Assessing the toxicity of sodium chloride to the glochidia of freshwater mussels: Implications for salinization of surface waters

Abstract

Chloride concentrations in surface waters have increased significantly, a rise attributed to road salt use. In Canada, this may be a concern for endangered freshwater mussels, many with ranges limited to southern Ontario, Canada’s most road-dense region. The acute toxicity of NaCl was determined for glochidia, the mussel’s larval stage. The 24 h EC50s of four (including two Canadian endangered) species ranged from 113–1430 mg Cl L −1 (reconstituted water, 100 mg CaCO 3 L −1). To determine how mussels would respond to a chloride pulse, natural river water (hardness 278–322 mg CaCO 3 L −1) was augmented with salt. Lampsilis fasciola glochidia were significantly less sensitive to salt in natural water (EC50s 1265–1559 mg Cl L −1) than in reconstituted water (EC50 285 mg L −1). Chloride data from mussel habitats revealed chloride reaches levels acutely toxic to glochidia (1300 mg L −1). The increased salinization of freshwater could negatively impact freshwater mussels, including numerous species at risk.