Viser treff 186-205 av 357

    • Langtidsstudie av næringsøkologi og vekst hos storørret i Pasvikvassdraget - en sammenligning mellom utsatt og vill ørret 

      Haugland, Øyvind (Master thesis; Mastergradsoppgave, 2014-05-15)
      Kraftutbyggingen i Pasvikvassdraget startet i 1964 og det finnes syv kraftverk i vassdraget. Storørretbestanden gikk kraftig tilbake som følge av kraftutbyggingen og i 1979 ble det startet et utsettingsprogram av ørret i elva for å kompensere for reduksjonen i størrelsen av den naturlige populasjonen. I dag settes det årlig ut 5000 ørret større enn 25 cm. Dette langtidsstudiet omhandler diett og ...
    • Let it glow! Adapting a method to detect microplastics in snow and evaluate the potential for long-range transport 

      Stürzinger, Vegard (Master thesis; Mastergradsoppgave, 2020-05-31)
      Harmonization of methods in microplastics research is lacking; this is affecting the comparability of results and hindering reproducibility. Investigating microplastics in snow is a relatively new field of research, and it can be used to answer questions about long-range atmospheric transport of microplastics. In this thesis, snow sampling methods were combined with the dye, Nile Red, to develop a ...
    • Life history strategies of a trimorphic population of Arctic charr (Salvelinus alpinus (L.)) in Skogsfjordvatn, northern-Norway 

      Smalås, Aslak (Master thesis; Mastergradsoppgave, 2013-05-15)
      Polymorphisms are widespread throughout many different taxa of vertebrates. Discrete polymorphisms or morphs usually differentiate in morphology, ecology and life history, most likely driven by adaptations to different habitats and resources. For sympatric morphs to be able to maximize fitness in different niches and habitats, they may develop differences in several life history traits. Arctic charr ...
    • Life-history strategies in two subarctic lakes with polymorphic Arctic charr Salvelinus alpinus L. populations. High across lakes stability in evolution of life-history strategies 

      Kjær, Runar (Master thesis; Mastergradsoppgave, 2018-05-13)
      Life history strategies of polymorphic Arctic charr in two sub-arctic lakes (Tårnvatn and Skøvatn) with similar environmental- and physiochemical conditions were studied. Disparities in life history traits may reflect ecological adaptations and is suggested an important factor in the incipient speciation process. In this region several lakes have polymorphic charr, and the designation of a fish to ...
    • Lik vinterbeite, ulik produksjon og vektutvikling: Et demografistudie på tamrein (Rangifer Tarandus) i Finnmark 

      Oskal, Ellen Margrethe (Mastergradsoppgave; Master thesis, 2009-08)
      Tetthetsavhengig næringsmangel som fører til lave vekter og påfølgende minket rekruttering er et velkjent fenomen i reindriften i Finnmark. Forskjeller i vekt og produksjon i reindriften i Norge har blitt forklart med ulikheter i høstingsstrategier og vinterforhold. Imidlertid har det blitt viet mindre oppmerksomhet til hvordan ulike sommerbeiteforhold påvirker reproduksjon og vektutvikling. I dette ...
    • Linking methane fluxes and oxidation rates to methane oxidizing bacteria in an Arctic terrestrial methane seep, Svalbard 

      Nagel, Franziska (Master thesis; Mastergradsoppgave, 2020-05-29)
      Global warming has especially detrimental effects on Arctic regions. One major issue is permafrost thaw and sub-permafrost methane escape via surface seeps. While the mitigation potential of methane-consuming bacteria on marine pingo-like methane seeps is well described, terrestrial methane seeps are still understudied. Recently, open system pingos have gained attention as terrestrial methane seeps. ...
    • Lipid content, composition and dynamics in northern marine diatoms. An experimental study using different analytical methods 

      Svenning, Jon Brage (Master thesis; Mastergradsoppgave, 2014-11-20)
      In this study, the fluorophore Nile Red was used as a probe for lipid accumulation during nutrient stress in the diatom Coscinodiscus concinnus, and to quantify lipid concentration fluorometrically in 5 monocultures of northern diatoms. The results from the fluorometrical quantification were validated by solvent extraction and HPLC-MS analysis in Bergen. In addition, 17 monocultures of 7 species of ...
    • Lipids and diapause in Calanus spp. in a high-Arctic fjord: state-dependent strategies? Tracking lipids through the polar night 

      Bailey, Allison M. (Master thesis; Mastergradsoppgave, 2010-11-15)
      Calanus copepods C. finmarchicus, C. glacialis and C. hyperboreus are keystone species in the Arctic marine ecosystem, constituting 70-90% of the zooplankton biomass. In high latitudes, the growing season is short and unpredictable, and the winter long and unproductive. These species have adapted flexible life histories, lipid accumulation, and a state of deep-water diapause to survive. Winter ...
    • Livssyklus hos løpebiller (Coleoptera, Carabidae) i en temperaturgradient i Nord-Norge 

      Hanssen, Vibeke Kristin Gellein (Master thesis; Mastergradsoppgave, 2007)
      Endringer i livssyklus hos løpebiller (Coleoptera, Carabidae) ble undersøkt langs en høydegradient i en subarktisk bjørkeskog i Nord-Norge, og funnene ble sammenlignet med studier som har blitt gjort av de samme artene på sørligere breddegrader. Av de 6 artene vi undersøkte var det kun en art som endret tidspunkt for reproduksjon med økende høyde. Patrobus assimilis hadde en interaksjon mellom ...
    • Local variation in mountain birch spring phenology along an altitudinal gradient in northern coastal Fennoscandia 

      Sjöskog, Maja Sofia (Master thesis; Mastergradsoppgave, 2011-06-10)
      Currently there is a lack of spring phenology studies covering small-scale altitudinal gradients of mountain birch in coastal northern Fennoscandia, a region characterized by exceptionally high precipitation of snow, which gives reason to investigate the influence of snow cover on birch budburst in this area. Furthermore, ground phenology studies are today increasingly replaced by satellite data ...
    • Long-Term Effects on Somatic Growth, Life History Traits and Population Biology of Arctic Charr (Salvelinus alpinus) Following the Fish Culling Experiment in Takvatn 

      Indrebø, Synne Nan (Master thesis; Mastergradsoppgave, 2023-11-14)
      Stunting in fish populations is a special case of density-dependent growth characterized by old slow-growing individuals with low recreational and resource use value. The phenomenon is commonly observed in lacustrine populations of Arctic charr (Salvelinus alpinus) in temperate regions. In Takvatn, a subarctic lake in northern Norway, stunted growth of Arctic charr was attributed to food shortage ...
    • Long-term fluctuations in an arctic fox (Vulpes lagopus) population: a matter of diet? 

      Berthelot, Fanny (Master thesis; Mastergradsoppgave, 2021-06-14)
      The long-term dynamics of predator populations may be driven by fluctuations in resource availability and reflect ecosystem changes in response to climate change. The Icelandic arctic fox population has known major fluctuations in size since the 1950s, starting with a decreasing period until late 1970s, followed by a six-fold increase until 2008 when the population dropped to half its size within ...
    • Long-term patterns (1980-2008) in the structure of a rocky-bottom macrobenthic community in Smeerenburgfjord, northwest Svalbard : assessment of density and cover using image analysis 

      Kortsch, Susanne (Master thesis; Mastergradsoppgave, 2010-12-01)
      Long-term patterns (1980-2008) in the structure of a macrobenthic sublittoral community on the rocky-bottom of a high Arctic fjord (Smeerenburgfjord) in northwest Svalbard were investigated using image analysis of underwater photographs from a permanently marked locality. Species composition revealed the locality to be characterized by calcareous algae, various brown- and red-algae, and several ...
    • Long-term population dynamics of Diphyllobothrium ditremum and D. dendriticum (Cestoda: Pseudophyllidea) in their salmonid hosts following a fish removal experiment 

      Henriksen, Eirik Haugstvedt (Master thesis; Mastergradsoppgave, 2014-02-15)
      Parasite-host interactions are important in understanding ecosystem processes, for instance by using trophically transmitted parasites as indicators of host ecology. Parasite infections are expected to correlate with host density, habitat choice and feeding behaviour. The importance of long-term data and perturbation experiments has been emphasized for advancing our knowledge of the parasite-host ...
    • Long-term reproductive effects of chronic dietary petroleum exposure on polar cod (Boreogadus saida) 

      Bender, Morgan Lizabeth (Master thesis; Mastergradsoppgave, 2015-11-15)
      Increased human activities in the Arctic pose a high risk for Arctic organisms to be chronically exposed to petroleum compounds. The endocrine disrupting properties of some of these compounds coupled with the metabolic costs of detoxification may have negative effects on the long and energy intensive reproductive development of polar cod, an Arctic keystone species. In the present study, selected ...
    • Makroalgesamfunn i littoralsonen på fem lokaliteter i Troms - endringer langs en enksponeringsgradient og endringer de siste 25 år 

      Nervold, Gunhild Garte (Master thesis; Mastergradsoppgave, 2008-06-05)
      Formålet med denne oppgaven var å se på kvantitative endringer av makroalge- og lavsamfunnet i littoralsonen på fem lokaliteter i Troms, langs en eksponeringsgradient fra fjord til kyst. Ofte finner man samfunnsendringer innover i fjordene som er nært korrelert med forandringer i substratets stabilitet, tekstur og lokaltopografiske forhold i fjæra (helning) (pers. med. Tor Eiliv Lein). Artsdiversiteten ...
    • Marine growth of introduced pink salmon (Oncorhynchus gorbuscha) caught in northern and central Norway 

      Paulsen, Tora (Master thesis; Mastergradsoppgave, 2022-05-16)
      The introduction of pink salmon in the White Sea area during the second half of the 20th century has resulted in the establishment of a self-sustaining population of pink salmon in rivers draining to the Barents Sea and North Atlantic Ocean. The size and abundance of pink salmon is dependent on survival during the marine phase, where they acquire more than 95% of their body weight. Investigating ...
    • The Marine Plastic Microbiome: Microbial Colonization of Polymer Surfaces in the Arctic Marine Environment 

      Stitzlein, Tarah Marie (Master thesis; Mastergradsoppgave, 2018-09-25)
      While the sources and fates of plastic pollution are receiving growing attention, major knowledge gaps exist. Among these, microbial degradation (aka biodegradation) of plastics remains poorly investigated. The process of biodegradation begins with the formation of biofilm on the polymer surface; our study aimed to investigate microbial colonization of polymer surfaces in the Arctic marine environment ...
    • The mating strategy of female Svalbard reindeer 

      Heatta, Maret Johansdatter (Mastergradsoppgave; Master thesis, 2009-08-15)
      The mating system of Svalbard reindeer was studied in detail on Nordenskiöld land, Svalbard during the mating season 2007. Little is known about the female mating systems of Svalbard reindeer. The aims of the study were to investigate the composition of harems in relation to male attractiveness, harem size and reproductive history and the associated behaviour of females. The movement patterns of ...
    • Melt season dynamics in a High Arctic estuarine tidal flat: A microbial perspective 

      Handler, Eleanor Ruth (Master thesis; Mastergradsoppgave, 2022-05-16)
      The substantial influx of freshwater to High Arctic coastal ecosystems influences nutrient, organic matter, and sediment dynamics, stratification, and light availability throughout the melt season. These changes shape pelagic microbial community composition and functioning, though little is known about impacts on nearshore benthic bacteria. Globally, mudflats are hotspots for biogeochemical cycling, ...