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    Drivers of functional ecology of the Alaskan Arctic epibenthos

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    Author
    Sutton, Lauren
    Chair
    Iken, Katrin
    Committee
    Bluhm, Bodil
    Hauri, Claudine
    Konar, Brenda
    Mueter, Franz
    Keyword
    Benthic ecology
    Bering Sea
    Chukchi Sea
    Beaufort Sea
    Metadata
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    URI
    http://hdl.handle.net/11122/13131
    Abstract
    This dissertation explored multiple facets of functional diversity for epibenthic invertebrate communities of Alaskan Arctic shelves. Functional diversity is the range of organismal traits within a community that determines ecosystem functioning. As a complement to taxonomic diversity, functional diversity reflects what species "do" as opposed to "who" they are, providing information on community-level ecosystem resilience and vulnerability. The Alaskan Arctic marine system is presently changing at an unprecedented rate, which impacts the biomass-rich benthos that is of great importance to upper trophic level fishes, birds, and marine mammals as a food source. In my first chapter, I tested the Biodiversity-Ecosystem-Functioning hypothesis that states ecosystem functioning increases with increasing diversity, using the functional composition of epibenthic communities on the Beaufort and Chukchi Sea shelves as case studies. Functional diversity generally followed taxonomic diversity patterns on both shelves; however, functional composition was more similar between the two shelf systems compared to taxonomic composition. Higher functional diversity on the Beaufort Sea shelf resulted from a more even distribution of functional traits, pointing to stronger resource partitioning and niche complementarity. This, in turn, suggests stronger maintenance of ecosystem function through more efficient nutrient cycling, energy turnover, and recovery from disturbances. In chapter 2, I applied the Community Assembly Theory that assumes species assemble in a non-random way due to a series of biotic and environmental filters using the same Chukchi and Beaufort seas epibenthic communities. Environmental conditions in the Chukchi Sea exerted a stronger environmental filter (i.e., stronger influence of cumulative environmental drivers) on epibenthic functional diversity, especially through gradients in temperature, depth, and mud, compared to weaker depth- and salinity-related filters in the Beaufort Sea. This suggests that the Beaufort Sea community may be less affected by climatic change compared to those in the Chukchi Sea. Strong environmental filtering in the Chukchi Sea can act as a barrier to invading taxa, who must possess a suite of functional traits that allows them to survive in the specific Arctic environment. Continued warming and declining sea ice are assumed to encourage poleward movements of boreal taxa, a process especially likely for taxa migrating from the Bering Sea into the Chukchi Sea. Thus, in the third chapter, I modeled future functional composition of epibenthic communities in the Northern Bering and Chukchi seas, based on past (2009-2019) and predicted environmental conditions under a warmer and fresher, "worst case" scenario for mid- and end of-century timeframes. All regions exhibited functional changes over time associated with specific shifts in trait composition in each region; however, the magnitude of these functional shifts varied among time periods. The rate of functional changes suggests that Northern Bering Sea and Chukchi Sea communities may have already undergone a major transformation during the past decade, with fewer shifts expected by the mid-century. This dissertation employed a new approach of using functional traits to examine Arctic epibenthic community function and stability in relation to environmental conditions. It created a much-needed benchmark to assess regions of ecosystem vulnerability and resilience in the Alaskan Arctic.
    Description
    Dissertation (Ph.D.) University of Alaska Fairbanks, 2022
    Table of Contents
    Chapter 1: Introduction -- References. Chapter 2: Comparison of functional diversity of two Alaskan Arctic shelf epibenthic communities -- Abstract -- 2.1. Introduction -- 2.2. Methods -- 2.2.1. Study sites -- 2.2.2. Sample collection -- 2.2.3. Biological traits analysis -- 2.2.4. Shelf comparisons of functional and taxonomic diversity metrics -- 2.2.5. Comparisons of functional and taxonomic composition -- 2.3. Results -- 2.3.1. Functional and taxonomic diversity metrics -- 2.3.2. Comparison in functional and taxonomic composition between shelves -- 2.3.3. Comparison of functional and taxonomic composition within each shelf -- 2.4. Discussion -- 2.4.1. Comparison of taxonomic and functional diversity metrics -- 2.4.2. Functional diversity metrics -- 2.4.3. Functional trait composition of Beaufort and Chukchi sea epibenthos -- 2.5. Conclusion -- Acknowledgements -- References -- 2.6. Appendix. Chapter 3: Environmental filtering influences community assembly of epibenthic communities -- Abstract -- 3.1. Introduction -- 3.2. Materials and methods -- 3.2.1. Study sites and sample collection -- 3.2.2. Epibenthic functional composition -- 3.2.3. Relationships between functional composition and environmental variables -- 3.2.4. Trait convergence -- 3.2.5. Trait convergence and environmental gradients -- 3.3. Results -- 3.3.1. Functional composition and relationship to environmental conditions -- 3.3.2. Relationship between environmental gradients and trait convergence -- 3.4. Discussion -- 3.4.1. Drivers of functional composition and environmental variables -- 3.4.2. The influence of environmental filters on trait convergence -- 3.5. Conclusion -- Acknowledgements -- References -- 3.6. Appendix. Chapter 4: Predicting epibenthic functional distribution on changing Arctic shelves -- Abstract -- 4.1. Introduction -- 4.2. Methods -- 4.2.1. Study site and sample collection -- 4.2.2. Epibenthic functional composition -- 4.2.3. Joint species distribution models using hierarchical modeling of species communities -- 4.3. Results -- 4.3.1. Epibenthic functional composition changes over time -- 4.3.2. Functional composition -- 4.4. Discussion -- 4.5. Conclusion -- Acknowledgments -- References -- 4.6. Appendix. Chapter 5: General conclusion.
    Date
    2022-12
    Type
    Dissertation
    Collections
    Marine Sciences

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