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Road Salt Impacts Freshwater Zooplankton at Concentrations below Current Water Quality Guidelines
Shelley E Arnott1, Martha P Celis-Salgado1,2, Robin E Valleau1
1Department of Biology, Queen's University, Kingston, ON, K7L 3N6 Canada.
Environmental Science & Technology
|June 30, 2020
Summary
Road salt runoff increases lake chloride levels, harming sensitive zooplankton like Daphnia. Current water quality guidelines may not protect aquatic life in soft water lakes from these chloride impacts.
Area of Science:
- Environmental Science
- Ecotoxicology
- Limnology
Background:
- Road deicing with sodium chloride (NaCl) elevates chloride concentrations in freshwater lakes.
- Existing water quality guidelines for chloride may not sufficiently protect aquatic organisms in soft water environments.
Purpose of the Study:
- To assess the toxicity of chloride to Daphnia species in soft water.
- To investigate the impact of road salt on cladoceran zooplankton communities in Canadian Shield lakes.
Main Methods:
- Laboratory experiments exposing six Daphnia species to varying chloride concentrations.
- Analysis of cladoceran remains in lake sediments from a highway-adjacent lake and a remote lake.
Main Results:
- Daphnia exhibited reduced reproduction and increased mortality at chloride levels between 5 and 40 mg Cl-/L.
- Cladoceran assemblage composition in sediments changed in the lake near the highway, correlating with road salt application.
- No significant changes were observed in the remote lake's sediment record.
Conclusions:
- Daphnia are sensitive to chloride concentrations found in many recreational lakes.
- Road salt contamination poses a threat to cladoceran zooplankton in soft water lakes.
- Current water quality standards may be inadequate for protecting these sensitive ecosystems.
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