Invasive mussels cleaned Great Lakes water; whitefish may vanish in 5 years

Invasive zebra and quagga mussels have transformed the Great Lakes ecosystem by reducing the tiny organisms that young lake whitefish depend on for food. While the mussels made the water cleaner, they disrupted the food chain, causing whitefish numbers to fall sharply. Scientists warn the species could vanish from some areas within five years.