Effects of Sediment Deposition on Macroinvertebrate Near Road Crossings

Abstract

Recently widened unpaved roads and increased traffic due to a new mining operation have the potential to increase sedimentation and impact fluvial biology in the Yellow Dog Plains region of the Upper Peninsula of Michigan. To assess sediment accumulation around road crossings, partially open chambers filled with natural rocky substrate were deployed in similar river habitats upstream and downstream of road crossings in three reaches to allow sediment accumulation and insect colonization. We observed spatial variability in sedimentation with significantly greater deposition upstream of road crossings and the lowest sediment accumulation at the site with recently widened roads. Proportion Ephemeroptera, Chironomidae, and EPT, EPT: C, HBI and family richness metrics varied spatially and were affected by sediment accumulation. The two diversity indices (Simpson’s and Shannon-Wiener) were not affected by sediment accumulation and only one functional family group (% predators) was affected by sediment accumulation. Insect abundance was significantly greater at downstream chamber location and significantly increased with greater sediment accumulation at all sites. This study provides evidence that sediment deposition may increase around road crossings, but invertebrates are not necessarily negatively affected by increase sedimentation. It also suggests that even if intensive road construction activities occur near streams, excess sedimentation and impacted stream invertebrate communities may not always be the outcome.