Tove Margrethe Gabrielsen

• Borg-Stoveland, Stian; Draganovic, Vukasin; Spilling, Kristian & Gabrielsen, Tove M. (2026). Microbial succession and dominance patterns in modular RAS and their implications for effluent-based Phaeodactylum tricornutum cultivation. Aquaculture. ISSN 0044-8486. 621. doi: 10.1016/j.aquaculture.2026.743977. Fulltekst i vitenarkiv Vis sammendrag

  Microbial communities are central to water quality, fish health, and operational stability in modular recirculating aquaculture systems (M-RAS). The composition and succession of microbial communities in the main production tank and the effluent were investigated during an Atlantic salmon grow-out period using 16S rRNA gene sequencing. Effluent from the aquaculture system was further reused for cultivation of Phaeodactylum tricornutum, enabling assessment of how effluent-derived microbial communities respond to algal growth conditions. In the main production tank, microbial communities showed an early shift from Rhodobacterales toward increasing dominance of Flavobacteriales, followed by a community assemblage with strong contributions by taxa of Thiotrichales and Chitinophagales. Operational disturbances, including reduced feeding and salinity adjustment, coincided with increased relative abundances of ASVs affiliated with Arcobacteraceae, Weeksellaceae, and Pseudoalteromonadaceae, taxonomic groups that include species described as opportunistic or pathogen-associated in marine fish systems. The effluent harboured a temporally variable microbial community throughout the grow-out period, characterized by fluctuations in the relative abundances of dominant orders such as Flavobacteriales, Enterobacterales, and Bacteroidales. Microbial communities in effluent studied during a two-week cultivation of P. tricornutum shifted toward taxa typical of algal phycospheres, including Caulobacterales and Rhodobacterales, which are often linked to mutualistic functions between algae and bacteria such as vitamin provision and nutrient remineralization. However, the effluent also harboured Bacteroidetes taxa (e.g., Maribacter, Zobellia, Aurantivirga), some of which have been reported in other systems to compete with diatoms for resources. Their presence during algal cultivation may therefore warrant consideration if the resulting biomass is intended for use in aquafeeds. These findings suggest that microbial community composition in M-RAS responds to operational adjustments, and that effluent reuse for algal cultivation not only enables resource recovery but also reshapes downstream microbial community assembly.

• Ho, Lik Theng; Horn, Henriette Gesine; Weeraman, Pabasara; Spilling, Kristian & Gabrielsen, Tove M. (2025). Vertical and temporal variability of protist and prokaryotic summer plankton communities in a North Sea fjord. Aquatic Microbial Ecology. ISSN 0948-3055. 91, s. 75–92. doi: 10.3354/ame02020. Fulltekst i vitenarkiv Vis sammendrag

  Microbial plankton communities play key roles in biogeochemical cycling and primary production in marine coastal ecosystems. Given the impacts of global change on Norwegian coastal waters, there is a need to understand the drivers of microbial plankton community structure and diversity. Environmental drivers such as temperature, salinity, and light influence the dynamics of microbial community structure and abundance in temperate oceans. Here we characterize the summer diversity of protist and prokaryotic plankton communities, using DNA metabarcoding and light microscopy, in the surface, upper mixed layer, and deep waters of Spindsfjorden, a South Norwegian fjord facing the North Sea. The sampling site was vertically stratified throughout the summer, with compositionally variable communities dominated by phototrophs and mixotrophs in the surface and upper mixed layers, and stable communities dominated by heterotrophs and parasites in the deep layer. Late summer blooms were dominated by the diatom Cerataulina pelagica in the surface and dinoflagellates of Tripos spp. in the upper mixed layer. Positive co-occurrences between certain diatom taxa and flavobacteria, and between diatoms and Alphaproteobacteria suggest potential symbiotic relationships or overlapping environmental preferences. Negative associations were observed between certain dinoflagellate groups and Syndiniales, possibly due to parasitic interactions. Temperature emerged as a key environmental driver of community change, underscoring its role in shaping the dynamics of microbial communities in temperate, coastal ecosystems.

• Marsden, Luke Harry; Godøy, Øystein; Gabrielsen, Tove M.; Ellingsen, Pål Gunnar; Reigstad, Marit & Marquardt, Miriam [Vis alle 10 forfattere av denne artikkelen] (2025). Best practices for data management in marine science: lessons from the Nansen Legacy project. Earth System Science Data. ISSN 1866-3508. 17(11), s. 5983–5996. doi: 10.5194/essd-17-5983-2025. Fulltekst i vitenarkiv Vis sammendrag

  This article explains how the Nansen Legacy project managed data from over 300 researchers and 20 expeditions in the northern Barents Sea. Shared rules for collecting samples kept the data consistent, and a searchable catalogue was provided details of the data collected on each cruise. The project also required early sharing and publishing of data in formats that computers can read and use, helping to maximise their impact. These approaches can guide future large research projects.

• Vader, Anna; Handler, Eleanor Ruth; Skogseth, Ragnheid; Larsen, Aud & Gabrielsen, Tove M. (2024). Seasonality and interannual variability of an Arctic marine time series, IsA. Arctic Science. ISSN 2368-7460. 11, s. 1–17. doi: 10.1139/as-2024-0044. Fulltekst i vitenarkiv
• Borg-Stoveland, Stian; Draganovic, Vukasin; Spilling, Kristian & Gabrielsen, Tove M. (2024). Successful growth of coastal marine microalgae in wastewater from a salmon recirculating aquaculture system. Journal of Applied Phycology. ISSN 0921-8971. 36, s. 2851–2861. doi: 10.1007/s10811-024-03310-1. Fulltekst i vitenarkiv Vis sammendrag

  As global demand for seafood increases, recirculating aquaculture systems (RAS) have gained prominence for sustainable fish rearing. The sustainability of RAS still requires improvement, particularly managing the fish waste. Here we investigated the growth and nutrient removal capabilities of three microalgal species (Isocrysis galbana, Phaeodactylum tricornutum and Skeletonema marinoi) in aquaculture wastewater (AWW) mixed at different concentrations with cultivation medium. All three microalgae showed growth in different concentrations of the AWW obtained from an Atlantic salmon RAS facility in Agder, Norway. The average growth rates for I. galbana, S. marinoi and P. tricornutum at 75% AWW concentration were 0.31± 0.00 day-1, 0.34 ± 0.00 day-1, 0.25 ± 0.02 day-1, respectively. All three species effectively contributed to nitrate, ammonium and phosphate removal. When cultivated in 75% AWW, the microalgae achieved nearly complete removal of nitrite, nitrate, and phosphate, while approximately 90% of ammonium was also removed. Our results confirm the viability of AWW for microalgal cultivation on a laboratory scale suggesting this presents a sustainable route to further develop a circular bioeconomy in aquaculture.

• Wutkowska, Magdalena; Vader, Anna; Logares, Ramiro; Pelletier, Eric & Gabrielsen, Tove M. (2023). Linking extreme seasonality and gene expression in Arctic marine protists. Scientific Reports. 13. doi: 10.1038/s41598-023-41204-3. Fulltekst i vitenarkiv Vis sammendrag

  At high latitudes, strong seasonal differences in light availability affect marine organisms and regulate the timing of ecosystem processes. Marine protists are key players in Arctic aquatic ecosystems, yet little is known about their ecological roles over yearly cycles. This is especially true for the dark polar night period, which up until recently was assumed to be devoid of biological activity. A 12 million transcripts catalogue was built from 0.45 to 10 μm protist assemblages sampled over 13 months in a time series station in an Arctic fjord in Svalbard. Community gene expression was correlated with seasonality, with light as the main driving factor. Transcript diversity and evenness were higher during polar night compared to polar day. Light-dependent functions had higher relative expression during polar day, except phototransduction. 64% of the most expressed genes could not be functionally annotated, yet up to 78% were identified in Arctic samples from Tara Oceans, suggesting that Arctic marine assemblages are distinct from those from other oceans. Our study increases understanding of the links between extreme seasonality and biological processes in pico- and nanoplanktonic protists. Our results set the ground for future monitoring studies investigating the seasonal impact of climate change on the communities of microbial eukaryotes in the High Arctic.

• Cleary, Alison Clare; Callesen, Trine A.; Berge, Jørgen & Gabrielsen, Tove M. (2022). Parasite–copepod interactions in Svalbard: diversity, host specificity, and seasonal patterns. Polar Biology. ISSN 0722-4060. 45, s. 1105–1118. doi: 10.1007/s00300-022-03060-1. Fulltekst i vitenarkiv Vis sammendrag

  Copepods of the genera Calanus and Pseudocalanus are important components of Arctic marine ecosystems. Despite the key roles of these zooplankters, little is known about the organisms they interact with most intimately, their parasites and symbionts. We applied metabarcode sequencing to uncover eukaryotic parasites present within these two copepod genera from three areas around the high Arctic archipelago of Svalbard. Ten distinct parasite groups were observed: four different Apostome ciliates, four different dinoflagellates (Chytriodinium sp., Ellobiopsis sp., Thalassomyces sp., and Hematodinium sp.), a Paradinium sp., and a trematode. Apostome ciliates closely related to Pseudocollinia spp. were the most commonly observed parasite, with overall infection rates of 21.5% in Calanus and 12.5% in Pseudocalanus. Infection by these ciliates varied seasonally, with no infections observed in early winter, but infection rates exceeding 75% in spring. Host specificity varied between parasites, with significant differences in infection rate between the two host copepod genera for four parasites (two ciliates, Chytriodinium, and a trematode). The diverse assemblage of parasites observed in these copepods, and the frequency of infection, with over one in five copepod individuals infected, suggest parasites may be playing a greater role in Arctic plankton communities than generally acknowledged.

• Ellingsen, Pål Gunnar; Ferrighi, Lara; Godøy, Øystein Arne & Gabrielsen, Tove M. (2021). Keeping track of samples in multidisciplinary fieldwork. Data Science Journal. 20(34), s. 1–13. doi: 10.5334/DSJ-2021-034. Fulltekst i vitenarkiv Vis sammendrag

  We here present methods, tools and results for efficiently collecting metadata and tracking samples collected in the field. The samples and metadata were collected during scientific cruises conducted by amongst others marine biologists, oceanographers, geochemists and marine geologists in the Nansen Legacy project. It is here reported on the successful development and implementation of a system for labeling, tracking and openly publishing metadata from the cruises. The results and tools have been made openly available, as they are suitable for a range of situations, from the individual scientist working in the field to large research missions.

• Dabrowska, Anna Maria; Wiktor, Józef Maria; Wiktor, Józef Mikolaj; Kristiansen, Svein; Vader, Anna & Gabrielsen, Tove M. (2021). When a year is not enough: Further study of the seasonality of planktonic protist communities structure in an ice-free high arctic fjord (adventfjorden, west spitsbergen). Water. 13(14), s. 1–18. doi: 10.3390/w13141990. Fulltekst i vitenarkiv Vis sammendrag

  As a contribution to understanding the ecological framework of protistan seasonal succession patterns, we present the weekly-to-monthly (January–October) light microscopy-based study of nano- and microplanktonic protist communities of Adventfjorden waters in 2013. In general, protist dynamics corresponded to the classic paradigm for the Arctic ice-free waters with extremely low abundance and diversity in winter, with the main abundance and chlorophyll-a peak in April-May, followed by a diverse but low abundant community during summer/autumn. However, the reference of the obtained data to the previously conducted year-round research in 2012 allows us to observe substantial variability in seasonal patterns between the two consecutive years. The most striking difference concerned the spring bloom composition and abundance, with clear domination of Phaeocystis pouchetii in Atlantified fjord waters in 2012 and Bacillariophyceae-dominated (mainly Fragilariopsis, Thalassiosira nordenskioeldii, and, in a lesser extent, also Pseudo-nitzschia seriata) bloom in 2013 when local water prevailed. On the other hand, a surprisingly high share of spring bloom taxa persisted throughout the summer/autumn of 2013 when they co-occurred with typical summer taxa (dinoflagellates and other small flagellates). Their extended growth could, at least in part, result from scarce Ciliophora throughout the season, which, in turn, can be attributed to the high grazing pressure of very numerous meroplankton and mesozooplankton. In light of this, our results may be relevant in discussions proposed for the West Spitsbergen waters link between the Atlantic water inflow and the spring bloom composition, as well as its further progression in the productive season. They also highlight the strong need for further high-resolution monitoring of annual plankton cycles and great caution when looking for phenological patterns within a single year or when interpreting short-term data.

• Kvernvik, Ane Cecilie; Hoppe, Clara Jule Marie; Greenacre, Michael; Verbiest, Sander; Wiktor, Józef Maria & Gabrielsen, Tove M. [Vis alle 8 forfattere av denne artikkelen] (2021). Arctic sea ice algae differ markedly from phytoplankton in their ecophysiological characteristics. Marine Ecology Progress Series. ISSN 0171-8630. 666, s. 31–55. doi: 10.3354/meps13675. Fulltekst i vitenarkiv Vis sammendrag

  Photophysiological and biochemical characteristics were investigated in natural communities of Arctic sea ice algae and phytoplankton to understand their respective responses towards variable irradiance and nutrient regimes. This study revealed large differences in photosynthetic efficiency and capacity between the 2 types of algal assemblages. Sea ice algal assemblages clearly displayed increased photoprotective energy dissipation under the highest daily average irradiance levels (>8 μmol photons m⁻² s⁻¹). In contrast, phytoplankton assemblages were generally light-limited within the same irradiance ranges. Furthermore, phytoplankton assemblages exhibited more efficient carbon assimilation rates in the low irradiance range compared to sea ice algae, possibly explaining the ability of phytoplankton to generate substantial under-ice blooms. They were also able to readily adjust and increase their carbon production to higher irradiances. The Arctic is warming more rapidly than any other oceanic region on the planet, and as a consequence, irradiance levels experienced by microalgae are expected to increase due to declining ice thickness and snow cover, as well as enhanced stratification. The results of this study suggest that sea ice algae may have less capacity to adapt to the expected environmental changes compared to phytoplankton. We therefore anticipate a change in sea ice-based vs. pelagic primary production with respect to timing and quantity in a future Arctic. The clearly distinct responses of sea ice algae vs. phytoplankton need to be incorporated into model scenarios of current and future Arctic algal blooms and considered when predicting implications for the entire ecosystem and associated biogeochemical fluxes.

• Kvernvik, Ane Cecilie; Rokitta, Sebastian D.; Leu, Eva; Harms, Lars; Gabrielsen, Tove M. & Rost, Björn [Vis alle 7 forfattere av denne artikkelen] (2020). Higher sensitivity towards light stress and ocean acidification in an Arctic sea-ice-associated diatom compared to a pelagic diatom. New Phytologist. ISSN 0028-646X. 226(6), s. 1708–1724. doi: 10.1111/nph.16501. Fulltekst i vitenarkiv Vis sammendrag

  Thalassiosira hyalina and Nitzschia frigida are important members of Arctic pelagic and sympagic (sea-ice-associated) diatom communities. We investigated the effects of light stress (shift from 20 to 380 µmol photons m−2 s−1, resembling upwelling or ice break-up) under contemporary and future pCO2 (400 vs 1000 µatm). The responses in growth, elemental composition, pigmentation and photophysiology were followed over 120 h and are discussed together with underlying gene expression patterns. Stress response and subsequent re-acclimation were efficiently facilitated by T. hyalina, which showed only moderate changes in photophysiology and elemental composition, and thrived under high light after 120 h. In N. frigida, photochemical damage and oxidative stress appeared to outweigh cellular defenses, causing dysfunctional photophysiology and reduced growth. pCO2 alone did not specifically influence gene expression, but amplified the transcriptomic reactions to light stress, indicating that pCO2 affects metabolic equilibria rather than sensitive genes. Large differences in acclimation capacities towards high light and high pCO2 between T. hyalina and N. frigida indicate species-specific mechanisms in coping with the two stressors, which may reflect their respective ecological niches. This could potentially alter the balance between sympagic and pelagic primary production in a future Arctic.

• Marquardt, Miriam; Skogseth, Ragnheid; Wiedmann, Ingrid; Vader, Anna; Reigstad, Marit & Cottier, Finlo Robert [Vis alle 7 forfattere av denne artikkelen] (2019). Vertical export of marine pelagic protists in an ice-free high-Arctic fjord (Adventfjorden, West Spitsbergen) throughout 2011-2012. Aquatic Microbial Ecology. ISSN 0948-3055. 83(1), s. 65–82. doi: 10.3354/ame01904. Fulltekst i vitenarkiv Vis sammendrag

  The ecosystem role of Arctic microbial communities is still largely unknown. Based on a time-series study at the IsA station (West Spitsbergen), the seasonality and contribution of pelagic protists to the vertical flux was investigated at 7 time points during 2011-2012. The hydrography of this high-Arctic fjord was evaluated to identify impacts on the community composition during the different seasons. Protists (<10 µm and >10 µm) were sampled at 4 depths from the water column and from short-time sediment traps, and investigated by 454 next-generation sequencing of the V4 region of the 18S ribosomal DNA. An advective event during winter, exchanging the cold and less saline water mass with warmer and saline Atlantic Water, was potentially responsible for an abrupt shift in the protist composition in March. Small cells (<10 µm) contributed significantly to the vertical flux during autumn and winter, while larger bloom taxa (e.g. diatoms) predominated the water and traps during spring. Parasitic species, such as MALV 1a and Chytriodinium sp., were also detected in the traps, possibly being transported along with their hosts. Vertical export of Arctic pelagic protists is not limited to the productive period; however, the contribution of small taxa that are important contributors in this study seems to be seasonally influenced and may alter the flux efficiency. Molecular tools revealed new taxa contributing to the vertical export, but also identified new potential mechanisms exemplified by parasite-host-induced transport, spurring increased attention onto parasitism in the study of carbon cycles and vertical flux.

• Walczyńska, Katarzyna S.; Søreide, Janne; Weydmann-Zwolicka, Agata; Ronowicz, Marta & Gabrielsen, Tove M. (2019). DNA barcoding of Cirripedia larvae reveals new knowledge on their biology in Arctic coastal ecosystems. Hydrobiologia. ISSN 0018-8158. 837(1), s. 149–159. doi: 10.1007/s10750-019-3967-y. Fulltekst i vitenarkiv
• Hegseth, Else Nøst; Assmy, Philipp; Wiktor, Józef M.; Jr, Józef Wiktor; Kristiansen, Svein & Leu, Eva [Vis alle 10 forfattere av denne artikkelen] (2019). Phytoplankton Seasonal Dynamics in Kongsfjorden, Svalbard and the Adjacent Shelf. I Hop, Haakon & Wiencke, Christian (Red.), The Ecosystem of Kongsfjorden, Svalbard. Springer. ISSN 9783319464237. s. 173–227. doi: 10.1007/978-3-319-46425-1_6. Fulltekst i vitenarkiv
• Vader, Anna; IV, Haywood Laughinghouse; Griffiths, Colin; Jakobsen, Kjetill Sigurd & Gabrielsen, Tove M. (2018). Proton-pumping rhodopsins are abundantly expressed by microbial eukaryotes in a high-Arctic fjord. Environmental Microbiology. ISSN 1462-2912. 20(2), s. 890–902. doi: 10.1111/1462-2920.14035. Fulltekst i vitenarkiv
• Renaud, Paul Eric; Daase, Malin; Banas, Neil S.; Gabrielsen, Tove M.; Søreide, Janne & Varpe, Øystein [Vis alle 12 forfattere av denne artikkelen] (2018). Pelagic food-webs in a changing Arctic: a trait-based perspective suggests a mode of resilience. ICES Journal of Marine Science. ISSN 1054-3139. 75(6), s. 1871–1881. doi: 10.1093/icesjms/fsy063. Fulltekst i vitenarkiv Vis sammendrag

  Arctic marine ecosystems support fisheries of significant and increasing economic and nutritional value. Commercial stocks are sustained by pelagic food webs with relatively few keystone taxa mediating energy transfer to higher trophic levels, and it remains largely unknown how these taxa will be affected by changing climate and the influx of boreal taxa. <i>Calanus</i> species store large quantities of lipids, making these zooplankton a critical link in marine food-webs. The Arctic <i>Calanus</i> species are usually larger and, importantly, have been suggested to contain disproportionately larger lipid stores than their boreal congeners. Continued climate warming and subsequent changes in primary production regimes have been predicted to lead to a shift from the larger, lipid-rich Arctic species, <i>Calanus glacialis</i> and <i>Calanus hyperboreus</i>, toward the smaller, boreal <i>Calanus finmarchicus</i> in the European Arctic, with negative consequences for top predators. Our data show that lipid content is closely related to body size for all three species, i.e. is not a species-specific trait, and that there is considerable overlap in size between <i>C. finmarchicus</i> and <i>C. glacialis</i>. A trait-based life-history model was used to examine an idealized scenario where, in a changed Arctic with a longer period of primary production, <i>C. glacialis</i>- and <i>C. hyperboreus</i>-like copepods are indeed replaced by <i>C. finmarchicus</i>-like individuals, whether through competition, plasticity, hybridization, or evolution. However, the model finds that transfer of energy from primary producers to higher predators may actually be more efficient in this future scenario, because of the changes in generation length and population turnover rate that accompany the body-size shifts. These findings suggest that Arctic marine food webs may be more resilient to climate-related shifts in the <i>Calanus</i> complex than previously assumed.

• Darnis, Gérald; Hobbs, Laura; Geoffroy, Maxime; Grenvald, Julie Cornelius; Renaud, Paul & Berge, Jørgen [Vis alle 13 forfattere av denne artikkelen] (2017). From polar night to midnight sun: Diel vertical migration, metabolism and biogeochemical role of zooplankton in a high Arctic fjord (Kongsfjorden, Svalbard). Limnology and Oceanography. ISSN 0024-3590. 62(4), s. 1586–1605. doi: 10.1002/lno.10519. Fulltekst i vitenarkiv Vis sammendrag

  Zooplankton vertical migration enhances the efficiency of the ocean biological pump by translocating car- bon (C) and nitrogen (N) below the mixed layer through respiration and excretion at depth. We measured C and N active transport due to diel vertical migration (DVM) in a Svalbard fjord at 79 8 N. Multifrequency analysis of backscatter data from an Acoustic Zooplankton Fish Profiler moored from January to September 2014, com- bined with plankton net data, showed that Thysanoessa spp. euphausiids made up > 90% of the diel migrant biomass. Classical synchronous DVM occurred before and after the phytoplankton bloom, leading to a mis- match with intensive primary production during the midnight sun. Zooplankton DVM resulted in C respira- tion of 0.9 g m 2 2 and ammonium excretion of 0.18 g N m 2 2 below 82 m depth between February and April, and0.2gCm 2 2 and 0.04 g N m 2 2 from 11 August to 9 September, representing > 25% and > 33% of sinking flux of particulate organic carbon and nitrogen, respectively. Such contribution of DVM active transport to the biological pump in this high-Arctic location is consistent with previous measurements in several equatorial to subarctic oceanic systems of the World Ocean. Climate warming is expected to result in tighter coupling between DVM and bloom periods, stronger stratification of the Barents Sea, and northward advection of boreal euphausiids. This may increase the role of DVM in the functioning of the biological pump on the Atlantic side of the Arctic Ocean, particularly where euphausiids are or will be prevalent in the zooplankton community.

• Kubiszyn, Anna Maria; Wiktor, Józef Maria; Wiktor, Józef Maria Jr.; Griffiths, Collin; Kristiansen, Svein & Gabrielsen, Tove M. (2017). The annual planktonic protist community structure in an ice-free high Arctic fjord (Adventfjorden, West Spitsbergen). Journal of Marine Systems. ISSN 0924-7963. 169, s. 61–72. doi: 10.1016/j.jmarsys.2017.01.013. Fulltekst i vitenarkiv
• Cleary, Alison C.; Søreide, Janne; Freese, Daniela; Niehoff, Barbara & Gabrielsen, Tove M. (2017). Feeding by Calanus glacialis in a high Arctic fjord: potential seasonal importance of alternative prey. ICES Journal of Marine Science. ISSN 1054-3139. 74(7), s. 1937–1946. doi: 10.1093/icesjms/fsx106. Fulltekst i vitenarkiv
• Rao, Archana Meshram; Vader, Anna; Kristiansen, Svein & Gabrielsen, Tove M. (2017). Microbial eukaryotes in an Arctic under-ice spring bloom north of Svalbard. Frontiers in Microbiology. 8. doi: 10.3389/fmicb.2017.01099. Fulltekst i vitenarkiv Vis sammendrag

  Microbial eukaryotes can play prominent roles in the Arctic marine ecosystem, but their diversity and variability is not well known in the ice-covered ecosystems. We determined the community composition of microbial eukaryotes in an Arctic under-ice spring bloom north of Svalbard using metabarcoding of DNA and RNA from the hypervariable V4 region of 18S nrDNA. At the two stations studied, the photosynthetic biomass was dominated by protists >3 μm and was concentrated in the upper 70–80 m, above the thermocline and halocline. Hierarchical cluster analyses as well as ordination analyses showed a distinct clustering of the microbial eukaryote communities according to a combination of water mass and local environmental characteristics. While samples collected in the surface mixed layer differed distinctly between the two sites, the deeper communities collected in Atlantic Water were fairly similar despite being geographically distant. The differentiation of the microbial eukaryote communities of the upper mixed water was probably driven by local development and advection, while the lack of such differentiation in the communities of Atlantic Water reflects the homogenizing effect of water currents on microbial communities.

• Sjøtun, Kjersti; Heggøy, Erling; Gabrielsen, Tove M. & Rueness, Jan (2016). Dasya adela sp. nov. (Rhodophyta, Ceramiales), an enigmatic new Dasya from a landlocked fjord in southwest Norway. Phycological Research. ISSN 1322-0829. 64(2), s. 79–94. doi: 10.1111/pre.12121. Fulltekst i vitenarkiv
• Wiedmann, Ingrid; Reigstad, Marit; Marquardt, Miriam; Vader, Anna & Gabrielsen, Tove M. (2016). Seasonality of vertical flux and sinking particle characteristics in an ice-free high arctic fjord—Different from subarctic fjords? Journal of Marine Systems. ISSN 0924-7963. 154(Part B), s. 192–205. doi: 10.1016/j.jmarsys.2015.10.003. Fulltekst i vitenarkiv Vis sammendrag

  The arctic Adventfjorden (78°N, 15°E, Svalbard) used to be seasonally ice-covered but has mostly been ice-free since 2007. We used this ice-free arctic fjord as a model area to investigate (1) how the vertical fl ux of biomass (chlorophyll a and particulate organic carbon, POC) follows the seasonality of suspended material, (2) how sink- ing particle characteristics change seasonally and affect the vertical fl ux, and (3) if the vertical fl ux in the ice-free arctic fjord with glacial runoff resembles the fl ux in subarctic ice-free fjords. During seven fi eld investigations (December 2011 – September 2012), suspended biomass was determined (5, 15, 25, and 60 m), and short-term sediment traps were deployed (20, 30, 40, and 60 m), partly modi fi ed with gel- fi lled jars to study the size and frequency distribution of sinking particles. During winter, resuspension from the sea fl oor resulted in large, detrital sinking particles. Intense sedimentation of fresh biomass occurred during the spring bloom. The highest POC fl ux was found during autumn (770 – 1530 mg POC m − 2 d − 1 ), associated with sediment-loaded glacial runoff and high pteropod abundances. The vertical biomass fl ux in the ice-free arctic Adventfjorden thus resem- bled that in subarctic fjords during winter and spring, but a higher POC sedimentation was observed during autumn.

• Brandner, Melissa Michelle; Stübner, Eike Ingrid; Reed, Adam J.; Gabrielsen, Tove M. & Thatje, Sven (2016). Seasonality of bivalve larvae within a high Arctic fjord. Polar Biology. ISSN 0722-4060. 40(2), s. 263–276. doi: 10.1007/s00300-016-1950-x. Fulltekst i vitenarkiv
• Leinaas, Hans Petter; Jalal, Marwa; Gabrielsen, Tove M. & Hessen, Dag Olav (2016). Inter- and intraspecific variation in body- and genome size in calanoid copepods from temperate and arctic waters. Ecology and Evolution. 6(16), s. 5585–5595. doi: 10.1002/ece3.2302. Fulltekst i vitenarkiv Vis sammendrag

  The tendency of ectotherms to get larger in the cold (Bergmann clines) has potentially great implications for individual performance and food web dynamics. The mechanistic drivers of this trend are not well understood, however. One fundamental question is to which extent variation in body size is attributed to variation in cell size, which again is related to genome size. In this study, we analyzed body and genome size in four species of marine calanoid copepods, Calanus finmarchicus, C. glacialis, C. hyperboreus and Paraeuchaeta norvegica, with populations from both south Norwegian fjords and the High Arctic. The Calanus species showed typical interspecific Bergmann clines, and we assessed whether they also displayed similar intraspecific variations—and if correlation between genome size and body size differed between species. There were considerable inter- as well as intraspecific variations in body size and genome size, with the northernmost populations having the largest values of both variables within each species. Positive intraspecific relationships suggest a functional link between body and genome size, although its adaptiveness has not been settled. Impact of additional drivers like phylogeny or specific adaptations, however, was suggested by striking divergences in body size – genome size ratios among species. Thus, C. glacialis and C. hyperboreus, had fairly similar genome size despite very different body size, while P. norvegica, of similar body size as C. hyperboreus, had the largest genome sizes ever recorded from copepods. The inter- and intraspecific latitudinal body size clines suggest that climate change may have major impact on body size composition of keystone species in marine planktonic food webs.

• Marquardt, Miriam; Vader, Anna; Stübner, Eike Ingrid; Reigstad, Marit & Gabrielsen, Tove M. (2016). Strong seasonality of marine microbial eukaryotes in a High-Arctic fjord (Isfjorden, in West Spitsbergen, Norway). Applied and Environmental Microbiology. ISSN 0099-2240. 82(6), s. 1868–1880. doi: 10.1128/AEM.03208-15. Fulltekst i vitenarkiv
• Leu, Eva; Mundy, Christopher John; Assmy, Philipp; Campbell, Karley; Gabrielsen, Tove M. & Gosselin, Michel [Vis alle 8 forfattere av denne artikkelen] (2015). Arctic spring awakening - Steering principles behind the phenology of vernal ice algal blooms. Progress in Oceanography. ISSN 0079-6611. 139, s. 151–170. doi: 10.1016/j.pocean.2015.07.012. Fulltekst i vitenarkiv
• Fredriksen, Stein; Gabrielsen, Tove M.; Kile, Maia Røst & Sivertsen, Knut (2015). Benthic algal vegetation in Isfjorden, Svalbard. Polar Research. ISSN 0800-0395. 34, s. 1–9. doi: 10.3402/polar.v34.25994. Fulltekst i vitenarkiv Vis sammendrag

  Benthic algal vegetation was investigated at 10 sites in Isfjorden, Svalbard. Five sites were visited during summer 2010 and five during summer 2012. Both the littoral and sublittoral vegetation were sampled, the littoral by hand-picking and use of a throwable rake and the sublittoral using a triangular dredge. A total of 88 different taxa were registered, comprising 17 Chlorophyta, 40 Ochrophyta, 30 Rhodophyta and the Xantophyceae Vaucheria sp. The green algae Ulvaria splendens (Ruprecht) Vinogradova was recorded in Svalbard for the first time. Most of the sites consisted of hard bottom substrate, but one site, Kapp Wijk, consisted of loose-lying calcareous red algae (rhodoliths) and had species not recorded elsewhere. The sublittoral at the other sites was dominated by kelp. Molecular analysis confirmed the presence of the red alga Ceramium virgatum and a dwarf form of the brown alga Fucus vesiculosus. This study provides a baseline for future studies investigating changes in the vegetation due to environmental changes.

• Alkire, Matthew B.; Nilsen, Frank; Falck, Eva; Søreide, Janne & Gabrielsen, Tove M. (2015). Tracing sources of freshwater contributions to first-year sea ice in Svalbard fjords. Continental Shelf Research. ISSN 0278-4343. 101, s. 85–97. doi: 10.1016/j.csr.2015.04.003. Fulltekst i vitenarkiv
• Berge, Jørgen; Renaud, Paul; Darnis, Gérald; Cottier, Finlo; Last, Kim & Gabrielsen, Tove M. [Vis alle 17 forfattere av denne artikkelen] (2015). In the dark: a review of ecosystem processes during the Arctic polar night. Progress in Oceanography. ISSN 0079-6611. 139, s. 258–271. doi: 10.1016/j.pocean.2015.08.005. Fulltekst i vitenarkiv Vis sammendrag

  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 to zero, but is rather characterized by a number of processes and interactions yet to be fully understood, including unanticipated high levels of feeding and reproduction in a wide range of taxa and habitats. Second, as more knowledge emerges, it is evident that a coupled physical and biological perspective of the ecosystem will redefine seasonality beyond the “calendar perspective”. Third, it appears that many organisms may exhibit endogenous rhythms that trigger fitness-maximizing activities in the absence of light-based cues. Indeed a common adaptation appears to be the ability to utilize the dark season for reproduction. This and other processes are most likely adaptations to current environmental conditions and community and trophic structures of the ecosystem, and may have implications for how Arctic ecosystems can change under continued climatic warming.

• Berge, Jørgen; Daase, Malin; Renaud, Paul; Ambrose, William G. Jr.; Darnis, Gérald & Last, Kim S [Vis alle 35 forfattere av denne artikkelen] (2015). Unexpected levels of biological activity during the polar night offer new perspectives on a warming Arctic. Current Biology. ISSN 0960-9822. 25(19), s. 2555–2561. doi: 10.1016/j.cub.2015.08.024. Fulltekst i vitenarkiv
• Vader, Anna; Marquardt, Miriam; Meshram, Archana R & Gabrielsen, Tove M. (2014). Key Arctic phototrophs are widespread in the polar night. Polar Biology. ISSN 0722-4060. 38(1), s. 13–21. doi: 10.1007/s00300-014-1570-2. Fulltekst i vitenarkiv
• Sørensen, Nikolaj; Daugbjerg, Niels & Gabrielsen, Tove M (2012). Molecular diversity and temporal variation of picoeukaryotes in two Arctic fjords, Svalbard. Polar Biology. ISSN 0722-4060. 35(4), s. 519–533. doi: 10.1007/s00300-011-1097-8. Fulltekst i vitenarkiv
• Gabrielsen, Tove M; Merkel, Benjamin; Søreide, Janne; Johansson-Karlsson, Emma; Bailey, Allison & Vogedes, Daniel Ludwig [Vis alle 9 forfattere av denne artikkelen] (2012). Potential misidentifications of two climate indicator species of the marine arctic ecosystem: Calanus glacialis and C. finmarchicus. Polar Biology. ISSN 0722-4060. 35(11), s. 1621–1628. doi: 10.1007/s00300-012-1202-7. Fulltekst i vitenarkiv Vis sammendrag

  Calanoid copepods of the genus Calanus represent an important, nutrient-rich food source for a multitude of Arctic marine organisms. Although morphologically very similar, their life histories and ecological roles differ. Because the distribution of Calanus glacialis and C. finmarchicus corresponds to Arctic and Atlantic water masses, respectively, they are regularly used as climate indicators. A correct identification of these species is therefore necessary in many ecological, environmental and climatological studies. In this study, we aimed at validating the traditionally used morphological characteristics (combining prosome length and copepodite stage) for separation of species of Calanus by using molecular tools (PCR–RFLP of the 16S mtDNA). A total of 418 specimens of copepodite stages CIV, CV and CVI(af) from three Arctic fjords have been identified both morphologically and genetically. We find that the morphological identification systematically overestimates the abundance of C. finmarchicus at the expense of C. glacialis. Hence, parts of the C. glacialis populations are found to be structurally smaller and the within population size range thus larger than previously assumed. Consequently, using the traditional morphological species delimitation poses a serious problem in the use of these two species as indicators of Atlantic versus Arctic water masses and thus as climatic indicators. Furthermore, it obscures our understanding of the life history differences between the two species and of their relative importance as food for a number of ecologically and economically important species in the Arctic.

• Berge, Jørgen; Gabrielsen, Tove M; Moline, Mark A. & Renaud, Paul (2012). Evolution of the Arctic Calanus complex: an Arctic marine avocado? Journal of Plankton Research. ISSN 0142-7873. 34(3), s. 191–195. doi: 10.1093/plankt/fbr103. Fulltekst i vitenarkiv Vis sammendrag

  Before man hunted the large baleen whales to near extinction by the end of the nineteenth century, Arctic ecosystems were strongly influenced by these large predators. Their main prey were zooplankton, among which the calanoid copepod species of the genus Calanus, long considered key elements of polar marine ecosystems, are particularly abundant. These herbivorous zooplankters display a range of adaptations to the highly seasonal environments of the polar oceans, most notably extensive energy reserves and seasonal migrations to deep waters where the non-feeding season is spent in diapause. Classical work in marine ecology has suggested that slow growth, long lifespan and large body size in zooplankton are specific adaptations to life in cold waters with short and unpredictable feeding seasons. Here, we challenge this understanding and, by using an analogy from the evolutionary and contemporary history of the avocado, argue that predation pressure by the now nearly extinct baleen whales was an important driving force in the evolution of life history diversity in the Arctic Calanus complex.

• Espelund, Mari; Minge, Marianne Aastebøl; Gabrielsen, Tove M; Nederbragt, Alexander Johan; Shalchian-Tabrizi, Kamran & Otis, Christian [Vis alle 9 forfattere av denne artikkelen] (2012). Genome Fragmentation Is Not Confined to the Peridinin Plastid in Dinoflagellates. PLOS ONE. 7(6). doi: 10.1371/journal.pone.0038809. Fulltekst i vitenarkiv Vis sammendrag

  When plastids are transferred between eukaryote lineages through series of endosymbiosis, their environment changes dramatically. Comparison of dinoflagellate plastids that originated from different algal groups has revealed convergent evolution, suggesting that the host environment mainly influences the evolution of the newly acquired organelle. Recently the genome from the anomalously pigmented dinoflagellate Karlodinium veneficum plastid was uncovered as a conventional chromosome. To determine if this haptophyte-derived plastid contains additional chromosomal fragments that resemble the mini-circles of the peridin-containing plastids, we have investigated its genome by in-depth sequencing using 454 pyrosequencing technology, PCR and clone library analysis. Sequence analyses show several genes with significantly higher copy numbers than present in the chromosome. These genes are most likely extrachromosomal fragments, and the ones with highest copy numbers include genes encoding the chaperone DnaK(Hsp70), the rubisco large subunit (rbcL), and two tRNAs (trnE and trnM). In addition, some photosystem genes such as psaB, psaA, psbB and psbD are overrepresented. Most of the dnaK and rbcL sequences are found as shortened or fragmented gene sequences, typically missing the 3′-terminal portion. Both dnaK and rbcL are associated with a common sequence element consisting of about 120 bp of highly conserved AT-rich sequence followed by a trnE gene, possibly serving as a control region. Decatenation assays and Southern blot analysis indicate that the extrachromosomal plastid sequences do not have the same organization or lengths as the minicircles of the peridinin dinoflagellates. The fragmentation of the haptophyte-derived plastid genome K. veneficum suggests that it is likely a sign of a host-driven process shaping the plastid genomes of dinoflagellates.

• Gabrielsen, Tove M; Minge, Marianne Aastebøl; Espelund, Mari; Tooming-Klunderud, Ave; Patil, Viswanath & Nederbragt, Alexander Johan [Vis alle 11 forfattere av denne artikkelen] (2011). Genome Evolution of a Tertiary Dinoflagellate Plastid. PLOS ONE. 6(4), s. e19132–e19132. doi: 10.1371/journal.pone.0019132. Fulltekst i vitenarkiv
• Westergaard, Kristine Bakke; Jørgensen, M.H.; Gabrielsen, Tove; Alsos, Inger Greve & Brochmann, C (2010). The extreme Beringian/Atlantic disjunction in Saxifraga rivularis (Saxifragaceae) has formed at least twice. Journal of Biogeography. ISSN 0305-0270. 37(7), s. 1262–1276. doi: 10.1111/j.1365-2699.2010.02278.x. Fulltekst i vitenarkiv Vis sammendrag

  Aim The oceanic Saxifraga rivularis L. presents one of the most extreme disjunctions known in the arctic flora: it has a small amphi-Beringian range and a larger amphi-Atlantic one. It was recently suggested to have had a single allopolyploid origin in Beringia at least one glacial cycle ago, followed by gradual expansion in a more humid period and differentiation into two allopatric subspecies (the Atlantic ssp. rivularis and the Beringian ssp. arctolitoralis). Here we explore the history of its extreme disjunction. Location The amphi-Beringian and northern amphi-Atlantic regions. Methods We obtained amplified fragment length polymorphisms (AFLPs) and chloroplast DNA sequences from 36 populations (287 individuals) and 13 populations (15 individuals), respectively. The data were analysed using principal coordinates analyses, Bayesian clustering methods, and analyses of molecular variance. Results Two distinctly divergent AFLP groups were observed, corresponding to the two described subspecies, but, surprisingly, four of the West Atlantic populations belonged to the supposedly Beringian endemic ssp. arctolitoralis. This was confirmed by re-examination of their morphological characteristics. The overall AFLP diversity in the species was low (26.4% polymorphic markers), and there was no variation in the five investigated chloroplast DNA (cpDNA) regions. There was little geographic structuring of the AFLP diversity within each subspecies, even across the extreme disjunction in ssp. arctolitoralis, across the Bering Sea, and across the Atlantic Ocean, except that most plants from the arctic Svalbard archipelago formed a separate genetic group with relatively high diversity. Main conclusions The extreme disjunction in S. rivularis has evidently formed at least twice. The first expansion from Beringia was followed by allopatric differentiation into one Beringian and one Atlantic subspecies, which are distinctly divergent at AFLP loci but still harbour identical cpDNA haplotypes, suggesting that the expansion was quite recent but before the last glaciation. The next expansion from Beringia probably occurred by means of several long-distance dispersals in the current interglacial, resulting in the colonization of the western Atlantic region by ssp. arctolitoralis. The poor geographic structuring within each subspecies suggests frequent long-distance dispersals from two main Weichselian refugia, one Beringian and one western-central European, but it is possible that the genetic group in Svalbard originates from an additional refugium.

• Kapralov, Maxim; Gabrielsen, Tove M; Sarapultsev, IE & Brochmann, Christian (2006). Genetic enrichment of the arctic clonal plant Saxifraga cernua at its southern periphery via the alpine sexual Saxifraga sibirica. Molecular Ecology. ISSN 0962-1083. 15, s. 3401–3411. Fulltekst i vitenarkiv
• Jørgensen, Marte Holten; Elven, Reidar; Tribsch, Andreas; Gabrielsen, Tove M; Stedje, Brita & Brochmann, Christian (2006). Taxonomy and Evolutionary Relationships in the Saxifraga rivularis Complex. Systematic Botany. ISSN 0363-6445. 31(4), s. 702–729. Fulltekst i vitenarkiv
• Skage, Morten; Gabrielsen, Tove M & Rueness, Jan (2005). A molecular approach to investigate the phylogenetic basis of three widely used species groups in the red algal genus Ceramium (Ceramiales, Rhodophyta). Phycologia. ISSN 0031-8884. 44(4), s. 353–360. Fulltekst i vitenarkiv
• Guldahl, AS; Gabrielsen, Tove; Scheen, A; Borgen, L.; Steen, Snorre Winger & Spjelkavik, Sigmund [Vis alle 7 forfattere av denne artikkelen] (2005). The Saxifraga rivularis complex in Svalbard: Molecules, ploidy and morphology. Flora: Morphologie, Geobotanik, Oekophysiologie. ISSN 0367-2530. 200(3), s. 207–221. doi: 10.1016/j.flora.2005.01.003. Fulltekst i vitenarkiv Vis sammendrag

  In many arctic plant groups, reticulate histories involving hybridization and polyploidization have resulted in problems with species delimitation and phylogeny reconstruction. The Saxifraga rivularis complex is a typical example. Two taxa, S. rivularis and S. hyperborea, have been reported from the arctic archipelago of Svalbard (‘Spitsbergen’), but their delimitation, relationship, and taxonomic status are uncertain. We analyzed variation in chromosome number and DNA content (using flow cytometry), two types of molecular markers (RAPDs and isozymes), and 59 morphological characters along transects in two large, mixed Svalbard populations. We also included presumedly ‘pure’ reference populations from other sites to address whether the tentative taxa are distinct and whether they hybridize in mixed populations. In the random amplified polymorphic DNA (RAPD) analysis, we identified two very distinct groups of multilocus phenotypes, corresponding to the tentative species. These groups also differed in DNA content, chromosome number (S. hyperborea: 2n=ca. 26; S. rivularis: 2n=ca. 52; but endopolyploidy was observed in several plants), some morphological characters, and isozyme phenotypes (with a few exceptions). The cytosolic Gpi locus was duplicated also at the 2n=26 level and fixed heterozygosity was observed in all populations, suggesting that S. hyperborea and S. rivularis may be secondary allotetraploid and allooctoploid, respectively, rather than diploid and tetraploid as traditionally assumed. We conclude that the Svalbard populations represent two distinct species at different ploidal levels and occurring in partly overlapping habitats, and that extensive hybridization presently does not occur between them even in mixed populations. Most molecular markers observed in S. hyperborea formed a subset of the S. rivularis markers, consistent with a hypothesis that S. rivularis is an allopolyploid lineage with the S. hyperborea lineage as one of its progenitors.

• Guldahl, AS; Gabrielsen, Tove M; Scheen, Anne-Cathrine; Borgen, Liv; Steen, SW & Spjelkavik, S [Vis alle 7 forfattere av denne artikkelen] (2005). The Saxifraga rivularis complex in Svalbard: Molecules, ploidy and morphology. Flora: Morphologie, Geobotanik, Oekophysiologie. ISSN 0367-2530. 200, s. 207–221. Fulltekst i vitenarkiv
• Mikalsen, Bjørg; Boison, G; Skulberg, Olav M.; Fastner, J; Davies, William & Gabrielsen, Tove M [Vis alle 8 forfattere av denne artikkelen] (2003). Natural variation in the microcystin synthetase operon mcyABC and impact on microcystin production in Microcystis strains. Journal of Bacteriology. ISSN 0021-9193. 185(9), s. 2774–2785. doi: 10.1128/JB.185.9.2774-2785.2003. Fulltekst i vitenarkiv Vis sammendrag

  Toxic Microcystis strains often produce several isoforms of the cyclic hepatotoxin microcystin, and more than 65 isoforms are known. This has been attributed to relaxed substrate specificity of the adenylation domain. Our results show that in addition to this, variability is also caused by genetic variation in the microcystin synthetase genes. Genetic characterization of a region of the adenylation domain in module mcyB1 resulted in identification of two groups of genetic variants in closely related Microcystis strains. Sequence analyses suggested that the genetic variation is due to recombination events between mcyB1 and the corresponding domains in mcyC. Each variant could be correlated to a particular microcystin isoform profile, as identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry. Among the Microcystis species studied, we found 11 strains containing different variants of the mcyABC gene cluster and 7 strains lacking the genes. Furthermore, there is no concordance between the phylogenies generated with mcyB1, 16S ribosomal DNA, and DNA fingerprinting. Collectively, these results suggest that recombination between imperfect repeats, gene loss, and horizontal gene transfer can explain the distribution and variation within the mcyABC operon.

• Maggs, Christine A. & Gabrielsen, Tove M (2003). Red algal systematics: 25 years of turbulent progress. British phycological Journal. ISSN 0007-1617. s. 102–114. Fulltekst i vitenarkiv
• Brochmann, Christian; Gabrielsen, Tove M; Nordal, Inger; Landvik, Jon Y & Elven, Reidar (2003). Glacial survival or tabula rasa? The history of North Atlantic biota revisited. Taxon. ISSN 0040-0262. 52, s. 417–450. Fulltekst i vitenarkiv
• Gabrielsen, Tove M; Brochmann, Christian & Rueness, Jan (2003). Phylogeny and interfertility of North Atlantic populations of "Ceramium strictum" (Ceramiales, Rhodophyta): how many species? European journal of phycology. ISSN 0967-0262. 38, s. 1–13. Fulltekst i vitenarkiv
• Gabrielsen, Tove M; Brochmann, Christian & Rueness, Jan (2002). The Baltic Sea as a model system for studying postglacial colonization and ecological differentiation, exemplified by the red alga Ceramium tenuicorne. Molecular Ecology. ISSN 0962-1083. 11, s. 2083–2095. Fulltekst i vitenarkiv Vis sammendrag

  'Ceramium strictum' is an illegitimate name that has been used in a wide sense to encompass non-spiny, partially corticated North Atlantic populations of Ceramium. At the other extreme, several species have been recognized even within a single restricted geographic region (Skagerrak-Baltic). We combined molecular and interfertility analyses to assess relationships among samples of 'C. strictum' from five geographic regions (Skagerrak-Baltic, northeastern America, the Canary Islands, western Norway, and the British Isles), with emphasis on the Skagerrak-Baltic Sea salinity gradient. Sequences of the nuclear ribosomal internal transcribed spacer 2 (ITS2) and the plastid rubisco spacer region were obtained from these samples, from two other partially corticated species (C. siliquosum and C. deslongchampsii) and from two species described as fully corticated (C. pallidum and C. secundatum). In phylogenetic analyses using the most divergent species, C. deslongchampsii, as an outgroup, C. secundatum was basal to a clade containing all other taxa. The populations from the Skagerrak-Baltic region had virtually identical sequences and were interfertile, suggesting that they belong to the same species (C. tenuicorne). The populations of ¿C. strictum¿ from the other geographic regions were highly divergent and may represent different species (tentatively named Ceramium strictum sensu Harvey, and Ceramium spp. 1-3). Formal taxonomic recognition of these putative species must await the results of thorough morphologic analyses. Unexpectedly, C. tenuicorne was sister to C. siliquosum-C. pallidum in a well-supported clade that did not include the other ¿C. strictum¿ populations. Thus, cortication is probably homoplastic and useless as indicator of species relationships in this group of Ceramium.

• Rueness, Jan; Gabrielsen, Tove M & Düwel, Lene (2002). Observations on Ceramium tenuicorne (Rhodophyta) and its reproduction. Cryptogamie. Algologie. ISSN 0181-1568. 23(3), s. 251–261. Fulltekst i vitenarkiv
• Gabrielsen, Tove M & Brochmann, Christian (1998). Sex after all: high levels of diversity detected in the arctic clonal plant Saxifraga cernua using RAPD markers. Molecular Ecology. ISSN 0962-1083. 7, s. 1701–1708. Fulltekst i vitenarkiv

Se alle arbeider i NVA

• Reigstad, Marit; Cnossen, Frida Anneke; Marsden, Luke Harry; Gabrielsen, Tove M. & Godøy, Øystein (2025). Data management in the Nansen Legacy. doi: https:/zenodo.org/records/10842823. Fulltekst i vitenarkiv
• Bluhm, Bodil; Aarflot, Johanna Myrseth; Gabrielsen, Tove M.; Lundesgaard, Øyvind; Fransson, Agneta & Handegard, Nils Olav [Vis alle 7 forfattere av denne artikkelen] (2025). Seasonality and interannual variability of physical, chemical and biological states and processes in the northern Barents Sea and adjacent areas. Progress in Oceanography. ISSN 0079-6611. 234. doi: 10.1016/j.pocean.2025.103469. Fulltekst i vitenarkiv
• Lien, Anne; Larsen, Jorunn; Nygård, Malene Østreng; Gabrielsen, Tove M.; Korslund, Lars & Marcussen, Johanna Bjånes [Vis alle 10 forfattere av denne artikkelen] (2024). Gimle: En gressplen erstatter ikke skog. s. 15–15. Fulltekst i vitenarkiv
• Sjøtun, Kjersti; Saavedra, Franz Ronald Goecke; Thorkildsen, Solveig; Bringloe, Trevor T.; Fredriksen, Stein & Gabrielsen, Tove M. [Vis alle 10 forfattere av denne artikkelen] (2024). DNA barcoding the brown algal diversity within the order Ectocarpales in Norway. Fulltekst i vitenarkiv
• Lien, Anne; Nygård, Malene Østreng; Laugen, Ane Timenes; Lie, Asbjørn; Slettan, Audun & Johansen, Beate Strøm [Vis alle 33 forfattere av denne artikkelen] (2023). Utbygging vil ødelegge for biologisk mangfold på campus Gimlemoen. NB! 34 forfattere totalt. s. 19–19. Fulltekst i vitenarkiv
• Kvernvik, Ane Cecilie; Gabrielsen, Tove M.; Krabberød, Anders Kristian & Vader, Anna (2023). Insights from Metatranscriptomics: Activity of Protist Communities between Seasons and along a North-South Transect in the Barents Sea. Fulltekst i vitenarkiv
• Reigstad, Marit; Gerland, Sebastian; Eldevik, Tor; Kunisch, Erin; Wiedmann, Ingrid & Sundfjord, Arild [Vis alle 21 forfattere av denne artikkelen] (2023). The Nansen Legacy project invites you to its upcoming international symposium in November 2023. Fulltekst i vitenarkiv
• Sjøtun, Kjersti; Fredriksen, Stein; Gabrielsen, Tove M.; Husa, Vivian; Goecke, Franz Ronald Saavedra & Gall, Line Le [Vis alle 9 forfattere av denne artikkelen] (2023). Mapping and DNA barcoding the brown algal diversity within the orders Ectocarpales, Ralfsiales and Sphacelariales in Norway. Fulltekst i vitenarkiv
• Marsden, Luke; Ellingsen, Pål Gunnar; Godøy, Øystein Arne & Gabrielsen, Tove M. (2021). FAIR and consistent data management in a large multidisciplinary project: The Nansen Legacy. Fulltekst i vitenarkiv Vis sammendrag

  The Nansen Legacy project is a collaboration of over 200 biologists, oceanographers, atmospheric scientists and geologists from 10 research institutions across Norway. They investigate the impact of climate change on the northern Barents Sea and adjacent Arctic Basin through multiple research expeditions into often ice-covered waters. Designing a system that ensures good and consistent data management across such a large, multidisciplinary project is challenging, as multiple documentation standards must be considered to encompass the wide range of data involved. Yet success in achieving this is particularly important to facilitate multidisciplinary collaborations, both across the project and beyond, as researchers are often less aware of the data available to them outside of their own field , which may compliment or strengthen their work. To ensure good data management across the project, we have developed a standardized spreadsheet template generator based on Darwin Core, also including terms from NetCDF-CF, that simplifies data publication. The populated templates are fed into a searchable metadata catalogue available through the SIOS (Svalbard Integrated Arctic Earth Observing System) website, that provides an overview of the data collection activities. Documented and published sampling protocols ensure consistent data collection procedures between different researchers, and to clarify how the data were collected for those not involved. The Nansen Legacy project adheres to the FAIR data management principles proposed by Wilksinson et al. (2016), and published datasets are harvested and made accessible via a single access point on the SIOS website. Frequent data management trainings are available to educate all project participants on the best practices for these procedures.

• Marsden, Luke; Ellingsen, Pål Gunnar; Godøy, Øystein Arne & Gabrielsen, Tove M. (2021). The role of digital platforms and technology in facilitating good management of scientific data. Fulltekst i vitenarkiv Vis sammendrag

  • How to keep up in a rapidly changing digital landscape. • Managing a large multidisciplinary project consistently. • Providing standardised rich metadata through digitisation and open-source software.

• Gabrielsen, Tove M. (2019). På isen i Nansenbassenget. Forskning.no. ISSN 1891-635X. Fulltekst i vitenarkiv
• Wutkowska, Magdalena; Vader, Anna; Logares, Ramiro & Gabrielsen, Tove M. (2019). Metatranscriptomics insights into seasonality of microbial eukaryotes in Adventfjorden. Fulltekst i vitenarkiv
• Wiedmann, Ingrid; Reigstad, Marit; Marquardt, Miriam; Vader, Anna & Gabrielsen, Tove M. (2018). Corrigendum to “Seasonality of vertical flux and sinking particle characteristics in an ice-free high arctic fjord – Different from subarctic fjords?” [J. Mar. Syst. 154 (2016) 192–205]. Journal of Marine Systems. ISSN 0924-7963. 178, s. 86–87. doi: 10.1016/j.jmarsys.2017.10.003. Fulltekst i vitenarkiv
• Wutkowska, Magdalena; Vader, Anna; Logares, Ramiro & Gabrielsen, Tove M. (2018). Exploring seasonal changes in functionality of microbial communities through comparative metatranscriptomics - a project presentation. Fulltekst i vitenarkiv
• Wutkowska, Magdalena; Eidesen, Pernille Bronken; Gabrielsen, Tove M. & Ehrich, Dorothee (2018). Arctic microbial eukaryotes and their functional importance in time and space. Fulltekst i vitenarkiv
• Gabrielsen, Tove M. & Johnsen, Geir (2018). Skogen på Svalbard. Svalbardposten. s. 16–16. Fulltekst i vitenarkiv Vis sammendrag

  Skogen på Svalbard må vi under havoverflaten for å oppleve. Store, flotte tareskoger finnes rundt hele øygruppen og kan sees fra land når tarebladene dupper rett under fjæra på lavvann. Tareskogen vokser i et belte fra 2 og ned til ca 30 meters dyp, blant annet på Rossøya helt nord på Sjuøyene (det nordligste punktet på Svalbard). Tareskogen rundt Svalbard er relativt dårlig undersøkt, men som på fastlandet har den flere viktige roller i det marine økosystemet; alger i tareskogen binder CO2 og representerer et svært produktivt system som er viktig for marine fisk, bunndyr og mikroorganismer som matfat, skjulested og leveområde.

• Eidesen, Pernille Bronken; Gabrielsen, Tove M. & Vader, Anna (2017). Unveiling the hidden communities of arctic eukaryotic microorganisms. Arctic Approach - The Northern Area Program. Fagbokforlaget. ISSN 9788245021127. s. 95–108. Fulltekst i vitenarkiv
• Daase, Malin; Søreide, Janne; Hatlebakk, Maja; Freese, Daniela; Berge, Jørgen & Renaud, Paul [Vis alle 8 forfattere av denne artikkelen] (2016). Lipid content in Arctic Calanus: a matter of season and size. Fulltekst i vitenarkiv
• Marquardt, Miriam; Vader, Anna; Skogseth, Ragnheid; Wiedmann, Ingrid; Reigstad, Marit & Gabrielsen, Tove M. (2016). Seasonality and fate of microbial eukaryotes in an high-Arctic fjord (Isfjorden, West Spitsbergen). Fulltekst i vitenarkiv
• Norrbin, Fredrika; Søreide, Janne; Gabrielsen, Tove M.; Halsband, Claudia; Hegseth, Else Nøst & Priou, Pierre (2016). Plankton phenology and community structure in ice-covered and open high-latitude fjords; a comparison between Isfjorden, Svalbard, and Porsangerfjord, northern Norway. Fulltekst i vitenarkiv
• Søreide, Janne E.; Gradinger, Rolf; Niehoff, Barbara; Bluhm, Bodil; Gabrielsen, Tove M. & Peeken, Ilka [Vis alle 8 forfattere av denne artikkelen] (2016). Arctic Ocean winter ecology – the Big Black Box. Fulltekst i vitenarkiv
• Daase, Malin; Berge, Jørgen; Renaud, Paul E.; Vogedes, Daniel Ludwig; Heggland, Kristin & Søreide, Janne [Vis alle 8 forfattere av denne artikkelen] (2015). Size Matters- Impact of climate change at the base of the Arctic food chain. Fulltekst i vitenarkiv
• Marquardt, Miriam; Vader, Anna & Gabrielsen, Tove M. (2015). Seasonality and diversity of arctic pelagic protist communities in Adventfjorden (West Spitsbergen). Fulltekst i vitenarkiv
• Marquardt, Miriam; Vader, Anna & Gabrielsen, Tove M. (2015). Unveiling the hidden: Seasonality of Arctic pelagic protist communities in Adventfjorden (West Spitsbergen). Fulltekst i vitenarkiv
• Wiedmann, Ingrid; Reigstad, Marit; Marquardt, Miriam & Gabrielsen, Tove M. (2015). Seasonal Changes in Sinking Particles' Qualitative Characteristics (Size, POC: Volume Ratio and 18S rDNA Composition) and the Impact on the Vertical Carbon Flux in Arctic Marine Ecosystems. Fulltekst i vitenarkiv
• Vogedes, Daniel Ludwig; Berge, Jørgen; Daase, Malin; Johnsen, Geir; Darnis, Gérald & Last, Kim S. [Vis alle 20 forfattere av denne artikkelen] (2015). Expect the unexpected - a new perspective and understanding of marine life at high latitudes. Fulltekst i vitenarkiv Vis sammendrag

  The polar night of the high Arctic is most commonly conceived as a period when marine organisms reduce their activity levels commensurate with a primary production close to zero. Food web interactions, annual routines and metabolic rates are thought to be at a minimum pending the return of the sun. Here we present a contrasting view, with new and compelling evidence of a system that is characterized by a high number of processes and interactions yet to be understood, both at the sea-surface, in the water-column and at the seafloor. We base our observations on regular surveys during the last five winters in a Svalbard fjord at 79°N. In contrast to a system that has entered a state of diapause, we can document a system in which abundance, activity levels and interactions across all trophic levels are at par or above those found at the peak of primary production during the spring bloom period. Ultimately, this new understanding of life in the Arctic oceans during the polar night will have strong implications both on the prevailing management regimes as well as our perception of high latitude marine ecosystems.

• Vogedes, Daniel Ludwig; Berge, Jørgen; Søreide, Janne & Gabrielsen, Tove M. (2014). Mare Incognitum. doi: https:/www.mare-incognitum.no/. Fulltekst i vitenarkiv Vis sammendrag

  Mare Incognitum - mission statement ‘Mare Incognitum’ is the umbrella for several research projects exploring one of the least known marine ecosystems of the planet – the Arctic. We are situated in the Arctic and have the unique opportunity to study this exceptional marine system year round, including the Polar Night.

• Marquardt, Miriam; Meshram, Archana R; Vader, Anna; Reigstad, Marit & Gabrielsen, Tove M. (2013). Marine eukaroytes in an arctic marine ecosystem: Diversity and Seasonality. Fulltekst i vitenarkiv
• Marquardt, Miriam; Meshram, Archana R; Vader, Anna; Reigstad, Marit & Gabrielsen, Tove M. (2012). Marine eukaryotes in an arctic marine ecosystem: Identity and Seasonality. Fulltekst i vitenarkiv
• Gabrielsen, Tove M; Quillfeldt, Cecilie von; Johnsen, Geir & Berge, Jørgen (2012). Varm vinter, sen vår i fjorden. Svalbardposten. Fulltekst i vitenarkiv
• Gabrielsen, Tove M.; Quillfeldt, Cecilie von; Johnsen, Geir & Berge, Jørgen (2012). Varm vinter, sen vår i fjorden. Fulltekst i vitenarkiv
• Espelund, Mari; Gabrielsen, Tove M; Nederbragt, Alexander Johan & Jakobsen, Kjetill Sigurd (2008). Kloroplastgenomet til Karlodinium micrum. Fulltekst i vitenarkiv
• Gabrielsen, Tove M; Eidesen, Pernille Bronken; Elven, Reidar & Brochmann, Christian (2005). Reticulate evolution and phylogeography in the Arctic: Saxifraga section Mesogyne. Fulltekst i vitenarkiv
• Jørgensen, Marte Holten; Gabrielsen, Tove M; Elven, Reidar; Stedje, Brita & Brochmann, Christian (2005). Evolutionary lineages and species delimitation in the Saxifraga rivularis complex. Fulltekst i vitenarkiv
• Brochmann, Christian; Ehrich, Dorothee; Gabrielsen, Tove M; Schönswetter, Peter & Tribsch, Andreas (2004). Postglacial colonization of northern Europe. Fulltekst i vitenarkiv
• Brochmann, Christian; Ehrich, Dorothee; Gabrielsen, Tove M; Schönswetter, Peter & Tribsch, Andreas (2004). Postglacial colonization of northern Europe. Fulltekst i vitenarkiv
• Brochmann, Christian; Ehrich, Dorothee; Gabrielsen, Tove M; Landvik, Jon; Schönswetter, Peter & Tribsch, Andreas (2004). Postglasial kolonisering av Nord-Europa. Fulltekst i vitenarkiv
• Gabrielsen, Tove M; Elven, Reidar & Brochmann, Christian (2004). Phylogeny and reticulate evolution in an arctic model group: Saxifraga section Mesogyne. Fulltekst i vitenarkiv
• Gabrielsen, Tove M & Jørgensen, Marte H (2003). Phylogeny and taxonomy of Saxifraga section Mesogyne. Fulltekst i vitenarkiv
• Gabrielsen, Tove M (2003). Phylogeny and reticulate evolution in an arctic model group: Saxifraga section Mesogyne. Fulltekst i vitenarkiv
• Kapralov, Maxim; Gabrielsen, Tove M & Brochmann, Christian (2003). The Ural Mountains as a model system for studying South-North differentiation in sexuality and polyploidy, exemplified by the Nodding Saxifrage (Saxifraga cernua). Fulltekst i vitenarkiv
• Jørgensen, Marte Holten; Gabrielsen, Tove M; Elven, Reidar; Stedje, Brita & Brochmann, Christian (2003). Reticulate evolution and species delimitation in the arctic Saxifraga rivularis (Highland Saxifrage) complex. Fulltekst i vitenarkiv
• Jørgensen, Marte H; Gabrielsen, Tove M; Elven, Reidar; Stedje, Brita & Brochmann, Christian (2003). Reticulate evolution and species delimitation in the arctic Saxifraga rivularis (Highland Saxifrage) complex. Fulltekst i vitenarkiv
• Gabrielsen, Tove M (2002). Artsbegrep og problemer knyttet til artsavgrensning hos alger i lys av molekylære data. Fulltekst i vitenarkiv
• Gabrielsen, Tove M (2002). Postglasial innvandring av planter og dyr til Nord-Europa. Fulltekst i vitenarkiv
• Gabrielsen, Tove M (2002). Østersjøen som modellområde for undersøkelser av postglasial immigrasjon og økotypisk differensiering, eksemplifisert ved rødalgen Ceramium tenuicorne. Fulltekst i vitenarkiv
• Gabrielsen, Tove M (2002). Phylogenetic studies in red algae - what has been achieved over the last 25 years and what are the major challenges for the next 25 years? Fulltekst i vitenarkiv
• Gabrielsen, Tove M & Rueness, Jan (1999). Molecular genetic variation in diaphanous Ceramium species in the Baltic Sea and adjacent areas. Fulltekst i vitenarkiv
• Reigstad, Marit; Gabrielsen, Tove M.; Amargant-Arumi, Marti; Amundsen, Rita; Bluhm, Bodil & Bodur, Yasemin V. [Vis alle 37 forfattere av denne artikkelen] (2022). Seasonal Cruise Q3: Cruise Report. Septentrio Academic Publishing. Fulltekst i vitenarkiv Vis sammendrag

  The Nansen Legacy Q3 cruise, 5-27 August 2019, initiated the seasonal investigations of the Nansen Legacy transect. The transect represent an environmental gradient going through the northern Barents Sea, and included 7 process stations (P1-P7) lasting 6-53 hrs. CTD stations were taken to increase the hydrographic resolution on the transect. The program included measurements and sampling from the atmosphere, sea ice, ocean and sea floor. Data collected ranged from physical observations, chemical, biological and geological data collection, and the aim was to link observations and measurements to improve our understanding of the systems involving both climate, human impacts and the ecosystems. Deployment of moorings and gliders extended the observational capacity in time and space, outside the cruise period.

• Kristiansen, Helga Bårdsdatter; Kauserud, Håvard; Davey, Marie Louise; Haverkamp, Thomas Hendricus Augustus & Gabrielsen, Tove M. (2014). Characterization of marine fungal communities using next generation sequencing techniques. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  As molecular and bioinformatics techniques are used more frequently and new marine habitats are analysed, a constant increase of marine fungal diversity has been reported, suggesting that marine fungi are a diverse but somewhat ignored organism group. The overall objective of this thesis was to further increase our knowledge about fungal diversity in marine environments by (1) investigating the fungal communities in the pelagic at different depths and dates using an Illumina amplicon sequencing approach, and (2) investigating the fungal communities in sediments using a 454 shotgun metagenomic pyrosequencing dataset. From the arctic marine environment only 14.3% of the DNA amplified was of fungal origin. This demonstrated that the primer pair ITS1F-ITS2 is not fungal specific in a marine environment. In the marine sediments, fungi accounted for, on average, 13.7% of the eukaryotic reads. Yeasts dominated in the sediments samples and are probably adapted to life in anoxic marine sediments. Mortierellales (Zygomycota), which includes known marine fungi, dominated the pelagic arctic fungal communities. What may be terrestrial fungi were detected in both habitats, but it is not clear whether they were deposited and dormant in the marine environment or if they were actively growing and adapted to marine environments. The pelagic fungal communities were not structured according to location or depth, but there seemed to be a seasonal fluctuation in the pelagic communities. Lack of taxonomic coverage of fungal taxa in the reference databases proved to be one of the major obstacles in determining the fungal diversity in both studies. While my study provides insight into the fungal communities in sediments and the pelagic, it also highlights the need for improved databases and further studies with proper sampling techniques and replicates in order to determine what factors actually structures these communities and what role fungi play in the marine system.

• Gabrielsen, Tove M (2002). Phylogeny and phylogeography of North Atlantic Ceramium (Ceramiales, Rhodophyta). Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  This thesis presents a study of the taxonomically complex red algal genus Ceramium and consists of four independent papers and a synopsis of the main results. The principal objective was to investigate molecular relationships and evolution of species occurring in the North Atlantic, with emphasis on phylogeography and differentiation of populations in the Skagerrak-Baltic region. This region, with its well-known and dynamic postglacial history including the recent establishment of a strong salinity gradient, may represent a unique model area for studies of combined genetic effects of postglacial colonisation and in situ ecological differentiation in marine organisms. Ceramium tenuicorne is known for conspicuous variation in growth and reproduction along this gradient, but its delimitation from other species (C. gobii and ¿C. strictum¿) is controversial. In paper I, we combined molecular (rubisco spacer region and nrDNA ITS2) and interfertility analyses and showed that the Skagerrak-Baltic populations belong to a single species, C. tenuicorne. We also identified four other, highly divergent North Atlantic lineages in material traditionally reported as ¿C. strictum¿; these lineages may represent distinct species. A high degree of intragenomic variation in ITS2 sequences was demonstrated in C. tenuicorne as well as in three other Ceramium species (paper IV). In paper II, we analysed two DNA regions (the rubisco spacer region and a segment of the nrDNA large subunit) in samples referred to 18 different species to assess the usefulness of these regions for phylogenetic reconstruction in red algae. We also tested whether three informal species groups often recognized in Ceramium have a phylogenetic basis. The inferred phylogeny was highly incongruent with the informal groups and suggested that cortical spines and internode cortication have evolved several times in the genus. We further investigated differentiation (papers III, IV) in C. tenuicorne along the Skagerrak-Baltic salinity gradient using one mtDNA marker (cox2-3 spacer) and two nuclear markers (RAPDs and ITS2). In spite of high frequencies of asexual reproduction in low-salinity regions, high levels of RAPD variation were found in all populations even at very small spatial scales. The combined data suggest that the Skagerrak-Baltic region was colonised twice from a diverse Atlantic glacial gene pool, and that the extant, very distinct geographic pattern with highly divergent Oslofjorden populations results from lineage sorting of mtDNA and ITS2 polymorphisms and strong differential selection among nuclear genotypes along the salinity gradient. The first immigration wave may have taken place already in the Yoldia Sea phase, when the Baltic basin was connected to the Atlantic via Central Sweden and Oslofjorden. The level of molecular divergence between Oslofjorden populations, which may represent relicts from a Yoldia immigration, and Kattegat/Baltic populations should be studied also in other marine organisms to establish whether this is a general pattern.

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