Heavy April showers are washing fertilizer off farm fields into rivers and into the Great Lake in amounts that will feed huge algae blooms that starve the lake of oxygen, the said.
Feeding on phosphorus and other fertilizer components, algae can create toxins that are absorbed by underwater life, choking it off, scientists with the U.S./Canadian International Joint Commission said.
"There's a 99 percent chance, there's a strong chance, that [we will] have very bad algae this year," commission scientist Raj Bejankiwar told the Canadian Broadcasting Corp.
It's normal to have some algae in the lake, he said, but not massive blooms.
Just two years ago, Lake Erie experienced the worst algae blooms on record, researchers said, citing warming temperatures that allowed the algae to get an early start.
Bejankiwar is the head of the Lake Erie Ecosystem Priority, a branch of the commission that is studying algae levels in Lake Erie.
Extra nutrients that feed algae also come from sewage treatment plants, recreational properties and golf courses, he said, although most of the phosphorus comes from farm run-off.