Viser treff 221-240 av 271

    • Scavenging amphipods in the high Arctic : Studies of benthic and sympagic amphipods in the genera Onisimus and Anonyx 

      Nygård, Henrik (Doctoral thesis; Doktorgradsavhandling, 2011-05-02)
      The main objective of this study was to increase our knowledge about the ecology of scavenging amphipods, particularly amphipods within the genera Onisimus and Anonyx. Specifically, the emphasis was to increase the knowledge of ice-associated (sympagic) Onisimus-species, but as these species are rather inaccessible, an approach using benthic congeners as proxies was chosen. By studying the shallow-water ...
    • Sea ice dependence in Arctic marine organisms: life cycles, resource use, and trophic linkages 

      Kunisch, Erin (Doctoral thesis; Doktorgradsavhandling, 2022-06-01)
      Climate warming in the Arctic has resulted in widespread changes in the physical oceanographic characteristics of the Arctic Ocean. One particularly visible change is the loss of sea ice both within the Arctic Ocean and in the surrounding shelf seas. Compared to the other shelf seas, the Barents Sea has experienced the largest declines in sea ice extent, with much of this loss occurring during winter. ...
    • Seabirds, climate and prey. A population study of two seabird species. 

      Reiertsen, Tone Kristin (Doctoral thesis; Doktorgradsavhandling, 2013-05-30)
      Many seabird populations have declined dramatically over recent decades, and studying the demography and population dynamic in seabird populations is important to gaining a better understanding of causes and mechanisms lying behind such changes and to identify targets for conservation and management. Climate and prey availability are known to affect demography and population dynamics of seabirds. ...
    • Seasonal adaptation, phenology and survival in gall-inducing sawflies (Tenthredinidae: Nematinae: Pontania) 

      Barstad, Trond Elling (Doctoral thesis; Doktorgradsavhandling, 2016-11-04)
      The phenological adaptation of herbivorous insects in the Arctic may be particularly prone to the negative impact of the current global climate change. Increasing temporal dissociation with their plant resources, and to their natural enemies such as parasitoids may be detrimental for their survival. The life history adaptations for gall-inducing sawflies in the Arctic (Tenthredinidae: Nematinae: ...
    • Seasonal and spatial dynamics of meroplankton in a sub-Arctic fjord With additional focus on larvae of the invasive red king crab 

      Michelsen, Helena Kling (Doctoral thesis; Doktorgradsavhandling, 2017-12-07)
      Many benthic marine organisms produce pelagic larvae, meroplankton, which spend from hours to months in the pelagic. During this time, they form an important part of the pelagic community. Few studies have focused on the year round dynamics of meroplankton, thus many aspects of meroplankton dynamics remains unknown at high-latitudes. In the 1960s the red king crab was intentionally introduced into ...
    • The seasonal migratory behavior of sympatric anadromous Arctic charr and brown trout 

      Jensen, Jenny Lovisa Alexandra (Doctoral thesis; Doktorgradsavhandling, 2013-09-20)
      This thesis used acoustic and archival telemetry to study fish migrations within and between freshwater and marine habitats. The main novel finding from this thesis work is that both Arctic charr and brown trout originating from rivers without access to lakes can be found in marine waters also during winter. The physical properties of the freshwater habitat may be the main factor controlling in which ...
    • Seasonality of Meroplankton in Svalbard Waters 

      Stübner, Eike Ingrid (Doctoral thesis; Doktorgradsavhandling, 2016-12-14)
      The temporal dynamics of meroplankton, manly comprised of larvae of benthic invertebrates that only temporarily inhabit the pelagic environment, is poorly understood in Arctic environments. The main objective of this thesis was to increase our knowledge on meroplankton dynamics and their ecological role in the Arctic marine coastal ecosystem. Three different approaches including high-frequency field ...
    • Seaweed proteins - how to get to them? Effects of processing on nutritional value, bioaccessibility and extractability 

      Mæhre, Hanne K (Doctoral thesis; Doktorgradsavhandling, 2016-03-11)
      As a consequence of the expected population growth towards 2050, the demand for food, and in particular proteins, will increase. Due to limited resources of arable land and freshwater, this increase cannot come in the agricultural sector alone. At present, the utilization of marine environments for food production is low and should be increased. Seaweeds are fast-growing plants occurring in marine ...
    • Sedimentary ancient DNA: Exploring methods of ancient DNA analysis for different taxonomic groups 

      Lammers, Youri (Doctoral thesis; Doktorgradsavhandling, 2020-02-28)
      This thesis explores the potential of sedimentary ancient DNA (sedaDNA) from lakes as a tool for studying past communities. First it sets out to determine what taxa in the environment are most likely to be detected in lake sediments. For this, vegetation surveys were carried out around eleven different lakes in Norway and the taxa detected based on plant metabarcoding of the lake sediments were ...
    • Sequence-Based Analysis of Eukaryotic Protein Evolution 

      Bockwoldt, Mathias (Doctoral thesis; Doktorgradsavhandling, 2018-10-12)
      The goal of this thesis was to comprehend evolutionary patterns in different contexts. To get a broad spectrum of methods, three projects were included of which one is published and two are in preparation. In the first project, we looked into the fate of new mutations in protein regions that do not have a defined three-dimensional structure. Generally, the fate of a new mutation is governed by ...
    • Short-term tundra plant-community nutrient responses to herbivory and warming: New insights from Near infrared-reflectance spectroscopy methodology 

      Petit Bon, Matteo (Doctoral thesis; Doktorgradsavhandling, 2020-09-22)
      In the long-term, herbivores and climate warming have been shown to alter nutrient levels in tundra plant communities by changing the functional composition of the vegetation. Here, I asked the extent to which they affect tundra plant-community nutrient levels in the short-term by directly modifying the chemistry of plants. I first developed a time- and cost-effective method that allowed me to ...
    • Sjarkfiske og ressursforvaltning 

      Maurstad, Anita (Doctoral thesis; Doktorgradsavhandling, 1997-11-07)
      <p>Med utgangspunkt i feltarbeid fra fiskevær i Troms, samt intervjuer med flere fiskere i Troms og Finnmark, drøfter jeg det nordnorske sjarkfisket i lys av to motstridende teorier om ressurshøsting og -regulering. Den ene sier at små enheter er mer ressursvennlige enn store. I småskalaproduksjon finnes innebygde begrensninger i produksjonsmåten, dels fordi vi står ovenfor husholdsbasert produksjon ...
    • Some methodological issues in economic evaluation in health care 

      Olsen, Jan Abel (Doctoral thesis; Doktorgradsavhandling, 1993)
    • Spatial and temporal patterns of foraging of harbour seals (Phoca vitulina) in Porsangerfjord: from behavioural interpretation to resource selection. 

      Ramasco, Virginie (Doctoral thesis; Doktorgradsavhandling, 2015-09-24)
      The coastal cod stock of the Porsangerfjord has drastically declined in the 80’s and never fully recovered since. A population of harbour seals, known to be resident in the fjord all year round, has been hypothesised to act as predator-pit for cod in the area, affecting its lack of recovery. In order to understand the role of these seals in this local marine ecosystem, their foraging behaviour ...
    • Spatial and temporal variations in parasite communities of freshwater fish in the subarctic 

      Kuhn, Jesper Andreas (Doctoral thesis; Doktorgradsavhandling, 2015-11-03)
      Parasite communities are complicated systems believed to be affected by multiple ecological and environmental factors, both in time and space. These communities might be disrupted by anthropogenic host introductions which unfortunately appear to be a common practice e.g. in freshwater fish management. By addressing parasite occurrences in three of the most common freshwater fish species in subarctic ...
    • The speciation landscape of European whitefish in Northern Fennoscandia – the importance of deglaciation history, standing genetic variation and natural selection 

      Häkli, Katja (Doctoral thesis; Doktorgradsavhandling, 2019-12-10)
      <p>During the last deglaciation, one clade of European whitefish (<i>Coregonus lavaretus</i> L.) colonized the lakes in the three contemporary watercourses of northern Fennoscandia (Pasvik, Tana and Alta) and diverged thereafter in sympatry. This thesis investigates the interplay between evolutionary processes and standing genetic variation in shaping phenotypic and genetic divergence, and how ...
    • Speciation reversal in sympatric eco-morphs of European whitefish (Coregonus lavaretus. L) – phenotypic and genomic consequences 

      Bhat, Shripathi (Doctoral thesis; Doktorgradsavhandling, 2016-09-20)
      Anthropogenic activities, such as introduction of non-native species, is considered as one of the most significant causes for declining biodiversity, since such introduction may destabilise ecological barriers to gene flow between native populations. In the 1960s a salmonid fish, vendace, was introduced to the upper parts of Pasvik watercourse and during the early 1990s it invaded the entire ...
    • Species concepts and functional aspects of cold-water diatoms (Bacillariophyceae) 

      Degerlund, Maria (Doctoral thesis; Doktorgradsavhandling, 2011-10-18)
      The choice of species concept when delineating phytoplankton species is decisive for our knowledge of species diversity and distribution, but will also affect our understanding of the functioning of marine ecosystems. This is particularly true for so-called cryptic species, which may show high degree of genetic and physiological heterogeneity although being morphologically similar. A precise species ...
    • Spectral changes in fillet of Atlantic salmon as affected by freshness loss and spoilage during cold storage. 

      Sone, Izumi (Doctoral thesis; Doktorgradsavhandling, 2012-12-03)
      Spectral effects of microbial growth, packaging atmosphere and heme oxidation were investigated with fresh salmon. The presence of microorganisms and their growth have little effect on the development of spectral features in fresh salmon during storage prior to extensive spoilage. Important spectral changes occur at 606 and 636 nm in the spectra of fresh salmon during storage. Heme oxidation is the ...
    • The spread of salmon lice (Lepeophtheirus salmonis Krøyer) from Norwegian fish farms and their impact on sea trout (Salmo trutta L.) 

      Serra-Llinares, Rosa Maria (Doctoral thesis; Doktorgradsavhandling, 2020-10-09)
      <p>The transmission of salmon lice (<i>Lepeophtheirus salmonis</i> Krøyer) from farm salmon to wild salmonids and the impact on wild populations are sources of intense debate in all salmon producing countries, and it is currently an issue of high political and economic relevance in Norway. Solid science-based evidence is therefore needed by decision makers to apply sound management strategies. Given ...