Western Lake Erie is projected to experience a mild to moderate harmful algal bloom (HAB) this summer, according to the first 2025 Lake Erie Harmful Algal Bloom Early Season Projection issued by NOAA’s National Centers for Coastal Ocean Science (NCCOS), with support from the National Center for Water Quality Research at Heidelberg University and NOAA’s Ohio River Forecast Center.
The severity of the western Lake Erie cyanobacterial harmful algal bloom (cyanoHAB) depends on input of total bioavailable phosphorus (TBP) from the Maumee River during the loading season, from March through July. Models currently indicate a likely bloom severity between 2 and 4.5.
Throughout the spring, conditions have been relatively dry except for a large rain and associated river discharge event early in April. Near-normal precipitation and river discharge are currently predicted for the remainder of the loading season. The uncertainty for the forecast should continue to narrow as additional river discharge and phosphorus loads are measured over the next two months.
Since 2009, NCCOS has used satellite data from sensors across three different satellite missions (MODIS, MERIS, and OLCI) to monitor the severity and impacts of annually occurring cyanoHABs in Lake Erie. Following the 2024 bloom season, NCCOS reprocessed the full time series with new calibrations, improved algorithms and additional data, generating a more complete, consistent and continuous data set for harmful algal bloom monitoring in Lake Erie. You can find more information about the updated time series here.
Projections of the bloom’s severity will be issued weekly through mid June. On June 26, NOAA will issue the official Lake Erie HAB Seasonal Forecast in coordination with Ohio Sea Grant. Any bloom that develops will change with time and move with the wind. NOAA will provide information on the presence and location of any bloom that develops throughout the summer.
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