Effects of Land Cover Disturbance on Stream Invertebrate Diversity and Metal Concentrations in a Small Urban Industrial Watershed

The landscape surrounding Sudbury, Ontario, has been severely affected by 100 years of mining and forestry and a recent, large-scale ecological risk assessment found that terrestrial plant communities continue to be impaired by remnant metals and poor soil conditions. We investigated the risks of these adverse landscape conditions on a small headwater stream by digitizing land cover at a fine scale and relating it to benthic invertebrate diversity and metal concentrations at 13 sites in the system. The combination of historically barren landscape and modern impervious surfaces such as asphalt, roofs, and hard gravel was associated with decreased benthic invertebrate community diversity at all four watershed spatial scales measured. The same combination of barren bedrock and impervious surface was associated with increased levels of potentially toxic Ni, whereas increased Cu was most strongly associated with bedrock alone. Our results highlight previously undocumented relationships in this historically impacted area between unrestored landscapes, modern impervious surfaces, and their potential risks to aquatic life. We suggest regreening at different watershed scales as a risk mitigation tactic worthy of consideration and further study.