Acute toxicity of polyacrylamide flocculants to early life stages of freshwater mussels

Sean B. Buczek, W. Gregory Cope, Richard A. McLaughlin, Thomas J. Kwak

Polyacrylamide (PAM) has become an effective tool for reducing construction related suspended sediment and turbidity, which are considered to have significant adverse impacts on aquatic ecosystems and are a leading cause of the degradation of North American streams and rivers. However, little is known about the effects of PAM on many freshwater organisms, and prior to this study, no information existed on the toxicity of PAM compounds to native freshwater mussels (Family Unionidae), one of the most imperiled faunal groups globally. Following standard test guidelines, we exposed juveniles mussels (test duration 96 h) and glochidia larvae (test duration 24 h) to 5 different anionic PAM compounds and 1 non-ionic compound. Species tested included the Yellow Lampmussel (Lampsilis cariosa), an Atlantic Slope species that is listed as endangered in North Carolina, the Appalachian Elktoe (Alasmidonta raveneliana), a federally endangered Interior Basin species, and the Washboard (Megalonaias nervosa), a common Interior Basin species. We found that median lethal concentrations (LC50) of PAM ranged from 411.7 to > 1000 mg/L for glochidia and from 128.7 to > 1000 mg/L for juveniles. All LC50s were orders of magnitude greater (2-3) than concentrations typically recommended for turbidity control (1-5 mg/L), regardless of their molecular weight or charge density. Our results demonstrate that the PAM compounds tested were not acutely toxic to the mussel species and life stages tested, indicating minimal risk of short-term exposure from PAM applications in the environment. However, other potential uses of PAM in the environment (e.g., wastewater treatment, paper processing, mining, algae removal) and their chronic or sublethal effects remain uncertain and warrant additional investigation. This article is protected by copyright. All rights reserved.