If they detect polluted water, clams immediately shut their shells, which triggers the alarm
This Polish Waterworks company claims that this biomonitoring method is one of the most effective proven technologies for water quality testing. According to them, mussels monitor water quality for over 8 million people in Poland. Turns out, Minneapolis is using this method as well. Minneapolis Water Treatment and Distribution Services credit 12 mussels for keeping the water clean and safe.