Assessing the Effect of Salinization (NaCl) on the Survival and Reproduction of Two Ubiquitous Cladocera Species (Bosmina longirostris and Chydorus brevilabris)

摘要

Salinization of freshwater lakes, largely linked to road salt (NaCl) runoff, is a serious threat to zooplankton across North America and Northern Europe. Chloride (Cl-) can be toxic to many freshwater species, and so water quality guidelines have been created to regulate it and protect aquatic life. However, these guidelines may not adequately protect organisms in low-nutrient, softwater lakes. To evaluate this issue, two Cladocera species that are common in softwater lakes (Bosmina longirostris and Chydorus brevilabris) were selected as test organisms for an experimental study. Fourteen-day bioassays were conducted with eight different Cl- treatments (ranging from 0.4 to 1200 mg/L) using a soft water medium, which reflects chemical conditions observed in Precambrian Shield lakes. We calculated 14-day Cl- LC50 values for both B. longirostris and C. brevilabris below the water quality guidelines for Cl- (LC50 = 24.3 mg/L and 60.3 mg/L, respectively), and a significant reduction in neonate production was observed for both taxa at a Cl- concentration of 15 mg/L. Our work illustrates the need to re-evaluate the current water quality guidelines for the protection of aquatic life.