Date of Completion
Dive, Pressure, Marine Mammal, Whale, Beluga, Seal, Decompression Sickness, Immune Function
Sylvain De Guise
Field of Study
Doctor of Philosophy
Marine mammals possess adaptations for repetitive and extended diving to great depths without suffering the ill effects seen in humans [e.g. decompression sickness (DCS)] which involve altered immune activity. In recent decades, DCS-like symptoms in marine mammals have increased concerns about marine mammal health and whether anthropogenic activities can interfere with adaptive dive responses, increasing susceptibility to dive related pathologies. The purpose of this work was to address these concerns by: 1) evaluating the in vitro response of marine mammal immune cells to increased pressure, 2) comparing the response of cells between baseline and stressor conditions, and 3) developing a non –invasive means of monitoring cortisol in belugas (Delphinapterus leucas). Blood samples were obtained from belugas during baseline and stressor (e.g. out of water examination, wild chase and capture) conditions, as well as from stranded harbor seals (Phoca vitulina), harp seals (Phoca groenlandica) and grey seals (Halichoerus grypus) at the time of admit to rehabilitation and again pre-release. Catecholamines and cortisol were measured to demonstrate a physiological stress response. Phagocytosis, lymphocyte proliferation and cell activation were compared between pressure exposed and non-exposed cells for each condition, between different pressure profiles and between conditions using mixed generalized linear models (α=0.05). The response of cells to pressure varied 1) between species, with baseline beluga samples and admit phocid samples showing opposite patterns of change than humans, 2) with stressor condition as responses differing from baseline but resembling human responses were detected for all stressor conditions in belugas, and 3) with exposure characteristics, with deeper exposures resulting in larger changes in phagocytosis but smaller changes in IL2R expression than shallower exposures. Blow (exhaled breath condensate) was also collected from belugas and validated as a matrix for monitoring cortisol using a commercial enzyme immunoassay. Changes in cortisol were observable in blow following known stressor conditions, supporting use of blow sampling for future endocrinology, dive physiology, health and conservation studies. This work validates non-invasive methodology for monitoring stress responses in cetaceans and provides the first evidence suggesting that anthropogenic stressors may impact marine mammal health by altering the relationship between dive behavior and immune function.
Thompson, Laura A., "The Combined Influence of Diving Physiology and Stressors on Immune Cell Function in a Deep Diving Monodontid and Three Shallow Diving Phocid Species" (2014). Doctoral Dissertations. 405.