Tove Margrethe Gabrielsen

• Wutkowska, Magdalena; Vader, Anna; Logares, Ramiro; Pelletier, Eric & Gabrielsen, Tove M. (2023). Linking extreme seasonality and gene expression in Arctic marine protists. Scientific Reports. ISSN 2045-2322. 13. doi: 10.1038/s41598-023-41204-3. Full text in Research Archive Show summary

  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, p. 1105–1118. doi: 10.1007/s00300-022-03060-1. Full text in Research Archive Show summary

  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.

• Kvernvik, Ane Cecilie; Hoppe, Clara Jule Marie; Greenacre, Michael; Verbiest, Sander; Wiktor, Józef Maria & Gabrielsen, Tove M. [Show all 8 contributors for this article] (2021). Arctic sea ice algae differ markedly from phytoplankton in their ecophysiological characteristics. Marine Ecology Progress Series. ISSN 0171-8630. 666, p. 31–55. doi: 10.3354/meps13675. Full text in Research Archive
• Ellingsen, Pål Gunnar; Ferrighi, Lara; Godøy, Øystein Arne & Gabrielsen, Tove M. (2021). Keeping track of samples in multidisciplinary fieldwork. Data Science Journal. ISSN 1683-1470. 20(34), p. 1–13. doi: 10.5334/DSJ-2021-034. Full text in Research Archive
• 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. ISSN 2073-4441. 13(14), p. 1–18. doi: 10.3390/w13141990. Full text in Research Archive
• Kvernvik, Ane Cecilie; Rokitta, Sebastian D.; Leu, Eva; Harms, Lars; Gabrielsen, Tove M. & Rost, Björn [Show all 7 contributors for this article] (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), p. 1708–1724. doi: 10.1111/nph.16501.
• Hegseth, Else Nøst; Assmy, Philipp; Wiktor, Józef M.; Wiktor Jr, Józef; Kristiansen, Svein & Leu, Eva [Show all 10 contributors for this article] (2019). Phytoplankton Seasonal Dynamics in Kongsfjorden, Svalbard and the Adjacent Shelf. In Hop, Haakon & Wiencke, Christian (Ed.), The Ecosystem of Kongsfjorden, Svalbard. Springer. ISSN 978-3-319-46423-7. p. 173–227. doi: 10.1007/978-3-319-46425-1_6.
• Marquardt, Miriam; Skogseth, Ragnheid; Wiedmann, Ingrid; Vader, Anna; Reigstad, Marit & Cottier, Finlo Robert [Show all 7 contributors for this article] (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), p. 65–82. doi: 10.3354/ame01904. Full text in Research Archive
• 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), p. 149–159. doi: 10.1007/s10750-019-3967-y.
• Renaud, Paul Eric; Daase, Malin; Banas, Neil S.; Gabrielsen, Tove M.; Søreide, Janne & Varpe, Øystein [Show all 12 contributors for this article] (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), p. 1871–1881. doi: 10.1093/icesjms/fsy063. Full text in Research Archive
• Vader, Anna; Laughinghouse IV, Haywood; 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), p. 890–902. doi: 10.1111/1462-2920.14035.
• 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), p. 1937–1946. doi: 10.1093/icesjms/fsx106.
• Darnis, Gérald; Hobbs, Laura; Geoffroy, Maxime; Grenvald, Julie Cornelius; Renaud, Paul & Berge, Jørgen [Show all 13 contributors for this article] (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), p. 1586–1605. doi: 10.1002/lno.10519. Full text in Research Archive Show summary

  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.

• Meshram Rao, Archana; Vader, Anna; Kristiansen, Svein & Gabrielsen, Tove M. (2017). Microbial eukaryotes in an Arctic under-ice spring bloom north of Svalbard. Frontiers in Microbiology. ISSN 1664-302X. 8. doi: 10.3389/fmicb.2017.01099. Full text in Research Archive Show summary

  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.

• 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, p. 61–72. doi: 10.1016/j.jmarsys.2017.01.013.
• 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. ISSN 2045-7758. 6(16), p. 5585–5595. doi: 10.1002/ece3.2302. Full text in Research Archive
• 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), p. 263–276. doi: 10.1007/s00300-016-1950-x. Full text in Research Archive
• 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), p. 79–94. doi: 10.1111/pre.12121.
• 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), p. 1868–1880. doi: 10.1128/AEM.03208-15.
• 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), p. 192–205. doi: 10.1016/j.jmarsys.2015.10.003. Full text in Research Archive
• Leu, Eva; Mundy, Christopher John; Assmy, Philipp; Campbell, Karley; Gabrielsen, Tove M. & Gosselin, Michel [Show all 8 contributors for this article] (2015). Arctic spring awakening - Steering principles behind the phenology of vernal ice algal blooms. Progress in Oceanography. ISSN 0079-6611. 139, p. 151–170. doi: 10.1016/j.pocean.2015.07.012.
• Berge, Jørgen; Daase, Malin; Renaud, Paul; Ambrose, William G. Jr.; Darnis, Gérald & Last, Kim S [Show all 35 contributors for this article] (2015). Unexpected levels of biological activity during the polar night offer new perspectives on a warming Arctic. Current Biology. ISSN 0960-9822. 25(19), p. 2555–2561. doi: 10.1016/j.cub.2015.08.024.
• Berge, Jørgen; Renaud, Paul; Darnis, Gérald; Cottier, Finlo; Last, Kim & Gabrielsen, Tove M. [Show all 17 contributors for this article] (2015). In the dark: a review of ecosystem processes during the Arctic polar night. Progress in Oceanography. ISSN 0079-6611. 139, p. 258–271. doi: 10.1016/j.pocean.2015.08.005. Full text in Research Archive Show summary

  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.

• Fredriksen, Stein; Gabrielsen, Tove M.; Kile, Maia Røst & Sivertsen, Knut (2015). Benthic algal vegetation in Isfjorden, Svalbard. Polar Research. ISSN 0800-0395. 34, p. 1–9. doi: 10.3402/polar.v34.25994. Full text in Research Archive
• 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, p. 85–97. doi: 10.1016/j.csr.2015.04.003.
• 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), p. 13–21. doi: 10.1007/s00300-014-1570-2.
• Gabrielsen, Tove M; Merkel, Benjamin; Søreide, Janne; Johansson-Karlsson, Emma; Bailey, Allison & Vogedes, Daniel Ludwig [Show all 9 contributors for this article] (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), p. 1621–1628. doi: 10.1007/s00300-012-1202-7. Full text in Research Archive
• Espelund, Mari; Minge, Marianne Aastebøl; Gabrielsen, Tove M; Nederbragt, Alexander Johan; Shalchian-Tabrizi, Kamran & Otis, Christian [Show all 9 contributors for this article] (2012). Genome Fragmentation Is Not Confined to the Peridinin Plastid in Dinoflagellates. PLOS ONE. ISSN 1932-6203. 7(6). doi: 10.1371/journal.pone.0038809. Full text in Research Archive
• 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), p. 519–533. doi: 10.1007/s00300-011-1097-8.
• 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), p. 191–195. doi: 10.1093/plankt/fbr103. Full text in Research Archive
• Gabrielsen, Tove M; Minge, Marianne Aastebøl; Espelund, Mari; Tooming-Klunderud, Ave ; Patil, Viswanath & Nederbragt, Alexander Johan [Show all 11 contributors for this article] (2011). Genome Evolution of a Tertiary Dinoflagellate Plastid. PLOS ONE. ISSN 1932-6203. 6(4). doi: 10.1371/journal.pone.0019132.
• 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), p. 1262–1276. doi: 10.1111/j.1365-2699.2010.02278.x. Show summary

  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.

• 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), p. 702–729.
• 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, p. 3401–3411.
• 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), p. 353–360.
• Guldahl, AS; Gabrielsen, Tove M; Scheen, Anne-Cathrine; Borgen, Liv; Steen, SW & Spjelkavik, S [Show all 7 contributors for this article] (2005). The Saxifraga rivularis complex in Svalbard: Molecules, ploidy and morphology. Flora: Morphologie, Geobotanik, Oekophysiologie. ISSN 0367-2530. 200, p. 207–221.
• Guldahl, AS; Gabrielsen, Tove; Scheen, A; Borgen, L.; Steen, Snorre Winger & Spjelkavik, Sigmund [Show all 7 contributors for this article] (2005). The Saxifraga rivularis complex in Svalbard: Molecules, ploidy and morphology. Flora: Morphologie, Geobotanik, Oekophysiologie. ISSN 0367-2530. 200(3), p. 207–221. doi: 10.1016/j.flora.2005.01.003. Show summary

  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.

• 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, p. 1–13.
• 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, p. 417–450.
• Maggs, Christine A. & Gabrielsen, Tove M (2003). Red algal systematics: 25 years of turbulent progress. British phycological Journal. ISSN 0007-1617. p. 102–114.
• Mikalsen, Bjørg; Boison, G; Skulberg, Olav M.; Fastner, J; Davies, William & Gabrielsen, Tove M [Show all 8 contributors for this article] (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), p. 2774–2785. doi: 10.1128/JB.185.9.2774-2785.2003. Show summary

  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.

• Rueness, Jan; Gabrielsen, Tove M & Düwel, Lene (2002). Observations on Ceramium tenuicorne (Rhodophyta) and its reproduction. Cryptogamie. Algologie. ISSN 0181-1568. 23(3), p. 251–261.
• 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, p. 2083–2095. Show summary

  '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.

• 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, p. 1701–1708.
• Brochmann, Christian; Gabrielsen, Tove M; Hagen, Aslaug Ragnhild; Steen, S.W. & Tollefsrud, M.M. (1997). Molecular phylogeography and diaspore dispersal in the Svalbard archipelago, Arctic Norway, Report from the workshop 'The ecosystem at the glacier edge areas in the Arctic'. National Institute of Polar Research, Tokyo, Japan..
• Gabrielsen, Tove M; Bachmann, K.; Jakobsen, Kjetill Sigurd & Brochmann, Christian (1997). Glacial survival does not matter: RAPD phylogeography of Nordic Saxifraga oppositifolia. Molecular Ecology. ISSN 0962-1083. 6, p. 831–842.
• Brysting, Anne Krag; Gabrielsen, Tove M; Sørlibråten, Ove; Ytrehorn, Oddmund & Brochmann, Christian (1996). The Purple Saxifrage, Saxifraga oppositifolia, in Svalbard: two taxa or one? Polar Research. ISSN 0800-0395. 15, p. 93–105.
• Brochmann, Christian; Gabrielsen, Tove M; Hagen, Aslaug Ragnhild & Tollefsrud, Mari Mette (1996). Seed dispersal and molecular phylogeography: glacial survival, tabula rasa, or does it really matter? Årbok / Det norske videnskaps-akademi. ISSN 0332-6209. 18, p. 53–67.
• Brochmann, Christian; Nilsson, T. & Gabrielsen, Tove M (1996). A classic example of postglacial allopolyploid speciation re-examined using RAPD markers and nucleotide sequences: Saxifraga osloensis (Saxifragaceae). Symbolae Botanicae Upsalienses. ISSN 0082-0644. 31(3), p. 75–89.

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• Reigstad, Marit; Gerland, Sebastian; Eldevik, Tor; Kunisch, Erin; Wiedmann, Ingrid & Sundfjord, Arild [Show all 21 contributors for this article] (2023). The Nansen Legacy project invites you to its upcoming international symposium in November 2023.
• 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.
• Lien, Anne; Nygård, Malene Østreng; Laugen, Ane Timenes; Lie, Asbjørn; Slettan, Audun & Johansen, Beate Strøm [Show all 33 contributors for this article] (2023). Utbygging vil ødelegge for biologisk mangfold på campus Gimlemoen. NB! 34 forfattere totalt. Fædrelandsvennen. ISSN 0805-3790. p. 19–19.
• Sjøtun, Kjersti; Fredriksen, Stein; Gabrielsen, Tove M.; Husa, Vivian; Goecke, Franz Ronald Saavedra & Le Gall, Line [Show all 9 contributors for this article] (2023). Mapping and DNA barcoding the brown algal diversity within the orders Ectocarpales, Ralfsiales and Sphacelariales in Norway.
• 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. Show summary

  • 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.

• 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. Show summary

  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.

• Gabrielsen, Tove M. (2019). På isen i Nansenbassenget. Forskning.no. ISSN 1891-635X.
• Wutkowska, Magdalena; Vader, Anna; Logares, Ramiro & Gabrielsen, Tove M. (2019). Metatranscriptomics insights into seasonality of microbial eukaryotes in Adventfjorden.
• Gabrielsen, Tove M. & Johnsen, Geir (2018). Skogen på Svalbard. Svalbardposten. p. 16–16. Show summary

  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.

• Wutkowska, Magdalena; Vader, Anna; Logares, Ramiro & Gabrielsen, Tove M. (2018). Exploring seasonal changes in functionality of microbial communities through comparative metatranscriptomics - a project presentation.
• Wutkowska, Magdalena; Eidesen, Pernille Bronken; Gabrielsen, Tove M. & Ehrich, Dorothee (2018). Arctic microbial eukaryotes and their functional importance in time and space.
• 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, p. 86–87. doi: 10.1016/j.jmarsys.2017.10.003.
• 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 978-82-450-2112-7. p. 95–108.
• 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).
• Søreide, Janne E.; Gradinger, Rolf; Niehoff, Barbara; Bluhm, Bodil; Gabrielsen, Tove M. & Peeken, Ilka [Show all 8 contributors for this article] (2016). Arctic Ocean winter ecology – the Big Black Box.
• 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.
• Daase, Malin; Søreide, Janne; Hatlebakk, Maja; Freese, Daniela; Berge, Jørgen & Renaud, Paul [Show all 8 contributors for this article] (2016). Lipid content in Arctic Calanus: a matter of season and size.
• Marquardt, Miriam; Vader, Anna & Gabrielsen, Tove M. (2015). Seasonality and diversity of arctic pelagic protist communities in Adventfjorden (West Spitsbergen). .
• Marquardt, Miriam; Vader, Anna & Gabrielsen, Tove M. (2015). Unveiling the hidden: Seasonality of Arctic pelagic protist communities in Adventfjorden (West Spitsbergen). .
• Daase, Malin; Berge, Jørgen; Renaud, Paul E.; Vogedes, Daniel Ludwig; Heggland, Kristin & Søreide, Janne [Show all 8 contributors for this article] (2015). Size Matters- Impact of climate change at the base of the Arctic food chain.
• Vogedes, Daniel Ludwig; Berge, Jørgen; Daase, Malin; Johnsen, Geir; Darnis, Gérald & Last, Kim S. [Show all 20 contributors for this article] (2015). Expect the unexpected - a new perspective and understanding of marine life at high latitudes. Show summary

  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.

• 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.
• Vogedes, Daniel; Berge, Jørgen; Søreide, Janne & Gabrielsen, Tove M. (2014). Mare Incognitum. Show summary

  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.
• Gabrielsen, Tove M; Quillfeldt, Cecilie von; Johnsen, Geir & Berge, Jørgen (2012). Varm vinter, sen vår i fjorden. Svalbardposten.
• Marquardt, Miriam; Meshram, Archana R; Vader, Anna; Reigstad, Marit & Gabrielsen, Tove M. (2012). Marine eukaryotes in an arctic marine ecosystem: Identity and Seasonality.
• Espelund, Mari; Gabrielsen, Tove M; Nederbragt, Alexander Johan & Jakobsen, Kjetill Sigurd (2008). Kloroplastgenomet til Karlodinium micrum.
• Gabrielsen, Tove M; Eidesen, Pernille Bronken; Elven, Reidar & Brochmann, Christian (2005). Reticulate evolution and phylogeography in the Arctic: Saxifraga section Mesogyne.
• Jørgensen, Marte Holten; Gabrielsen, Tove M; Elven, Reidar; Stedje, Brita & Brochmann, Christian (2005). Evolutionary lineages and species delimitation in the Saxifraga rivularis complex.
• Gabrielsen, Tove M; Elven, Reidar & Brochmann, Christian (2004). Phylogeny and reticulate evolution in an arctic model group: Saxifraga section Mesogyne.
• Brochmann, Christian; Ehrich, Dorothee; Gabrielsen, Tove M; Schönswetter, Peter & Tribsch, Andreas (2004). Postglacial colonization of northern Europe.
• Brochmann, Christian; Ehrich, Dorothee; Gabrielsen, Tove M; Schönswetter, Peter & Tribsch, Andreas (2004). Postglacial colonization of northern Europe.
• Brochmann, Christian; Ehrich, Dorothee; Gabrielsen, Tove M; Landvik, Jon; Schönswetter, Peter & Tribsch, Andreas (2004). Postglasial kolonisering av Nord-Europa.
• Gabrielsen, Tove M & Jørgensen, Marte H (2003). Phylogeny and taxonomy of Saxifraga section Mesogyne.
• Gabrielsen, Tove M (2003). Phylogeny and reticulate evolution in an arctic model group: Saxifraga section Mesogyne.
• 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).
• 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.
• 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.
• Gabrielsen, Tove M (2002). Østersjøen som modellområde for undersøkelser av postglasial immigrasjon og økotypisk differensiering, eksemplifisert ved rødalgen Ceramium tenuicorne.
• 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?
• Gabrielsen, Tove M (2002). Postglasial innvandring av planter og dyr til Nord-Europa.
• Gabrielsen, Tove M (2002). Artsbegrep og problemer knyttet til artsavgrensning hos alger i lys av molekylære data.
• Gabrielsen, Tove M & Rueness, Jan (1999). Molecular genetic variation in diaphanous Ceramium species in the Baltic Sea and adjacent areas.
• Gabrielsen, Tove M; Spjelkavik, S. & Brochmann, Christian (1997). Sex after all: high clonal diversity observed in arctic Saxifraga cernua using RAPD-PCR.
• Gabrielsen, Tove M; Bachmann, K.; Jakobsen, Kjetill Sigurd & Brochmann, Christian (1995). RAPD variation in an arctic-alpine, mainly diploid outbreeder: Saxifraga oppositifolia.
• Reigstad, Marit; Gabrielsen, Tove M.; Amargant-Arumi, Marti; Amundsen, Rita; Bluhm, Bodil & Bodur, Yasemin V. [Show all 37 contributors for this article] (2022). Seasonal Cruise Q3: Cruise Report . Septentrio Academic Publishing. ISSN 2703-7525. Show summary

  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.

• Bårdsdatter Kristiansen, Helga; 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.
• Gabrielsen, Tove M (2002). Phylogeny and phylogeography of North Atlantic Ceramium (Ceramiales, Rhodophyta). Universitetet i Oslo. Show summary

  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.

• Hagen, Aslaug Ragnhild; Brochmann, Christian; Gabrielsen, Tove M & Tollefsrud, M.M. (1995). Lab-manual for RAPD-analyser. 7Letras.

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