Increasing use of de-icing salt on roads and paved surfaces is contributing to rising salinity in freshwater, threatening aquatic ecosystems. In response, novel road de-icers advertised as “eco-friendly” have been developed. Despite rising use of road salt alternatives, research on their toxicities rarely extends beyond individual species, and community and ecosystem-level testing remains limited. We used outdoor mesocosms to test how zooplankton communities, important primary consumers in aquatic systems, responded to three de-icers: rock salt (NaCl), an organic alternative (beet /NaCl-brine), and an inorganic alternative (NaCl, CaCl2, MgCl2). Each de-icer was tested along a gradient of 20 concentrations ranging from ~6 to ~1500 mg Cl- /L. We found that both alternatives were more toxic to zooplankton and decreased total abundance at lower concentrations than rock salt. However, the mechanisms of toxicity among de-icers may have differed; a decline in oxygen in the organic alternative correlated with the decline in zooplankton abundance. Within each treatment, cladocerans and copepods were more sensitive than rotifers, indicating differential sensitivities that would impact community composition, species interactions, and ecosystem function. Further, we saw an increase in chlorophyll a, suggesting an ecosystem trophic response likely driven by a loss of grazers. These results suggest that de-icer alternatives might not be as “eco-friendly” as advertised and we advise that additional testing is necessary, especially when considering effects such as trophic interactions.

Primary Presenter: Troy Martin, Queen's University (troy.martin@queensu.ca)

Authors:

Troy Martin, Queen's University  (troy.martin@queensu.ca)

Shelley Arnott, Queen's University  (arnotts@queensu.ca)