WINDOWS INTO THE PAST: MUSEUM COLLECTIONS OF FRESHWATER MUSSELS FOR THE STUDY OF LONG-TERM WATERSHED DISTURBANCE

Freshwater mussels comprise a diverse fauna with multistage life histories. Their shells provide a unique opportunity to conduct investigations of historical changes in aquatic ecosystems. Mussels deposit annual growth rings in their calcareous shells, much like tree growth rings, so that shells from archeological and museum collections can serve as records of long-term environmental change over the past 1000 years. We used sclerochronology techniques to evaluate changes in age-and-growth patterns in two mussel species collected from the Illinois River near Havana, IL from 1894-2013 as well as archaeological shells from circa 1000 A.D. Age-and-growth analyses indicated that modern animals are growing at a 50% greater rate and reaching a maximum size that is 20 mm larger than their 1894 counterparts. We also used mussel shells to evaluate changes in stable isotopes and legacy contaminants over the same time period. By constructing a historical biochronology response to environmental changes, we can better understand the dynamics of aquatic systems and the recovery rate after substantial perturbations and restoration efforts.