Drier spring leads to smaller nutrient load than last year’s
NOAA and its research partners are forecasting 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, Ph.D., director of Ohio Sea Grant and Stone Laboratory. “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. 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, Ph.D., 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.”
Gathering data, refining models
NOAA is now routinely using the high quality satellite imagery from both of European Union’s Copernicus Sentinel-3 satellites offsite link, which were designed to detect blooms in large lakes and estuaries. The cells that cause the bloom can float and sink in the water, allowing them to collect nutrients through the water and get to sunlight near the surface. This information is especially of interest to water treatment plant operators because intake structures are usually located below the surface, so the risk of toxins in their raw water may be greater when these cells sink. This year’s forecast includes an improved model that provides more accurate predictions and visualizations of where the bloom is located within the water column. View the new visualization on the updated Lake Erie harmful algal bloom forecast website.
Nutrient load data for the forecasts came from Heidelberg University. The various forecast models are run by NOAA’s NCCOS, the University of Michigan, North Carolina State University, LimnoTech, Stanford University, and the Carnegie Institution for Science. Field observations used for monitoring and modeling are done in partnership with a number of NOAA services, including its Ohio River Forecast Center, National Centers for Coastal Ocean Science, Center for Operational Oceanographic Products and Services, Great Lakes Environmental Research Laboratory, and Cooperative Institute for Great Lakes Research offsite link, as well as Ohio Sea Grant offsite link and Stone Laboratory at The Ohio State University, University of Toledo and Ohio EPA.