Doctoral Defense in Biology - Maria Glarou

Zoom link:
https://eu01web.zoom.us/j/66947774663

Doctoral candidate:
Maria Glarou

Title of thesis:
Life in a cold-water environment: Allometric adaptations of cetaceans in Skjálfandi Bay, Iceland

Opponents:
Dr. Edda Elísabet Magnúsdóttir, Assistant Professor at the Faculty of Subject Teacher Education, University of Iceland
Dr. Lars Folkow, Professor at the Department of Arctic and Marine Biology, UiT The Arctic University of Norway

Advisor:
Dr. Arnar Pálsson, Professor at the Faculty of Life and Environmental Sciences, University of Iceland

Other members of the doctoral committee:
Dr. Marianne H. Rasmussen, Director of the University of Iceland Research Centre in Húsavík, University of Iceland
Dr. Fredrik Christiansen, Senior Researcher at the Department of Ecoscience, Aarhus University, Denmark
Dr. Takashi Iwata, Associate Professor at the Faculty of Environment and Information Studies, Keio University, Japan

Chair of Ceremony:
Dr. Ingi Agnarsson, Program Director of biology at the Faculty of Life and Environmental Sciences, University of Iceland

Abstract:
Energy drives all biological processes and constrains how animals acquire, allocate, and expend resources to maintain fitness. This thesis investigates bioenergetic strategies in sympatric cetaceans inhabiting cold subarctic waters. Focusing on five different-sized species in Skjálfandi Bay, Iceland (harbour porpoises, white-beaked dolphins, minke whales, humpback whales, and blue whales), this study combines UAV photogrammetry and bioenergetic modelling to examine how body size influences heat loss (Article I), field metabolic rate (FMR; Article II), and energetic requirements (Article III) under shared environmental conditions. Heat loss scaled predictably with body size, with absolute heat loss increasing and volume-specific heat loss decreasing across species. Smaller cetaceans exhibited higher surface-area-to-volume ratios (SVR) and therefore higher relative heat loss, partly offset by increased blubber thickness and lower thermal conductivity. In contrast, larger species benefited from reduced SVR and lower relative heat loss. FMR also scaled with body size, with absolute FMR increasing and mass-specific FMR decreasing. Species with higher SVR exhibited higher mass-specific FMR, indicating a correlation between thermoregulatory costs and metabolic scaling. Cetacean FMR estimates were generally higher than predictions for similarly sized terrestrial mammals. Energetic requirements and prey consumption followed the same pattern, with larger species having higher absolute but lower mass-specific requirements. Smaller cetaceans required a greater proportion of their body mass in prey, whereas larger species dominated total prey removal at the population level. Overall, the findings of this thesis show that body size is a primary driver of bioenergetic strategies in cetaceans, shaping their life-history traits and ecological roles.

About the doctoral candidate:
Maria Glarou was born in Athens, Greece, in 1994. She completed a Bachelor’s degree in Biology at the University of Patras, Greece, in 2017, followed by a Master’s degree in Marine Biology at Stockholm University, Sweden, in 2020. Her interest in cetacean ecophysiology and bioenergetics led her to pursue a PhD at the University of Iceland, where she investigated the allometric adaptations across five sympatric cetacean species in subarctic Icelandic waters.