ANN ARBOR—University of Michigan researchers and their partners predict that western Lake Erie will experience a significant harmful algal bloom this summer, potentially reaching levels last seen in 2013 and 2014, though smaller than the record bloom of 2015.
The Lake Erie forecast was released Thursday by the National Oceanic and Atmospheric Administration, which funds the research.
This year's Lake Erie bloom is expected to measure 7.5 on the severity index but could range between 6.5 and 9. An index above 5 indicates a potentially harmful bloom. The severity index is based on a bloom's biomass—the amount of its harmful algae—over a sustained period. The largest blooms, in 2011 and 2015, were 10 and 10.5, respectively.
Early season predictions from NOAA and its partners called for a larger than normal bloom. This is the final seasonal forecast.
The size of an algal bloom isn't necessarily an indication of how toxic it is. The toxins in a large bloom may not be as concentrated as in a smaller bloom. NOAA is currently developing tools to predict how toxic blooms will be.
"This year's bloom is likely to be significantly larger than the average, approaching some of the largest blooms on record, including the one that caused the city of Toledo to issue a 'do not drink or boil' advisory in 2014," affecting more than 400,000 area residents, said U-M aquatic ecologist Don Scavia, a member of the forecast team.
"But bloom predictions—regardless of size—do not necessarily correlate with public health risk. Local weather conditions, such as wind direction and water temperature, also play a role. Even so, we cannot continue to cross our fingers and hope that seasonal fluctuations in weather will keep us safe."
The main driver of Lake Erie's harmful algal blooms is elevated phosphorus from watersheds draining to the lake's western basin, particularly from the heavily agricultural Maumee River watershed. An estimated 85 percent of the phosphorus entering Lake Erie from the Maumee River comes from agricultural sources.
"These blooms are driven by diffuse phosphorus sources from the agriculturally dominated Maumee River watershed. Until the phosphorus inputs are reduced significantly and consistently so only the mildest blooms occur, the people, ecosystem and economy of this region are being threatened," said Scavia, a professor of natural resources and environmental engineering and a member of NOAA-funded teams that produce annual forecasts for the Gulf of Mexico, Chesapeake Bay and Lake Erie.
The forecast team led by Scavia consists of Daniel Obenour of North Carolina State University, U-M's Isabella Bertani and Nathan Manning, and Drew Gronewold and Craig Stow of NOAA's Great Lakes Environmental Research Laboratory in Ann Arbor.
Recently, algal blooms have appeared in late July in the far western basin of Lake Erie and increased in early August, although heavy rain in mid-July may push the late-July bloom further into the basin. Calm winds tend to allow the algal toxins to concentrate, making blooms more harmful. Most of the rest of the lake will not be affected.
"A bloom of this size is evidence that the research and outreach efforts currently underway to reduce nutrient loading, optimize water treatment, and understand bloom dynamics need to continue," said Christopher Winslow, director of the Ohio Sea Grant College Program. "Despite the predicted size of this year's bloom, much of the lake will be algae free throughout the bloom season, and the lake remains a key asset for the state."
The seasonal outlook uses models that translate spring nutrient loading into predicted algal blooms. Persistent wet weather in May is a factor in the relatively high spring phosphorus load into the lake. The outlook reflects this additional load.
The seasonal outlook models use nutrient load data collected by Heidelberg University.
The forecast models are run by scientists at NOAA's National Centers for Coastal Ocean Science, the University of Michigan, North Carolina State University, LimnoTech, Stanford University and the Carnegie Institution for Science.
"The Lake Erie harmful algal bloom forecast is another example of NOAA's ongoing efforts to provide science-based information to water managers and public health officials as they make decisions to protect their communities," said Russell Callender, assistant NOAA administrator for the National Ocean Service. "We will continue to work with our partners to bring the most accurate data and tools to future forecasts for the region."
In addition to the seasonal forecast, NOAA also issues bi-weekly forecasts during the bloom season. This year, NOAA will begin incorporating additional satellite data to its Lake Erie Harmful Algal Bloom Forecast System that will enhance accuracy and detail. The data come from Sentinel-3, a new satellite that measures coastal water color as part of the European Union's Copernicus program. NOAA's Lake Erie HAB forecast bulletins are available online and by subscription.
"Sentinel-3 will provide additional detail and sensitivity, and it will assure our ability to assess the state of Lake Erie well into the next decade," said Richard Stumpf, NOAA's National Centers for Coastal Ocean Science's lead for the seasonal Lake Erie bloom forecast. "A second Sentinel 3 will be launched later this year. The pair will assure that we can consistently see features that are one-tenth the size of blooms we can see now."
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, the NOAA-funded Cooperative Institute for Great Lakes Research at the University of Michigan, Ohio State University's Sea Grant Program and Stone Laboratory, University of Toledo, and Ohio EPA.
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. NOAA also provides, or is developing, HAB and hypoxia forecasts for the Gulf of Maine, Chesapeake Bay, Gulf of Mexico and Pacific Northwest.