Viser treff 1481-1500 av 1636

    • Experimentally determined temperature thresholds for Arctic plankton community metabolism 

      Holding, Johnna; Duarte, Carlos M.; Arrieta, Jesús M.; Vaquer-Suyner3, Riser; Coello-Camba, Alexandra; Wassmann, Paul; Agusti, Susana (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      Climate warming is especially severe in the Arctic, where the average temperature is increasing 0.4 C per decade, two to three times higher than the global average rate. Furthermore, the Arctic has lost more than half of its summer ice extent since 1980 and predictions suggest that the Arctic will be ice free in the summer as early as 2050, which could increase the rate of warming. Predictions ...
    • Local and regional determinants of colonisation-extinction dynamics of a riparian mainland-island root vole metapopulation 

      Glorvigen, Petter; Andreassen, Harry Peter; Ims, Rolf Anker (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      The role of local habitat geometry (habitat area and isolation) in predicting species distribution has become an increasingly more important issue, because habitat loss and fragmentation cause species range contraction and extinction. However, it has also become clear that other factors, in particular regional factors (environmental stochasticity and regional population dynamics), should be taken ...
    • Floating Ice-Algal Aggregates below melting Arctic Sea Ice 

      Assmy, P; Ehn, Jens K.; Fernandez-Mendez, M; Hop, H; Katlein, C; Sundfjord, Arild; Bluhm, K; Daase, Malin; Engel, A.; Fransson, A.; Granskog, M.A.; Hudson, SR; Kristiansen, Svein; Nicolaus, M.; Peeken, I.; Renner, AHH; Spreen, Gunnar; Tatarek, Agnieszka; Wiktor, Josef (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      During two consecutive cruises to the Eastern Central Arctic in late summer 2012, we observed floating algal aggregates in the melt-water layer below and between melting ice floes of first-year pack ice. The macroscopic (1-15 cm in diameter) aggregates had a mucous consistency and were dominated by typical ice-associated pennate diatoms embedded within the mucous matrix. Aggregates maintained ...
    • The thuEFGKAB Operon of Rhizobia and Agrobacterium tumefaciens Codes for Transport of Trehalose, Maltitol, and Isomers of Sucrose and Their Assimilation through the Formation of Their 3-Keto Derivatives 

      Ampomah, Osei Yaw; Avetisyan, Anna; Hansen, Espen; Svenson, Johan; Huser, Thomas; Jensen, John Beck; Bhuvaneswari, T.V (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      The thu operon (thuEFGKAB) in Sinorhizobium meliloti codes for transport and utilization functions of the disaccharide trehalose. Sequenced genomes of members of the Rhizobiaceae reveal that some rhizobia and Agrobacterium possess the entire thu operon in similar organizations and that Mesorhizobium loti MAFF303099 lacks the transport (thuEFGK) genes. In this study, we show that this operon is ...
    • Seasonality of occurrence and recruitment of Arctic marine benthic invertebrate larvae in relation to environmental variables 

      Kuklinski, Piotr; Berge, Jørgen; McFadden, Laurel; Dmoch, Katarzyna; Zajaczkowski, Marek; Nygård, Henrik Andreas; Piwosz, Kasia; Tatarek, Agnieszka (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      The Arctic system is one of the regions most influenced by ongoing global climate change, but there are still critical gaps in our knowledge regarding a substantial number of biological processes. This is especially true for processes taking place during the Arctic winter but also for seasonal processes, such as the dynamics of intra-annual meroplankton occurrence. Here, we report on a ...
    • Diversity and abundance of water birds in a subarctic lake during three decades 

      Klemetsen, Anders; Knudsen, Rune (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      The numbers of divers, ducks, gulls, terns and waders in the 15 km2 oligotrophic lake Takvatn, North Norway, were estimated six times during 1983-2012. Systematic mapping surveys were done by boat within the first week after the ice-break in June. Twenty-one species were observed over the years and 12 were regarded as breeding on the lake. Red-breasted merganser Mergus serrator was the dominant diving ...
    • Speciation reversal in European whitefish (Coregonus lavaretus (L.)) caused by competitor invasion 

      Bhat, Shripathi; Amundsen, Per-Arne; Knudsen, Rune; Gjelland, Karl Øystein; Fevolden, Svein-Erik; Bernatchez, Louis; Præbel, Kim (Journal article; Tidsskriftartikkel; Peer reviewed, 2014)
      Invasion of exotic species has caused the loss of biodiversity and imparts evolutionary and ecological changes in the introduced systems. In northern Fennoscandia, European whitefish (Coregonus lavaretus (L.)) is a highly polymorphic species displaying adaptive radiations into partially reproductively isolated and thus genetically differentiated sympatric morphs utilizing the planktivorous and ...
    • State-dependent migratory timing of postspawned Atlantic salmon (Salmo salar) 

      Halttunen, Elina; Jensen, Jenny; Næsje, Tor; Davidsen, Jan Grimsrud; Thorstad, Eva Bonsak; Chittenden, Cedar; Hamel, Sandra; Primicerio, Raul; Rikardsen, Audun H. (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      Atlantic salmon (Salmo salar) often survive spawning and migrate back to the sea to feed, either shortly after spawning in autumn or the following spring. We conducted a 4-year observational field study using telemetry to evaluate the determinants of migration timing in Atlantic salmon postspawners (kelts). We found that individuals with low energy reserves migrated early to the risky but productive ...
    • Experimental harvest reveals the importance of territoriality in limiting the breeding population of Svalbard rock ptarmigan 

      Pedersen, Åshild Ønvik; Soininen, Eeva M; Unander, Sigmund; Willebrand, Maria Hörnell; Fuglei, E. (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      The Svalbard rock ptarmigan (Lagopus muta hyperborea) is an endemic subspecies of rock ptarmigan inhabiting the high Arctic archipelagos of Svalbard and Franz Josefs Land. This ptarmigan species exists at low population densities, with little interannual variations in population numbers, and limited habitat for breeding with less than 5 % of the land area in Svalbard constituting medium to high ...
    • New insights into regulation of anthocyanin biosynthesis in fruits 

      Jaakola, Laura (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      Anthocyanins are important health-promoting pigments that make a major contribution to the quality of fruits. The biosynthetic pathway leading to anthocyanins is well known and the key regulatory genes controlling the pathway have been isolated in many species. Recently, a considerable amount of new information has been gathered on the developmental and environmental regulation of anthocyanin ...
    • What are the impacts of reindeer/caribou (Rangifer tarandus L.) on arctic and alpine vegetation? A systematic review protocol 

      Bernes, Claes; Bråthen, Kari Anne; Forbes, Bruce C.; Hofgaard, Annika; Moen, Jon; Speed, James David Mervyn (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      Abstract Background: Reindeer and caribou (both belonging to the species Rangifer tarandus L.) are among the most important large herbivores in Eurasia’s and North America’s arctic, alpine and boreal zones. In Sweden, the impact of reindeer grazing on arctic and alpine vegetation has recently been re-evaluated. In the 1990s, records of grazing-related vegetation degradation helped to form a ...
    • Shedding new light on the diet of Norwegian lemmings: DNA metabarcoding of stomach content 

      Soininen, Eeva Marjatta; Zinger, Lucie; Gielly, Ludovic; Bellemain, Eva; Bråthen, Kari Anne; Brochmann, Christian; Epp, Laura; Gusarova, Galina; Hassel, Kristian; Henden, John-André; Killengreen, Siw Turid; Rämä, Teppo; Stenøien, Hans; Yoccoz, Nigel; Ims, Rolf Anker (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      Lemmings are key herbivores in many arctic food webs, and their population dynamics have major impacts on the functioning of tundra systems. However, current knowledge of lemming diet is limited, hampering evaluation of lemming–vegetation interactions. This lack of knowledge is mainly due to methodological challenges, as previously used microhistological methods result in large proportions of poorly ...
    • Fjellrev i Finnmark : Årsrapport 2013 

      Ims, Rolf Anker; Killengreen, Siw Turid; Jensvoll, Ingrid; Yoccoz, Nigel Gilles; Henden, John-André; Arriola, Aline; Mørk, Torill; Sarre, Arne Petter; Ørjebu, Alfred; Kristoffersen, Bjørn Hugo; Bye, Åshild (Research report; Forskningsrapport, 2013)
      Prosjekt Fjellrev i Finnmark har pågått siden 2004. Prosjektet har fra starten av hatt to målsetninger: Å gjøre grunnleggende forskning på økosystembetingelser som begrenser fjellrevenbestandens nåværende utbredelse og bestandsvekst i Øst-Finnmark spesielt, og i sub- og lav-Arktis generelt, med fokus på to hypoteser; a) mer uregelmessige og dempede smågnagersykler og b) øket konkurranse med ...
    • Parallel and non-parallel morphological divergence among foraging specialists in European whitefish (Coregonus lavaretus) 

      Siwertsson, Anna; Knudsen, Rune; Adams, Colin Ean; Præbel, Kim; Amundsen, Per-Arne (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      Parallel phenotypic evolution occurs when independent populations evolve similar traits in response to similar selective regimes. However, populations inhabiting similar environments also frequently show some phenotypic differences that result from non-parallel evolution. In this study, we quantified the relative importance of parallel evolution to similar foraging regimes and nonparallel lake-specific ...
    • Cellulase activity screening using pure carboxymethylcellulose: Application to soluble cellulolytic samples and to plant tissue prints. 

      Johnsen, Hanne Risan; Krause, Kirsten (Journal article; Tidsskriftartikkel; Peer reviewed, 2014)
      Reliable, rapid and inexpensive detection of cellulolytic enzymes that can be used for a wide variety of biological and environmental samples are currently in high demand. Here, a new cellulase detection protocol is described that circumvents problems observed with popular agar-based methods by exploiting the ability of carboxymethylcellulose (CMC) to form gel-like surfaces on its own. These pure ...
    • Chemical Diversity as a Function of Temperature in Six Northern Diatom Species 

      Huseby, Siv; Degerlund, Maria; Eriksen, Gunilla Kristina; Ingebrigtsen, Richard Andre; Eilertsen, Hans Christian; Hansen, Espen (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      In this study, we investigate how metabolic fingerprints are related to temperature. Six common northern temperate diatoms (Attheya longicornis, Chaetoceros socialis, Chaetoceros furcellatus, Porosira glacialis, Skeletonema marinoi, and Thalassiosira gravida) were cultivated at two different temperatures, 0.5 and 8.5 °C. To exclude metabolic variations due to differences in growth rates, the growth ...
    • Snow cover and extreme winter warming events control flower abundance of some, but not all species in high arctic Svalbard 

      Semenchuk, Philipp; Elberling, Bo; Cooper, Elisabeth J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      The High Arctic winter is expected to be altered through ongoing and future climate change. Winter precipitation and snow depth are projected to increase and melt out dates change accordingly. Also, snow cover and depth will play an important role in protecting plant canopy from increasingly more frequent extreme winter warming events. Flower production of many Arctic plants is dependent on melt ...
    • Model of Tryptophan Metabolism, Readily Scalable Using Tissue-specific Gene Expression Data 

      Stavrum, Anne-Kristin; Heiland, Ines; Schuster, Stefan; Puntervoll, Pål; Ziegler, Mathias (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      Tryptophan is utilized in various metabolic routes including protein synthesis, serotonin, and melatonin synthesis and the kynurenine pathway. Perturbations in these pathways have been associated with neurodegenerative diseases and cancer. Here we present a comprehensive kinetic model of the complex network of human tryptophan metabolism based upon existing kinetic data for all enzymatic conversions ...
    • Discrete foraging niches promote ecological, phenotypic, and genetic divergence in sympatric whitefish (Coregonus lavaretus) 

      Siwertsson, Anna; Knudsen, Rune; Præbel, Kim; Adams, Colin Ean; Newton, Jason; Amundsen, Per-Arne (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)
      Natural populations often vary in their degree of ecological, morphological and genetic divergence. This variation can be arranged along an ecological speciation continuum of increasingly discrete variation, with high inter-individual variation at one end and well defined species in the other. In postglacial fishes, evolutionary divergence has commonly resulted in the co-occurrence of a pelagic and ...
    • A range-wide synthesis and timeline for phylogeographic events in the red fox (Vulpes vulpes) 

      Kutschera, Verena E.; Lecomte, Nicolas; Janke, Axel; Selva, Nuria; Sokolov, Alexander A.; Haun, Timm; Steyer, Katharina; Nowak, Carsten; Hailer, Frank (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      Many boreo-temperate mammals have a Pleistocene fossil record throughout Eurasia and North America, but only few have a contemporary distribution that spans this large area. Examples of Holarctic-distributed carnivores are the brown bear, grey wolf, and red fox, all three ecological generalists with large dispersal capacity and a high adaptive flexibility. While the two former have been examined ...