Each clam in Warsaw Waterworks serves for three months, is later returned to the exact lake where it came from, and is marked so that scientists won’t pick up the same clams again
“They are filter feeders, so they are feeding off of the water that’s in there, pulling the nutrients down,” said George Kraynick of Minneapolis Water Works. “They live for up to 50 years, they are there 24/7 and they are happy in the tank, just feeding. [After they’ve served their time] most likely, we will just set them free in the river. […] They’re still young, they have a long life to lead,” he also explained. Minneapolis is currently the only city in the US that uses clams for biomonitoring.