WHY are clams used as live sensors? The water supply systems | Why?

WHY are clams used as live sensors?

The water supply systems in Warsaw and some other Polish cities use clams as live sensors.

They are connected to water that needs to enter the city's water supply, and if it contains any contaminants such as heavy metals or pesticides, the clam shells close.

The computer system monitors this thanks to the coils and magnets installed on the flaps and automatically shuts off the water supply until specialists can conduct the necessary tests.