The algae bloom that spread across Lake Erie this summer was the largest on record and left behind a thick, paint-like scum that covered an area roughly the size of New York City, government scientists said Tuesday.
The bloom fueled by heavy summer rains surpassed the record-setting algae outbreak in 2011 that stretched from Toledo to Cleveland, said the National Oceanic and Atmospheric Administration.
Scum from the bloom covered about 300 square miles in early and mid-August, the agency said.
But the actual bloom was much larger. Just how big is still being determined, though it was clearly bigger than anything measured so far, said Richard Stumpf, a NOAA researcher.
The massive algae colony this year stayed toward the center of the lake between Canada and Ohio and away from the shoreline, which lessened the impact on boaters and drinking water plants, he said.
Toxins from a much smaller bloom in August 2014 contaminated the tap water for 400,000 people in the Toledo area and a sliver of southeastern Michigan.
Heavy rains across northern Ohio in June and July washed huge amounts of algae-feeding phosphorus into the lake.
Algae blooms—linked to phosphorus from farm fertilizers, livestock manure and sewage treatment plants—have taken hold in the western third of the lake over the last decade and colored some of its waters a shade of green that looks like pea soup.
The blooms, which typically peak from the middle of August through the end of September, also have been blamed for contributing to oxygen-deprived dead zones where fish can't survive.
Ohio, along with Michigan and the Canadian province of Ontario, agreed in June to sharply reduce the amount of phosphorus flowing into western Lake Erie within the next 10 years.
Some changes limiting when farmers can spread fertilizer and manure on fields already have been made, but it will take at least a few years to see improvements.
"It would be hard to find much evidence of progress based on what we saw this year," said Jeff Reutter, former director of the Ohio Sea Grant Program, which studies water quality issues.
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