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    Exploring the North American Arctic benthos: community structure and oil degradation potential of sediment bacteria and archaea

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    Author
    Walker, Alexis M.
    Chair
    Mincks, Sarah L.
    Leigh, Mary Beth
    Committee
    Islas, Ana Aguilar
    Lopez, Andres
    Collins, Eric R.
    Keyword
    Benthos
    Arctic regions
    Microbiology
    Beaufort Sea
    Chukchi Sea
    Marine bacteria
    Petroleum
    Biodegradation
    Metadata
    Show full item record
    URI
    http://hdl.handle.net/11122/13134
    Abstract
    The Chukchi and Beaufort seas benthic habitats are home to a multitude of ecologically and commercially important organisms that are subject to ongoing environmental changes, including the impacts of climate change and increased exposure to contaminants. Benthic bacteria and archaea can be considered biogeochemical engineers. They play a major role in organic matter (OM) degradation and nutrient cycling and their community structure can reflect changes in environmental conditions such as OM composition and quantity, nutrient availability, redox conditions, and natural/anthropogenic contaminants (e.g. petroleum hydrocarbons). Yet, sediment microbial communities have rarely been examined in these marginal seas of North American Arctic. In this dissertation, I characterized marine sediment microbial communities along environmental gradients in the Beaufort (Chapter 2) and Chukchi seas (Chapter 3) and assess Arctic benthic microbial community response to oil exposure (Chapter 4). I assessed diversity, community structure, and environmental correlates of prokaryotic communities via 16S rRNA amplicon sequencing in surface sediments (upper 1 cm) from the Northern Bering Sea to the Amundsen Gulf in the southern Beaufort Sea. On a broad spatial scale encompassing the whole study area, I observed three distinct microbial assemblages. One assemblage was characteristic of the Northern Bering-Chukchi seas shelf, and two distinguished nearshore and offshore sediments in the Beaufort Sea. Within the Beaufort Sea, four assemblages were identified, reflecting habitat heterogeneity with respect to OM loading, water depth, and nearshore/riverine input, including a major influence of the Mackenzie River. Two assemblages were distinguished within the Bering-Chukchi region, including one representative of suboxic sediments and one suggesting influence of phytodetrital OM input as evidenced by the abundance of diatom/particle-associated microbes. These two assemblages may also reflect differences between local versus advective OM inputs. Incubation experiments exposing Arctic marine sediments to fresh and weathered crude oil under anaerobic and aerobic conditions were performed to assess oil biodegradation potential and identify putative oil-degrading microbes in the benthos. Molecular analyses revealed that significant community shifts occurred in the oiled treatments, with distinct communities emerging following exposure to fresh versus weathered oil, and in oxic versus anoxic conditions. The work presented here constitutes the first large-scale survey of benthic microbes in this region of the North American Arctic, including their response to petroleum contamination, generating valuable baseline data for the changes to come.
    Description
    Dissertation (Ph.D.) University of Alaska Fairbanks, 2022
    Table of Contents
    Chapter 1: General introduction -- Chapter 2: Patterns in benthic microbial community structure across environmental gradients in the Beaufort Sea shelf and slope -- Chapter 3: Benthic bacteria and archaea in the North American Arctic reflect food supply regimes and impacts of coastal and riverine inputs -- Chapter 4: Microbial community response to crude oil exposure in Arctic marine sediments -- Chapter 5: General conclusion.
    Date
    2022-12
    Type
    Dissertation
    Collections
    Marine Sciences

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