Mussels are very sensitive to changes in the environment which makes them good indicators of the health of an aquatic ecosystem. Mussel shells, like growth rings from a tree, can show scientists the age and growth rate of the animal. The scientists in this study wanted to know how streamflow affected mussels and their growth. Topics: Water, Wildlife, Ecosystem Changes, Indicator Species, Mollusks, Mussels, Sclerochronology, Streamflow.