Trophic interactions and contaminant exposures under climate-driven species redistribution

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Global change-induced shifts in species interactions, such as resource competition and predation, may have profound but unpredictable impacts on wildlife populations and whole ecosystems. Ecological theory suggests that key species may act as “biotic multipliers” of climate change and that these species are likely to take the form of top predators. Top predators are highly sensitive to global change and cause top-down impacts on prey populations. Given their apex trophic position, such predators also accrue effects occurring throughout the food web, e.g., trophic magnification of chemical pollutants. Thus, through studies on apex predators in a rapidly transforming Arctic, I will address the long-term objective of this research program, which is to answer the question: what are the key interspecific interactions of native and northward-redistributing non-native species and how do these interactions shape exposures to, and effects of, environmental stressors, particularly pollutants, pathogens, and parasites? In the next five years, my research group will work towards answering this question by focussing on competition, pollutant exposures, and predation in two key apex predators in the Arctic through three short-term objectives, respectively: (1) determine feeding niche breadth and overlap between the native Arctic marine top predator and the redistributing sub-Arctic marine top predator; (2) assess the comparative influence of novel trophic interactions on pollutant exposure, i.e., biomagnification, in these two predators; and (3) develop and implement quantitative models to estimate composition of native and non-native prey species in the diets of the native and new apex predator of Arctic marine ecosystems. Understanding changing species relationships and stressor exposures will inform robust models of population and community projections under future global change. As mitigation of impacts relies on ability to predict future outcomes, results will contribute to improved sustainability of living marine natural resources in Canada and beyond. Results will also support federal monitoring requirements for United Nations agreements on pollutants. Lastly, findings will improve knowledge on the security and safety of traditional marine foods by evaluating shifting country food baskets and contaminant loads, and thus the health benefits of wild foods for Northern communities.