Road salt impacts on phytoplankton and periphyton communities in urban ponds

Urban ecosystems contend with an array of environmental stressors, including salinization by deicing road salts. While application to city streets and sidewalks helps to reduce accidents in temperate regions that experience winter freezing, salt is readily transported during runoff events and can accumulate in the environment. As urban runoff is often funneled into retention basins to dampen hydrological responses and provide opportunity for contaminants to settle out, stormwater ponds are potential hotspots for freshwater salinization and useful venues for understanding its ecological consequences. To assess the extent of salinization and its impact on the midsummer functioning of urban ponds, we sampled 50 stormwater retention basins in the Greater Toronto Area, Canada. We deployed artificial colonization substrates and collected near-surface grab samples to evaluate periphyton and phytoplankton communities based on their taxonomically diagnostic pigments (chlorophylls and xanthophylls). Pigments were measured using high-performance liquid chromatography and assessed in relation to pond water quality. Depth profiles were also collected at each site to assess water density gradients and the vertical distributions of chlorophyll a and phycocyanin pigments (using a fluorescence sensor). By contrasting how phytoplankton and periphyton respond to variation in chloride concentrations (among other factors), we offer insights into the use of these communities as bioindicators of urban water quality and the risk of salinization facilitating growth of toxin-producing cyanobacteria.

Primary Presenter: Charlie Loewen, Iowa State University (cloewen@iastate.edu)

Authors:

Charlie Loewen, Iowa State University  (cloewen@iastate.edu)

Jenna Cook, University of Alberta  (jlcook2@ualberta.ca)

Rolf Vinebrooke, University of Alberta  (rolf@ualberta.ca)

Donald Jackson, University of Toronto  (don.jackson@utoronto.ca)