CANCELLED - Road salt reduces foraging success in larval dragonflies and carries-over to affect adult performance

Background/Question/Methods

The salinization of freshwater ecosystems is a growing global issue. In cold climates, deicing road salts applied during the winter months are a major contributor to the salinization of freshwater. Because salt is an effective (both economically and practically) way of improving winter road safety, high road density in rapidly urbanizing areas combined with climate change-induced precipitation changes have increased road salt use in recent decades, particularly in cities. This project used salinity measurements taken from urban stormwater management ponds and performed a mesocosm experiment investigating the effect of road salt on multiple species of dragonfly larvae.

Results/Conclusions

We show that while dragonfly survival and growth is unchanged in high salinity, larvae exposed to high salinity display multiple sub-lethal effects: dragonflies displayed decreased activity, and consumed significantly fewer mosquito larvae. Additionally, we observed carry-over effects from high-salinity mesocosms: dragonflies that experienced road salt pollution during their juvenile period were not able to mount a strong immune defence as adults. Our results highlight the importance of measuring sub-lethal effects in urban areas to understand how cities impact freshwater wildlife. Our work (indirectly) links road salt pollution to two important urban issues: mosquito abundance and disease ecology.