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    Seaweeds across ecosystem boundaries: from habitat formation to harvest implications

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    Ulaski_B_2022.pdf
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    Author
    Ulaski, Brian P.
    Chair
    Konar, Brenda
    Committee
    Iken, Katrin
    Otis, Edward O.
    Gorman, Kristen B.
    Sikes, Derek S.
    Keyword
    Marine algae
    Ecology
    Habitat
    Harvesting
    Regeneration
    Saccharina
    Zostera marina
    Necreocystis luetkeana
    Kelps
    Kelp bed ecology
    Metadata
    Show full item record
    URI
    http://hdl.handle.net/11122/13133
    Abstract
    This dissertation broadly investigates the response of wild stock seaweeds to harvesting, and their role as biogenic habitat formers when cast ashore. Seaweeds are important primary producers and foundation species that maintain their functional roles across coastal ecosystem boundaries. Climate-driven loss of seaweed biomass, including that of kelp forests, is exacerbated by other human-related activities that directly impact their persistence, such as overharvesting. Attached rockweeds and kelps are commonly harvested for food, while diverse assemblages of beach-cast seaweed wrack are collected for fertilizer. The importance of wrack habitat in Alaska has not been extensively explored, especially in regions where there is a growing interest in harvesting by coastal communities. This research explores precautionary approaches to lessen wild stock seaweed decline in the face of increased harvest interests by: 1) characterizing information on reproductive timing, standing crop, and regrowth potential of attached populations; 2) investigating reproductive viability of seaweed wrack and identifying how landscape variables influence wrack distribution through paired on-the-ground and aerial surveys; and 3) characterizing wrack-associated macrofaunal communities and determining successional states in aging wrack. Regrowth following harvest of attached focal seaweeds (i.e., Fucus distichus, Saccharina latissima, and Nereocystis luetkeana) was generally low after two months, but the amount of biomass after four- and six-months post-harvest was more comparable to non-harvested areas. Depending on the species (e.g., F. distichus), attached individuals that became reproductive at larger sizes were associated with lower density and lower biomass areas with slower recovery. Differences in diversity and composition of wrack were correlated with coastline (substrate type, slope, and exposure) and adjacent watershed characteristics (percent glacial cover and range in seawater salinity). On-the-ground and drone-based surveys of beach-cast wrack both revealed seasonal patterns of patchy (spring) and continuous (summer) distribution. Macroinvertebrate community diversity was positively correlated with seaweed biomass and tidal height of the wrack line. Furthermore, succession experiments revealed that aged wrack harbored diverse and changing macroinvertebrate communities over time, with decomposers being early colonizers, and predators arriving later. Altogether, the findings of this research offer key information to developing sustainable harvest regulations in Alaska, as human use of seaweed increases.
    Description
    Dissertation (Ph.D.) University of Alaska Fairbanks, 2022
    Table of Contents
    Introduction -- Chapter 1: Seaweed reproduction and harvest rebound in Southcentral Alaska: Implications for wild stock management -- Chapter 2: How landscape variables influence the relative abundance, composition, and reproductive viability of macroalgal wrack in a glacial estuary -- Chapter 3: The importance of beach-cast and drifting wrack habitat for macrofauna in a high latitude estuary -- Conclusions.
    Date
    2022-12
    Type
    Dissertation
    Collections
    Marine Sciences

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