Long-term effects of highway construction on the ecology of a Southern Ontario stream

Abstract

Long-term sampling of a small stream revealed changes up to 6 years after completion of a major highway crossing. Suspended solids and rates of sedimentation declined below the construction site as silt was flushed downstream. Upstream conditions were not re-established for 5 years; incomplete recovery occurred downstream.

Complex changes in invertebrate communities occurred; for $\text{2}\text{1}\text{2}$ years after construction, populations increased downstream, and diversity declined. Trichoptera and Diptera proliferated, while Plecoptera and Ephemeroptera remained unchanged, or declined. Five years after construction diversity had rebounded, as flushing of silt allowed repopulation, and silt-tolerant Diptera declined. Few species were lost or gained, but a restructuring of invertebrate communities was evident, especially among the Trichoptera.

Blacknose dace and creek chub increased disproportionately for 2 years, but bottom-feeding species rebounded when sedimentation rates declined. The creek is apparently still changing in response to nutrients and sediments introduced by erosion, and elevated production appears to be relatively persistent.