Road salts and dragonflies: How does winter salt pollution impact pond macroinvertebrate communities?

Monday, November 11, 2024

11:42 AM – 11:54 AM MST

Location: Phoenix Convention Center, 222 C, PCC

Presenting Author(s)

Hannah M. Bodmer (she/her/hers)

PhD student
University of Toronto
Chanhassen, Minnesota

Co-Author(s)

NE

Nihal Ercin

Undergraduate student
University of Toronto
Mississauga, Ontario, Canada
RM

Rosalind Murray

Assistant Professor
University of Toronto
Mississauga, Ontario, Canada
SM

Shannon McCauley

Associate Professor
University of Toronto
Mississauga, Ontario, Canada

Winter deicing road salts improve public safety by making roadways safer during winter storm events. However, stormwater runoff washes road salts into ponds, lakes, and streams and significantly increases freshwater salt concentrations, especially in urban areas. Many urban waterbodies already surpass the US EPA’s freshwater salinity guideline of 230mg/L, with many stormwater ponds regularly exceeding 1000mg/L. This salinized freshwater is harmful for aquatic life and may reduce survivorship, reproductive success, and community diversity and abundance in aquatic species. However, responses to salt pollution vary across taxa. Odonata (dragonflies and damselflies) are relatively tolerant of salt pollution, although recent studies suggest salt may cause sub-lethal effects that could escalate into community-level disturbances. Our work seeks to understand the long-term impacts of salt pollution on odonates and other aquatic macroinvertebrates using experimental mesocosm ponds. Mesocosm ponds salted at 1000mg/L reflect salt concentrations found in urban waterbodies and allow us to study community dynamics under complex natural conditions while controlling for confounding variables. These ponds will be sampled regularly over multiple years to study seasonal and long-term impacts of salt pollution on water quality, amphibian development, and macroinvertebrate diversity. Here we present our findings on Odonata and macroinvertebrate community dynamics in salted and unsalted ponds. This research will improve our understanding of salt pollution and inform better conservation and management practices to conserve freshwater biodiversity in the face of urban expansion.