"We think that [publicly owned treatment works] are a good place to start because, in many waterways between Chicago and the Mississippi, they are the dominant contributor to the algae," Alexander says. "They're not the dominant contributor everywhere, but they are certainly a significant contributor, and that means [the publicly owned treatment works] need to curb their nutrients."

One of the lawsuits was filed in U.S. District Court for the Southern District of New York; the other lawsuit was filed in U.S. District Court for the Eastern District of Louisiana.