Excess chloride and impervious surfaces reduce over-winter quality of stream algal assemblages

Abstract

Winter road salt use leads to the salinization of freshwater habitats. Freshwater organisms experience negative effects due to increased chloride ions, including algae in periphyton biofilms. This study examines the effects of road salt on algal assemblage composition, lipid production, and enzyme activity. Five streams throughout Erie County, New York, US were sampled monthly from October 2018 to March 2019. Chloride concentrations in all streams averaged 203.6 Cl- mg/L throughout the winter and had a highly significant relationship (rs = 0.82) with developed land use. Algal biodiversity scores decreased with elevated salinity (rs = 0.11). Algae exhibited the greatest total lipids in January (2.92 mg/m2) and the lowest in March (1.03 mg/m2). Similar trends were observed with ω3 and ω6 compounds. Overall desaturase Δ6 activity trended with stream Cl- concentrations, mainly along ω6 pathways, suggesting an inflammatory stress response. Algal assemblages exhibited evidence of chronic salt exposure through impaired taxonomic composition and patterns of lipid production that followed trends in stream water salinity. These effects suggest road salt applications have negative effects on stream primary producers with consequences for higher trophic levels.