The amount of phosphorus going into the lake has risen every year since the mid-1990s.
Almost a year ago, one township just east of Toledo told its 2,000 residents not to drink or use the water coming from their taps. That was believed to be the first time a city has banned residents from using the water because of toxins from algae in the lake.
Researchers largely blame the algae’s resurgence on manure and chemical fertilizer from farms that wash into the lake along with sewage treatment plants. Leaky septic tanks and stormwater drains have contributed, too. Combined, they flush huge amounts of phosphorus into the lake.