Now showing items 1-20 of 10604

    • Control and inverse problems for the wave equation on metric graphs

      Zhao, Yuanyuan; Avdonin, Sergei; Rhodes, John; Rybkin, Alexei; Avdonina, Nina (2022-12)
      This thesis focuses on control and inverse problems for the wave equation on finite metric graphs. The first part deals with the control problem for the wave equation on tree graphs. We propose new constructive algorithms for solving initial boundary value problems on general graphs and boundary control problems on tree graphs. We demonstrate that the wave equation on a tree is exactly controllable if and only if controls are applied at all or all but one of the boundary vertices. We find the minimal controllability time and prove that our result is optimal in the general case. The second part deals with the inverse problem for the wave equation on tree graphs. We describe the dynamical Leaf Peeling (LP) method. The main step of the method is recalculating the response operator from the original tree to a peeled tree. The LP method allows us to recover the connectivity, potential function on a tree graph and the lengths of its edges from the response operator given on a finite time interval. In the third part we consider the control problem for the wave equation on graphs with cycles. Among all vertices and edges we choose certain active vertices and edges, and give a constructive proof that the wave equation on the graph is exactly controllable if Neumann controllers are placed at the active vertices and Dirichlet controllers are placed at the active edges. The control time for this construction is determined by the chosen orientation and path decomposition of the graph. We indicate the optimal time that guarantees the exact controllability for all systems of a described class on a given graph. While the choice of the active vertices and edges is not unique, we find the minimum number of controllers to guarantee the exact controllability as a graph invariant.
    • Thermokarst-pond plant community characteristics and effects on icewedge degradation in the Prudhoe Bay region, Alaska

      Watson-Cook, Emily; Walker, Donald A.; Breen, Amy L.; Raynolds, Martha K.; Ruess, Roger W. (2022-12)
      Ice-wedge thermokarst ponds are forming in many areas of the Arctic as a result of climate warming and infrastructure development. Previous research suggests that development of aquatic vegetation within these ponds may create negative feedbacks to the process of ice-wedge degradation by reducing pond-bottom temperatures and thaw depths. The objectives of this research were to characterize thermokarst-pond plant communities and to evaluate the effects of vegetation on within-pond sediment temperatures and thaw depths. Aquatic vegetation was sampled in 39 plots within 29 thermokarst ponds in the Prudhoe Bay region of Alaska. Five floristically distinct plant communities were identified: Calliergon richardsonii comm., Scorpidium scorpioides comm., Pseudocalliergon turgescens comm., Hippuris vulgaris comm., and Ranunculus gmelinii comm. These communities had low species diversity (mean species richness 3.2 ± 1.5 SD) and were best differentiated by the single dominant species included in plant-community names. Ordination of species composition data revealed a temperature gradient, along which high biomass was associated with low sediment temperature and shallow thaw depth. The C. richardsonii and P. turgescens moss-dominated communities had very high biomass values (3079 g/m² ± 1895 SD and 3135 g/m² ± 585 SD, respectively). Examinations of temperature and thaw differences between communities were limited by sample size, as several communities were described based on only two plots each. To evaluate the potential insulative role of pond vegetation on pond-bottom temperature and thaw depth, differences between broad vegetation types (i.e., moss, forb, sparse) rather than communities were examined. Vegetation cover, total biomass, biomass of plant functional types, and soil organic horizon thickness were sampled, along with mean thaw depth and sediment temperature. Linear mixed-effects models were used to identify vegetation-related parameters with the highest predictive power of thaw and temperature. Mean sediment temperatures measured during 19 July - 23 August 2021 were warmest in the sparse plots (8.9 °C ± 0.2 SE) compared to the forb plots (8.2 °C ± 0.3 SE) and the moss plots (6.7 °C ± 0.4 SE). Moss plots also had shallower late-August thaw depths (42.5 cm ± 1.3 SE) compared to forb (52.7 cm ± 1.7 SE) and sparse (52.7 cm ± 1.4 SE) plots. Vegetation cover was negatively correlated with sediment temperature, whereas vegetation cover, moss thickness, and organic layer thickness were all negatively correlated with thaw depth. The stronger relationships observed between vegetation-related factors and thaw depth compared to sediment temperature were probably affected by the short period of temperature observations within this study. Although stochastic factors likely play a role in community establishment within thermokarst ponds, additional sampling is needed across all pond ages, ice-wedge degradation/stabilization stages, and a broader range of habitats within ponds to discern if there is a clear successional trajectory for thermokarst-pond plant communities. This study provided descriptions of relatively understudied aquatic plant communities that play an important role in Arctic landscape change. Notably, very high biomass values were found in young ponds (one with an age of only 8 years) dominated by moss communities. Results indicate that aquatic plant communities with high moss biomass have high capacity for insulation that potentially reduces permafrost thaw and ice-wedge degradation, leading to ice-wedge stabilization.
    • Exploring the North American Arctic benthos: community structure and oil degradation potential of sediment bacteria and archaea

      Walker, Alexis M.; Mincks, Sarah L.; Leigh, Mary Beth; Islas, Ana Aguilar; Lopez, Andres; Collins, Eric R. (2022-12)
      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.
    • Seaweeds across ecosystem boundaries: from habitat formation to harvest implications

      Ulaski, Brian P.; Konar, Brenda; Iken, Katrin; Otis, Edward O.; Gorman, Kristen B.; Sikes, Derek S. (2022-12)
      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.
    • Compound-specific stable isotopes of amino acids reveal the influence of trophic level and primary production sources on mercury concentrations in fishes from the Aleutian Islands, Alaska

      Barst, Benjamin; Wooller, Matthew; Horstmann, Lara (2022-12)
      Total mercury (THg) concentrations exceed thresholds of concern in some Steller sea lion (Eumetopias jubatus; SSL) tissues from certain portions of the Aleutian Islands, Alaska. Here, compound-specific stable isotope analyses (CSIA) of carbon in essential amino acids ([delta]¹³CEAA values) and nitrogen in AAs ([delta]¹⁵NAA values) in fish muscle tissue was applied to quantify the proportional contributions of primary production sources and trophic positions of eight prey species (n = 474 total) that are part of SSL diets. Previous THg analyses of fish muscle, coupled with additional monomethylmercury (MMHg) analyses of a subset of samples, substantiated previous findings that fishes from the west of Amchitka Pass, a discrete oceanographic boundary of the Aleutian Archipelago, have higher muscle THg concentrations relative to fishes from east of the pass. All fish muscle samples were analyzed separately for, both, CSIA-AA of carbon and nitrogen. The [delta]¹³CEAA values in fish muscle demonstrated that although most fishes obtained their EAAs primarily from algae, some species varied in the extent to which they relied on this primary production source. Certain [delta]¹⁵NAA values of the same fish samples indicated that trophic positions of fishes were higher from the west relative to the east of the pass for some species. Total Hg was positively correlated with bulk [delta]¹⁵N values, [delta]¹⁵N values of glutamic acid ([delta]¹⁵NGlu), and trophic positions. However, only trophic magnification slopes using [delta]¹⁵NGlu values indicated a higher rate of Hg biomagnification to the west of Amchitka Pass. Broad and species-level multiple linear regression models revealed that trophic position was the most important driver of fish muscle THg with a smaller amount of variation explained by other parameters, such as proportional contributions of primary production sources, fish body condition, and catch location. Collectively, results indicate that differences in fish trophic positions were the most consistent determinants of the higher fish THg concentrations to the west of Amchitka Pass. However, a higher rate of THg biomagnification to the west of Amchitka Pass may also play a role in the regional differences in fish muscle THg.
    • Drivers of functional ecology of the Alaskan Arctic epibenthos

      Sutton, Lauren; Iken, Katrin; Bluhm, Bodil; Hauri, Claudine; Konar, Brenda; Mueter, Franz (2022-12)
      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.
    • Finding solutions to the world's pending critical minerals supply crisis: developing new geochemical analytical methods and evaluating the potential for Te and Bi extraction from existing Au mines

      Spaleta, Karen Joy; Newberry, Rainer J.; Hayes, Sarah M.; Keskinen, Mary J.; Piatak, Nadine M.; Trainor, Thomas P. (2022-12)
      Bismuth (Bi) and tellurium (Te) are technologically critical elements (TCEs), also known as critical minerals, primarily recovered as byproducts in the extraction of lead (Pb) and copper (Cu), respectively. Global demand for Bi and Te is expected to rise signicantly in the coming decades as energy production becomes carbon neutral. In order to meet this demand, alternative sources of Bi and Te must be identifed. Bismuth and Te are commonly enriched in granitoid-related gold (Au) deposits and epithermal Au-Ag-Te deposits but are not presently recovered. Identifying which Bi and Te minerals are present throughout the Au extraction process is essential to determining where these elements might be recovered and in what quantities. Concurrent with the need to identify potential sources of TCEs is the need to validate advancements in analytical geochemical methods. Energy Dispersive Spectrometry (EDS) methods have become a go-to mineralogical identication tool in the mineral exploration and mining industries due to their rapid automated analysis. However, little cross-validation has been done to verify the results and determine the limitations of these tools. Here I present the results of three studies: 1) an EDS bulk mineralogy phase mapping method validation study on Au and Cu mill processing samples; 2) a detailed elemental composition and mineralogical analysis of samples from the Pogo Mine Mill (Interior Alaska, USA) identifying potential annual byproduct recovery of 13.5 and 7.5 metric tonnes of Bi and Te, respectively; and 3) a detailed elemental composition and mineralogical analysis of mill samples from the Golden Sunlight Mine Mill (Whitehall, Montana, USA) identifying Te primarily hosted in pyrite. Using this approach for similar metallurgical studies at other Au mines with known signicant Bi and Te could yield additional targets for recovery and provide a framework for identifying other potential TCEs/critical minerals in other deposits.
    • Freshwater pressures on Pacific salmon in the coastal watersheds of Alaska

      Sergeant, Christopher J.; Falke, Jeffrey; Bellmore, J. Ryan; Mueter, Franz; Westley, Peter (2022-12)
      This dissertation explores the implications of a warmer and wetter climate on the freshwater life stages of Pacific salmon (Oncorhynchus spp.) in the focal region of southern coastal Alaska. Recent trends and long-term climate change predictions support the notion that arctic and subarctic watersheds will be subject to warming air temperatures, increased rainfall in the autumn and winter, diminishing snowpack, and continued glacial recession. Such atmospheric and terrestrial changes will shift patterns of streamflow, water temperature, and habitat diversity that comprise the basic building blocks of freshwater ecosystems that support Pacific salmon. Alaska's Pacific salmon populations sustain a multi-billion-dollar economy and have supported Indigenous Peoples' way of life for millennia. The character of Alaska is defined, in part, by being one of the last places in North America to support a harvestable bounty of fishes and wildlife. Therefore, studies that describe and inventory current freshwater habitat diversity, predict future habitat change, and model the responses of Alaska Pacific salmon populations to a range of future habitat scenarios will not only advance general ecological understanding, but also provide valuable insights into the trajectory and range of Pacific salmon futures for the remainder of the 21st century. In Chapter 1, A classification of streamflow patterns across the coastal Gulf of Alaska, I classify and map 4,140 coastal Alaska watersheds according to 13 unique patterns of rain, snow, and glacier ice runoff. In Chapter 2, Hypoxia vulnerability in the salmon watersheds of Southeast Alaska, I demonstrate the utility of a mechanistic model of dissolved oxygen dynamics in streams based on low-flow channel hydraulics, water temperature, and spawning salmon density. In Chapter 3, Pacific salmon population responses to a warmer, wetter climate at northern latitudes, I apply a newly established life cycle model to quantify the population responses of chum (O. keta), pink (O. gorbuscha), and coho salmon (O. kisutch) to daily variation in discharge and water temperature patterns, including extreme floods and droughts. Taken together, these findings contribute to the growing body of knowledge on the impacts of a warmer and wetter atmosphere on high-latitude freshwater ecosystems and demonstrate the value of land and water management actions that conserve ecological functioning and promote Pacific salmon resilience.
    • Exploring the evolution of fishes at high latitudes

      Rix, Anna S.; Wolf, Diana; López, J. Andrés; Podlutsky, Andrej; Stecyk, Jonathan; Takebayashi, Naoki (2022-12)
      Fish species found in high latitude waters are especially vulnerable to climatic changes due to their inability to regulate body temperature and long evolution in cold, oxygen-rich aquatic environments. Antarctic notothenioid fishes have evolved to thrive in an extremely stable, cold, oxygen-rich environment. Likewise, lake trout live in a cold, oxygen-rich environment, but commonly experience a wider range of temperatures than notothenioids. Millions of years of evolution in the cold have shaped the genetics of these fishes, but the effects on their biology remain largely unexplored. This dissertation seeks to learn from the past evolution of these two evolutionarily distant types of high latitude fishes to enhance predictions for how these animals can cope with future environmental changes. Specifically, this dissertation examines the genetics of fishes with limited thermal tolerance from the population level down to a single gene. These studies relied on DNA sequence evidence produced with two different technologies and analyzed under functional, phylogenetic, and population genetic frameworks. In the first study, mitochondrial DNA (mtDNA) variation is examined to determine ancestral affinities and geographic distribution of mtDNA variants in lake trout across Alaska. Lake trout in Alaska descend from two distinct mtDNA lineages. One mtDNA lineage is restricted to Arctic Alaska, north of the Brooks Range, while the other lineage is found across Alaska. Lake trout likely dispersed from glacial refugia in western Canada to recolonize Alaska and the movement patterns from recolonization assist in determining how lake trout are likely to move across the landscape in the future. In the second study, genome wide genetic diversity of lake trout in seven Alaskan lakes is explored to determine ancestral affinities and colonization pathways. Despite past movement, the lake trout population currently found in each of the sampled lakes is genetically distinct from all other sampled populations and no migration currently seems to be occurring, even between lakes less than 20 km from each other. This research shows lake trout in Alaska are genetically diverse, but with little gene flow, genetic rescue and transfer of genetic variation between populations is unlikely to occur. In the third component of this dissertation, the evolution of the critical hypoxia transcription factor is examined in Antarctic notothenioids. The hypoxia-inducible factor-1alpha (HIF-1alpha) of Antarctic notothenioids contains a polyglutamine/glutamic acid insert that may impact the function of this key transcription factor. Thus, Antarctic notothenioids may have difficulties in responding to climate change induced hypoxia. Overall, the adaptive consequences of evolution in high latitude aquatic environments may be detrimental to fishes as they face climate changes. Other high latitude freshwater fishes like lake trout may have limited gene flow among populations, reducing potential for adaptation and genetic rescue in response to climate change. More research into the evolution and functional implications of different natural genetic variants is needed to protect these unique high latitude species.
    • Acute toxicity of copper to three species of pacific salmon in water with low hardness and low dissolved organic carbon

      Porter, Drew E.; Barst, Benjamin; Wooller, Matthew; Westley, Peter; Gorman, Kristen (2022-12)
      Despite a history of investigation, the toxicity of copper (Cu) to fishes remains difficult to predict due to the complex influential effects of water chemistry. Water hardness and dissolved organic carbon (DOC) concentrations can vary significantly within a watershed and also attenuate the toxicity of Cu to fishes. To account for location-specific water chemistry and predict Cu toxicity to aquatic organisms the United States Environmental Protection Agency (USEPA) endorses use of the biotic ligand model (BLM). Though the BLM has proven useful in many instances, it has performed inaccurately for waters low in hardness and DOC; this has raised questions regarding the model's applicability in certain regions. One such region is Alaska's Bristol Bay watershed, where tributaries low in hardness and DOC support an abundance of Pacific salmon (Oncorhynchus spp.) life. The Bristol Bay watershed also contains one of the largest Cu deposits on earth. Here, to determine empirical lethal Cu concentrations for water conditions relevant to the Bristol Bay watershed, and to assess the accuracy of the BLM in such waters, juvenile sockeye salmon (O. nerka), Chinook salmon (O. tshawytscha), and coho salmon (O. kisutch) were exposed to Cu in low-hardness (5.6-13.7 mg/L) and low-DOC (0.4-2.7 mg/L) water during 96 h flow-through bioassays. Juveniles were used to assess toxicity at a known Cu-sensitive life stage. The experimentally determined acute median lethal concentrations (LC50s) were 35.2 µg Cu/L (95% confidence interval [CI]: 32.3, 38.1) for sockeye salmon, 23.9 µg Cu/L (95% CI: 20.3, 27.4) for Chinook salmon, and 6.3 µg Cu/L (95% CI: 5.6, 7.0) for coho salmon. The BLM consistently under-predicted LC50s; predictions were 62.6 µg Cu/L for sockeye salmon, 35.4 µg Cu/L for Chinook salmon, and 15.1 µg Cu/L for coho salmon. These discrepancies demonstrate that the BLM is inaccurate for waters with low hardness and DOC and that currently assessed levels of risk of Cu to salmon are incorrect. These findings reveal a need for further calibration of the BLM for use in areas like the Bristol Bay watershed and provide information necessary to accurately assess Cu toxicity to three important species of Pacific salmon.
    • Controllability of non-self-adjoint systems of partial differential equations

      Park, Jeff; Avdonin, Sergei; Rhodes, John; Allman, Elizabeth; Rybkin, Alexei (2022-12)
      In this dissertation, we first consider the problem of exact controllability of a system of N one-dimensional coupled wave equations when the control is exerted on a part of the boundary by means of one control. We provide a Kalman condition (necessary and sufficient) and give a description of the attainable set. The second problem we consider is the inverse problem for the vector Schrödinger equation on the interval with a non-self-adjoint matrix potential. In doing so, we prove controllability of the system and develop a method to recover spectral data from the system. Then, we solve the inverse problem using techniques of the Boundary Control method. The final problem is that of internal null controllability of a beam equation on an interval. We provide a partial characterization for controllability for arbitrary open subsets where the control is applied.
    • Development of an active vacuum insulation panel for use in building applications

      Nelson, Haley D.; Marsik, Tom; Peterson, Rorik; Huang, Daisy (2022-12)
      Vacuum insulation panels, or VIPs, are among the highest performing forms of building insulation available on the commercial market, with some per inch R-values advertised as 60°F·ft²·hr/(BTU·inch). Though there is strong market demand for high-performing forms of insulation, the adoption of VIPs is hindered by their relatively high costs, uncertain service lifespans, sensitivity to internal pressure changes, susceptibility to thermal bridging along their edges, and other issues. Particularly in building applications, typical VIPs are often passed over in favor of insulation types that can be easily customized on-site, are produced to larger dimensions, and are not as vulnerable to damage or rough handling. Many of these challenges can be addressed by VIPs equipped with the means to be evacuated as often as is necessary to reestablish a desired internal pressure, termed "active VIPs." The primary aim of this research was to develop and assess the thermal performance of an active VIP prototype. A system assembly for testing active VIP prototypes was first developed, and its testing capabilities assessed. Following confirmation of its testing efficacy, an active VIP prototype was constructed using a metallized barrier laminate and fiberglass core insulation, and its performance profiled in terms of its thermal conductivity as a function of the internal pressure. The active VIP prototype was found to have an R-value per inch of about 38°F·ft²·hr/(BTU·inch) at internal pressures on the scale of 10⁰ mTorr. This R-value per inch is about an order of magnitude higher than conventional types of insulation used in building applications. From results obtained, the active VIP prototype may be considered a viable candidate for further research and development.
    • I'm a killer whale: the process of cultural identity development from the perspectives of young indigenous children

      Lunda, Angela; John, Theresa; Green, Carie; Richardson, Lisa; Hyslop, Polly (2022-12)
      This qualitative single case study examined the phenomenon of cultural identity development from the perspective of young Indigenous children situated within the context of their southeast Alaskan community. Decades of assimilationist policies have eroded cultural identity among many Indigenous Alaskans, yet a strong cultural identity is known to be a protective factor for Indigenous peoples. Building on Indigenous identity development theory, the study sought to answer the research questions: (1) How do young children demonstrate their cultural identity through interactions on the Land? (2) How do community organizations support cultural identity development (CID) in young Indigenous children? (3) What role do peers play in nurturing cultural identity development (CID)? And (4) How do teachers and families nurture CID? The primary data source was video collected by children wearing forehead cameras as they engaged in semi-structured activities on the Land; video data were augmented by surveys, interviews, children's drawings, and careful observations. These methods allowed the researcher to examine the child's lived experiences to begin to untangle the rich interactions between children, the Land, parents, and educators, and to describe CID nurturing factors. Reflexive thematic analysis was employed to discover themes and patterns in the data. Findings reveal that children demonstrate their Indigenous identity by learning and exhibiting traditional ecological knowledge, which includes intricate knowledge of the Land, subsistence practices, and core cultural values. The process of cultural identity development was supported by the community through vision and funding for cultural initiatives. Peers, parents, and educators contributed to the cultural identity development of the young participants by enacting moves to increase confidence and competence on the Land. This study has implications for policymakers, educators, families, and others interested in nurturing healthy identity development among young Indigenous children.
    • Effects of diet and hibernation in skeletal muscle performance

      Krishnan, Jishnu K.S.; Oliver, S. Ryan; Drew, Kelly L.; Weltzin, Maegan D.; Kuhn, Thomas B. (2022-12)
      Hibernating animals, such as the arctic ground squirrel (AGS), are subjected to a wide range of temperature variations. During hibernation, when they are predominantly physically inactive, body temperature can drop as low as -3°C, while in summer, body temperature can climb as high as 40°C. Torpor is a state of inactivity in an animal induced by a lack of food, which is followed by a fall in body temperature and metabolic rate. Torpor lasts around 21 days in AGS, and the progression of torpor begins with early torpor, followed by mid and late torpor, and culminates with interbout arousal lasting less than 24 hours. AGS exhibit reduced muscular atrophy and protein loss despite lengthy periods of immobility, hypometabolism, and severe hypothermic conditions during hibernation. Skeletal muscle plasticity, unique to mammalian hibernators, may explain why cardiac and respiratory skeletal muscle can function at hypothermic temperatures during and after hibernation. As a result, understanding the effects of ambient temperature on muscle physiology and contractile function is critical. The focus of this research was to investigate skeletal muscle contractile performance and fatigue resistance in ex vivo muscle tissues during hypothermic temperature stress. Ex vivo tissue organ bath functional assays were performed in hibernator and/or non-hibernator rodent models to determine changes in performance and fatigue resistance in the AGS diaphragm induced by polyunsaturated fatty acid dietary modification or ambient hypothermic stress. This study lends support to the idea that diet and hypothermic stress might modify certain functional aspects of skeletal muscle, most likely via membrane lipid composition, ambient temperature, and torpor interaction. Furthermore, summer active AGS has a higher fatigue resistance than mid torpor AGS during the hibernating season. Furthermore, skeletal muscle fatigue resistance was significantly lower in Sprague Dawley rats than in both summer active and hibernating AGS. Preliminary data also suggested that hypothermic stress, to some extent, enhanced fatigue resistance regardless of torpor status or species difference.
    • Architects of abundance: indigenous regenerative food and land management systems and the excavation of hidden history

      Johnston, Lyla June; Black, Jessica; Cajete, Gregory; Nelson, Melissa; Collin, Yvette Running Horse; Hum, Richard (2022-12)
      Pre-Columbian and contemporary Indigenous Nations of North and South America (hereafter referred to as Turtle Island and Abya Yala) have managed ecosystems extensively to produce prolific and predictable food systems for themselves and non-humans, whom they often view as relatives. The elements of earth, water, fire, and air are explored to analyze Indigenous soil management, Indigenous aquaculture, Indigenous pyrogenic land management, and Indigenous oral histories, respectively. First, a review of four Indigenous societies and their soil management techniques revealed that none of these systems require outside fertilizer or irrigation to sustain ecocentric food systems on millennial scales. Second, a comparative analysis of six Indigenous fisheries showed how these communities operate on regional-scales, manually augment habitat for key species, are thousands of years old, and are driven by value systems rooted in reciprocity, reverence, respect, restraint, and responsibility to homeland. Third, an in-depth analysis of fire regime data from a variety of sources indicates that Diné and Pueblo Ancestors did indeed manage the Ch'ooshgai (Chuska) Mountain Range with routine burning during the Holocene epoch and negates theories that these fire regimes were due to lightning ignition. Fourth, a synthesis of interviews with four contemporary Indigenous land managers confirms that these cultural groups were and are active managers of local ecosystems. Despite coming from different places, all interviewees are driven by a similar set of principles: reverence for the sacredness of life, non-humans are the equal and sacred relatives of humans, and a belief that human groups are divinely assigned to care for their respective homelands. The next chapter offers an articulation of a theory of Indigenous Regenerative Ecosystem Design (IRED) to support the field and outline potential avenues for future research. The eighth chapter offers policy recommendations based on successful Indigenous food systems for federal, tribal, and nongovernmental agencies to help us effectively address the social and environmental challenges of our times. The ninth chapter proposes that the extent and sophistication of Indigenous food systems were minimized in the historical record precisely because they are living contradictions to the narratives used to legitimize land seizure and attempted genocide. Overall, it was found that most traditional Indigenous communities are not passive observers of nature but are instead influential facilitators of landscape scale abundance, rooted in an ethic of kinship and reverence.
    • Species distribution modeling of northern sea otters (Enhydra lutris kenyoni) in a data-limited ecosystem

      Hasan, Elizabeth L.; Konar, Brenda; Gorman, Kristen; Coletti, Heather (2022-12)
      Species distribution models are used to map and predict geographic distributions of animals based on environmental covariates. However, species distribution models often require high resolution habitat data and time-series data on animal locations. In data-limited regions with little animal survey data or habitat information, modeling is more challenging and often ignores important environmental attributes. For sea otters (Enhydra lutris), a federally protected keystone species with variable population trends across their range, predictive modeling of distributions has been successfully conducted in areas with an abundance of sea otter and habitat data. Here, we used open-access data across a single time step and leveraged a presence-only model, Maximum Entropy (MaxEnt), to investigate subtidal habitat associations (substrate and algal cover, bathymetry, and rugosity) of northern sea otters (E. lutris kenyoni) in a data-limited ecosystem, Kachemak Bay, Alaska. These habitat associations corroborated previous findings regarding the importance of bathymetry and understory kelp as predictors of sea otter presence. Novel associations were detected, as filamentous algae and shell litter were positively and negatively associated with sea otter presence, respectively. This study provides a quantitative framework for conducting species distribution modeling with limited temporal and spatial animal distribution and abundance data and utilized drop camera information as a novel approach to better understand habitat requirements of a stable sea otter population.
    • Acoustic and seismic signature of sustained volcanic eruptions

      Gestrich, Julia E.; Fee, David; Tape, Carl; Haney, Matthew; Larsen, Jessica (2022-12)
      Volcanic eruptions of any size can pose a significant risk to the life and livelihood of humans, as well as to infrastructure and the economy. Understanding the dynamics of an eruption is crucial to providing timely and accurate assessments of the eruption and associated hazard. Ideally the monitoring of volcanic unrest and eruption dynamics is done remotely to minimize exposure to volcanologists and maximize the spatial monitoring coverage of instruments. Another important factor is to have real-time data to facilitate rapid analysis and interpretation. Seismic and acoustic (infrasound) waves have proven useful in terms of remote real-time volcano monitoring. However, accurate interpretation of these signals is a challenge due to the complexity of each volcano and each eruption. In this dissertation I present three projects that aim to improve the interpretation of seismic and acoustic signals, specifically their spectral properties, generated by multiphase flow during an eruption. In Chapter 2 we derive a seismic tremor model for a source underground but above the fragmentation level where the gas and particles rush through the volcanic conduit. This physical model assumes ash particles and gas turbulence impact the conduit wall and exert a force that generates seismic waves and is recorded as eruption tremor. We show that it is possible to model the seismic spectral amplitude and shape of a large sustained volcanic eruption, the eruption of Pavlof Volcano in 2016, with particle impacts and turbulence as seismic sources. Our modeling provides a framework to 1) narrow down the parameters associated with eruption dynamics and source processes, and 2) highlight that seismic amplitude and mass eruption rate are not necessarily correlated. Both findings are crucial for the successful interpretation of seismic data during a sustained eruption. In Chapter 3 we move further up above the vent to investigate the acoustic expression of sustained eruptions. The rapid discharge of the multiphase flow through the relatively small vent has been successfully compared to jetting in the past. We develop an algorithm to automatically fit laboratory-derived jet noise spectral shapes (similarity spectra) to the spectrum of three volcanic eruptions: Mount St. Helens 2005, Tungurahua 2006 and Kīlauea 2018. Our quantitative analysis of the misfit between the jet noise spectra and volcanic eruption shows that: 1) the jet noise spectra show a very good fit during the eruption, so we can assume it produces a volcanic form of jet noise, 2) we can distinguish between non-eruptive noise and eruption by the higher misfit of the former and the lower misfit of the latter, and 3) changes in spectral shape correspond to changes in eruption dynamics, which are highlighted by changes in the misfit in time and frequency space. To further look into how changes in spectral properties correspond to changes in eruption dynamics, Chapter 4 focuses in detail on the eruption of fissure 8 on Kilauea volcano in 2018. With the knowledge that the eruption produced jet noise (Chapter 3) we apply jet noise scaling laws and develop a model that relates the changes in infrasound amplitude and peak frequency to changes in jet velocity and diameter. Our analysis shows that in mid-June the infrasound amplitude peaks and the peak frequency decreases. Our jet noise scaling model explains this change through a decrease in jet velocity and increase in jet diameter. This interpretation fits video observations that show a decrease in lava fountain height and a widening of the fountain base around the same time. Our work demonstrates the potential to estimate lava fountain dimensions from infrasound recordings that could be useful for real-time, remote monitoring.
    • Cryptic population structure and differentiation in three species of Alaska Claytonia

      Gabbitas, Robert W.; Ickert-Bond, Stefanie M.; Takebayashi, Naoki; Webb, Campbell O. (2022-12)
      Beringia is an extensive geographic region noted for high levels of taxonomic complexity among closely related species. Three such species distributed across Beringia (Claytonia arctica, C. scammaniana, and C. sarmentosa,) exhibit low morphological differentiation between the species, while C. scammaniana includes two additional described morphologies of questionable taxonomic standing, C. "noatakensis" and C. "porsildii". Taxonomic boundaries within this group have been historically disagreed upon and are susceptible to confounding factors such as isolation-by-distance (IBD), discontinuous sampling of continuous variation, and low sequence divergence and morphological differentiation. To assist in species delimitation, multiple approaches combining phylogenomics and spatially explicit population genetics analyses should be used. Genetic material was collected from herbarium specimens at the University of Alaska Museum Herbarium (ALA). Sequence data were extracted and sequenced using the GoFlag target probe set. Phylogenomic analysis and consensus tree reconstruction were performed in ASTRAL. Principal Component Analysis (PCA), Discriminate Analysis of Principal Components (DAPC), and spatial Principal Component Analysis (sPCA) were performed in R ("adegenet" package), and ancestral clustering was calculated in ADMIXTURE. We found clear genetic differentiation between all three species with a close genetic relationship between C. arctica and C. sarmentosa. Neither of the morphotypes "noatakensis" or "porsildii" were genetically differentiable from C. scammaniana, but a strong genetic signal divided the species into northern and southern populations. We conclude that species delineations between C. arctica, C. sarmentosa and C. scammaniana are genetically defensible despite low morphological differentiation. The genetic relationship between C. sarmentosa and C. arctica appears to be closer than previously thought, and further research including the western C. joanneana is needed. The current circumscription of C. scammaniana is correctly inclusive of "noatakensis" and "porsildii", but further research is needed to investigate the genetic divide between northern and southern populations.
    • Implications of spatial population dynamics for abundance estimation and catch apportionment of Alaska sablefish (Anoplopoma fimbria)

      Fenske, Kari Hammarsten; Cunningham, Curry; Beaudreau, Anne; Criddle, Keith; Hanselman, Dana (2022-12)
      Spatial dynamics in fish populations are challenging to identify and incorporate into population dynamics models due to the large amount of data required and the uncertainty associated with spatial processes. However, ignoring spatial dynamics can result in biased population estimates and negatively affect population sustainability or the ability to meet fishery management goals. My research explored implications of spatial dynamics for the assessment and management of Alaska sablefish (Anoplopoma fimbria). Sablefish are highly mobile, targeted in commercial and recreational fisheries, and documented to have spatial variation in population dynamics such as abundance and biomass. However, gaps remain in understanding the drivers of these spatial dynamics and their effects on fishery management. Chapter 1 focused on sablefish population dynamics in Alaska by developing a spatial stock assessment model with movement between modeled areas. Chapters 2 and 3 detail the development (Chapter 2) and application of a simulation and estimation model framework (Chapter 3) to examine alternative management scenarios and inform fisheries management. The spatial stock assessment models developed in Chapter 1 showed that a combination of population processes (movement, recruitment) and fishing have resulted in spatial differences in sablefish spawning biomass and fishing mortality, and some management areas are likely below target biomass levels despite the population as a whole being at or near biomass targets. The implications of this apparent localized depletion are unknown, but could negatively impact recruitment success if depleted areas are crucial to population sustainability. Chapter 1 also highlights the complexity of spatial stock assessment models, which require large quantities of data and pose challenges for parameter estimation. In Chapters 2 and 3, sablefish spatial population processes were simulated based on parameters estimated in the spatial stock assessment developed for Chapter 1 then assessed using a single-area, panmictic stock assessment model. Chapter 2 focuses on the simulation framework development and tests a suite of alternative population assumptions regarding movement and recruitment, which were found to be very influential in preliminary analyses. The analyses also revealed the challenges associated with a simulation framework that relies on a relatively complex stock assessment model and cannot rely on human scientists to monitor and tweak assessment model estimation processes during the automated simulations. In Chapter 3, five alternative methods for apportioning harvest opportunity among management areas were examined through the simulation to understand whether there were unexpected consequences of how catch opportunities were apportioned across space, given the assumed underlying population dynamics. We found that recruitment was poorly estimated by the single-area stock assessment model, and recruitment and movement rates between areas were drivers of population dynamics in each modeled region. We also found that no method for apportioning sablefish resulted in long-term population declines under the simulation and management assumptions, but recommended an apportionment method that used data from an annual survey so that catch opportunities are relational to observed spatial biomass. Each apportionment method resulted in different levels of catch for management areas and different year-to-year stability in catch, and these differences may be meaningful to stakeholders. This research highlights the challenges and benefits of incorporating spatial population dynamics in assessment of a relatively data-rich species with high movement rates. For species with known processes that could create spatial dynamics but insufficient data for development of spatial stock assessment models, the development and implementation of monitoring and research plans to close data gaps could be a long-term strategy for improving understanding of the species' dynamics. However, monitoring can be logistically challenging and economically prohibitive in some situations, so simulation analyses such as those conducted here may help understand which data are most important to collect or inform the development of management procedures which are robust to the most plausible hypothetical population dynamics or future environmental conditions.
    • Sled dogs as gifts. An ethnography of dog exchanges among kennels in Alaska.

      Cruz, Allison K.; Plattet, Patrick; Yamin-Pasternak, Sveta; Koester, David (2022-12)
      This thesis investigates the social relationships that develop through the circulation of sled dogs among Alaskan kennels. It is based on multi-sited ethnographic fieldwork at racing events, in sled dog kennels, as well as semi-structured interviews around Fairbanks. The research is informed by anthropological literature on kinship, personhood, and gift-giving economies. It examines how sled dogs are acquired and exchanged in Alaska and offers a novel perspective on the value of dog bloodlines and the relationships that unite breeders, mushers and sled dogs. The main argument is that Alaskan sled dogs are exchanged as gifts (rather than commodities) with the result that sled dog exchanges reestablish social connections between two or more kennels through the passage of the animals and their blood. The possession and ownership of specific bloodlines carries not only the genetic characteristics of the sled dog breed, but also the accomplishments of the breeder's kennel. The exchange of dogs ensures a continued cycle of interactions and cooperation within the dog mushing community. This continued cycle of dog exchanges allows for kennels to further develop and continue their breed in the mushing community. The overall findings of this work show that sled dogs, as relational gifts, are central figures within the mushing community and play a key role in creating multifaceted connections within and among kennels in Alaska.