The best way to rid the Great Lakes region of invasive zebra mussels may be to zap them with radio waves, Purdue University researchers told the American Chemical Society at its meeting in Chicago yesterday. The fast-breeding zebra mussels, which were brought to the U.S. in the ballast water of cargo ships, are threatening native aquatic life and clogging pipes at water purification and power plants. The Purdue researchers exposed the pesky mollusks to low-frequency electromagnetic waves that affected their ability to develop a shell, causing them to die within 40 days. The researchers are hopeful that the treatment, which was far less harmful to other organisms, will replace the more toxic chlorine now used to control the mussels.