Causes and consequences of contaminant-induced chemosensory deficits in aquatic animals

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Aquatic animals rely on chemosensory information to mediate a range of behaviours that are vital for survival. For example, chemosensory stimuli can inform an animal about the risk of predation, the location of food or migratory routes, and the appropriateness of a potential mate. Environmental contaminants such as metals, pesticides, hydrocarbons, and pharmaceuticals and personal care products (PPCPs) can impair olfaction leading to maladaptive behavioural deficits. Failure to successfully evaluate the risk of predation, find food, or identify potential mates can lead to `ecological death.' Consequently, understanding the processes that lead to contaminant-induced chemosensory impairment is critical to evaluating ecological risk and predicting adverse ecological outcomes. Although we have identified a number of contaminants that can impair olfactory-mediated behaviours in freshwater animals, we still have very little understanding about the mechanisms of those effects, or of their ecological consequences. Moreover, almost no research has addressed the confounding influence of multiple stressors, such as mixtures of contaminants and climate change, on chemosensory function and behaviour. The purpose of this research program is to understand the mechanistic nature of contaminant-induced olfactory impairment as a means to predict maladaptive behavioural responses, and how those effects are modified by multiple stressors. Species will be selected to represent several levels of a typical aquatic ecosystem (e.g., pelagic zooplankton, benthic invertebrates, and fish). During the first phase, chemosensory thresholds will be determined using established neurophysiological and behavioural techniques. These thresholds will then be challenged by exposure to one of a number of common environmental contaminants, such as metals, hydrocarbons, pesticides, or PPCPs. Chemosensory and behavioural responses will be characterized using gene expression analysis, histology, electro-olfactography (EOG), and behavioural video-tracking. A secondary stressor will be applied to Phase 1 exposure scenarios during the second phase, such as elevated temperature or salinity. During the third phase, animals will be collected from natural systems, including both clean and contaminated water bodies, and characterized for their chemosensory or behavioural function. Together, this research combines both laboratory and field techniques using a range of organisms representing several trophic levels typical of most freshwater ecosystems, in order to determine how multiple stressors related to changing environments affect chemosensory function and behaviour. Ultimately, a major objective is to determine the extent to which freshwater animals can adapt to changing environmental conditions, using chemosensory function and behaviour as a sensitive indicator of biological effect.