Even if toxic chemicals are found at very tiny concentrations in lake water, they can become dangerous to animals through processes called bioaccumulation and biomagnification.

Bioaccumulation and biomagnification happen when plants and animals absorb more toxins from their environment than their bodies can get rid of. When these organisms get eaten, they pass those accumulated toxins on to their predators. Because predators have to eat a lot of prey, toxins get increasingly concentrated as they move up the food chain. And there’s nothing higher on the food chain than humans.

As vast and immutable as they might look, the Great Lakes are vulnerable to dangerous contaminants.