The Arctic isundergoing rapid change, and top predators are considered sentinels of the impacts of climate change on northern ecosystems. Research collaborationswith northern communitiesarecritical formonitoring Arctic climatechange. Beaufort Sea beluga whales (Delphinapterus leucas) and thick-billed murres (Uria lomvia) aretwo predators thatare experiencingthe effects of environmental change and are also important traditional foods to communitiesin the North.In partnershipwith Inuvialuit communities, the objective of my research was to examine inter-annual variation and potential environmental factors affectingtheprey, body condition, and physiology of beluga whales, for insights into changes in the Beaufort Sea ecosystem. The estimated proportional contributions of Arctic cod (Boreogadus saida) to beluga diet decreased from 2011 to 2014, coinciding with an increase in capelin (Mallotus villosus). Belugas consumed the highest proportions of capelin and the lowest proportions of cod in 2014. Body condition of whaleswas positively correlated with myoglobin,hemoglobin concentrations, and % hematocrit.The relationship between body condition and oxygen storage capacity may represent a positive feedback mechanism, in which environmental changes resulting in decreased body condition may impact foraging ability.We also investigatedthe effects of Arctic warming on murre physiology. In response to increasing temperatures, murres exhibited limited heat tolerance and low ability to dissipate heat, with one of the lowest evaporative cooling efficiencies recorded in birds.These results highlight the importance of community-based monitoring andthe various impacts of climate change on marine predators and Arctic ecosystems.

Dr. Emily Choy