Using diatoms to track road-salt seepage into small, shallow, softwater Ontario lakes

Since the 1950s, widespread application of road salt for winter maintenance and safety in cold regions has led to increased conductivity levels many freshwater systems. Salting practices have adversely affected biota; however, magnitude ecological impacts may vary by species ecosystem. Here, we examine diatom assemblage changes during past ∼200 years from sedimentary records five impacted lakes (measured specific conductance values 149–350 µS·cm −1 ) a reference lake (18 located Muskoka River Watershed, south-central Ontario, Canada. Diatom compositional road-salt-impacted sites were consistent with increasing diatom-inferred (DI)-conductivity was evident latter half 20th century lakes, concurrent known road-salt application. The strongest predictor DI-conductivity among six kilometre equivalents roads within watershed (i.e., kilometres × number lanes). Similar observed previous study focusing on cladoceran assemblages, conclude that even modest applications can affect assemblages softwater lakes.