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Abstract

Road salt, with sodium chloride (NaCl) as its main constituent, is a common de-icer used during cold months. Despite the widespread use of road salt, its application is largely unregulated and unrestricted. In the Vancouver Lower Mainland (VLM) of British Columbia (BC), Canada, road salt has been found to contaminate local streams, rivers, and retention ponds, resulting in spikes in specific conductance, a proxy for salinity. In BC, chloride concentrations should never exceed the acute water quality guideline of 600 mg L⁻¹ Cl⁻, to protect aquatic life. However, water quality data supported by Fisheries Oceans Canada’s (DFO) Community Outreach Science Monitoring Project (CoSMo) estimates that road salt contamination leads to pulses in chloride concentrations that can exceed this guideline by over 11-fold. These pulses occur during the spawning and subsequent rearing period of Pacific salmon. This thesis investigates the effects of road salt contamination on the development and physiology of two species of Pacific salmon: rainbow trout (Oncorhynchus mykiss) and coho salmon (Oncorhynchus kisutch). Laboratory experiments simulated a 24-h road salt pulse at six ecologically relevant salt concentrations to which developing salmonids were exposed at various developmental stages. Immediately following fertilization, developing salmonids were particularly sensitive to road salt pulses which can elicit significant mortality and long-term disruptions to ion regulation and embryonic development. This research highlights that current road salt contamination events in the VLM pose a serious threat to the survival and development of rearing Pacific salmon, emphasizing the need for improved road salting practices.