The Effect of Road Salt on Benthic Macroinvertebrate Community Health: A Comparison of Vermont and New York Streams

Maintaining the health of freshwater ecosystems is critically important as they provide valuable natural resources and economic value. In 2023, New York applied more than 600,000 tons of dry sodium chloride road salt, the highest amount in the United States. Research shows the negative effects of chloride pollution on drinking water quality, fish, and amphibian health but there has been little investigation into how New York's high road salt usage is affecting the base of the freshwater food web. Benthic macroinvertebrates, aquatic insects who feed on the bottom of stream beds, are key biological indicators for overall stream health in part due to their low tolerance to dissolved chloride. Research indicates that exposure to high amounts of chloride can cause invertebrates physiological stress, death, or to shift their ecological niche. In summer 2024 we collected benthic macroinvertebrates, water samples, and stream attribute data from 12 streams, six in Vermont and six in New York, to investigate how road salt is affecting stream health. We selected streams based on proximal land use, hypothesizing that streams in New York would have higher dissolved chloride concentrations and lower invertebrate diversity metrics. We found that concentrations of chloride in Vermont streams ranged from 0.3 ppm - 15.9 ppm while they ranged from 14.4 ppm - 188.9 ppm in New York with only one stream having a lower chloride concentration than any Vermont stream. Furthermore, increasing chloride concentration decreased benthic macroinvertebrate diversity, abundance, and species richness. The most common taxa in New York streams were Scud (Amphipoda: Gammaridae) which are pollution tolerant while the most common taxa in Vermont were pollution-intolerant Small Minnow Mayflies (Ephemeroptera: Baetidae). Benthic macroinvertebrates are a key food source for many organisms and an important component of aquatic nutrient cycles. Our research suggests that road salt usage in New York is negatively affecting stream health by shifting the abundance and composition of benthic macroinvertebrates. Documenting these effects is crucial for regulatory agencies who can enforce data-informed pollution limits to preserve stream health and the resources which they provide us.