• Caught in broad daylight: Topographic constraints of zooplankton depth distributions 

      Aarflot, Johanna Myrseth; Aksnes, Dag Lorents; Opdal, Anders Frugård; Skjoldal, Hein Rune; Fiksen, Øyvind (Peer reviewed; Journal article, 2019-05)
      For visual predators, sufficient light is critical for prey detection and capture. Because light decays exponentially with depth in aquatic systems, vertical movement has become a widespread strategy among zooplankton for ...
    • Centennial changes in water clarity of the Baltic Sea and the North Sea 

      Dupont, Nicolas; Aksnes, Dag Lorents (Peer reviewed; Journal article, 2013-10-10)
      Secchi depth is a valuable proxy for detecting long term changes in the water clarity of oceanic and coastal ecosystems. We analyse approximately 40 000 observations, which are available from ICES, from the Baltic Sea and ...
    • Centennial decline in North Sea water clarity causes strong delay in phytoplankton bloom timing 

      Opdal, Anders Frugård; Lindemann, Christian; Aksnes, Dag Lorents (Peer reviewed; Journal article, 2019-08-23)
      With climate warming, a widespread expectation is that events in spring, such as flowering, bird migrations, and insect bursts, will occur earlier because of increasing temperature. At high latitudes, increased ocean ...
    • Ecosystem model for evaluating potential cod production in a west Norwegian fjord 

      Salvanes, Anne Gro Vea; Aksnes, Dag Lorents; Giske, Jarl (Peer reviewed; Journal article, 1992-12-08)
      The carrying capacity for cod in a Norwegian fjord was analysed by means of a simulation model. Four age groups of cod were represented as well as the maln prey groups labrids, gobies and benthic organisms. These groups ...
    • The emotion system promotes diversity and evolvability 

      Giske, Jarl; Eliassen, Sigrunn; Fiksen, Øyvind; Jakobsen, Per Johan; Aksnes, Dag Lorents; Mangel, Marc; Jørgensen, Christian (Peer reviewed; Journal article, 2014-08-06)
      Studies on the relationship between the optimal phenotype and its environment have had limited focus on genotype-to-phenotype pathways and their evolutionary consequences. Here, we study how multi-layered trait architecture ...
    • Evidence for light-controlled migration amplitude of a sound scattering layer in the Norwegian Sea 

      Norheim, Eirik; Klevjer, Thor A.; Aksnes, Dag Lorents (Peer reviewed; Journal article, 2016)
      The oceanic sound scattering layer (SL) is an ubiquitous acoustic signature of mesopelagic fishes and invertebrates that are important food sources for the oceanic macrofauna and players in the biological carbon pump. We ...
    • Evidence of diel vertical migration in Mnemiopsis leidyi 

      Haraldsson, Matilda; Båmstedt, Ulf; Tiselius, Peter; Titelman, Josefin; Aksnes, Dag Lorents (Peer reviewed; Journal article, 2014-01-22)
      The vertical distribution and migration of plankton organisms may have a large impact on their horizontal dispersal and distribution, and consequently on trophic interactions. In this study we used video-net profiling to ...
    • First reports of a mass mortality event across multiple life stages in a mesopelagic jellyfish in high latitude coastal waters 

      Bozman, Andrea; Aksnes, Dag Lorents; Eiane, Ketil (Peer reviewed; Journal article, 2018-04)
      Mass mortality events can occur naturally and may have important ecological impacts on local populations. The abundance and stage structure of the coronate scyphozoan Periphylla periphylla in a Northern Norwegian fjord ...
    • Herding mesopelagic fish by light 

      Kaartvedt, Stein; Røstad, Anders; Opdal, Anders Frugård; Aksnes, Dag Lorents (Peer reviewed; Journal article, 2019)
      To assess organisms forming mesopelagic scattering layers in the Red Sea, we took advantage of their reactions to light. We used a remotely operated vehicle (ROV) equipped with LED lamps for herding the acoustic targets ...
    • Jellyfish distribute vertically according to irradiance 

      Bozman, Andrea; Titelman, Josefin; Kaartvedt, Stein; Eiane, Ketil; Aksnes, Dag Lorents (Peer reviewed; Journal article, 2017-03)
      We tested the hypothesis that the coronate jellyfish Periphylla periphylla distributes vertically according to a preferential range of absolute light intensities. The study was carried out in Lurefjorden, Norway, a fjord ...
    • Large mesopelagic fishes biomass and trophic efficiency in the open ocean 

      Irigoien, Xabier; Klevjer, Thor A.; Røstad, Anders; Martinez, U.; Boyra, G.; Acuna, J. L.; Bode, A.; Echevarria, F.; Gonzalez-Gordillo, J. I.; Hernández-León, Santiago; Augsti, S.; Aksnes, Dag Lorents; Duarte, C. M.; Kaartvedt, Stein (Peer reviewed; Journal article, 2014-02-07)
      With a current estimate of ~1,000 million tons, mesopelagic fishes likely dominate the world total fishes biomass. However, recent acoustic observations show that mesopelagic fishes biomass could be significantly larger ...
    • Light comfort zone in a mesopelagic fish emerges from adaptive behaviour along a latitudinal gradient 

      Langbehn, Tom; Aksnes, Dag Lorents; Kaartvedt, Stein; Fiksen, Øyvind; Jørgensen, Christian (Peer reviewed; Journal article, 2019)
      Throughout the oceans, small fish and other micronekton migrate between daytime depths of several hundred meters and near-surface waters at night. These diel vertical migrations of mesopelagic organisms structure pelagic ...
    • Light comfort zones of mesopelagic acoustic scattering layers in two contrasting optical environments 

      Røstad, Anders; Kaartvedt, Stein; Aksnes, Dag Lorents (Peer reviewed; Journal article, 2016-07)
      We make a comparison of the mesopelagic sound scattering layers (SLs) in two contrasting optical environments; the clear Red Sea and in murkier coastal waters of Norway (Masfjorden). The depth distributions of the SL in ...
    • Light penetration structures the deep acoustic scattering layers in the global ocean 

      Aksnes, Dag Lorents; Røstad, Anders; Kaartvedt, Stein; Martinez, Udane; Duarte, Carlos M.; Irigoien, Xabier (Peer reviewed; Journal article, 2017)
      The deep scattering layer (DSL) is a ubiquitous acoustic signature found across all oceans and arguably the dominant feature structuring the pelagic open ocean ecosystem. It is formed by mesopelagic fishes and pelagic ...
    • Multi-decadal warming of Atlantic water and associated decline of dissolved oxygen in a deep fjord 

      Aksnes, Dag Lorents; Aure, Jan; Johansen, Per-Otto; Johnsen, Geir Helge; Salvanes, Anne Gro Vea (Peer reviewed; Journal article, 2019-11)
      Previous studies have shown decline in dissolved oxygen of the ocean basins. A hypothesis for this development is that ocean warming through increased stratification has caused reduced ventilation of the interior ocean. ...
    • Scaling laws in phytoplankton nutrient uptake affinity 

      Lindemann, Christian; Fiksen, Øyvind; Andersen, Ken Haste; Aksnes, Dag Lorents (Peer reviewed; Journal article, 2016-03-11)
      Nutrient uptake affinity affects the competitive ability of microbial organisms at low nutrient concentrations. From the theory of diffusion limitation it follows that uptake affinity scales linearly with the cell radius. ...
    • Sensitivity of euphotic zone properties to CDOM variations in marine ecosystem models 

      Urtizberea, Agurtzane; Dupont, Nicolas; Rosland, Rune; Aksnes, Dag Lorents (Peer reviewed; Journal article, 2013-05-10)
      In marine ecosystem models, the underwater light intensity is commonly characterized by the shading of phytoplankton in addition to a background light attenuation coefficient. Colour dissolved organic matter (CDOM) is an ...
    • Structure and functioning of four North Atlantic ecosystems - A comparative study 

      Melle, Webjørn Raunsgård; Klevjer, Thor A.; Drinkwater, Kenneth F.; Strand, Espen; Naustvoll, Lars Johan; Wiebe, Peter H.; Aksnes, Dag Lorents; Knutsen, Tor; Sundby, Svein; Slotte, Aril; Dupont, Nicolas; Salvanes, Anne Gro Vea; Korneliussen, Rolf; Huse, Geir (Journal article; Peer reviewed, 2020)
      The epi- and mesopelagic ecosystems of four sub-polar ocean basins, the Labrador, Irminger, Iceland and Norwegian seas, were surveyed during two legs from Bergen, Norway, to Nuuk, Greenland, and back to Bergen. The survey ...
    • Sverdrup critical depth and the role of water clarity in Norwegian Coastal Water 

      Aksnes, Dag Lorents (Peer reviewed; Journal article, 2015-02-25)
      The critical depth concept was first recognized by Gran and Braarud (1935). During summer, in the Bay of Fundy, they observed an unexpected no bloom situation. Their interpretation was that high amounts of detritus of ...
    • Unclear associations between small pelagic fish and jellyfish in several major marine ecosystems 

      Opdal, Anders Frugård; Brodeur, Richard D.; Cieciel, Kristin; Daskalov, Georgi; Mihneva, Vesselina; Ruzicka, James J; Verheye, Hans M.; Aksnes, Dag Lorents (Peer reviewed; Journal article, 2019-02-28)
      During the last 20 years, a series of studies has suggested trends of increasing jellyfish (Cnidaria and Ctenophora) biomass in several major ecosystems worldwide. Some of these systems have been heavily fished, causing a ...