McCormack_whole_thesis.pdf (40.9 MB)
Alternative energy pathways in Southern Ocean food webs : combining theoretical, empirical and modelling approaches
thesisposted on 2023-05-27, 09:05 authored by Stacey McCormackStacey McCormack
The flow of biomass and energy in Southern Ocean food webs is not well characterised, but is crucial in determining how Antarctic marine ecosystems may respond to environmental change and harvesting, and for formulating appropriate management and conservation strategies. Energy flow in Southern Ocean ecosystems is often described in terms of the short, highly efficient food chain, with Antarctic krill (Euphausia superba) dominating energy transfer from primary producers to higher trophic levels. However, there is increasing evidence that alternative energy pathways through other types of zooplankton and mesopelagic fish and squid are equally, if not more important in some regions or years. The question of the importance of these alternative pathways has not yet been examined at a circumpolar scale. The thesis draws together diverse approaches from theoretical ecology, empirical research and quantitative ecosystem modelling to generate novel and important insights into Southern Ocean food web structures and the pathways for energy flow through mid-trophic levels at varying spatial scales ranging from regional to circumpolar. Chapter 1 reviews the ecosystem modelling process and how data signatures, in particular stable isotopes, may be more powerfully used in the development and evaluation of size- and species- based food web models to address questions of ecosystem structure and energy flow. Chapter 2 used network analyses informed by dietary data available from the SCAR Southern Ocean Diet and Energetics Database (SODD) to show that food web structures are fundamentally different between the major oceanic sectors of the Southern Ocean; the mid-trophic groups responsible for maintaining marine mammal and bird populations vary between each sector. Chapter 3 develops a decision framework for species aggregation in Antarctic food web models utilising information from the SODD to justify the functional group structure of an Ecopath model for Prydz Bay, East Antarctica. Chapter 4 presents the development and implementation of a Prydz Bay Ecopath model and provides the first quantitative analysis of the importance of different mid-trophic-level groups for directing energy flow in East Antarctic marine food webs. Finally, Chapter 5 synthesises these new insights into alternative energy pathways in Southern Ocean food webs and considers future research directions for identifying key environmental drivers of these differences.
Rights statementCopyright 2019 the author Chapter 1 appears to be the equivalent of a post-peer-review, pre-copyedit version of an article published in Reviews in fish biology and fisheries. The final authenticated version is available online at: http://dx.doi.org/10.1007/s1116 Chapter 3 appears to be the equivalent of a post-print version of an article published as: McCormack, S. A., Melbourne-Thomas, J., Trebilco, R., Blanchard, J. L., Constable, A., 2017. Simplification of complex ecological networks - species aggregation in Antarctic food web models. In Syme., G., Hatton MacDonald, D., Fulton, B., Piantadosi, J. (eds) MODSIM2017, 22nd International Congress on Modelling and Simulation. Modelling and Simulation Society of Australia and New Zealand, December 2017, pp. 264-270. ISBN: 978-0-9872143-7-9. These proceedings are licensed under the terms of the Creative Commons Attribution 4.0 International CC BY License (http://creativecommons.org/licenses/by/4.0), which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you attribute MSSANZ and the original author(s) and source, provide a link to the Creative Commons licence and indicate if changes were made. Images or other third party material are included in this licence, unless otherwise indicated in a credit line to the material. Chapter 4 appears to be the equivalent of a post-print version of an article published as: McCormack, S. A., Melbourne-Thomas, J., Trebilco, R., Blanchard, J. L., Constable, A. 2019. Alternative energy pathways in Southern Ocean food webs: insights from a balanced model of Prydz Bay, Antarctica, Deep sea research, Part II: Topical studies in oceanography, In-Press, 6 July 2019.