Blar i NTNU Open på forfatter "Johnsen, Geir"

Viser treff 41-60 av 105

    • Improved Classification of Underwater Hyperspectral Images using Sensor Fusion 

      Owren, Lars Berge (Master thesis, 2018)
      The underwater hyperspectral imager allows for acquiring high spectral resolution images under water. The hyperspectral images may be used for classification of objects under water, and applications for the imager are being ...

    • In situ biomass estimation of cultivated kelp using RGB imagery 

      Overrein, Martin Molberg (Master thesis, 2023)
      Global produksjon i makroalgeoppdrett utgjør over en fjerdedel av total oppdrettsproduksjon, med et produksjonsvolum på opptil 35.1 millioner tonn i 2020. I Norge er det stadig økt innsats for å utvikle makroalgeoppdrett ...

    • In situ recordings of large gelatinous spheres from NE Atlantic, and the first genetic confirmation of egg mass of Illex coindetii (Vérany, 1839) (Cephalopoda, Mollusca) 

      Ringvold, Halldis; Taite, Morag; Allcock, A. Louise; Vecchione, Michael; Péan, Michel; Sandulli, Roberto; Johnsen, Geir; Fjellheim, Arne; Bakke, Snorre; Sannæs, Hanne; Synnes, Ann-Elin; Coronel, José; Hansen, Martin; Olejar, Peter; Eliassen, Geir; Eliassen, Anita; Klungland, Karl (Peer reviewed; Journal article, 2021)
      In total, 90 gelatinous spheres, averaging one meter in diameter, have been recorded from ~ 1985 to 2019 from the NE Atlantic Ocean, including the Mediterranean Sea, using citizen science. More than 50% had a dark streak ...

    • In the dark: a review of ecosystem processes during the Arctic polar night 

      Berge, Jørgen; Renaud, Paul; Darnis, Gérald; Cottier, Finlo; Last, Kim; Gabrielsen, Tove M.; Johnsen, Geir; Seuthe, Lena; Weslawski, Jan Marcin; Leu, Eva; Moline, Mark A.; Nahrgang, Jasmine; Søreide, Janne; Varpe, Øystein; Lønne, Ole Jørgen; Daase, Malin; Falk-Petersen, Stig (Journal article, 2015)
      Several recent lines of evidence indicate that the polar night is key to understanding Arctic marine ecosystems. First, the polar night is not a period void of biological activity even though primary production is close ...

    • Information-driven robotic sampling in the coastal ocean 

      Fossum, Trygve Olav; Eidsvik, Jo; Ellingsen, Ingrid H.; Alver, Morten; Fragoso, Glaucia Moreira; Johnsen, Geir; mendes, renato; Ludvigsen, Martin; Rajan, Kanna (Journal article; Peer reviewed, 2018)
      Efficient sampling of coastal ocean processes, especially mechanisms such as upwelling and internal waves and their influence on primary production, is critical for understanding our changing oceans. Coupling robotic ...

    • Integrated Environmental Mapping and Monitoring: A methodological approach for end-users 

      Nilssen, Ingunn (Doctoral theses at NTNU;2016:279, Doctoral thesis, 2016)
      Summary of thesis The thesis presents a methodological approach for flexible mapping and environmental monitoring that in each case are adjusted to purpose and the present ambient conditions, including anthropogenic ...

    • Is ambient light during the high Arctic polar night sufficient to act as a visual cue for zooplankton? 

      Cohen, Jonathan H.; Berge, Jørgen; Moline, Mark A.; Sørensen, Asgeir Johan; Last, Kim; Falk-Petersen, Stig; Renaud, Paul; Leu, Eva; Grenvald, Julie Cornelius; Cottier, Finlo; Cronin, Heather; Menze, Sebastian; Norgren, Petter; Varpe, Øystein; Daase, Malin; Darnis, Gérald; Johnsen, Geir (Journal article, 2015)
      The light regime is an ecologically important factor in pelagic habitats, influencing a range of biological processes. However, the availability and importance of light to these processes in high Arctic zooplankton communities ...

    • Leads in Arctic pack ice enable early phytoplankton blooms below snow-covered sea ice 

      Assmy, Philipp; Fernández-Méndez, Mar; Duarte, Pedro; Meyer, Amelie; Randelhoff, Achim; Mundy, Christopher John; Olsen, Lasse; Kauko, Hanna M.; Bailey, Allison; Chierici, Melissa; Cohen, Lana; Doulgeris, Anthony Paul; Ehn, Jens K.; Fransson, Agneta; Gerland, Sebastian; Hop, Haakon; Hudson, Stephen R.; Hughes, Nick; Itkin, Polona; Johnsen, Geir; King, Jennifer A.; Koch, Boris P.; Koenig, Zoe; Kwasniewski, Slawomir; Laney, Samuel R.; Nikolaus, Marcel; Pavlov, Alexey K.; Polashenski, Christopher M.; Provost, Christine; Rösel, Anja; Sandbu, Marthe; Spreen, Gunnar; Smedsrud, Lars H.; Sundfjord, Arild; Taskjelle, Torbjørn; Tatarek, Agnieszka; Wiktor, Josef; Wagner, Penelope Mae; Wold, Anette; Steen, Harald; Granskog, Mats A. (Journal article; Peer reviewed, 2017)
      The Arctic icescape is rapidly transforming from a thicker multiyear ice cover to a thinner and largely seasonal first-year ice cover with significant consequences for Arctic primary production. One critical challenge is ...

    • Life and Light at the Dead of Night 

      Berge, Jørgen; Johnsen, Geir (Chapter, 2020)
      The Polar Nigth as a unique beauty. The aurora borealis, the moonlight, the faint glow of the sun behind white mountains, and, not the least, the mysteries of the living creatures that we have found in the Polar Night – ...

    • Light in the Polar Night 

      Cohen, Jonathan H.; Berge, Jørgen; Moline, Mark A.; Johnsen, Geir; Zolich, Artur Piotr (Chapter, 2020)
      How much light isa vailable for biological processes during Polar Night? This question appears simple enough. But the reality is that conventional light sen- sors for measuring visible light (~350 to ~700 nm) have not been ...

    • Light response and acclimation of microalgae in a changing Arctic 

      Kauko, Hanna Maria (Doctoral theses at NTNU;2018:270, Doctoral thesis, 2018)
      Summary of thesis: This thesis investigates ice-associated and under-ice algal communities, and the controlling role of light in the Arctic pack ice region. Changes in the light regime are a consequence of the substantial ...

    • Macroalgal detritus: Physical variables and impacts on the benthic macrofaunal community 

      Fjærtoft, Kaja Lønne (Master thesis, 2018)
      Marine primary productivity by micro- and macroalgae in Norway, limited to the photic zone (0 200 m depth), controls the amount of organic carbon (food) available to higher trophic levels, and is the basis for marine ...

    • Mapping distribution patterns of brittle stars using ROV-based imaging 

      Marnor, Camilla Mult (Master thesis, 2022)
      Stor etterspørsel etter marine økosystemtjenester og konkurranse om havrom presser marine økosystemer til det ytterste. Det er et behov for effektive metoder for identifisering, kartlegging og overvåking for å forstå ...

    • Mapping of a seagrass habitat in Hopavågen, Sør-Trøndelag, with the use of an Autonomous Surface Vehicle combined with optical techniques 

      Alvsvåg, Dora Marie (Master thesis, 2017)
      Mapping and monitoring of marine habitats are important for proper management and decision making. However, shallow coastal habitats (0 5 meters depth) are largely under-sampled in time and space. Knowledge about morphology, ...

    • Mapping of demersal fish and benthos by Autonomous Underwater Vehicle equipped with optical and acoustic imagers at 600 meters depth in Trondheimsfjorden 

      Håpnes, Sverre Julian H (Master thesis, 2015)
      The marine environment is largely under-sampled both in time and space. There is a growing need for more automated approaches to provide a better understanding, identification, mapping and monitoring of biogeochemical ...

    • Mapping of Zostera habitat in the Sublittoral Zone using Underwater Hyperspectral Imaging and Unmanned Surface Vehicle 

      Søreng, Marte Opsahl (Master thesis, 2022)
      Sjøgressenger over hele verden trues av menneskeskapte habitatødeleggelser og global oppvarming. Det er et behov for kartlegging med høy oppløsning for å øke overvåkningsevnene våre og fylle kunnskapshull knyttet til disse ...

    • Mapping the Historical Shipwreck Figaro in the High Arctic Using Underwater Sensor-Carrying Robots 

      Mogstad, Aksel Alstad; Ødegård, Øyvind; Nornes, Stein Melvær; Ludvigsen, Martin; Johnsen, Geir; Sørensen, Asgeir Johan; Berge, Jørgen (Peer reviewed; Journal article, 2020)
      In 2007, a possible wreck site was discovered in Trygghamna, Isfjorden, Svalbard by the Norwegian Hydrographic Service. Using (1) a REMUS 100 autonomous underwater vehicle (AUV) equipped with a sidescan sonar (SSS) and (2) ...

    • Marine Micro- and Macroalgae in the Polar Night 

      Johnsen, Geir; Leu, Eva; Gradinger, Rolf (Chapter, 2020)
      Microalgae have unique adaptions including low metabolic activity, utilization of lipid storage, and resting stage formation to survive the Polar Night. Some species are mixotrophic or heterotrophic and do survive periods ...

    • A Methodology for Consistent Georegistration in Underwater Hyperspectral Imaging 

      Løvås, Håvard; Mogstad, Aksel Alstad; Sørensen, Asgeir Johan; Johnsen, Geir (Peer reviewed; Journal article, 2021)
      This article proposes a novel methodology for precise georegistration in underwater hyperspectral imaging (UHI) using a red–green–blue (RGB) camera to build a photogrammetry model that estimates the pose and a 3-D seabed ...

    • Midnight Sun to Polar Night: A Model of Seasonal Light in the Barents Sea 

      Connan-McGinty, Stacey; Banas, Neil S.; Berge, Jørgen; Cottier, Finlo Robert; Grant, Stephen; Johnsen, Geir; Kopec, Tomasz Piotr; Porter, Marie; Mckee, David (Peer reviewed; Journal article, 2022)
      Arctic marine ecosystems are strongly influenced by the extreme seasonality of light in the region. Accurate determination of light is essential for building a comprehensive understanding of the dynamics of animal and ...