Effects of freshwater salinization on a salt‐naïve planktonic eukaryote community

Abstract Freshwater salinization is a widespread issue, but evidence of ecological effects on aquatic communities remains scarce. We experimentally exposed salt‐naive plankton communities of a north‐temperate, freshwater lake to a gradient of chloride (Cl−) concentration (0.27–1400 mg Cl L−1) with in situ mesocosms. Following 6 weeks, we measured changes in the diversity, composition, and abundance of eukaryotic 18S rRNA gene. Total phytoplankton biomass remained unchanged, but we observed a shift in dominant phytoplankton groups with increasing salt concentration, from Cryptophyta and Chlorophyta at lower chloride concentrations ( 185 mg Cl− L−1). Crustacean zooplankton and rotifers were sensitive to the salinity, and disappeared at low chloride concentrations ( 640 mg Cl− L−1).