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UBC Theses and Dissertations

An Arctic mercury mystery : exploring environmental drivers of methylmercury bioaccumulation in the Beaufort Sea food web Gillies, Emma


While mercury occurs naturally in the environment, human activity has significantly disturbed its biogeochemical cycle. Inorganic mercury entering aquatic systems can be transformed into methylmercury, a strong neurotoxicant that builds up in organisms and affects animal and public health. In the Arctic, top predators such as beluga whales—an ecologically and culturally significant species for many Inuit communities—can contain very high concentrations of methylmercury. Historical mercury concentrations in beluga in the western Canadian Arctic’s Beaufort Sea cannot be explained by mercury emissions trends alone, but they could potentially be driven by other factors in the rapidly changing Arctic, including rising temperatures, changes in food web structure, and melting sea ice and permafrost. This study explores the main drivers of mercury bioaccumulation in various species in the Beaufort Sea beluga food web using an ecosystem modelling software called Ecopath with Ecosim (EwE) and scenarios of environmental change informed by both Western science and Inuvialuit Knowledge. Through literature review, interviews with scientists, and engagement with Inuvialuit knowledge holders, I find that many environmental changes in the region have been climate-driven and have the potential to affect mercury cycling via three broad mechanisms: Mercury flows into the Beaufort Sea, mercury methylation, and food web effects. Comparing the effect of historical sea ice, sea surface temperature, and freshwater discharge time-series, exploratory ecosystem modelling highlighted that historical trends in beluga methylmercury were best explained by productivity-driven changes rather than mercury inputs, and that all three environmental drivers could help explain the decrease in mercury concentrations in beluga after the mid-1990s. This research identifies drivers of mercury variability, highlights knowledge gaps in both the Beaufort Sea ecosystem and mercury research more broadly, and makes space for different ways of knowing. Moving forward, methods employed here, such as fuzzy cognitive mapping and ecosystem modelling, could help us make fisheries and pollution management decisions and explore scenarios of change in an uncertain future.

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