Rhea Storlund

PhD Candidate


Twitter: @RheaStorlund

Co-supervisors: Dr. David Rosen & Dr. Andrew Trites

(2019) MSc Zoology, University of British Columbia, Canada
(2015) BSc Biology, University of British Columbia, Canada

Research Interests: Marine mammal cardiovascular physiology, diving ability, and conservation

Research Location: The Vancouver Aquarium

Circulation during diving: aortic bulb comparisons among marine mammals and cardiovascular responses in Steller sea lions


Cardiovascular adjustments during diving are critical for facilitating the dive behaviour of marine mammals. Despite its importance, many questions remain about the cardiovascular anatomy and physiology of marine mammals—particularly about the structure and function of the aortic bulb, heart rate regulation, and the electrical activity of marine mammal hearts. My objective is to examine how the structure and function of the aortic bulb and cardiac electrical activity of marine mammals are related to their dive behaviour and health. Evaluating cardiovascular anatomy, physiology, and health in marine mammals will aid in determining cardiovascular limits to diving which will have implications for understanding marine mammal foraging ecology and the ability of marine mammals to respond to disturbances when diving.

Aortic bulbs

Some marine mammal species have an enlarged ascending aorta compared to terrestrial mammals. This enlargement, termed the aortic bulb, is thought to be beneficial for diving as it can maintain continuous blood flow during diving bradycardia and reduce the amount of work performed by the heart. However, the link between aortic bulb properties and diving ability has not been established. My research explores how aortic bulb size and compliance relate to cardiovascular physiology, hemodynamics, and diving ability. Using echocardiography and anatomical examinations, I measure aortic bulb dimensions, aortic bulb compliance, blood flow, and stroke volume and compare these measurements across species. Knowing how the aortic bulb constrains diving ability will allow us to assess which species are diving at their cardiovascular limits and the impact of cardiovascular characteristics on the foraging ecology of marine mammals.

Electrical activity of Steller sea lion hearts

Electrocardiograms (ECGs) provide information about the timing of cardiac chamber contractions and heart health—information that cannot be learned by only studying heart rate. Heart rate has been the focus of many investigations in marine mammals, but the electrical activity of the heart has only been described for a few species, and comparisons between resting, diving, and surfacing ECGs are scarce. In addition, the effect of anaesthesia on the electrical activity of marine mammal hearts is poorly understood and this lack of information makes it difficult to anaesthetize some marine mammals safely. My objective is to assess how cardiac electrical activity in Steller sea lions is affected by diving, surfacing, and anaesthesia and to evaluate ECG and heart rate monitoring as a tool for health assessments of captive and wild marine mammals. Understanding how cardiac electrical activity changes with behaviour will provide insight into how marine mammal hearts support circulation during diving.


Storlund, R.L., D.A.S. Rosen and A.W. Trites. 2021. Electrocardiographic scaling reveals differences in ECG interval durations between marine and terrestrial mammals. Frontiers in Physiology 12:690029. View.

Storlund, R.L., D.A.S. Rosen, M. Margiocco, M. Haulena and A.W. Trites. 2021. Cardiac examinations of anesthetized Steller sea lions (Eumetopias jubatus), northern fur seals (Callorhinus ursinus), and a walrus (Odobenus rosmarus). Journal of Zoo and Wildlife Medicine 52(2):507-519. View.