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, long-term research into the effects of deicers on benthic macroinvertebrates is needed.