How clams help keep Polish water clean

A WATER PUMP known as (Fat Kathy) is a local landmark in Warsaw. To get there, you must walk 300 metres through a slimy tunnel under the Vistula river. There you will find eight clams hooked up to computers. They are monitoring the city’s drinking water.The system is nifty. When the molluscs encounter heavy metals, pesticides or other pollutants, they close their shells, explains Piotr Domek of Adam Mickiewicz University in Poznan, who has worked on the project for three decades. To create a natural early-warning system, Mr Domek and his colleagues collect the clams from rivers or reservoirs, and attach a coil and a magnet to their shells. Computers register whether their shells are open or closed by detecting changes in the magnetic field.