NOAA predicts significant harmful algal bloom

PUT-IN-BAY, Ohio — Western Lake Erie will likely experience a significant harmful algal bloom, according to the National Oceanic Atmospheric Administration and its research partners.

They say the bloom could potentially reach levels last seen in 2013 and 2014, though it will be smaller than the record bloom of 2015.

This year’s bloom is expected to measure 7.5 on the severity index, but could range between 6.5 and nine. An index above five 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, 2011 and 2015, were 10 and 10.5, respectively.

Early season projections predicted a larger than normal bloom. This is the final seasonal forecast.

Bloom toxicity

The size of a 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.

“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.”

Heavy rains

Recently, 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.

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 into 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.

“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.”

Learn more

Nutrient load data for the forecasts came from Heidelberg University. The 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.
NOAA’s Lake Erie HAB forecast bulletins are available online and by subscription. For more information, visit www.coastalscience.noaa.gov/research/habs/forecasting.