Evaluation of lethality and genotoxicity in the freshwater mussel Utterbackia imbecillis (Bivalvia: Unionidae) exposed singly and in combination to chemicals used in lawn care

Lethal toxicity and genotoxicity of a suite of chemicals that are frequently used in non-agricultural settings, and also are sometimes detected in surface waters, was tested on glochidia (larval form) of the freshwater mussel Utterbackia imbecillis in the laboratory. The tested chemicals included copper (a component of many fertilizers and fungicides), atrazine (a triazine herbicide), glyphosate (a phosphanoglycine herbicide), carbaryl (a carbamate insecticide), and diazinon (an organophosphate insecticide). The chemicals were tested individually, and in equitoxic and environmentally relevant mixtures. Lethal toxicity was measured as LC50s after 24hrs of exposure, and genotoxicity was measured via a Comet assay after exposing glochidia to lower concentrations of the chemicals.

For most chemicals tested, Utterbackia imbecillis glochidia were more sensitive than other invertebrates that were tested in other studies. U. imbecillis were less sensitive to diazinon exposure as compared to other invertebrates, and comparisons could not be made for atrazine exposure. Copper was the most acutely toxic chemical to U. imbecillis glochidia in this study, with an LC50 of 37.4 µg/L. Of the pesticides, carbaryl was the most toxic evaluated with an LC50 of 7.9 mg/L. Atrazine was the least toxic chemical evaluated. Genotoxic responses were observed in mussels exposed to copper, atrazine, and diazinon. The authors suggest that DNA could be a useful screening tool to evaluate potential sublethal effects of chemicals and pesticides on organisms.