Wet spring enhanced the flow of nutrients into lake, providing fuel for algal growth
NOAA and its research partners are forecasting that western Lake Erie will experience a significant harmful algal bloom (HAB) this summer.
This year’s bloom is expected to measure 7.5 on the severity index, but could range between 6 and 9. An index above 5 indicates blooms having greater impact. The severity index is based on 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. Last year’s bloom had a severity index of 3.6, while 2017's was 8.0.
Lake Erie blooms consist of cyanobacteria, also called blue-green algae, that are capable of producing the liver toxin microcystin that 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 tourism economy. These effects will vary in location and severity due to winds that may concentrate or dissipate the bloom.
“Communities along Lake Erie rely upon clean, healthy water to support their community’s well-being and economic livelihoods,” said Nicole LeBoeuf, acting director of NOAA’s National Ocean Service. “This forecast provides timely and trusted science-based information to water managers and public health officials so they can better anticipate blooms, mitigate impacts and reduce future outbreaks.”
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 to local communities. NOAA is actively developing tools to detect and predict how toxic blooms will be.
Bloom expected in late July
This year, the lake temperature has remained relatively cool due to the higher-than-average rainfall in the region, so the bloom is not expected to start until late July when the water temperature reaches 65 to 70 degrees F. This contrasts with 2018, when exceptionally warm weather at the beginning of June caused an early start. Calm winds in July, especially in western Lake Erie, tend to allow the algal toxins to concentrate, making blooms more harmful. The bloom typically peaks in the western part of the lake in September. Most of the rest of the lake will not be affected.
“This extremely wet spring has shed light on the movement of nutrients from the land into Lake Erie,” said Christopher Winslow, Ph.D., director of Ohio Sea Grant and Stone Laboratory. “Despite the predicted size of this year’s bloom, portions of the lake will be algae free during the bloom season and the lake will remain a key asset for the state. Ongoing research continues to help us understand bloom movement and toxin production, and remains vital to providing our water treatment facilities with the tools, technology and training they need to keep our drinking water safe.”
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 bulletins twice a week during the bloom season.
Gathering data, refining models
NOAA continues to expand the use of satellite data into its Lake Erie Harmful Algal Bloom Forecast System, which is helping improve the accuracy of bloom forecast products. The data comes from the European Union’s Copernicus Sentinel-3 satellite offsite link, which has instruments that measure coastal water color, and have proven to be especially useful for detecting and tracking algal blooms. NOAA is also continuing to work with its academic partners to refine and improve the models used to develop the forecasts.
“This spring brought regular, heavy rainfall to the Maumee River watershed which would normally carry a lot of nutrients into the lake,” said Richard Stumpf, Ph.D., NOAA’s National Centers for Coastal Ocean Science’s lead scientist for the seasonal Lake Erie bloom forecast. “However, due to the amount of rain this year, farmers were unable to plant their fields which reduced the nutrient concentration. That combined with higher than normal lake levels, presents an opportunity to test the accuracy of our models.”
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 NOAA’s Ohio River Forecast Center, NOAA’s National Centers for Coastal Ocean Science, NOAA’s Great Lakes Environmental Research Laboratory, NOAA’s Cooperative Institute for Great Lakes Research offsite link, Ohio Sea Grant offsite link and Stone Laboratory at The Ohio State University, University of Toledo and Ohio EPA.