Road deicing agents can enter nearby wetlands and alter the composition of aquatic communities by directly eliminating salt-intolerant
species and modifying ecological interactions between tolerant species. We conducted field experiments to examine the sensitivity
of taxa that inhabit seasonal wetlands and to determine whether salt contamination could increase the production of ovipositing
insects. In two outdoor mesocosm experiments, cladocerans and copepods rarely survived concentrations of commercial road salt
>1,200 mg L−1, while wood frog eggs and hatchlings (Lithobates sylvaticus) were not strongly impacted until concentrations exceeded 4,500 mg L−1. Shore flies (Ephydridae), mosquitoes (Culex restuans; Anopheles punctipennis) and midge larvae (Chironomidae) were more salt tolerant than macrozooplankton. These taxa tended to be absent or relatively
rare in experimental mesocosms with low salinities, but abundant in mesocosms with intermediate to high salinities. We conducted
two additional experiments to examine whether adult choice of oviposition sites may in part explain the rarity of Cx. restuans in pools with low salinity. These revealed that Cx. restuans reduced oviposition rates in water-filled containers with cladocerans, and reduced clutch size in the presence of Lithobates larvae. However, salt concentration per se did not influence the propensity of Cx. restuans to oviposit. Collectively, our results suggest that aquatic habitats that are biologically compromised by deicing agents
favor salt-tolerant insects, and that the use of road salts could increase the production of adult mosquitoes that are pests
and vectors of disease.
Keywords Amphibians - Community composition -
Culex restuans
- Macrozooplankton - Mosquito oviposition - Road salts - Seasonal wetlands