Effects of road deicer runoff on benthic macroinvertebrate communities in Korean freshwaters with toxicity tests of Calcium Chloride (CaCl₂)

We investigated the effects of road deicer runoff on benthic macroinvertebrate communities in Korean freshwaters focusing on the effects of CaCl₂ deicer. Quantitative field sampling was conducted at eight sites (lakes and streams) in South Korea, and toxicity tests were conducted on 48-h lethal and effective concentrations (LC₅₀ and EC₅₀) of road deicer (CaCl₂ 74%) and high-grade CaCl₂ (96%) on five selected macroinvertebrate species (Gammarus sobaegensis, Caridina denticulata denticulata, Glyptotendipes tokunagai, Cloeon dipterum, and Ecdyonurus levis). Although Cl^- concentrations were significantly different between the seasons (before and after snowfall) at most of the study sites, community values (species richness, density, dominance index, and diversity index) were not significantly different between the seasons. In the bioassay, 2.85 g L^-1 CaCl₂ elicited abnormal swimming behavior of test organisms based on EC₅₀ values. The LC₅₀ values of the five test species ranged from 3.54 to 20.73 g L^-1. For all tested species, the LC₅₀ of road deicer was higher than that of high-grade CaCl₂. This study shows that despite the heavy application of road deicers during the snowy season, the deicer may not directly affect benthic macroinvertebrate communities over short time periods because Cl ^- concentrations in the field sites (<0.025 g L^-1) were much lower than the LC₅₀ values. Because the quantity of deicers used in this region continues to increase, longterm research into the effects of deicers on benthic macroinvertebrates is needed.