Nature's Perfect Pollution Detector Is A Clam #genius Clams are being used as natural water-quality sensors because they react instantly to pollution. In clean water, they stay open and feed normally. When contaminants appear, they snap shut to protect themselves. By attaching a small magnet to each clam’s shell and placing a magnetic proximity sensor nearby, researchers can detect when the clam opens or closes. If several clams close at the same time, the system automatically flags a possible w