Doctoral Defense in Biology - Sammi Lai

30. Aug - 13:00 to 15:00  | Location: Aðalbygging The Aula

Doctoral candidate:
Sum Yi Lai

Title of thesis:
Temporal and spatial differences in the food web of Atlantic salmon

Opponents:
Dr. Stefán Óli Steingrímsson, Professor at Hólar University,  Lee Brown, Professor at the School of Geography, University of Leeds

Advisors:
Hlynur Bárðarson and Jón S. Ólafsson

Also in the doctoral committee:
Hlynur Bárðarson, Biologist at the Freshwater and Aquaculture sector, Marine and Freshwater Research Institute, Jón S. Ólafsson, Aquatic Biologist at the Freshwater and Aquaculture sector, Marine and Freshwater Research Institute, Arnar Pálsson, Professor at the Faculty of Life and Environmental Sciences, University of Iceland, Ingi Rúnar Jónsson, Biologist at the Freshwater and Aquaculture sector, Marine and Freshwater Research Institute, Jóhannes Guðbrandsson, Specialist at the Freshwater and Aquaculture sector, Marine and Freshwater Research Institute

Chair of Ceremony:
Dr. Snæbjörn Pálsson, Professor and Head of the Faculty of Life and Environmental Sciences, University of Iceland

Abstract:
In recent decades, Atlantic salmon populations have been declining. The aim of this thesis is to increase our understanding of the impact of prey availability on Atlantic salmon juveniles and the role of Atlantic salmon in riverine food webs, with a focus on northern, low-productivity rivers. Predator-prey relationships of Atlantic salmon were investigated in NE Iceland. Further, the food webs of Atlantic salmon rivers in the North Atlantic were compared over space and time. The thesis identified that larvae and pupae of the insect family Chironomidae were the most abundant benthic invertebrates and constituted the majority of the diet of juvenile salmon in NE Iceland. This thesis also shows that prey availability in a nutrient-poor river in NE Iceland decreased over a 23-year period. Food webs were found to be spatially similar within and between rivers in the same geographical region, owing to its biogeographical isolation and homogenous catchment characteristics. Furthermore, in comparison the food webs in the North Atlantic have increasingly complex trophic interactions with decreasing latitudes, corresponding to temperature and vegetation increases. Juvenile Atlantic salmon populations in the simple food webs of cold, northern latitudes have low food availability; thus, these populations are at risk from impacts of climate change. For that reason, it may be appropriate that northern salmon populations should be used as ‘sentinel’ systems for monitoring and predicting global trends of salmon population dynamics and their prey availability.

About the candidate:
Sum Yi Lai completed her Bachelor’s degree in Environmental Sciences from the University of East Anglia in 2018, before completing her Master’s degree in Ecosystem and Environmental Change at Imperial College London in 2019. Her interest in investigating the impacts of climate change on ecological communities led her to join a doctorate project at the University of Iceland and the Marine and Freshwater Research Institute. Sum Yi will continue pursuing her research interest as a postdoctoral researcher at the University of Helsinki.