Detecting changes in the benthic invertebrate community in response to increasing chloride in streams in Toronto, Canada

Abstract

AbstractSalinization of streams is a growing ecological concern in urban areas. Winter application of deicers to roads (road salt) in cold climates strongly influences stream water chemistry. Total salt use and associated stream Cl– concentrations have increased in North American cities over the past few decades such that current elevated Cl– levels represent an evolutionarily novel stressor to freshwater biological communities. We investigated changes in stream Cl– concentrations between 2002 and 2012 in Toronto, Canada, and related Cl– concentrations to corresponding changes in benthic macroinvertebrates over the same period. Median stream Cl– concentrations in 2012 were almost 2× higher than the median concentrations in 2002, despite the mild winter in 2012. We used the strong relationship between field conductivity and laboratory Cl– concentrations (R2 = 0.93) to model summer Cl– values for 51 benthic macroinvertebrate (BMI) sampling sites in 2002 and 2012. We investigated BMI community shifts with re...