Just east of Indiana State University’s fountain in the College of Arts and Sciences building, professor of Geography and Geology Dr. Jim Speer can be found working at a microscope in his lab. He pushes the slides back and forth, adjusting the microscope's magnification to enhance his ability to see the cross-sections on a material epoxied to slides. What local creature is Dr. Speer investigating? They are mussel shells from the Wabash River!
This deep dive into mussel shells were inspired by a talk given by County Commissioner Brendan Kearns. Dr. Speer was inspired by Commissioner Kearns’ observations of mussel shells in the Wabash River during his time with the Indiana Department of Natural Resources Healthy Rivers INitiative. Dr. Speer and Commissioner Kearns began their journey into mussel research side-by-side. Mussels are protected in Indiana and across the US. The public is prohibited from collecting living and dead mussel shells from the banks of the Wabash River. Therefore, Commissioner Kearns and Dr. Speer worked together to obtain a scientific collection permit to allow Dr. Speer and his students to collect, study, and handle dead mussel shells from the Wabash River.
By exploring the world of ScleroChronology, Dr. Speer and his students are learning the age of these mussels not only from their visible rings along their backs but also through the magnification of cross-sections of these mussels under a microscope. Dr. Speer’s lab takes these cross-sections and mounts them on a glass slide. These cross-sections are then sanded down and polished so that light can be transmitted through those slides. From there, the scientists can see all the rings in the mussel shell. The scientists count the annual rings to figure out the age of the mussel. Dr. Speer explains, “We hope to be able to cross date these mussels. So we hope to be able to date one set of mussel shell rings against another mussel and do that for probably one hundred or two hundred from this collection that we have and from that build a long-term chronology.”
The goal for these scientists is to map a continuous chronology of the life of these mussels. This information reveals their age and how old the mussels were when they died. Dr. Speer, alongside his students, hopes to drill into them and look at their chemistry as well. Dr. Speer explains that these mussels shells contain information about their own lives and the environment. “If we can look at before the Clean Water Act and after the Clean Water Act, we can see if that law had a change in the chemistry in the Wabash River.” ScleroChronology is an essential step in understanding the life of these mussels and the health of the Wabash River.