CAN LATE HOLOCENE AQUATIC MOLLUSK ASSEMBLAGES BE USED TO INFORM STREAM RESTORATION DESIGN?

Streams in the midwestern U.S. have been impacted severely by land-use changes, channel modifications, and an overall decline in water quality. Efforts are underway to restore streams, but little is known about what streams were like prior to European settlement, making stream restoration design problematic. Here we examine a Late Holocene assemblage of aquatic mollusk shells from Four Mile Creek, a small watershed in southwestern Ohio. This fossil assemblage was collected from one outcrop, which was freshly exposed during a bank stabilization project. A radiocarbon age of 4,270 ±25 14C yrs BP constrains the age of the channel deposits that contains the mollusk shells. The shell assemblage was transported by the channel and does not necessarily represent the primary habitat for these organisms. The aquatic mollusk assemblage includes a large component of fingernail clams (Pisidium species and Sphaerium species), a few specimens of larger bivalve taxa yet to be identified, and a wide range of aquatic gastropods, including Physidae sp., Elimia sp., Mimic lymnaea, as well as several limpet shells. Here we report on the complete assemblage and assess if this corpus of shell material can identify a range of hydrologic conditions and habitats present in Four Mile Creek at that time.