Officials in Michigan, Ohio and Canada have signed an agreement to drastically reduce water runoff flowing into Lake Erie that has caused a series of toxic algae blooms.
The algae contaminates drinking water and causes oxygen-depleted dead zones where fish cannot live.
The pea green patches of toxic algae along the lake fouled public drinking water for more than 400,000 people last year in Toledo and southeastern Michigan.
One algae bloom in 2011 spread over 100 miles from Toledo to Cleveland.
Researchers say the algae comes from farm fertilizers, manure and sewage that runs off into tributaries that feed the lake.
Ohio already bans farmers from spreading manure on frozen or rain-soaked fields.
Now officials in Michigan, Ohio and Ontario say they will seek to cut that run off by 40 percent over the next decade.
Some of the runoff also comes from Indiana, but officials there refused to join the agreement.