Open Collections

Fast, Julia

University of British Columbia

Nutritional quality is an essential component in the development, growth, reproduction, and survival of marine consumers. However, knowledge gaps remain about how nutritional quality relates to ecosystem food web dynamics. Indices such as the content and composition of essential micronutrients, essential fatty acids (EFAs), essential amino acids, lipids, and proteins, as well as stoichiometric ratios and energy density are widely used to measure nutritional quality, but these indices have yet to be integrated to comprehensively describe food web dynamics. An important application of nutritional indices is understanding spatial differences in prey quality. The British Columbia (BC) coast encompasses a range of habitats with differences in regional oceanic processes, making it an ideal place for a case study on how spatial differences impact prey nutritional quality. This thesis addresses these two aspects of food web nutrition. In chapter 2, I identify common marine nutritional indices, their applications, and the relationships between them through literature review. Nutritional quality indices were applied differently across trophic levels. Stoichiometric ratios were mainly applied to herbivore consumers, and macromolecule indices focused on lipid content for fish, mammals and seabirds and protein content for zooplankton. Researchers’ choices of indices also varied with research goals and focal organisms. Based on these results, I discuss considerations for researchers when selecting indices. I also discuss the use of relationships between indices for comparing between studies, and next steps towards integration, which include resolving species-specific requirements for essential nutrients and interactions between indices. In chapter 3, I investigated spatial differences in zooplankton assemblage nutritional quality for four BC bioregions. I applied order-level fatty acid averages to summer biomass data and generated assemblage essential fatty acid (EFA) averages for each bioregion. EFA quantities and concentrations were high in deep fjord assemblages and lower in nearshore and offshore assemblages. DHA/EPA, an important fatty acid quality index, was higher offshore and lower in deep shelf, deep fjord, and nearshore bioregions. Lower DHA/EPA in nearshore and deep fjord bioregions may pose a risk for juvenile salmon, though in fjords, these limitations may be offset by higher EFA quantities.

Text

2024-11-21

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/89700

Oceans and Fisheries

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/