The interconnectedness of diet, physiology, and physical condition in beluga whales as a sentinel species for environmental change in the Beaufort Sea ecosystem
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Date
2016-10, 2017-07
Authors
Choy, Emily Sarah
Journal Title
Journal ISSN
Volume Title
Publisher
Marine Biology
Marine Ecology Progress Series
Marine Ecology Progress Series
Abstract
Arctic ecosystems are changing at an alarming rate, with the Arctic Ocean predicted to be
summer sea ice free within the next few decades. Beluga whales (Delphinapterus leucas) are the most abundant Arctic odontocete, exhibiting a circumpolar distribution and a strong association to sea ice, and are thus a sentinel species for the effects of climate change. The vulnerability of belugas to changing environmental conditions will depend on their adaptive capacity and resilience to changes in the prey base. The overall objective of my thesis was to examine the potential effects of prey shifts due to changing environmental conditions on Beaufort Sea beluga whales by examining relationships among body condition, dietary tracers, and physiology. Differences in lipid content and carbonates in the tissues of beluga and their potential prey affected both carbon (δ13C) and nitrogen (δ15N) stable isotope ratios, which could lead to incorrect ecological interpretations. Inter-annual variation in blubber fatty acid signatures and liver δ13C and δ15N values in beluga whales may be related to annual differences in environmental conditions and abundances of Arctic cod (Boreogadus saida). To establish an effective approach for identifying prey, I used Bayesian mixing model Fatty Acid Source Tracking Algorithm in R (FASTAR) to reconstruct the known diets of two captive beluga whales
using fatty acid signatures. FASTAR was then used to reconstruct the offshore diets of Beaufort Sea belugas. Although diets varied annually, Arctic cod and capelin (Mallotus villosus) were identified as the main prey of belugas. Finally, I examined physiological limits and the relationships between body condition and physiological parameters pertaining to oxygen storage capacity in belugas. Males had higher oxygen stores than females due to larger body size and higher hemoglobin concentrations. Body condition indices positively correlated with myoglobin and hemoglobin concentrations, and hematocrit, resulting in lower calculated aerobic dive limits in whales with lower body condition. Overall, prey shifts that reduce fitness will lead to lower oxygen stores, a positive feedback mechanism. The interconnectedness of diet, body condition, and physiology should be a conservation priority to monitor the long-term effects of climate change on belugas and other Arctic marine mammals.
Description
Keywords
Beluga whales, Arctic, Physiology, Fatty acid signatures, Stable isotope ratios, Bayesian mixing models, Body condition, Marine mammals, Climate change
Citation
Choy ES, Roth JD, Loseto LL. 2016. Lipid removal and acidification affect nitrogen and carbon stable isotope ratios of beluga whales and their potential prey species in the Beaufort Sea ecosystem. Marine Biology 163 (10): 1-13.
Choy ES, Rosenberg B, Roth JD, Loseto LL. 2017. Inter-annual variations in environmental conditions affect prey and body condition of eastern Beaufort Sea beluga whales (Delphinapterus leucas). Marine Ecology Progress Series: https://doi.org/10.3354/meps12256
Choy ES, Rosenberg B, Roth JD, Loseto LL. 2017. Inter-annual variations in environmental conditions affect prey and body condition of eastern Beaufort Sea beluga whales (Delphinapterus leucas). Marine Ecology Progress Series: https://doi.org/10.3354/meps12256