Moderate summer harmful algal bloom predicted for western Lake Erie

Scientists expect this year's bloom to measure 4.5 on the severity index. The 2018 bloom had a severity of 3.5. Photo: Ohio Sea Grant.

COLUMBUS, Ohio -- The National Oceanic and Atmospheric Administration and its research partners predict that western Lake Erie will experience a moderate harmful algal bloom this summer. This year’s bloom is expected to measure 4.5 on the severity index – among the smaller blooms since 2011 – but could possibly range between 4 and 5.5, compared to 7.3 last year. An index above 5 indicates the more severe blooms.

Lake Erie blooms consist of cyanobacteria, also called blue-green algae, capable of producing the liver toxin microcystin which poses a risk to human and wildlife health. Such blooms may result in higher costs for cities and local governments that need to treat drinking water, prevent people from enjoying fishing, swimming, boating and visiting the shoreline, and harm the region’s vital summer economy. These effects will vary in location and severity due to winds that may concentrate or dissipate the bloom.

“A smaller bloom forecast for Lake Erie and the surrounding coastal communities is encouraging, but we cannot be complacent,” said Nicole LeBoeuf, acting director of NOAA’s National Ocean Service. “It is our hope that these science-based tools will help local leaders plan for the predicted bloom and best position the community and its visitors to deal with what comes.”

The severity index is based on the bloom’s biomass – the amount of algae – over a sustained period. The largest blooms occurred in 2011, with a severity index of 10, and 2015, at 10.5. NOAA, the Environmental Protection Agency, Environment and Climate Change Canada and its other partners have set a goal of 3, which was last seen in 2012.

The size of a bloom isn’t necessarily an indication of how toxic it is. For example, the toxins in a large bloom may not be as concentrated as in a smaller bloom. Each algal bloom is unique in terms of size, toxicity and ultimately its impact on local communities. NOAA is actively developing tools to detect and predict how toxic blooms will be.

Bloom expected in late July

With cool lake temperatures in May and early June, the cyanobacteria only started growing in the last week. NOAA expects a more typical start of the visible bloom in mid to late July. The extremely high lake levels are not expected to have a significant effect on the bloom size. While the bloom typically produces some toxins, it is too early to predict how toxic the bloom will be when it starts. 

However, calm winds tend to allow the algal toxins to concentrate near the lakes’ surface. The duration of the bloom depends on how windy September may be, which cannot be predicted this far in advance. The bloom will remain mostly in some areas of the western basin, and most of the rest of the lake will not be affected.

“The expectation of a smaller bloom than 2019 is clearly something we should welcome. Nevertheless, we still have work to do,” said Christopher Winslow, director of the Ohio Sea Grant College Program, and Stone Laboratory at Put-in-Bay on Lake Erie. Both programs are a part of The Ohio State University College of Food, Agricultural and Environmental Sciences (CFAES).

“Thankfully, the support of Governor DeWine to address water quality issues through the H2Ohio initiative and the research being funded through the Ohio Department of Higher Education’s Harmful Algal Bloom Research Initiative are important parts of that work,” Winslow said. “Additionally, we are fortunate that Ohio has capitalized on productive working relationships between our state agencies and our research institutions. Addressing nutrient loading and harmful algal blooms clearly demands an ‘all-hands-on-deck’ approach.”

The Lake Erie forecast is part of a NOAA ecological forecasting initiative that aims to deliver accurate, relevant, timely and reliable ecological forecasts directly to coastal resource managers and the public. In addition to the early season projections from NOAA and its partners, NOAA also issues HAB forecasts during the bloom season. These forecasts provide the current extent and 5-day outlooks of where the bloom will travel and what concentrations are likely to be seen, allowing managers to determine whether to take preventative actions.

“The mild rainfall this spring compared to last year will lead to a much smaller bloom,” said Richard Stumpf, NOAA’s National Centers for Coastal Ocean Science’s lead scientist for the seasonal Lake Erie bloom forecast. “While the bloom this year probably will not be as mild as in 2018, we still expect to see large areas without substantial effects. This depends on where the bloom gets pushed by the wind, so anyone using the lake needs to regularly check the location of the bloom.

CFAES News Team
For more information, contact: 

Chris Winslow