Summer is the season for harmful algae blooms in many U.S. lakes and bays. They occur when water bodies become overloaded with nitrogen and phosphorus from farms, water treatment plants and other sources. Warm water and lots of nutrients promote rapid growth of algae that can be toxic and potentially fatal to aquatic life and people.

Eventually algae settle to the bottom and decay, depleting dissolved oxygen in the water, creating hypoxia—“dead zones” where oxygen levels are low enough to kill fish.

As a senior scientist at the National Oceanographic and Atmospheric Administration (NOAA) between 1975 and 2003, I developed annual hypoxia forecasts for the Chesapeake Bay and the Gulf of Mexico—two of our nation’s water bodies most harmed by these blooms. At the University of Michigan, I helped develop harmful algae bloom forecasts for Lake Erie and continue to work with public and private organizations on these issues.

States around Lake Erie and in the Mississippi River basin, which drains to the Gulf of Mexico, have been trying to reduce nutrient pollution for years. They rely primarily on voluntary steps, such as offering grants to farmers to take steps to prevent fertilizer from washing off their fields.

In contrast, states around the Chesapeake have had more success with a federally enforced plan that can impose mandatory actions across the bay’s 64,000-square-mile watershed. From my perspective, when we compare these two approaches it is clear that voluntary measures are not even making modest dents in nutrient pollution.