated, but more spread out across the western basin and spilling into the central basin," Justin Chaffin, Ohio Sea Grant and Ohio State University Stone Laboratory research coordinator, said. NOAA, with help from numerous other government, university, and privately employed researchers, predicted in late June that the 2021 bloom would have a severity index of 3.0, with a low-to-high range of 2.0 to 4.5. Stumpf said the worse-than-expected result will prompt researchers to fine-tune their prediction modeling in the off-season, with possible changes to the severity index. "We will be revisiting the severity metric," he said. The science for such forecasts has been evolving since western Lake Erie's modern era of blooms began in 1995. NASA began sending NOAA weekly satellite imagery in 2002. There also are periodic flyovers with planes, and observations at the surface level by boat. The imagery has been coming from the European Union's Copernicus Sentinel-3 satellites in recent years, sophisticated enough to provide digital looks at algae as it forms into scum beneath the lake's surface. The Severity Index NOAA and others develop reflects the amount of bloom biomass over the peak 30 days of each season. It takes into account the density and dispersion across the lake. One of the biggest variables it is unable to consider are changes in wind speed and direction each season, Stumpf said. This year's bloom developed slower than some in the past, forming in late July. It peaked from late August to early September, mostly on the U.S. side of the lake and primarily near the shoreline between Monroe and Sandusky, while also spreading out at times into the open water past the Lake Erie islands, NOAA said in its seasonal assessment. It re-intensified near the Michigan coast at the end of September, the agency said. "The bloom lasted longer than recent years, through the end of October, which was likely due to persistent warm water temperatures," NOAA said. Toxic microcystin was detected throughout the season, but at lower concentrations than some years, NOAA said. A larger bloom does not necessarily equate to a more toxic one. The 2021 bloom was twice as bad as the 2020 bloom, which was ranked as a 3.0 on NOAA's Severity Index. Each season's forecast is based on an ensemble of models, each of which considers actual and anticipated phosphorus loading into the lake between early March and late July. "The large bioavailable phosphorus load in July, 2021, the third highest since 2008, may have led to the larger than forecasted bloom," NOAA said. This year's ensemble included work from NOAA, Heidelberg University, the University of Michigan, Stanford University, and the Washington-based Carnegie Institution for Science. Researchers from North Carolina State University, the University of Toledo, Ohio State University, and Ann Arbor-based LimnoTech also contributed. The region had a drier-than-average spring this year, which NOAA said suggests "the relative importance of July loads on the bloom." "We will continue our assessment of the models in order to make improvements to the forecast and severity metrics," NOAA said. The most severe bloom on record is the one from the Summer of 2015. Similar modeling is being considered for other algae-prone parts of the Great Lakes region, such as Saginaw Bay and Green Bay. The forecasts and monitoring are important to water-treatment plant operators, charter fishing boat captains, ecotourism, and other businesses that depend on water quality. George Bullerjahn, director of Bowling Green State University's Great Lakes Center for Fresh Waters and Human Health, said it's still unclear why Lake Erie's Sandusky Bay had a smaller bloom than it has in the past. In years past, Sandusky Bay has been overwhelmed by a different type of toxin-producing algae, plantothrix, than the most dominant type in other parts on the lake, microcystis. Both produce the toxin known as microcystin, which has the potential of being fatal to humans and their pets if ingested in large doses. In a related matter, the office of U.S. Sen. Sherrod Brown (D., Ohio) announced the release of more than $1.5 million of additional federal money to advance research into Lake Erie algal blooms. The University of Toledo has been awarded $715,992 to develop and test the use of microcystin-degrading bacteria in water-treatment plants. A $323,191 grant will be split between BGSU, LimnoTech, MBio Diagnostics, Ohio State, the University of Toledo, and the University of Michigan to create portable toxin-detection monitors. A $303,503 grant is being split between MBio Diagnostics, BGSU, and State University of New York to enhance existing technology for rapid, portable devices. And the Great Lakes Observing System is receiving $200,000 to upgrade existing instrumentation to improve telemetry and harmful algal bloom data integration. The money is coming from NOAA. ___ (c)2021 The Blade (Toledo, Ohio) Visit The Blade (Toledo, Ohio) at www.toledoblade.com Distributed by Tribune Content Agency, LLC.