Western Lake Erie is too big to correct its noxious algae problem with large doses of aluminum sulfate, or alum, alone. Still, alum treatments appear to be having at least a limited positive effect on Grand Lake St. Marys.
At 12,500 acres, Grand Lake St. Marys is the largest open body of water in Ohio. Like Lake Erie, its recreational activities are afflicted by algae.
The state of Ohio has spent $8.5 million to apply alum to 4,900 acres of Grand Lake St. Marys over the past two summers. The compound is supposed to keep algae from feeding on its main food source, phosphorus.
This year’s drought cut off the farm runoff that feeds Lake Erie algae. But algae in Grand Lake St. Marys rely more heavily on phosphorus embedded in lake sediment, so this year’s dry conditions did not do as much to curb algae there.
Preliminary alum results for Grand Lake St. Marys look good, according to a researcher. But the success needs to be quantified for state officials to decide whether to apply more.
No matter what results emerge, Ohio may need to take more than a two-and-out approach using alum to generate more data, especially in non-drought years. More-proactive efforts are needed to keep runoff and untreated household waste out of Ohio waterways.
The most cost-effective way to manage natural resources is to prevent pollution. Alum treatments are, at best, short-term responses to algae.
Ohio needs to enhance wetlands statewide and, when necessary, dredge the most polluted sediment from Grand Lake St. Marys. Alum research can help unlock algae mysteries. But it is no panacea for what ails Ohio’s lakes.