Bente Edvardsen

Gran-Stadniczeñko, S., Šupraha, L., Egge, E. D., Edvardsen, B. Haptophyte diversity and vertical distribution explored by 18S and 28S ribosomal RNA gene metabarcoding and scanning electron microscopy. J. Euk. Microbiol. In press.

Eikrem, E., Medlin, L.K., Henderiks, J., Rokitta, S., Rost, B., Probert, I., Throndsen, J., Edvardsen, B. 2016. Haptophyta. In: Handbook of the Protists. Archibald, J. et al. (Eds.). p. 1-61.

Edvardsen, B., Egge, E.S., Vaulot, D. 2016. Diversity and distribution of haptophytes revealed by environmental sequencing and metabarcoding - a review. Perspectives in Phycology 3(2): 77-91.

Banguera-Hinestroza, E., Eikrem, W., Mansour, H., Solberg, I., Curdia, J., Holtermann, K., Edvardsen, B., Kaartvedt, S. 2016. Seasonality and toxin production of Pyrodinium bahamense in a Red Sea lagoon. Harmful Algae 55: 163–171.

Engesmo, A., Eikrem, W., Seoane, S., Smith, K., Edvardsen, B. Hofgaard, A and Tomas, C.R. 2016. New insights into the morphology and phylogeny of Heterosigma akashiwo (Raphidophyceae), with the description of Heterosigma minor sp. nov. Phycologia, 55: 279-294.

Forster, D., et al. 2016. Benthic protists: The under-charted majority. FEMS Microbiol. Ecol. 92:fiw120(8).

McNamee, S.E., Medlin, L.K., Kegel, J., McCoy G.R., Raine R., Barra L., Ruggiero, M.V., Kooistra W.H.C.F., Montresor, M., Hagstrom, J., Perez Blanc, E., Granéli, E., Rodríguez, F., Escalera, L., Reguera, B., Dittami, S., Edvardsen, B., Taylor, J., Lewis, J.M., Pazo, Y., Elliot, C.T., Campbell, K. 2016. Distribution, occurrence and biotoxin composition of the main shellfish toxin producing microalgae within European waters: A comparison of methods of analysis. Harmful Algae 55: 112-120.

Kopf, A. et al. 2015. The ocean sampling day. GigaScinece 4:27.

Massana R, et al. 2015. Marine protist diversity in European coastal waters and sediments as revealed by high-throughput sequencing. Env. Microbiol. 17(10):4035-4049

Gerecht, A., Šupraha, L., Edvardsen, B., Langer, G. Henderiks, J. 2015. Phosphorus availability modifies carbon production in Coccolithus pelagicus subsp. braarudii (Wallich) Schiller 1930. J. Exp. Mar. Biol. Ecol. 472: 24-31.

Egge, E. S., Johannessen, T. V., Andersen, T., Eikrem, W., Bittner, L., Larsen, A., Sandaa, R.-A. and Edvardsen, B. 2015. Seasonal diversity and dynamics of haptophytes in the Skagerrak, Norway, explored by high-throughput sequencing. Mol. Ecol. 24:3026-3042.

Johannessen, T.V., Bratbak, G., Larsen, A., Ogata, H., Egge, E.S., Edvardsen, B., Eikrem, W., Sandaa, R.A. 2015. Characterisation of three novel giant viruses reveals huge diversity among viruses infecting Prymnesiales (Haptophyta). Virology. 476:180-188.

Egge, E.S. Eikrem, W., Edvardsen, B. 2015. Deep-branching novel lineages and high diversity of haptophytes in the Skagerrak (Norway) uncovered by 454 pyrosequencing. J. Euk. Microbiol. 62(1):121-140.

Duffield, C.J., Edvardsen, B., Eikrem, W., Alve, E. 2014. Effects of different potential food sources on upper-bathyal benthic foraminifera: an experiment with propagules. J. foram. Res., 44(4): 427–444.

Egge, E.S. Eikrem, W., Edvardsen, B. 2014. Deep-branching novel lineages and high diversity of haptophytes in the Skagerrak (Norway) uncovered by 454 pyrosequencing. J. Euk. Microbiol. 08/2014

Keeling, P.J. et al. 2014. The Marine Microbial Eukaryote Transcriptome Sequencing Project (MMETSP): Illuminating the functional diversity of eukaryotic life in the oceans through transcriptome sequencing. PLoS Biology, 12(6): e1001889.

Logares, R. et al. 2014. Patterns of rare and abundant marine microbial eukaryotes. Curr. Biol. 24(8): 813-21.

Dunthorn et al. 2014. Placing environmental next generation sequencing amplicons from microbial eukaryotes into a phylogenetic context. Mol. Biol. Evol. 31(4): 993–1009.

Egge E, Bittner L, Andersen T, Audic S, de Vargas C, Edvardsen B. 2013. 454-pyrosequencing to describe microbial eukaryotic community composition, diversity and relative abundance: a test for marine haptophytes. PLOS One, 8(9): e74371.

Stüken, A, Dittami, S.M., Wenche, W., McNamee, S., Campbell, K., Jakobsen, K.S., Edvardsen, B. 2013. Novel hydrolysis-probe based qPCR assay to detect dinoflagellate saxitoxin transcripts in environmental samples, Harmful Algae, 28:108-117.

Dittami S.M., Hostyeva V., Egge E.S., Kegel J.U, W. Eikrem, Edvardsen, B. 2013. Seasonal dynamics of harmful algae in outer Oslofjorden monitored by microarray, qPCR, and microscopy. Environ. Sci. Pollut. Res., 20: 6719-6732.

Dittami, S.M., Riisberg, I., Edvardsen, B. 2013. Molecular probes for the detection and identification of ichthyotoxic marine flagellates of the genus Pseudochattonella (Dictyochophyceae, Heterokonta). Environ. Sci. Pollut. Res., 20: 6719-6732.

Edvardsen, B., Dittami, S.M., Chen, J., Groben, R., Brubak, S., Medlin, L.K. 2013. Molecular probes for the detection and identification of harmful algae in the genera Dinophysis and Phalacroma. 2012. Environ. Sci. Pollut. Res., 20: 6733-6750.

Guillou, L., Bachar, D., Audic, S., Bass, D., Berney, C., Bittner, L., Boutte, C., Burgaud, G., de Vargas, C., Decelle, J., del Campo, J., Dolan, J., Dunthorn, M., Edvardsen, B. Holzmann, M., Kooistra, W. H. C. F., Lara, E., Lebescot, N., Logares, R., Mahé, F., Massana, R., Montresor, M., Morard, R., Not, F., Pawlowski, J., Probert, I., Sauvadet, A.-L., Siano, R., Stoeck, T., Vaulot, D., Zimmermann, P. & Christen, R. submitted. The Protist Ribosomal Reference database (PR2): a catalog of unicellular eukaryote Small SubUnit rRNA sequences with curated taxonomy. Nucleic Acids Res. 41(DI): D597-D604.

Bittner L, Audic S, Gobet, A, Romac S, Egge ES, Edvardsen B, Santini S, Ogata H, Probert I, de Vargas C. 2013. Diversity patterns of uncultured haptophytes unravelled by pyrosequencing in Naples Bay. Mol. Ecol. 22:87-101.

Dittami, S.M. & B. Edvardsen 2013. GPR-Analyzer: a simple tool for quantitative analysis of hierarchical multispecies microarrays. Environ. Sci. Pollut. Res., 20: 6808-6815.

Skjelbred, B., Edvardsen, B., Andersen, T. 2013. Environmental optima for seven strains of Pseudochattonella (Dictyochophyceae, Heterokonta). J. Phycol., 49:54-60.

McCoy GR, Raine R, Medlin LK, Chen J, Kooistra W, Barra L, Ruggiero MV, Graneli E, Hagström J, Salomon PS, Reguera B, Rodríguez F, Escalera L, Edvardsen B, Dittami SM, Eikrem W, Lewis JM, Berzano M, Elliott CT, Campbel K & Pazos Y. 2012. Field testing for toxic algae with a microarray: initial results from the MIDTAL project, In Proceedings of the 14th International Conference on Harmful Algae. International Society for the Study of Harmful Algae and Intergovernmental Oceanographic Commission of UNESCO 2012, I.3. pp. 209-211.

Hostyeva, V., Eikrem, W., Edvardsen, B., Hasle G.R. 2012. Annual cycle of Pseudo-nitzschia species in Outer Oslofjorden, In Proceedings of the 14th International Conference on Harmful Algae. International Society for the Study of Harmful Algae and Intergovernmental Oceanographic Commission of UNESCO 2012, C. 6. pp. 81-83.

Dittami, S.M., Edvardsen, B. 2012. Culture conditions influence cellular RNA content in ichthyotoxic flagellates of the genus Pseudochattonella (Dictyochophyceae). J. Phycol. 48: 1050-1055.

Skjelbred, B., Edvardsen, B., Andersen, T. 2012. A high-throughput method for measuring growth and respiration in microalgal cultures, J. Appl. Phycol. 24:1589-1599.

Ota, S., Eikrem, W., Edvardsen, B. 2012. Ultrastructure and molecular phylogeny of thaumatomonads (Cercozoa) with emphasis on Thaumatomastix salina from Oslofjorden, Norway. Protist, 163:560-573.

Granéli, E., B. Edvardsen, D.L. Roelke and J.A. Hagström. 2012. The ecophysiology and bloom dynamics of Prymnesium spp. Harmful Algae 14:260-270.

Dittami S.M., Riisberg I., John U, Orr R.J.S., Jakobsen K.S., Edvardsen B. 2012. Analysis of expressed sequence tags from the marine microalga Pseudochattonella farcimen (Dictyochophyceae). Protist, 163:143-161.

Dittami SM, Aas HTN, Smestad Paulsen B, Boyen C, Edvardsen B, Tonon T. 2011. Mannitol in six autotrophic stramenopiles and Micromonas. Plant Signaling & Behavior 6: 1237-1239.

Sym, S. Pienaar, R., Edvardsen, B., Egge, E. 2011. Fine structure and systematics of Prymnesium radiatum sp. nov. (Prymnesiophyceae) from False Bay and Franskraal, South Africa. Eur. J. Phycol. 46: 229-248.

Edvardsen, B., Eikrem, W., Throndsen, J., Sáez, A.G., Probert, I., Medlin, L.K. 2011. Ribosomal DNA phylogenies and a morphological revision set the basis for a revised taxonomy of Prymnesiales (Haptophyta). Eur. J. Phycol. 46: 202-228.

Strand D.A., Holst-Jensen A., Viljugrein H., Edvardsen B., Klaveness D., Jussila J., Vrålstad T. 2011. Detection and quantification of the crayfish plague agent in natural waters – an approach for direct monitoring of aquatic environments. Dis. Aquat. Org. 95:9–17.

Skjelbred, B., Horsberg, T.E, Tollefsen, K.E., Andersen, T., Edvardsen, B. 2011. Toxicity of the ichthyotoxic marineflagellate Pseudochattonella (Dictyochophyceae, Heterokonta) assessed by six bioassays. Harmful Algae 10:144-154.

Oftedal, L., Skjærven, K.H., Coyne, R.T., Edvardsen, B, Rohrlack, T., Skulberg, O.M., Døskeland, S.O., Herfindal, L. 2010. The apoptosis-inducing activity towards leukemia and lymphoma cells in a cyanobacterial culture collection is not associated with mouse bioassay toxicity. J Ind Microbiol Biotechnol. 38:489–501.

Haande, S., Rohrlack, Semyalo, R.P., T., Brettum, P., Edvardsen, B., Solheim A.L., Sørensen, K. and Larsson, P. 2010. Phytoplankton dynamics and cyanobacterial dominance in Murchison Bay of Lake Victoria (Uganda) in relation to environmental conditions. Limnologica 41(1): 20-29.

Rounge, T.B., Rohrlack, T., Decenciere, B., Edvardsen, B., Kristensen, T., K.S. Jakobsen. 2010. Subpopulation differentiation is associated with nonribosomal peptide gene cluster dynamics in Planktothrix. J. Phycol.46(4): 645-652.

Skjelbred, B., Horsberg, T.E, Tollefsen, K.E., Andersen, T. and Edvardsen, B. 2011. Toxicity of the ichthyotoxic marineflagellate Pseudochattonella (Dictyochophyceae, Heterokonta assessed by six bioassays. Harmful Algae 10(2): 144-154

Seoane, S,. Eikrem, W, Pienaar, R. and Edvardsen, B. 2009. Chrysochromulina palpebralis sp. nov. (Prymnesiophyceae): the description of a new haptophyte species, possessing two alternative morphologies. Phycologia 48:165-176.

Riisberg, I., Orr, R.J.S., Kluge, R., Shalchian-Tabrizi, K., Bowers H.A., Patil, V., Edvardsen, B. and Jakobsen, KS. 2009. Seven gene phylogeny of heterokonts. Protist. 160(2): 191-204

Riisberg, I. and Edvardsen, B. 2008. Genetic variation in bloom-forming ichthyotoxic Pseudochattonella species (Dictyochophyceae, Heterokonta) using nuclear, mitochondrial and plastid DNA sequence data. European J. Phycol. 43 (4): 413-422.

Halstvedt, C.B., Rohrlack, Ptacnik, R., Edvardsen, B. 2008. On the effect of abiotic environmental factors on production of bioactive oligopeptides in field populations of Planktothrix spp. (Cyanobacteria). J. Plankton Res. 30(5): 607-617.

Rohrlack, T., B. Edvardsen, R. Skulberg, C.B. Halstvedt, H.C. Utkilen, R. Ptacnik, and O.M. Skulberg. 2008. Oligopeptide chemotypes of the toxic freshwater cyanobacterium Planktothrix can form sub-populations with dissimilar ecological traits Limnology and Oceanography 53 (4): 1279-1293.

Edvardsen, B., Eikrem, W., Shalchian-Tabrizi, K., Riisberg, I., Johnsen, G., Naustvoll, L., Throndsen, J. 2007. Verrucophora farcimen gen. et sp. nov. (Dictyochophyceae, Heterokonta) - a bloom forming ichthyotoxic flagellate from the Skagerrak, Norway. J. Phycol. 43(5), 1054-1070.

Edvardsen, B. and Medlin, L.K. 2007. Molecular systematics of Haptophyta. In: Unravelling the algae – the past, present and future of algal molecular systematics. Lewis, J. and J. Brodie (eds.). The Systematics Association. pp. 183-196. Taylor and Francis, ISBN: 084937989X

Halstvedt, C.B., T. Rohrlack, T.Andersen, O. Skulberg, B. Edvardsen. 2007. Seasonal dynamics of Planktothrix spp. in Lake Steinsfjorden (Norway) related to environmental factors. J. Plankton Res. 29:471-482.

Haande, S., Ballot, A., Rohrlack, T., Wiedner, C., Fastner, J., and Edvardsen, B. 2007. Diversity of toxic and non-toxic Microcystis aeruginosa isolates (Chroococales, Cyanobacteria) from East-African water bodies. Arch. Microbiol. 188:15-25.

Lekve, K., Bagøien, E., Dahl, E., Edvardsen, B., Skogen, M. and Stenseth, N-C. 2006. Environmental forcing as a main determinant of bloom dynamics of the Chrysochromulina algae. Proc. Biol. Sci. 273(1605):3047-3055.

Edvardsen, B., Imai, I. 2006. The ecology of harmful flagellates within Prymnesiophyceae and Raphidophyceae. In: Granéli E., Turner J.T. (eds) Ecology of Harmful Algae, Ecological Studies, Vol. 189, Springer, Berlin, pp. 67-79.

Vestheim, H, B. Edvardsen, S. Kaartvedt. 2005. Assessing feeding of a carnivorous copepod using species-specific PCR. Mar. Biol. 147: 381-385.

Eschbach, E., Uwe J., M. Reckermann, A. D. Cembella, B. Edvardsen, L.K. Medlin 2005. Cell cycle dependent expression of toxicity by the ichthyotoxic prymnesiophyte Chrysochromulina polylepis. Aquat. Microb. Ecol. 39: 85-95.

Vestheim, H., S. Kaartvedt, B. Edvardsen. 2005. State-dependent vertical distribution of the carnivore copepod Pareuchaeta norvegica. J. Plankt. Res. 27: 19-26.

Dahl, E., Bagøien, E., Edvardsen, B., & Stenseth, N.-C 2005. The dynamics of Chrysochromulina species in the Skagerrak in relation to environmental conditions. J. Sea Res. 54:15-24.

Edvardsen, B., R. Skulberg, & O.M. Skulberg 2004. NIVA Culture Collection of Algae - microalgae for science and technology. Nova Hedwigia Beiheft 79: 99-114.

Sáez, A.G., Probert, I., Young, J.R., Edvardsen, B., Eikrem, W., & Medlin, L.K. 2004. A Review of the Phylogeny of the Haptophyta. In: H.R. Thierstein & J.R. Young (Eds.), Coccolithophores: from molecular processes to global impact. Springer Verlag, Berlin, pp 251-269.

Edvardsen, B., Shalchian-Tabrizi, K., Jakobsen, K.S., Medlin, L.K., Dahl, E. & Brubak, S., Paasche, E. 2003. Genetic variability and molecular phylogeny of Dinophysis species (Dinophyceae) from Norwegian waters inferred from single cell analyses of rDNA. J. Phycol. 39(2): 395-408.

Zapata, M., Edvardsen, B., Rodríguez, F., Maestro, M. & Garrido, J.L. 2001. Chlorophyll c2 monogalactosyldiacylglyceride ester (chl c2 -MGDG). A novel marker for Chrysochromulina species. Mar. Ecol. Prog. Ser. 219: 85-98.

Edvardsen, B., Eikrem, W., Green, J.C., Andersen, R.A., Moon-van der Staay, S.Y. & Medlin, L.K. 2000. Phylogenetic reconstructions of the Haptophyta inferred from 18S ribosomal DNA sequences and available morphological data. Phycologia 39 (1): 19-35.

Eikrem, W. & Edvardsen, B. 1999.Chrysochromulina fragaria sp. nov. (Prymnesiophyceae) description of a new haptophyte flagellate from Norwegian waters. Phycologia 38(2): 149-155.

Dahl, E., Edvardsen, B. & Eikrem, W. 1998. ı blooms in the Skagerrak after 1988. In: Harmful Algae, Algas Nocivas. B. Reguera, J. Blanco, M. Fernández, T. Wyatt [Eds.]. UNESCO, Vigo, Spain, pp. 104-105.

Larsen, A. & Edvardsen, B. 1998. A study of relative ploidy levels in Prymnesium parvum and P. patelliferum (Haptophyta) analysed by flow cytometry. Phycologia 37(6): 412-424.

Edvardsen, B. & Medlin, L. 1998. Genetic analyses of authentic and alternate forms of Chysochromulina polylepis (Haptophyta). Phycologia 37(4): 275-283.

Edvardsen, B. & Paasche, E. 1998. Bloom dynamics and physiology of Prymnesium and Chrysochromulina. In: Physiological Ecology of Harmful Algal Blooms. NATO ASI Series G, vol. 41. Anderson, D.M., Cembella, A.D., Hallegraeff, G.M. [Eds.], Springer-Verlag, Heidelberg, pp. 193-208.

Simon, N., Brenner, J., Edvardsen, B. & Medlin, L. 1997. The identification of Chrysochromulina and Prymnesium (Haptophyta, Prymnesiophyceae) using fluorescent or chemiluminescent oligonucleotide probes: a means for improving studies on toxic algae. Eur. J. Phycol. 32: 393-401.

Edvardsen, B., Eikrem, W., Vaulot, D. & Paasche E. 1996. Comparison between authentic and alternate cells of Chrysochromulina polylepis: morphology, growth, toxicity and ploidy level. In: Yasumoto, T., Oshima, Y. [Eds.] Harmful and Toxic Algal Blooms. UNESCO, Japan, pp. 231-234.

Edvardsen, B. & Vaulot, D. 1996. Ploidy analysis of the two motile forms of Chrysochromulina polylepis (Prymnesiophyceae). J. Phycol. 32: 94-102.

Meldahl. A.-S., Kvernstuen, J., Grasbakken, G. J., Edvardsen, B. & Fonnum, F. 1995. Toxic activity of Prymnesium spp. and Chrysochromulina spp. tested by different methods. In: Harmful Marine Algal Blooms. Lassus, P., Arzul, G., Erard-Le Denn, E., Gentien, P., Marcaillou-Le Baut, C. [Eds.], Lavouisier, Paris, pp. 315-320.

Meldahl. A. -S., Edvardsen, B. & Fonnum, F.1994. The toxicity of four potentially ichthyotoxic marine phytoflagellates determined by four different test methods. J. Toxicol. Environ. Health 42: 289-301.

Meldahl. A. -S., Edvardsen, B. & Fonnum, F. 1993. The effect of Prymnesium-toxin on neurotransmitter transport mechanisms: the development of a sensitive test method. In: Smayda, T. J. & Shimizu, Y. [Eds.] Toxic Phytoplankton Blooms in the Sea. Elsevier, Amsterdam, pp. 895-900.

Edvardsen, B. 1993. Toxicity of Chrysochromulina species (Prymnesiophyceae) to the brine shrimp, Artemia salina. In: Smayda, T. J. & Shimizu, Y. [Eds.] Toxic Phytoplankton Blooms in the Sea. Elsevier, Amsterdam, pp. 681-86.

Edvardsen, B. & Paasche, E. 1992. Two motile stages of Chrysochromulina polylepis (Prymnesiophyceae): morphology, growth and toxicity. J. Phycol. 28: 104-114.

Paasche, E., Edvardsen, B. & Eikrem, W. 1990. A possible alternate stage in the life cycle of Chrysochromulina polylepis Manton et Parke (Prymnesiophyceae). Nova Hedwigia, Beiheft 100: 91-99.

Edvardsen, B., Moy, F. & Paasche, E. 1990. Hemolytic activity in extracts of Chrysochromulina polylepis grown at different levels of selenite and phosphate. In: Toxic Marine Phytoplankton. E. Granéli, B. Sundstrøm, L. Edler, D.M. Anderson [Eds.]. Elsevier, New York. pp. 284-289.

• Wood, Ethan; Edvardsen, Bente; Skjånes, Kari & Šupraha, Luka (2026). Effects of Culture History and Algal Taxonomy on Bacterial Communities in Long-maintained Filamentous Green Algae. Microbial Ecology. ISSN 0095-3628. 89(1). doi: 10.1007/s00248-026-02840-0. Full text in Research Archive Show summary

  Abstract Algal cultures are widely used to study algae–bacteria interactions, yet the relative roles of algal taxonomy, culturing environment, and historical contingency in shaping bacterial communities of long-maintained monoalgal cultures remain unclear. In a two-stage experimental design, we used 16 S rRNA metabarcoding to first profile the bacterial communities of 14 filamentous freshwater algal strains from three orders (Chaetophorales, Oedogoniales, Zygnematales) maintained in two distinct culture collections, and then, in a second experiment to test community mixing using a co-culture and re-isolation design with two algal strains ( Stigeoclonium sp. and Oedogonium sp.). The 14-strain profiling showed that bacterial communities were broadly similar at higher taxonomic ranks, with many shared orders within Pseudomonadota, whereas composition at the ASV level was largely algal-strain-specific. Ordination of phylogeny-aware UniFrac distances showed that culture collection of origin explained more variation in community composition than algal order, an effect reduced but not eliminated after standardizing the culture medium. The co-culture and re-isolation experiment showed that the two algal strains exchanged many bacterial community members, yet algal strain identity remained detectable after re-isolation. These results support a framework where culture history results in strain-specific ASV-level composition within recurrent higher-rank structure, and where algal-strain-specific effects on bacterial community composition become evident when cultures are exposed to a shared bacterial pool. Co-culture followed by algal re-isolation offers a practical approach to examine the persistence of algal-culture bacterial communities under mixing and may help identify candidate bacterial partners with potentially strong host-specific interactions without requiring axenic hosts.

• Gran-Stadniczeñko, Sandra; Anestis, Konstantinos; Bunse, Carina; Edvardsen, Bente; Egbers, Philipp & Henkel, Rohan [Show all 17 contributors for this article] (2026). Spatial Diversity of Marine Protists Along the Northern Norway Fjords During the Sub-Arctic Summer. Journal of Eukaryotic Microbiology. ISSN 1066-5234. 73(6), p. 1–17. doi: 10.1111/jeu.70133.
• Kline, Simon Hasselø; Hyvärinen, Olli Petteri; Valestrand, Louise; Andersen, Tom; Eikrem, Wenche & Titelman, Josefin [Show all 8 contributors for this article] (2026). 15-year shift in protist communities and a decline of heterotrophic dinoflagellates in the Oslofjord and Skagerrak. Frontiers in Marine Science. 13. doi: 10.3389/fmars.2026.1876109. Full text in Research Archive
• Hofmann, Laurie Carol; Bartsch, Inka; Pehlke, Hendrik; Alves-Lima, Cicero; Barreto, Luís M. & Bermejo, Ricardo [Show all 27 contributors for this article] (2026). Assessment of the macroalgal genetic resources maintained in European germplasm banks. Journal of Applied Phycology. ISSN 0921-8971. doi: 10.1007/s10811-026-03882-0. Full text in Research Archive Show summary

  Germplasm banks are important for preserving genetic diversity, yet the availability and long-term maintenance of macroalgal strains in germplasm banks is currently limited in European collections. To support future food security, restoration efforts, and biotechnological innovation, a strategy was recently developed for the long-term preservation of macroalgal genetic diversity. A foundational step in this effort is to assess the existing biodiversity, biogeographical distribution, and commercial relevance of seaweed cultures maintained in European collections. Using a universal data-collection template distributed widely across European seaweed networks, we compiled and analysed information on these seaweed cultures. As of November 2025, the resulting SeaStrains Database of European Seaweed Collections contains 2541 cultures representing 426 species, accounting for only 4% of global and 15% of European macroalgal diversity. The dataset reveals strong taxonomic bias: 74% are brown seaweeds (Ochrophyta), dominated by Laminaria, Saccharina, and Ectocarpus. Saccharina latissima is the most preserved species due to its scientific and commercial importance. Red and green algae are markedly underrepresented (11% and 14%, respectively), likely reflecting cultivation challenges and life-cycle knowledge gaps. Biogeographically, most cultures originate from cold- to warm-temperate zones, with limited representation of the South Atlantic, Indian Ocean, polar and remote regions. Over 60% of cultures are maintained at two institutions: the Culture Collection of Algae and Protozoa (Scotland) and the Alfred Wegener Institute (Germany). This work provides transparent, accessible information on Europe’s macroalgal germplasm resources and represents a crucial step toward a more robust and sustainable European seaweed sector aligned with UN SDG Target 2.5.

• Wang, Xinhui; Solhaug, Anita; Garrido, Bruno C.; Mudge, Elizabeth M.; Fon, Mathias & Andersen, Aaron John Christian [Show all 12 contributors for this article] (2026). Structure elucidation of leadbeaterin-1, an ichthyotoxin associated with fish-killing blooms of Chrysochromulina leadbeateri in Northern Norwegian fjords. Harmful Algae. ISSN 1568-9883. 156. doi: 10.1016/j.hal.2026.103104. Full text in Research Archive
• Wood, Ethan; Edvardsen, Bente; Skjånes, Kari & Supraha, Luka (2026). Phycosphere microbiome succession tracks algal growth dynamics during phosphorus-limited wastewater treatment. Algal Research. ISSN 2211-9264. 95. doi: 10.1016/j.algal.2026.104652. Full text in Research Archive Show summary

  Algal-based wastewater treatment (phycoremediation) relies on microbial interactions within the algal phycosphere that are associated with algal growth and nutrient removal. However, the temporal dynamics of these communities under operational conditions remain poorly resolved. Using 16S and 18S rRNA gene metabarcoding, this study characterized bacterial and eukaryotic communities across alga-attached and free-living size fractions and over time in a raceway-based, pilot-scale phycoremediation system using a filamentous algal co-culture under semicontinuous municipal wastewater flow. Bacterial community composition in the phycosphere overlapped substantially with that observed in a previous laboratory-scale study using the same algal co-culture, with many highly abundant ASVs shared across studies, supporting consistency of key community members across scales. Phycosphere community dynamics were temporally aligned with algal growth, with bacterial alpha diversity in the alga-attached fraction highest during periods of active algal growth and declining with the onset of algal phosphorus limitation. During this high-diversity phase, several orders within Alphaproteobacteria were enriched, followed by declines as the algal culture progressed toward reduced growth. Eukaryotic communities also showed clear successional trends, with Perkinsids (Alveolata) increasing during peak algal biomass before giving way to diverse protists and rotifers. These findings demonstrate coordinated temporal patterns between algal growth dynamics and phycosphere microbial succession in pilot-scale wastewater raceways, providing operational insight into microbial community structure under phosphorus-limited phycoremediation.

• Goraguer, Lucie Helene Marie; Marquardt, Miriam; Gradinger, Rolf Rudolf; Kohlbach, Doreen; Reigstad, Marit & Assmann, Karen [Show all 17 contributors for this article] (2026). Environmental drivers shaping protist plankton seasonality in the northwestern Barents Sea. Progress in Oceanography. ISSN 0079-6611. 244. doi: 10.1016/j.pocean.2026.103702. Full text in Research Archive Show summary

  Unicellular marine eukaryotes (protists) are important components of the biological carbon pump and form the base of marine food webs, ultimately supporting commercially important fish stocks. However, seasonally resolved data on protist composition, abundance and biomass are rare, especially in high latitude ice-covered oceans. This study presents unique seasonal data on protist community composition and abundance from the northwestern Barents Sea, spanning a latitudinal gradient from open Atlantic waters south of the Polar Front to the seasonally ice-covered Barents Sea shelf and across the shelf break into the Arctic Nansen Basin. Observations were conducted during seven cruises (2018 to 2022) covering periods from early winter to late summer. Protist standing stocks and community composition exhibited pronounced seasonality. Dinoflagellates, particularly Gymnodinium species, dominated the low protist stocks in winter whereas summer communities were more diverse and characterized by dinoflagellates, ciliates and flagellates. Mixo- and heterotrophic feeding modes enable these taxa to persist through the polar night and thrive during the stratified and nutrient-poor conditions in summer. Seasonal differences between dinoflagellates and ciliates likely reflect contrasting feeding and survival strategies. The onset of the phytoplankton spring bloom, dominated by rapidly growing centric diatoms of the genera Thalassiosira and Chaetoceros, occurred in a deeply mixed water column in both open and ice-covered waters. This may have been facilitated by diatoms’ effective defense against protozoan grazers and temporal mismatch between the phytoplankton spring bloom and copepod grazers in Atlantic influenced waters. Our seasonally resolved observations highlight the strong seasonality in both the quantity and quality of protist plankton in the Barents Sea, dynamics which will likely shift with the ongoing decline in sea-ice cover.

• Otte, Antonia; Wohlrab, Sylke; Moritz, Franco; Müller, Constanze; Janouskovec, Jan & Michálek, Jan [Show all 14 contributors for this article] (2025). High-resolution multiomics links nutrients and mixotrophy to toxicity in a harmful bloom of the haptophyte Chrysochromulina leadbeateri. Science Advances. 11(26). doi: 10.1126/sciadv.adv3390. Full text in Research Archive Show summary

  Harmful algal blooms (HABs) of the toxigenic haptophyte Chrysochromulina are known to cause fish mortalities and collateral ecosystem damage. The ichthyotoxic mechanisms are poorly understood but likely dependent on toxigenesis by polyketide synthases (PKSs). We hypothesize that induction of PKS activity facilitates mixotrophic behavior during nutrient-depleted bloom conditions. To identify potential in situ stimuli for growth, toxigenicity, and bloom persistence, we compared environmental factors and biological processes identified by metaomics to Chrysochromulina leadbeateri HABs between two fjords in northern Norway. We identified the polyketide ichthyotoxin leadbeaterin-1 from the C. leadbeateri bloom and found potentially associated candidate PKS genes of which most were higher expressed at bloom stations. A relative depletion of inorganic nitrogen and phosphate during the bloom was correlated with higher expression of genes involved in endocytosis, autophagy, and lysosomal activity. Mixotrophy is evidently a compensatory nutritional strategy coupled to induction of toxigenesis and other metabolomic processes as biotic factors linked to Chrysochromulina bloom dynamics.

• Egge, Elianne Dunthorn; Vaulot, Daniel; Larsen, Aud & Edvardsen, Bente (2025). The community of marine alveolate parasites in the Atlantic inflow to the Arctic Ocean is structured by season, depth, and water mass. Arctic Science. ISSN 2368-7460. 11, p. 1–16. doi: 10.1139/as-2024-0016. Full text in Research Archive Show summary

  The marine alveolates (MALVs) are a highly diverse group of parasitic dinoflagellates, which may regulate populations of a wide range of hosts, including other dinoflagellates, copepods, and fish eggs. Knowledge on their distribution and ecological role is still limited, as they are difficult to study with morphological methods. In this work, we describe the taxonomic composition and seasonal and depth distribution of MALVs in the Arctic Ocean west and north of Svalbard, based on 18S V4 rRNA metabarcoding data from five cruises. We recovered amplicon sequence variants (ASVs) representing all major groups previously described from environmental sequencing studies (Dino-Groups I–V), with Dino-Groups I and II being the most diverse. The community was structured by season, depth, and water mass. In the epipelagic zone, the taxonomic composition varied strongly by season; however, there was also a difference between Arctic and Atlantic water masses in winter. The spring and summer epipelagic communities were characterized by a few dominating ASVs present in low proportions during winter and in mesopelagic summer samples, suggesting that they proliferate under certain conditions, e.g., when specific hosts are abundant. Mesopelagic samples were more similar across months, and may harbor parasites of deep-dwelling organisms, little affected by season.

• Fon, Mathias; Chen, Anyuan; Ghesquière, Rosalie; Uhlig, Silvio; Edvardsen, Bente & Solhaug, Anita (2025). The cytotoxicity of the haptophyte Chrysochromulina leadbeateri towards the Atlantic salmon gill cell line ASG-10. Harmful Algae. ISSN 1568-9883. 142. doi: 10.1016/j.hal.2024.102797. Full text in Research Archive Show summary

  Fish-killing harmful algal blooms (HABs) threaten fisheries and aquaculture globally. In May and June 2019, the haptophyte Chrysochromulina leadbeateri formed the most devastating fish-killing algal bloom ever recorded in Northern Norway. Despite the severe impact of HABs on farmed fish, our understanding of their toxic mechanisms is limited. Here, we investigated the ichthyotoxicity of C. leadbeateri by using the gill epithelial cell line ASG-10 from Atlantic salmon. Extracts of C. leadbeateri showed potent hemolytic activity towards Atlantic salmon red blood cells, and toxicity to the ASG-10 cells with an EC50 of 3.41 × 106 algal cells mL−1 measured by the Alamar Blue viability assay. Furthermore, lower extract concentrations increased caspase-3/7 activity, suggesting induction of apoptosis, while higher concentrations of the extract showed compromised cell membrane integrity. No intracellular reactive oxygen species (ROS) induction was observed. Exposure to C. leadbeateri extracts cultured under different irradiances or with putrescine supplementation to the algal medium did not increase the toxicity. Exposure of living C. leadbeateri cells to ASG-10 did not show any cytotoxicity from imaging or barrier integrity impairment, but the activity of leaked dead-cell proteases revealed a concentration-dependent effect on the ASG-10 cells. Furthermore, incubation of C. leadbeateri in culture with putrescine for 72 h resulted in increased dead-cell proteases leaked from the ASG-10 cells compared to cultures without putrescine. Our findings suggest that living C. leadbeateri cells exert sublethal effects on Atlantic salmon gill cells. Additionally, putrescine seems to increase the ichthyotoxicity of living C. leadbeateri towards ASG-10 cells.

• Wood, Ethan; Edvardsen, Bente; Skjånes, Kari & Supraha, Luka (2025). Phycosphere of an algal co‑culture phycoremediation system: Stability of bacterial communities in an Oedogonium‑Stigeoclonium co‑culture during cultivation in microbially rich wastewater. Journal of Applied Phycology. ISSN 0921-8971. 37, p. 837–853. doi: 10.1007/s10811-025-03455-7. Full text in Research Archive Show summary

  Algal-based wastewater remediation systems (phycoremediation) include phycosphere bacterial communities that influence algal growth, pollutant remediation, and downstream applications of biomass as fertilizers or bio-stimulants. This study investigated the bacterial community dynamics in a novel phycoremediation system using a co-culture of the green algae Stigeoclonium sp. and Oedogonium vaucheri. Bacterial abundance was estimated using flow cytometry (FCM), while community composition was assessed through 16S rRNA gene metabarcoding. Additionally, 28 bacterial strains were isolated from the bioremediation experiment, cultured, genetically characterized for identification and screened for production of the auxin phytohormone indole-3-acetic acid (IAA). Metabarcoding showed that the free-living bacterial community consisted of bacteria from both the wastewater effluent and the algal inocula, while the attached phycosphere community was dominated by bacteria from the algal inocula, indicating the stability of the algae-associated phycosphere. Taxa known to include plant growth-promoting bacteria (PGPB) were abundant, and several strains produced IAA. The bacterial community composition, combined with the potential production of phytohormone by isolated bacteria indicates symbiotic or commensal algae-microbe interactions within the phycosphere bacterial communities. Sterile filtration of wastewater effluent, including only the algal inoculum bacterial communities, reduced algal biomass production and increased bacterial abundance. This study highlights the critical role of microbial interactions in engineered ecosystems and provides insights for optimizing algal-based wastewater treatment technologies.

• Fon, Mathias; Supraha, Luka; Andersen, Tom; Uhlig, Silvio & Edvardsen, Bente (2024). Optimal growth conditions of the haptophyte Chrysochromulina leadbeateri causing massive fish mortality in Northern Norway. Harmful Algae. ISSN 1568-9883. 139. doi: 10.1016/j.hal.2024.102709. Full text in Research Archive Show summary

  The haptophyte Chrysochromulina leadbeateri formed the most devastating fish-killing algal bloom ever recorded in Norway, in May and June 2019. The bloom resulted in the death of 14,500 tons of farmed salmon in Nordland and Troms Counties and large economic losses to the aquaculture industry in the region. Fish mortalities due to blooms of this species have occurred before in this region in 1991. Environmental conditions promoting bloom formation and growth of C. leadbeateri are, however, still poorly understood. Here we investigated growth as a function of temperature, salinity and irradiance in combinations using a high throughput experimental set-up. Three strains of C. leadbeateri isolated from the 2019 event and an earlier bloom in 1991 were examined. The highest maximal specific growth rate was found at salinities 28–30 and temperatures between 13 and 15 °C, with growth rate generally increasing with irradiance. The upper temperature tolerance for growth for all strains was at 17–19 °C. Further, analyses of the geographical distribution of C. leadbeateri in previous DNA-based studies compiled in the metaPR2 database revealed several ribotypes, and that a cold-water ribotype of C. leadbeateri caused both the 1991 and 2019 blooms.

• Wang, Xinhui; Fon, Mathias; Andersen, Aaron John Christian; Solhaug, Anita; Ingebrigtsen, Richard Andre & Samdal, Ingunn Anita [Show all 10 contributors for this article] (2024). Insights into the nature of ichthyotoxins from the Chrysochromulina leadbeateri blooms in Northern Norwegian fjords. Harmful Algae. ISSN 1568-9883. 137. doi: 10.1016/j.hal.2024.102681. Full text in Research Archive Show summary

  In May–June 2019, the microalga Chrysochromulina leadbeateri caused a massive fish-killing event in several fjords in Northern Norway, resulting in the largest direct impact ever on aquaculture in northern Europe due to toxic algae. Motivated by the fact that no algal toxins have previously been described from C. leadbeateri, we set out to investigate the chemical nature and toxicity of secondary metabolites in extracts of two strains (UIO 393, UIO 394) isolated from the 2019 bloom, as well as one older strain (UIO 035) isolated during a bloom in Northern Norway in 1991. Initial LC–DAD–MS/MS-based molecular networking analysis of the crude MeOH extracts of the cultivated strains showed that their profiles of small organic molecules, including a large number of known lipids, were very similar, suggesting that the same class of toxin(s) were likely the causative agents of the two harmful algal bloom (HAB) events. Next, bioassay-guided fractionation using the RTgill-W1 cell line and metabolomics analysis pointed to a major compound affording [M + H]+ ions at m/z 1399.8333 as a possible toxin, corresponding to a compound with the formula C67H127ClO27. Moreover, our study unveiled a series of minor analogues exhibiting distinct patterns of chlorination and sulfation, together defining a new family of compounds, which we propose to name leadbeaterins. Remarkably, these suspected toxins were detected in situ in samples collected during the 2019 bloom close to Tromsø, thereby consistent with a role in fish kills. The elemental compositions of the putative C. leadbeateri ichthyotoxins strongly indicate them to be long linear polyhydroxylated polyketides, structurally similar to sterolysins reported from a number of dinoflagellates.

• Marquardt, Miriam; Goraguer, Lucie Hélène Marie; Assmy, Philipp Kurt Wolf; Bluhm, Bodil Annikki Ulla Barbro; Aaboe, Signe & Down, Emily [Show all 12 contributors for this article] (2023). Seasonal dynamics of sea-ice protist and meiofauna in the northwestern Barents Sea. Progress in Oceanography. ISSN 0079-6611. 218. doi: 10.1016/j.pocean.2023.103128. Full text in Research Archive Show summary

  The rapid decline of Arctic sea ice makes understanding sympagic (ice-associated) biology a particularly urgent task. Here we studied the poorly known seasonality of sea-ice protist and meiofauna community composition, abundance and biomass in the bottom 30 cm of sea ice in relation to ice properties and ice drift trajectories in the northwestern Barents Sea. We expected low abundances during the polar night and highest values during spring prior to ice melt. Sea ice conditions and Chlorophyll a concentrations varied strongly seasonally, while particulate organic carbon concentrations were fairly stable throughout the seasons. In December to May we sampled growing first-year ice, while in July and August melting older sea ice dominated. Low sea-ice biota abundances in March could be related to the late onset of ice formation and short time period for ice algae and uni- and multicellular grazers to establish themselves. Pennate diatoms, such as Navicula spp. and Nitzschia spp., dominated the bottom ice algal communities and were present during all seasons. Except for May, ciliates, dinoflagellates, particularly of the order Gymnodiales, and small-sized flagellates were co-dominant. Ice meiofauna (here including large ciliates and foraminifers) was comprised mainly of harpacticoid copepods, copepod nauplii, rotifers, large ciliates and occasionally acoels and foraminifers, with dominance of omnivore species throughout the seasons. Large ciliates comprised the most abundant meiofauna taxon at all ice stations and seasons (50–90%) but did not necessarily dominate the biomass. While ice melt might have released and reduced ice algal biomass in July, meiofauna abundance remained high, indicating different annual cycles of protist versus meiofauna taxa. In May highest Chlorophyll a concentrations (29.4 mg m-2) and protist biomass (107 mg C m-2) occurred, while highest meiofauna abundance was found in August (23.9 × 103 Ind. m-2) and biomass in December (0.6 mg C m-2). The abundant December ice biota community further strengthens the emerging notion of an active biota during the dark Arctic winter. The data demonstrated a strong and partially unexpected seasonality in the Barents Sea ice biota, indicating that changes in ice formation, drift and decay will significantly impact the functioning of the ice-associated ecosystem.

• Bachmann, Lutz; Beermann, Jan; Brey, Thomas; Boer, Hugo de; Dannheim, Jennifer & Edvardsen, Bente [Show all 20 contributors for this article] (2023). The role of systematics for understanding ecosystem functions: Proceedings of the Zoologica Scripta Symposium, Oslo, Norway, 25 August 2022. Zoologica Scripta. ISSN 0300-3256. 52(3), p. 187–214. doi: 10.1111/zsc.12593. Full text in Research Archive Show summary

  Abstract On 25 August 2022, the Zoologica Scripta ‐ An International Journal of Systematic Zoology and the Norwegian Academy of Sciences and Letters arranged a symposium entitled ‘The role of systematics for understanding ecosystem functions’ in the Academy's premises in Oslo, Norway. The symposium aimed at offering a forum for exploring and discussing trends and future developments in the field of systematics. Eleven international experts contributed expertise on various issues related to global challenges, such as biodiversity assessments, databases, cutting‐edge analysis tools, and the consequences of the taxonomic impediment. Here, we compiled a multi‐author proceedings paper of the symposium contributions that are arranged in chapters and presents the content and the key conclusions of the majority of the presentations.

• Kohlbach, Doreen; Goraguer, Lucie; Bodur, Yasemin V.; Müller, Oliver; Arumí, Martí Amargant & Blix, Katalin [Show all 23 contributors for this article] (2023). Earlier sea-ice melt extends the oligotrophic summer period in the Barents Sea with low algal biomass and associated low vertical flux. Progress in Oceanography. ISSN 0079-6611. 213. doi: 10.1016/j.pocean.2023.103018. Full text in Research Archive Show summary

  The decrease in Arctic sea-ice extent and thickness as a result of global warming will impact the timing, duration, magnitude and composition of phytoplankton production with cascading effects on Arctic marine food-webs and biogeochemical cycles. Here, we elucidate the environmental drivers shaping the composition, abundance, biomass, trophic state and vertical flux of protists (unicellular eukaryotes), including phytoplankton, in the Barents Sea in late August 2018 and 2019. The two years were characterized by contrasting sea-ice conditions. In August 2018, the sea-ice edge had retreated well beyond the shelf break into the Nansen Basin (>82◦N), while in 2019, extensive areas of the northwestern Barents Sea shelf (>79◦N) were still ice-covered. These contrasting sea-ice conditions resulted in marked interannual differences in the pelagic protist community structure in this area. In August 2018, the protist community was in a post-bloom stage of seasonal succession characterized by oligotrophic surface waters and dominance of small-sized phytoplankton and heterotrophic protists (predominantly flagellates and ciliates) at most stations. In 2019, a higher contribution of autotrophs and large-celled phytoplankton, particularly diatoms, to total protist biomass compared to 2018 was reflected in higher chlorophyll a concentrations and suggested that the protist community was still in a late bloom stage at some stations. It is noteworthy that particularly diatoms contributed a considerably higher proportion to the protist biomass at the ice-covered stations in both years compared to the open-water stations. This pattern was also evident in the higher vertical protist biomass flux in 2019, dominated by dinoflagellates and diatoms, compared to 2018. Our results suggest that the predicted transition toward an ice-free Barents Sea will lengthen the oligotrophic summer period with low algal biomass and associated low vertical flux.

• John, Uwe; Supraha, Luka; Gran-Stadniczeñko, Sandra; Bunse, Carina; Cembella, Allan & Eikrem, Wenche [Show all 13 contributors for this article] (2022). Spatial and biological oceanographic insights into the massive fish-killing bloom of the haptophyte Chrysochromulina leadbeateri in northern Norway. Harmful Algae. ISSN 1568-9883. 118. doi: 10.1016/j.hal.2022.102287. Full text in Research Archive Show summary

  A bloom of the fish-killing haptophyte Chrysochromulina leadbeateri in northern Norway during May and June 2019 was the most harmful algal event ever recorded in the region, causing massive mortalities of farmed salmon. Accordingly, oceanographic and biodiversity aspects of the bloom were studied in unprecedented detail, based on metabarcoding and physico-chemical and biotic factors related with the dynamics and distribution of the bloom. Light- and electron-microscopical observations of nanoplankton samples from diverse locations confirmed that C. leadbeateri was dominant in the bloom and the primary cause of associated fish mortalities. Cell counts by light microscopy and flow cytometry were obtained throughout the regional bloom within and adjacent to five fjord systems. Metabarcoding sequences of the V4 region of the 18S rRNA gene from field material collected during the bloom and a cultured isolate from offshore of Tromsøy island confirmed the species identification. Sequences from three genetic markers (18S, 28S rRNA gene and ITS region) verified the close if not identical genetic similarity to C. leadbeateri from a previous massive fish-killing bloom in 1991 in northern Norway. The distribution and cell abundance of C. leadbeateri and related Chrysochromulina species in the recent incident were tracked by integrating observations from metabarcoding sequences of the V4 region of the 18S rRNA gene. Metabarcoding revealed at least 14 distinct Chrysochromulina variants, including putative cryptic species. C. leadbeateri was by far the most abundant of these species, but with high intraspecific genetic variability. Highest cell abundance of up to 2.7 × 107 cells L 􀀀 1 of C. leadbeateri was found in Balsfjorden; the high cell densities were associated with stratification near the pycnocline (at ca. 12 m depth) within the fjord. The cell abundance of C. leadbeateri showed positive correlations with temperature, negative correlation with salinity, and a slightly positive correlation with ambient phosphate and nitrate concentrations. The spatio-temporal succession of the C. leadbeateri bloom suggests independent initiation from existing pre-bloom populations in local zones, perhaps sustained and supplemented over time by northeastward advection of the bloom from the fjords

• Lundsør, Elisabeth; Eikrem, Wenche; Stige, Leif Christian; Engesmo, Anette; Gran-Stadniczeñko, Sandra & Edvardsen, Bente (2022). Changes in phytoplankton community structure over a century in relation to environmental factors. Journal of Plankton Research. ISSN 0142-7873. 44(6), p. 854–871. doi: 10.1093/plankt/fbac055. Full text in Research Archive Show summary

  Changes in phytoplankton abundance and biomass during the period 1933–2020 were examined by statistical modeling using data from the Inner Oslofjorden phytoplankton database. The phytoplankton abundances increased with eutrophication from 1930s to 1970s, but with the implementation of sewage cleaning measures and a resulting reduction in nutrient releases, the phytoplankton abundance has since then decreased significantly. The onset of the seasonal blooms has started progressively later during the last 15 years, especially the spring bloom. The delayed spring bloom co-occurred with increasing temperature in winter and spring. The diatom biomass decreased more than that of dinoflagellates and other microeukaryotes. The diatom genus Skeletonema dominated the spring bloom and was found to be the key taxa in explaining these changes in abundance and phenology. Extensive summer blooms of the coccolithophore Emiliania huxleyi, which has been characteristic for the inner Oslofjorden, has also gradually decreased during the last decades, along with reducing eutrophication. Dinoflagellates have not had the same reduction in abundance as the other groups. Despite an increasing proportion of dinoflagellates compared with other taxa, there are no clear indications of increased occurrence of toxic algal blooms in inner Oslofjorden. However, the introduction of new “toxin-producing” species may cause concern.

• Supraha, Luka; Klemm, Kerstin; Gran-Stadniczeñko, Sandra; Hörstmann, Cora; Vaulot, Daniel & Edvardsen, Bente [Show all 7 contributors for this article] (2022). Diversity and biogeography of planktonic diatoms in Svalbard fjords: The role of dispersal and Arctic endemism in phytoplankton community structuring. Elementa: Science of the Anthropocene. 10(1). doi: 10.1525/elementa.2021.00117. Full text in Research Archive Show summary

  Understanding the processes that shape the community structure of Arctic phytoplankton is crucial for predicting responses of Arctic ecosystems to the ongoing ocean warming. In particular, little is known about the importance of phytoplankton dispersal by the North Atlantic Current and the prevalence and maintenance of Arctic endemism. We investigated the diversity and biogeography of diatoms from five Svalbard fjords and the Hausgarten observatory (Fram Strait) by combining diatom cultivation and 18S rRNA gene metabarcoding. In total, 50 diatom strains were isolated from the area during the HE492 cruise in August 2017. The strains were identified taxonomically using molecular and morphological approaches, and their biogeographic distribution was mapped using the local metabarcoding dataset and a global compilation of published metabarcoding datasets. Biogeographic analysis was also conducted for the locally most abundant diatom metabarcoding amplicon sequence variants. The biogeographic analyses demonstrated that Arctic diatoms exhibit three general biogeographic distribution types: Arctic, Arctic-temperate, and cosmopolitan. At Hausgarten and in outer Isfjorden on the west coast of Svalbard, the communities were dominated by genotypes with Arctic-temperate and cosmopolitan distribution. Diatom communities in nearby Van Mijenfjorden, inner Isfjorden and Kongsfjorden were dominated by genotypes with Arctic-temperate distribution, and cosmopolitan species were less abundant. The genotypes endemic to the Arctic had lower abundance on the west coast of Svalbard. The two northernmost fjords (Woodfjorden and Wijdefjorden) had a higher abundance of genotypes endemic to the Arctic. Our results demonstrate that the diatom communities in the Svalbard area consist of genotypes endemic to the Arctic, and genotypes with broader biogeographic distribution, all of which are further structured by local environmental gradients. Finer biogeographic patterns observed within Arctic-temperate and cosmopolitan genotypes suggest that certain genotypes can be used as indicators of increasing influence of Atlantic waters on the phytoplankton community structure in the Svalbard area.

• Lundsør, Elisabeth; Lømsland, Evy Rigmor; Johnsen, Torbjørn Martin; Engesmo, Anette; King, Andrew Luke & Staalstrøm, Andre [Show all 11 contributors for this article] (2022). Marine phytoplankton community data and corresponding environmental properties from eastern Norway, 1896–2020. Scientific Data. 9. doi: 10.1038/s41597-022-01869-3. Full text in Research Archive Show summary

  Time series are essential for studying the long-term effects of human impact and climatic changes on the natural environment. Although data exist, no long-term phytoplankton dataset for the Norwegian coastal area has been compiled and made publicly available in a standardised format. Here we report on a compilation of phytoplankton data from inner Oslofjorden going back more than a century. The database contains 605 sampling events from 1896 to 2020, and environmental data has also been provided when available. Although the sampling frequency has varied over time, the high taxonomic quality and relatively similar methodology make it very useful. For the last 15 years (2006–2020), the sampling frequency has been almost monthly throughout the year. This dataset can be used for time series analysis to understand community structure and changes over time. It can also be used to study common taxa’ responses to environmental variables and changes, seasonal or annual species diversity and be useful for developing ecological indicators.

• Sandaa, Ruth-Anne; Saltvedt, Marius Rydningen; Dahle, Håkon; Wang, Haina; Våge, Selina & Blanc-Mathieu, Romain [Show all 11 contributors for this article] (2021). Adaptive evolution of viruses infecting marine microalgae (haptophytes), from acute infections to stable coexistence. Biological Reviews. ISSN 1464-7931. 97(1), p. 179–194. doi: 10.1111/brv.12795. Full text in Research Archive Show summary

  Collectively known as phytoplankton, photosynthetic microbes form the base of the marine food web, and account for up to half of the primary production on Earth. Haptophytes are key components of this phytoplankton community, playing important roles both as primary producers and as mixotrophs that graze on bacteria and protists. Viruses influence the ecology and diversity of phytoplankton in the ocean, with the majority of microalgae–virus interactions described as ‘boom and bust’ dynamics, which are characteristic of acute virus–host systems. Most haptophytes are, however, part of highly diverse communities and occur at low densities, decreasing their chance of being infected by viruses with high host specificity. Viruses infecting these microalgae have been isolated in the laboratory, and there are several characteristics that distinguish them from acute viruses infecting bloom-forming haptophytes. Herein we synthesise what is known of viruses infecting haptophyte hosts in the ocean, discuss the adaptive evolution of haptophyte-infecting viruses -from those that cause acute infections to those that stably coexist with their host - and identify traits of importance for successful survival in the ocean.

• Egge, Elianne Dunthorn; Elferink, Stephanie; Vaulot, Daniel; John, Uwe; Bratbak, Gunnar & Larsen, Aud [Show all 7 contributors for this article] (2021). An 18S V4 rDNA metabarcoding dataset of protist diversity in the Atlantic inflow to the Arctic Ocean, through the year and down to 1000 m depth. Earth System Science Data. 13, p. 4913–4928. doi: 10.5194/essd-13-4913-2021. Full text in Research Archive Show summary

  Arctic marine protist communities have been understudied due to challenging sampling conditions, in particular during winter and in deep waters. The aim of this study was to improve our knowledge on Arctic protist diversity through the year, in both the epipelagic (< 200 m depth) and mesopelagic zones (200–1000 m depth). Sampling campaigns were performed in 2014, during five different months, to capture the various phases of the Arctic primary production: January (winter), March (pre-bloom), May (spring bloom), August (post-bloom), and November (early winter). The cruises were undertaken west and north of the Svalbard archipelago, where warmer Atlantic waters from the West Spitsbergen Current meet cold Arctic waters from the Arctic Ocean. From each cruise, station, and depth, 50 L of seawater was collected, and the plankton was size-fractionated by serial filtration into four size fractions between 0.45–200 µm, representing picoplankton (0.45–3 µm), small and large nanoplankton (3–10 and 10–50 µm, respectively), and microplankton (50–200 µm). In addition, vertical net hauls were taken from 50 m depth to the surface at selected stations. The net hauls were fractionated into the large nanoplankton (10–50 µm) and microplankton (50–200 µm) fractions. From the plankton samples DNA was extracted, the V4 region of the 18S rRNA-gene was amplified by polymerase chain reaction (PCR) with universal eukaryote primers, and the amplicons were sequenced by Illumina high-throughput sequencing. Sequences were clustered into amplicon sequence variants (ASVs), representing protist genotypes, with the dada2 pipeline. Taxonomic classification was made against the curated Protist Ribosomal Reference database (PR2). Altogether, 6536 protist ASVs were obtained (including 54 fungal ASVs). Both ASV richness and taxonomic composition varied between size fractions, seasons, and depths. ASV richness was generally higher in the smaller fractions and higher in winter and the mesopelagic samples than in samples from the well-lit epipelagic zone during summer. During spring and summer, the phytoplankton groups diatoms, chlorophytes, and haptophytes dominated in terms of relative read abundance in the epipelagic zone. Parasitic and heterotrophic groups such as Syndiniales and certain dinoflagellates dominated in the mesopelagic zone all year, as well as in the epipelagic zone during the winter. The dataset is available at https://doi.org/10.17882/79823 (Egge et al., 2014).

• Ribeiro, Catherine Gérikas; Santos, Adriana Lopes dos; Probert, Ian; Vaulot, Daniel & Edvardsen, Bente (2020). Taxonomic reassignment of Pseudohaptolina birgeri comb. nov. (Haptophyta). Phycologia. ISSN 0031-8884. 59(6), p. 606–615. doi: 10.1080/00318884.2020.1830255. Full text in Research Archive
• Lundsør, Elisabeth; Stige, Leif Christian; Sørensen, Kai & Edvardsen, Bente (2020). Long-term coastal monitoring data show nutrient-driven reduction in chlorophyll. Journal of Sea Research. ISSN 1385-1101. 164. doi: 10.1016/j.seares.2020.101925. Full text in Research Archive Show summary

  In this study we have compiled a long-term monitoring dataset from the inner Oslofjorden and supplemented it with short-term research data from the same station. Using generalized additive models analysing the data from this time series, we have examined how chlorophyll-a, hydrography, and various nutrient concentrations have changed during 1973–2017 and how they correlate. We describe the seasonality in chlorophyll-a, nitrogen, phosphorus, Secchi-depth, temperature and salinity and how the levels of each variable have changed the last forty years. The results show specifically how levels of chlorophyll-a have decreased significantly and how this correlates with decrease in nitrogen and phosphorus levels. Our results show a significantly positive correlation between chlorophyll-a and phosphorus during spring bloom and between chlorophyll-a and nitrogen during autumn bloom. However, phosphorus levels have increased again during the last 20 years, but chlorophyll-a levels are still low, indicating that the chlorophyll-a level currently may be controlled by the continuous decreasing trend in nitrogen. If nitrogen increase again, the chlorophyll-a level may also begin to increase. The impact of increasing temperature and possible change in starting point for the growing season should be studied further.

• Stadniczeñko, Sandra Gran; Krabberød, Anders Kristian; Sandaa, Ruth-Anne; Yau, Sheree; Egge, Elianne Dunthorn & Edvardsen, Bente (2019). Seasonal dynamics of algae-infecting viruses and their inferred interactions with protists. Viruses. 11(11), p. 1–16. doi: 10.3390/v11111043. Full text in Research Archive Show summary

  Viruses are a highly abundant, dynamic, and diverse component of planktonic communities that have key roles in marine ecosystems. We aimed to reveal the diversity and dynamics of marine large dsDNA viruses infecting algae in the Northern Skagerrak, South Norway through the year by metabarcoding, targeting the major capsid protein (MCP) and its correlation to protist diversity and dynamics. Metabarcoding results demonstrated a high diversity of algal viruses compared to previous metabarcoding surveys in Norwegian coastal waters. We obtained 313 putative algal virus operational taxonomic units (vOTUs), all classified by phylogenetic analyses to either the Phycodnaviridae or Mimiviridae families, most of them in clades without any cultured or environmental reference sequences. The viral community showed a clear temporal variation, with some vOTUs persisting for several months. The results indicate co-occurrences between abundant viruses and potential hosts during long periods. This study gives new insights into the virus-algal host dynamics and provides a baseline for future studies of algal virus diversity and temporal dynamics.

• Chambouvet, Aurélie; Monier, Adam; Maguire, Finlay; Itoiz, Sarah; Campo, Javier del & Elies, Philippe [Show all 9 contributors for this article] (2019). Intracellular Infection of Diverse Diatoms by an Evolutionary Distinct Relative of the Fungi. Current Biology. ISSN 0960-9822. 29(23), p. 4093–4101.e4. doi: 10.1016/j.cub.2019.09.074. Full text in Research Archive Show summary

  The Fungi are a diverse kingdom, dominating terrestrial environments and driving important ecologies. Although fungi, and the related Opisthosporidia, interact with photosynthetic organisms on land and in freshwater as parasites, symbionts, and/or saprotrophic degraders [1, 2], such interactions in the marine environment are poorly understood [3, 4, 5, 6, 7, 8]. One newly identified uncultured marine lineage has been named novel chytrid-like-clade-1 (NCLC1) [4] or basal-clone-group-I [5, 6]. We use ribosomal RNA (rRNA) encoding gene phylogenies to demonstrate that NCLC1 is a distinct branch within the Opisthosporidia (Holomycota) [7]. Opisthosporidia are a diverse and largely uncultured group that form a sister branch to the Fungi or, alternatively, the deepest branch within the Fungi, depending on how the boundary to this kingdom is inferred [9]. Using culture-free lineage-specific rRNA-targeted fluorescent in situ hybridization (FISH) microscopy, we demonstrate that NCLC1 cells form intracellular infection of key diatom species, establishing that intracellular colonization of a eukaryotic host is a consistent lifestyle across the Opisthosporidia [8, 9, 10, 11]. NCLC1 infection-associated loss and/or envelopment of the diatom nuclei infers a necrotrophic-pathogenic interaction. Diatoms are one of the most diverse and ecologically important phytoplankton groups, acting as dominant primary producers and driving carbon fixation and storage in many aquatic environments [12, 13, 14]. Our results provide insight into the diversity of microbial eukaryotes that interact with diatoms. We suggest that such interactions can play a key role in diatom associated ecosystem functions, such as the marine carbon pump through necrotrophic-parasitism, facilitating the export of diatoms to the sediment [15, 16].

• Adl, Sina M.; Bass, David; Lane, Christopher E.; Lukes, Julius; Schoch, Conrad L & Smirnov, Aleksey [Show all 47 contributors for this article] (2019). Revisions to the Classification, Nomenclature, and Diversity of Eukaryotes. Journal of Eukaryotic Microbiology. ISSN 1066-5234. 66(1), p. 4–119. doi: 10.1111/jeu.12691. Full text in Research Archive Show summary

  This revision of the classification of eukaryotes follows that of Adl et al., 2012 [J. Euk. Microbiol . 59(5)] and retains an emphasis on protists. Changes since have improved the resolution of many nodes in phylogenetic analyses. For some clades even families are being clearly resolved. As we had predicted, environmental sampling in the intervening years has massively increased the genetic information at hand. Consequently, we have discovered novel clades, exciting new genera and uncovered a massive species level diversity beyond the morphological species descriptions. Several clades known from environmental samples only have now found their home. Sampling soils, deeper marine waters and the deep sea will continue to fill us with surprises. The main changes in this revision are the confirmation that eukaryotes form at least two domains, the loss of monophyly in the Excavata, robust support for the Haptista and Cryptista. We provide suggested primer sets for DNA sequences from environmental samples that are effective for each clade. We have provided a guide to trophic functional guilds in an appendix, to facilitate the interpretation of environmental samples, and a standardized taxonomic guide for East Asian users.

• Gran-Stadniczenko, Sandra; Egge, Elianne; Hostyeva, Vladyslava; Logares, Ramiro; Eikrem, Wenche & Edvardsen, Bente (2019). Protist Diversity and Seasonal Dynamics in Skagerrak Plankton Communities as Revealed by Metabarcoding and Microscopy. Journal of Eukaryotic Microbiology. ISSN 1066-5234. 66(3), p. 494–513. doi: 10.1111/jeu.12700. Full text in Research Archive Show summary

  Protist community composition and seasonal dynamics are of major importance for the production of higher trophic levels, such as zooplankton and fish. Our aim was to reveal how the protist community in the Skagerrak changes through the seasons by combining high‐throughput sequencing and microscopy of plankton collected monthly over two years. The V4 region of the 18S rRNA gene was amplified by eukaryote universal primers from the total RNA/cDNA. We found a strong seasonal variation in protist composition and proportional abundances, and a difference between two depths within the euphotic zone. Highest protist richness was found in late summer‐early autumn, and lowest in winter. Temperature was the abiotic factor explaining most of the variation in diversity. Dinoflagellates was the most abundant and diverse group followed by ciliates and diatoms. We found about 70 new taxa recorded for the first time in the Skagerrak. The seasonal pattern in relative read abundance of major phytoplankton groups was well in accordance with microscopical biovolumes. This is the first metabarcoding study of the protist plankton community of all taxonomic groups and through seasons in the Skagerrak, which may serve as a baseline for future surveys to reveal effects of climate and environmental changes.

• Mossige, Endre Joachim; Edvardsen, Bente; Jensen, Atle & Mielnik, Michal Marek (2019). A tunable, microfluidic filter for clog‑free concentration and separation of complex algal cells. Microfluidics and Nanofluidics. ISSN 1613-4982. 23(56). doi: 10.1007/s10404-019-2209-y. Full text in Research Archive Show summary

  An inherent problem with microfluidic filters is the tendency to clog, especially when applied to cells due to their geometrical complexity, deformability, and tendency to adhere to surfaces. In this work, we handle live algal cells of high complexity without signs of clogging, achieved by exploiting hydrodynamic interactions around trilobite-shaped filtration units. To characterize the influence of cell complexity on the separation and concentration mechanisms, we compare the hydrodynamic interactions to those of synthetic, rigid microparticles. We discover that simple rolling along the filter structures, which prevents clogging for particles, cannot be applied to cells. Instead, we find that inertial effects must be employed to minimize the filter interactions and that this modification leads to only a minor reduction in device performance.

• Tillmann, Urban; Edvardsen, Bente; Krock, Bernd; Smith, Kirsty F; Paterson, Ruth F & Voss, Daniela H. (2018). Diversity, distribution, and azaspiracids of Amphidomataceae (Dinophyceae) along the Norwegian coast. Harmful Algae. ISSN 1568-9883. 80, p. 15–34. doi: 10.1016/j.hal.2018.08.011. Full text in Research Archive
• Piredda, Roberta; Claverie, Jean-Michel; Decelle, Johan; Vargas, Colomban de; Dunthorn, Micah & Edvardsen, Bente [Show all 19 contributors for this article] (2018). Diatom diversity through HTS-metabarcoding in coastal European seas. Scientific Reports. 8(1), p. 1–12. doi: 10.1038/s41598-018-36345-9. Full text in Research Archive Show summary

  Diatoms constitute a diverse lineage of unicellular organisms abundant and ecologically important in aquatic ecosystems. Compared to other protists, their biology and taxonomy are well-studied, offering the opportunity to combine traditional approaches and new technologies. We examined a dataset of diatom 18S rRNA- and rDNA- (V4 region) reads from different plankton size-fractions and sediments from six European coastal marine sites, with the aim of identifying peculiarities and commonalities with respect to the whole protistan community. Almost all metabarcodes (99.6%) were assigned to known genera (121) and species (236), the most abundant of which were those already known from classic studies and coincided with those seen in light microscopy. rDNA and rRNA showed comparable patterns for the dominant taxa, but rRNA revealed a much higher diversity particularly in the sediment communities. Peculiar to diatoms is a tight bentho-pelagic coupling, with many benthic or planktonic species colonizing both water column and sediments and the dominance of planktonic species in both habitats. Overall metabarcoding results reflected the marked specificity of diatoms compared to other protistan groups in terms of morphological and ecological characteristics, at the same time confirming their great potential in the description of protist communities.

• Engesmo, Anette; Strand, David; Gran-Stadniczeñko, Sandra; Edvardsen, Bente; Medlin, Linda K. & Eikrem, Wenche (2018). Development of a qPCR assay to detect and quantify ichthyotoxic flagellates along the Norwegian coast, and the first Norwegian record of Fibrocapsa japonica (Raphidophyceae). Harmful Algae. ISSN 1568-9883. 75, p. 105–117. doi: 10.1016/j.hal.2018.04.007. Full text in Research Archive Show summary

  Blooms of ichthyotoxic microalgae pose a great challenge to the aquaculture industry world-wide, and there is a need for fast and specific methods for their detection and quantification in monitoring programs. In this study, quantitative real-time PCR (qPCR) assays for the detection and enumeration of three ichthyotoxic flagellates: the dinoflagellate Karenia mikimotoi (Miyake & Kominami ex Oda) Hansen & Moestrup and the two raphidophytes Heterosigma akashiwo (Hada) Hada ex Hara & Chihara and Fibrocapsa japonica Toriumi & Takano were developed. Further, a previously published qPCR assay for the dinoflagellate Karlodinium veneficum (Ballantine) Larsen was used. Monthly samples collected for three years (Aug 2009–Jun 2012) in outer Oslofjorden, Norway were analysed, and the results compared with light microscopy cell counts. The results indicate a higher sensitivity and a lower detection limit (down to 1 cell L−1) for both qPCR assays. Qualitative and semi-quantitative results were further compared with those obtained by environmental 454 high throughput sequencing (HTS, metabarcoding) and scanning electron microscopy (SEM) examination from the same samplings. All four species were detected by qPCR and HTS and/or SEM in outer Oslofjorden (Aug 2009–Jun 2012); Karlodinium veneficum was present year-round, whereas Karenia mikimotoi, Heterosigma akashiwo and Fibrocapsa japonica appeared mainly during the autumn in all three years. This is the first observation of Fibrocapsa japonica in Norwegian coastal waters. This species has previously been recorded off the Swedish west coast and German Bight, which may suggest a northward dispersal.

• Stadniczenko, Sandra Gran; Supraha, Luka; Egge, Elianne Dunthorn & Edvardsen, Bente (2017). Haptophyte Diversity and Vertical Distribution Explored by 18S and 28S Ribosomal RNA Gene Metabarcoding and Scanning Electron Microscopy. Journal of Eukaryotic Microbiology. ISSN 1066-5234. 64(4), p. 514–532. doi: 10.1111/jeu.12388. Full text in Research Archive Show summary

  Haptophyta encompasses more than 300 species of mostly marine pico‐ and nanoplanktonic flagellates. Our aims were to investigate the Oslofjorden haptophyte diversity and vertical distribution by metabarcoding, and to improve the approach to study haptophyte community composition, richness and proportional abundance by comparing two rRNA markers and scanning electron microscopy (SEM). Samples were collected in August 2013 at the Outer Oslofjorden, Norway. Total RNA/cDNA was amplified by haptophyte‐specific primers targeting the V4 region of the 18S, and the D1‐D2 region of the 28S rRNA. Taxonomy was assigned using curated haptophyte reference databases and phylogenetic analyses. Both marker genes showed Chrysochromulinaceae and Prymnesiaceae to be the families with highest number of Operational Taxonomic Units (OTUs), as well as proportional abundance. The 18S rRNA data set also contained OTUs assigned to eight supported and defined clades consisting of environmental sequences only, possibly representing novel lineages from family to class. We also recorded new species for the area. Comparing coccolithophores by SEM with metabarcoding shows a good correspondence with the 18S rRNA gene proportional abundances. Our results contribute to link morphological and molecular data and 28S to 18S rRNA gene sequences of haptophytes without cultured representatives, and to improve metabarcoding methodology.

• Johannessen, Torill Vik; Larsen, Aud; Bratbak, Gunnar; Pagarete, António; Edvardsen, Bente & Egge, Elianne Dunthorn [Show all 7 contributors for this article] (2017). Seasonal dynamics of haptophytes and dsDNA algal viruses suggest complex virus-host relationship. Viruses. 9(4). doi: 10.3390/v9040084. Full text in Research Archive Show summary

  Viruses influence the ecology and diversity of phytoplankton in the ocean. Most studies of phytoplankton host–virus interactions have focused on bloom-forming species like Emiliania huxleyi or Phaeocystis spp. The role of viruses infecting phytoplankton that do not form conspicuous blooms have received less attention. Here we explore the dynamics of phytoplankton and algal viruses over several sequential seasons, with a focus on the ubiquitous and diverse phytoplankton division Haptophyta, and their double-stranded DNA viruses, potentially with the capacity to infect the haptophytes. Viral and phytoplankton abundance and diversity showed recurrent seasonal changes, mainly explained by hydrographic conditions. By 454 tag-sequencing we revealed 93 unique haptophyte operational taxonomic units (OTUs), with seasonal changes in abundance. Sixty-one unique viral OTUs, representing Megaviridae and Phycodnaviridae, showed only distant relationship with currently isolated algal viruses. Haptophyte and virus community composition and diversity varied substantially throughout the year, but in an uncoordinated manner. A minority of the viral OTUs were highly abundant at specific time-points, indicating a boom-bust relationship with their host. Most of the viral OTUs were very persistent, which may represent viruses that coexist with their hosts, or able to exploit several host species.

• Engesmo, Anette; Eikrem, Wenche; Seoane, Sergio; Smith, Kirsty; Edvardsen, Bente & Hofgaard, Antje [Show all 7 contributors for this article] (2016). New insights into the morphology and phylogeny of Heterosigma akashiwo (Raphidophyceae), with the description of Heterosigma minor sp. nov. Phycologia. ISSN 0031-8884. 55(3), p. 279–294. doi: 10.2216/15-115.1. Full text in Research Archive
• Banguera-Hinestroza, E; Eikrem, W; Mansour, H; Solberg, I; Cúrdia, J & Holtermann, K [Show all 8 contributors for this article] (2016). Seasonality and toxin production of Pyrodinium bahamense in a Red Sea lagoon. Harmful Algae. ISSN 1568-9883. 55, p. 163–171. doi: 10.1016/j.hal.2016.03.002. Full text in Research Archive
• Edvardsen, Bente; Egge, Elianne Dunthorn & Vaulot, Daniel (2016). Diversity and distribution of haptophytes revealed by environmental sequencing and metabarcoding – a review. Perspectives in Phycology. ISSN 2364-6993. 3(2), p. 77–91. doi: 10.1127/pip/2016/0052. Full text in Research Archive
• Forster, Dominik; Dunthorn, Micah; Mahé, Frédéric; Dolan, John R.; Audic, Stéphane & Bass, David [Show all 35 contributors for this article] (2016). Benthic protists: The under-charted majority. FEMS Microbiology Ecology. ISSN 0168-6496. 92(8), p. 1–11. doi: 10.1093/femsec/fiw120. Full text in Research Archive
• McNamee, Sara E.; Medlin, Linda K.; Kegel, Jessica; McCoy, Gary R.; Raine, Robin & Barra, Lucia [Show all 22 contributors for this article] (2016). Distribution, occurrence and biotoxin composition of the main shellfish toxin producing microalgae within European waters: A comparison of methods of analysis. Harmful Algae. ISSN 1568-9883. 55, p. 112–120. doi: 10.1016/j.hal.2016.02.008. Full text in Research Archive
• Massana, Ramon; Gobet, Angelique; Audic, Stéphane; Bass, David; Bittner, Lucie & Boutte, Christophe [Show all 35 contributors for this article] (2015). Marine protist diversity in European coastal watersand sediments as revealed by high-throughputsequencing. Environmental Microbiology. ISSN 1462-2912. 17(10), p. 4035–4049. doi: 10.1111/1462-2920.12955. Full text in Research Archive
• Egge, Elianne Sirnæs; Eikrem, Wenche & Edvardsen, Bente (2015). Deep-branching novel lineages and high diversity of haptophytes in the Skagerrak (Norway) uncovered by 454 pyrosequencing. Journal of Eukaryotic Microbiology. ISSN 1066-5234. 62(1), p. 121–140. doi: 10.1111/jeu.12157. Full text in Research Archive Show summary

  Microalgae in the division Haptophyta may be difficult to identify to species by microscopy because they are small and fragile. Here, we used high-throughput sequencing to explore the diversity of haptophytes in outer Oslofjorden, Skagerrak, and supplemented this with electron microscopy. Nano- and picoplanktonic subsurface samples were collected monthly for 2 yr, and the haptophytes were targeted by amplification of RNA/cDNA with Haptophyta-specific 18S ribosomal DNA V4 primers. Pyrosequencing revealed higher species richness of haptophytes than previously observed in the Skagerrak by microscopy. From ca. 400,000 reads we obtained 156 haptophyte operational taxonomic units (OTUs) after rigorous filtering and 99.5% clustering. The majority (84%) of the OTUs matched environmental sequences not linked to a morphological species, most of which were affiliated with the order Prymnesiales. Phylogenetic analyses including Oslofjorden OTUs and available cultured and environmental haptophyte sequences showed that several of the OTUs matched sequences forming deep-branching lineages, potentially representing novel haptophyte classes. Pyrosequencing also retrieved cultured species not previously reported by microscopy in the Skagerrak. Electron microscopy revealed species not yet genetically characterised and some potentially novel taxa. This study contributes to linking genotype to phenotype within this ubiquitous and ecologically important protist group, and reveals great, unknown diversity.

• Johannessen, Torill Vik; Bratbak, Gunnar; Larsen, Aud; Ogata, Hirotaka; Egge, Elianne Sirnæs & Edvardsen, Bente [Show all 8 contributors for this article] (2015). Characterisation of three novel giant viruses reveals huge diversity among viruses infecting Prymnesiales (Haptophyta). Virology. ISSN 0042-6822. 476, p. 180–188. doi: 10.1016/j.virol.2014.12.014. Full text in Research Archive
• Gerecht, Andrea Cornelia; Supraha, Luka; Edvardsen, Bente; Langer, Gerald & Henderiks, Jorijntje (2015). Phosphorus availability modifies carbon production in Coccolithus pelagicus (Haptophyta). Journal of Experimental Marine Biology and Ecology. ISSN 0022-0981. 472, p. 24–31. doi: 10.1016/j.jembe.2015.06.019. Full text in Research Archive
• Egge, Elianne Sirnæs; Johannessen, Torill Vik; Andersen, Tom; Eikrem, Wenche; Bittner, Lucie & Larsen, Aud [Show all 8 contributors for this article] (2015). Seasonal diversity and dynamics of haptophytes in the Skagerrak, Norway, explored by high-throughput sequencing. Molecular Ecology. ISSN 0962-1083. 24(12), p. 3026–3042. doi: 10.1111/mec.13160. Full text in Research Archive Show summary

  Microalgae in the division Haptophyta play key roles in the marine ecosystem and in global biogeochemical processes. Despite their ecological importance, knowledge on seasonal dynamics, community composition and abundance at the species level is limited due to their small cell size and few morphological features visible under the light microscope. Here, we present unique data on haptophyte seasonal diversity and dynamics from two annual cycles, with the taxonomic resolution and sampling depth obtained with high-throughput sequencing. From outer Oslofjorden, S Norway, nano- and picoplanktonic samples were collected monthly for 2 years, and the haptophytes targeted by amplification of RNA/cDNA with Haptophyta-specific 18S rDNA V4 primers. We obtained 156 operational taxonomic units (OTUs), from c. 400.000 454 pyrosequencing reads, after rigorous bioinformatic filtering and clustering at 99.5%. Most OTUs represented uncultured and/or not yet 18S rDNA-sequenced species. Haptophyte OTU richness and community composition exhibited high temporal variation and significant yearly periodicity. Richness was highest in September–October (autumn) and lowest in April–May (spring). Some taxa were detected all year, such as Chrysochromulina simplex, Emiliania huxleyi and Phaeocystis cordata, whereas most calcifying coccolithophores only appeared from summer to early winter. We also revealed the seasonal dynamics of OTUs representing putative novel classes (clades HAP-3–5) or orders (clades D, E, F). Season, light and temperature accounted for 29% of the variation in OTU composition. Residual variation may be related to biotic factors, such as competition and viral infection. This study provides new, in-depth knowledge on seasonal diversity and dynamics of haptophytes in North Atlantic coastal waters.

• Keeling, Patrick J.; Burki, Fabien; Wilcox, Heather M.; Allam, Bassem; Allen, Eric E. & Amaral-Zettler, Linda A. [Show all 81 contributors for this article] (2014). The Marine Microbial Eukaryote Transcriptome Sequencing Project (MMETSP): Illuminating the Functional Diversity of Eukaryotic Life in the Oceans through Transcriptome Sequencing. PLoS Biology. ISSN 1544-9173. 12:e1001889(6). doi: 10.1371/journal.pbio.1001889. Full text in Research Archive Show summary

  Microbial ecology is plagued by problems of an abstract nature. Cell sizes are so small and population sizes so large that both are virtually incomprehensible. Niches are so far from our everyday experience as to make their very definition elusive. Organisms that may be abundant and critical to our survival are little understood, seldom described and/or cultured, and sometimes yet to be even seen. One way to confront these problems is to use data of an even more abstract nature: molecular sequence data. Massive environmental nucleic acid sequencing, such as metagenomics or metatranscriptomics, promises functional analysis of microbial communities as a whole, without prior knowledge of which organisms are in the environment or exactly how they are interacting. But sequence-based ecological studies nearly always use a comparative approach, and that requires relevant reference sequences, which are an extremely limited resource when it comes to microbial eukaryotes [1]. In practice, this means sequence databases need to be populated with enormous quantities of data for which we have some certainties about the source. Most important is the taxonomic identity of the organism from which a sequence is derived and as much functional identification of the encoded proteins as possible. In an ideal world, such information would be available as a large set of complete, well-curated, and annotated genomes for all the major organisms from the environment in question. Reality substantially diverges from this ideal, but at least for bacterial molecular ecology, there is a database consisting of thousands of complete genomes from a wide range of taxa, supplemented by a phylogeny-driven approach to diversifying genomics [2]. For eukaryotes, the number of available genomes is far, far fewer, and we have relied much more heavily on random growth of sequence databases [3],[4], raising the question as to whether this is fit for purpose.

• Gerecht, Andrea Cornelia; Supraha, Luka; Edvardsen, Bente; Probert, I. & Henderiks, Jorijntje (2014). High temperature decreases the PIC/POC ratio and increases phosphorus requirements in Coccolithus pelagicus (Haptophyta). Biogeosciences. ISSN 1726-4170. 11(13), p. 3531–3545. doi: 10.5194/bg-11-3531-2014. Full text in Research Archive
• Dunthorn, Micah; Otto, Johannes; Berger, Simon A.; Stamatakis, Alexandros; Mahé, Frédéric & Romac, Sarah [Show all 16 contributors for this article] (2014). Placing environmental next-generation sequencing amplicons from microbial eukaryotes into a phylogenetic context. Molecular Biology and Evolution (MBE). ISSN 0737-4038. 31(4), p. 993–1009. doi: 10.1093/molbev/msu055. Full text in Research Archive
• Logares, Ramiro; Audic, Stéphane; Bass, David; Bittner, Lucie; Boutte, Christophe & Christen, Richard [Show all 29 contributors for this article] (2014). Patterns of Rare and Abundant Marine Microbial Eukaryotes. Current Biology. ISSN 0960-9822. 24(8), p. 813–821. doi: 10.1016/j.cub.2014.02.050. Full text in Research Archive
• Duffield, Christopher James; Edvardsen, Bente; Eikrem, Wenche & Alve, Elisabeth (2014). Effects of different potential food sources on upper-bathyal benthic foraminifera: an experiment with propagules. Journal of Foraminiferal Research. ISSN 0096-1191. 44(4), p. 416–433. doi: 10.2113/gsjfr.44.4.416. Full text in Research Archive
• Egge, Elianne Sirnæs; Bittner, Lucie; Andersen, Tom; Audic, Stéphane; Vargas, Colomban de & Edvardsen, Bente (2013). 454 Pyrosequencing to Describe Microbial Eukaryotic Community Composition, Diversity and Relative Abundance: A Test for Marine Haptophytes. PLOS ONE. 8(9). doi: 10.1371/journal.pone.0074371. Full text in Research Archive Show summary

  Next generation sequencing of ribosomal DNA is increasingly used to assess the diversity and structure of microbial communities. Here we test the ability of 454 pyrosequencing to detect the number of species present, and assess the relative abundance in terms of cell numbers and biomass of protists in the phylum Haptophyta. We used a mock community consisting of equal number of cells of 11 haptophyte species and compared targeting DNA and RNA/cDNA, and two different V4 SSU rDNA haptophyte-biased primer pairs. Further, we tested four different bioinformatic filtering methods to reduce errors in the resulting sequence dataset. With sequencing depth of 11000–20000 reads and targeting cDNA with Haptophyta specific primers Hap454 we detected all 11 species. A rarefaction analysis of expected number of species recovered as a function of sampling depth suggested that minimum 1400 reads were required here to recover all species in the mock community. Relative read abundance did not correlate to relative cell numbers. Although the species represented with the largest biomass was also proportionally most abundant among the reads, there was generally a weak correlation between proportional read abundance and proportional biomass of the different species, both with DNA and cDNA as template. The 454 sequencing generated considerable spurious diversity, and more with cDNA than DNA as template. With initial filtering based only on match with barcode and primer we observed 100-fold more operational taxonomic units (OTUs) at 99% similarity than the number of species present in the mock community. Filtering based on quality scores, or denoising with PyroNoise resulted in ten times more OTU99% than the number of species. Denoising with AmpliconNoise reduced the number of OTU99% to match the number of species present in the mock community. Based on our analyses, we propose a strategy to more accurately depict haptophyte diversity using 454 pyrosequencing. © 2013 Egge et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

• Stüken, Anke; Dittami, Simon; Eikrem, Wenche; McNamee, Sara; Campbell, Katrina & Jakobsen, Kjetill Sigurd [Show all 7 contributors for this article] (2013). Novel hydrolysis-probe based qPCR assay to detect saxitoxin transcripts of dinoflagellates in environmental samples. Harmful Algae. ISSN 1568-9883. 28, p. 108–117. doi: 10.1016/j.hal.2013.06.003. Full text in Research Archive
• Dittami, Simon; Hostyeva, Vladyslava; Egge, Elianne Sirnæs; Kegel, Jessica U.; Eikrem, Wenche & Edvardsen, Bente (2013). Seasonal dynamics of harmful algae in outer Oslofjorden monitored by microarray, qPCR, and microscopy. Environmental Science and Pollution Research. ISSN 0944-1344. 20(10), p. 6719–6732. doi: 10.1007/s11356-012-1392-0. Full text in Research Archive
• Bittner, Lucie; Gobet, Angelique; Audic, Stéphane; Romac, Sarah; Egge, Elianne Sirnæs & Santini, Sebastien [Show all 10 contributors for this article] (2013). Diversity patterns of uncultured Haptophytes unravelled by pyrosequencing in Naples Bay. Molecular Ecology. ISSN 0962-1083. 22(1), p. 87–101. doi: 10.1111/mec.12108. Full text in Research Archive
• Skjelbred, Birger; Edvardsen, Bente & Andersen, Tom (2013). Environmental Optima for Seven Strains of Pseudochattonella (Dictyochophyceae, Heterokonta). Journal of Phycology. ISSN 0022-3646. 49(1), p. 54–60. doi: 10.1111/jpy.12008. Full text in Research Archive Show summary

  The ichthyotoxic flagellate Pseudochattonella has formed recurrent blooms in the North Sea, Skagerrak and Kattegat since 1998. Five strains of Pseudochattonella farcimen and two strains of P. verruculosa were examined in an assay comparing the light response of specific growth rates over a range of temperatures and salinities to get further knowledge on the autecology of members of this genus. Temperature optima were lower in P. farcimen (9°C–15°C) than in P. verruculosa (12°C–20°C). P. farcimen also showed a somewhat lower salinity optimum (18–26) than P. verruculosa (20–32). All strains showed light‐dependent growth responses reaching saturation between 18 and 52 μmol · photons · m−2 · s−1 at optimal temperature and salinity conditions. Compensation point estimates ranged from 4.2 to 15 μmol · photons · m−2 · s−1. Loss rates increased with temperature and were lowest at salinities close to optimal growth conditions. Blooms of P. farcimen have been recorded in nature under conditions more similar to those minimizing loss rates rather than those maximizing growth rates in our culture study.

• Dittami, Simon; Riisberg, Ingvild & Edvardsen, Bente (2013). Molecular probes for the detection and identification of ichthyotoxic marine microalgae of the genus Pseudochattonella (Dictyochophyceae, Ochrophyta). Environmental Science and Pollution Research. ISSN 0944-1344. 20(10), p. 6824–6837. doi: 10.1007/s11356-012-1402-2. Full text in Research Archive
• Dittami, Simon & Edvardsen, Bente (2013). GPR-Analyzer: a simple tool for quantitative analysis of hierarchical multispecies microarrays. Environmental Science and Pollution Research. ISSN 0944-1344. 20(10), p. 6808–6815. doi: 10.1007/s11356-012-1051-5. Full text in Research Archive
• Guillou, L; Bachar, Dipankar; Audic, Stéphane; Bass, David; Berney, Cedric & Bittner, Lucie [Show all 32 contributors for this article] (2013). The Protist Ribosomal Reference database (PR2): a catalog of unicellular eukaryote Small Sub-Unit rRNA sequences with curated taxonomy. Nucleic Acids Research (NAR). ISSN 0305-1048. 41(D1), p. D597–D604. doi: 10.1093/nar/gks1160. Full text in Research Archive
• Edvardsen, Bente; Dittami, Simon; Groben, René; Brubak, Sissel Irene; Escalera, Laura & Rodriguez, Francisco [Show all 9 contributors for this article] (2013). Molecular probes and microarrays for the detection of toxic algae in the genera Dinophysis and Phalacroma (Dinophyta). Environmental Science and Pollution Research. ISSN 0944-1344. 20(10), p. 6733–6750. doi: 10.1007/s11356-012-1403-1. Full text in Research Archive
• Medlin, Linda K.; Montresor, Marina; Graneli, Edna; Reugera, Beatrix; Raine, Robin & Edvardsen, Bente [Show all 10 contributors for this article] (2013). MIDTAL (Microarrays for the Detection of toxic Algae). Phytotaxa. ISSN 1179-3155. 127(1), p. 201–210. doi: 10.11646/phytotaxa.127.1.19. Full text in Research Archive
• Ota, Shuhei; Eikrem, Wenche & Edvardsen, Bente (2012). Ultrastructure and Molecular Phylogeny of Thaumatomonads (Cercozoa) with Emphasis on Thaumatomastix salina from Oslofjorden, Norway. Protist. ISSN 1434-4610. 163(4), p. 560–573. doi: 10.1016/j.protis.2011.10.007. Full text in Research Archive Show summary

  A culture of Thaumatomastix was isolated from a sediment sample collected in Oslofjorden and established as a monospecific strain (UIO286). Based on this culture, light and transmission electron microscopy and phylogenetic analyses were carried out. Thaumatomastix species are confined within the order Thaumatomonadida of the class Imbricatea and phylum Cercozoa. They are heterotrophic and their cell bodies are covered with silica scales. Observations of thin sections as well as whole mounts indicate that the morphology and ultrastructure of UIO286 is identical to T. salina, which was initially described from salt pools in Denmark. Detailed examination revealed some new features such as the presence of pseudopodia and silica deposition vesicles producing spine scales. The phylogeny presented here includes ribosomal DNA sequences from both imbricatean cultures and environmental samples. The 18S rDNA phylogenetic tree suggests that (i) Thaumatomastix is paraphyletic within the Thaumatomonadida clade, (ii) there is no close affinity between T. salina and other cultured and sequenced strains, but it is closely related to a sequence obtained from environmental DNA; we propose the present strain to serve as a reference culture of Thaumatomastix species and T. salina. Further, we discuss the distribution, habitats, and evolution of scale formation among euglyphids and thaumatomonads.

• Graneli, Edna; Edvardsen, Bente; Roelke, Daniel & Hagström, Johannes A. (2012). The ecophysiology and bloom dynamics of Prymnesium spp. Harmful Algae. ISSN 1568-9883. 14(1), p. 260–270. doi: 10.1016/j.hal.2011.10.024. Full text in Research Archive Show summary

  Members of Prymnesium belong to the division Haptophyta, class Prymnesiophyceae, order Prymnesiales and family Prymnesiaceae. As most haptophytes, members of the genus Prymnesium are unicellular and planktonic. The most known of these species is the ichthyotoxic P. parvum, which may form nearly monospecific dense blooms in coastal and inland waters. This species possesses extraordinary plasticity concerning life survival strategies, and is specifically addressed in this review. Toxins produced by P. parvum have hemolytic properties, that not only kill fish but also co-existing plankton. These substances are allelopathic (when other algae are killed) and grazer deterrent (when grazers are killed). Allelopathy enables P. parvum to utilize inorganic nutrients present in the surrounding water without competition from other algal species; and by eliminating its grazers P. parvum reduces cell losses. The paralized microalgae and/or zooplankton, are therefter ingested by the P. parvum cells, a process called phagotrophy. P. parvum is also able of osmotrophy, i.e. utilization of dissolved organic matter. In this review, the cellular characteristics, life cycles, bloom formation, and factors affecting toxicity, allelopathy, phagotrophy, and osmotrophy of P. parvum are discussed.

• Dittami, Simon & Edvardsen, Bente (2012). CULTURE CONDITIONS INFLUENCE CELLULAR RNA CONTENT IN ICHTHYOTOXIC FLAGELLATES OF THE GENUS PSEUDOCHATTONELLA (DICTYOCHOPHYCEAE). Journal of Phycology. ISSN 0022-3646. 48(4), p. 1050–1055. doi: 10.1111/j.1529-8817.2012.01183.x. Full text in Research Archive
• McCoy, Gary; Raine, Robin; Medlin, Linda K.; Chen, Jixin; Kooistra, Wiebe & Barra, Luciana [Show all 21 contributors for this article] (2012). Field testing for toxic algae with a microarray: initial results from the MIDTAL project. In Pagou, Kalliopi & Hallegraeff, Gustaaf (Ed.), Proceedings of the 14th International Conference on Harmful Algae. International Society for the Study of Harmful Algae and Intergovernmental Oceanographic Commission of UNESCO. Unesco. ISSN 9788799082735. p. 209–211. Full text in Research Archive Show summary

  In: Pagou, P. and Hallegraeff, G. (eds). Proceedings of the 14th International Conference on Harmful Algae. International Society for the Study of Harmful Algae and Intergovernmental Oceanographic Commission of UNESCO 2012 ISBN 978-87-990827-3-5 Archived in DUO with permission from ISSHA.

• Hostyeva, Vladyslava; Eikrem, Wenche; Edvardsen, Bente & Hasle, Grethe Rytter (2012). Annual cycle of Pseudo-nitzschia species in Outer Oslofjorden, Norway. In Pagou, Kalliopi & Hallegraeff, Gustaaf (Ed.), Proceedings of the 14th International Conference on Harmful Algae. International Society for the Study of Harmful Algae and Intergovernmental Oceanographic Commission of UNESCO. Unesco. ISSN 9788799082735. p. 81–83. Full text in Research Archive Show summary

  In: Pagou, P. and Hallegraeff, G. (eds). Proceedings of the 14th International Conference on Harmful Algae. International Society for the Study of Harmful Algae and Intergovernmental Oceanographic Commission of UNESCO 2012 Archived in DUO with permission from ISSHA.

• Dittami, Simon; Riisberg, Ingvild; John, Uwe; Orr, Russell; Jakobsen, Kjetill Sigurd & Edvardsen, Bente (2012). Analysis of Expressed Sequence Tags from the Marine Microalga Pseudochattonella farcimen (Dictyochophyceae). Protist. ISSN 1434-4610. 163(1), p. 143–161. doi: 10.1016/j.protis.2011.07.004. Full text in Research Archive
• Skjelbred, Birger; Edvardsen, Bente & Andersen, Tom (2012). A high-throughput method for measuring growth and loss rates in microalgal cultures. Journal of Applied Phycology. ISSN 0921-8971. 24(6), p. 1589–1599. doi: 10.1007/s10811-012-9819-z. Full text in Research Archive
• Edvardsen, Bente; Eikrem, Wenche; Throndsen, Jahn; Sáez, Alberto; Probert, Ian & Medlin, Linda K. (2011). Ribosomal DNA phylogenies and a morphological revision provide the basis for a revised taxonomy of Prymnesiales (Haptophyta). European journal of phycology. ISSN 0967-0262. 46(3), p. 202–228. doi: 10.1080/09670262.2011.594095. Full text in Research Archive Show summary

  Nucleotide sequences of the nuclear-encoded small subunit (18S rDNA) and partial large subunit (28S rDNA) ribosomal DNA were determined in 30 different species of the haptophyte genera Prymnesium, Chrysocampanula, Chrysochromulina, Imantonia and Platychrysis, all belonging to the order Prymnesiales. Phylogenies based on these and other available haptophyte 18S, 28S and plastid 16S rDNA sequences were reconstructed, and compared with available morphological and ultrastructural data. The rDNA phylogenies indicate that the genus Chrysochromulina is paraphyletic and is divided into two major clades. This is supported by ultrastructural and morphological data. There is a major split between Chrysochromulina species with a saddle-shaped cell form (clade B2) and the remaining species in the genus (clade B1). Clade B2 includes the type species C. parva and taxa belonging to this clade thus retain the name Chrysochromulina. The non-saddle-shaped Chrysochromulina species analysed are closely related to Hyalolithus, Prymnesium and Platychrysis species. Imantonia species are sister taxa to these species within clade B1. An amendment to the classification of the order Prymnesiales and the genera Prymnesium, Platychrysis and Chrysochromulina is proposed with one new and one emended family (Chrysochromulinaceae and Prymnesiaceae, respectively), two new genera (Haptolina and Pseudohaptolina), and one new species (Pseudohaptolina arctica). We suggest a revision of the taxonomy of the Prymnesiales that is in accordance with available molecular evidence and supported by morphological data.

• Sym, Stuart; Pienaar, Richard; Edvardsen, Bente & Egge, Elianne Sirnæs (2011). Fine structure and systematics of Prymnesium radiatum sp. nov. (Prymnesiophyceae) from False Bay and Franskraal, South Africa. European journal of phycology. ISSN 0967-0262. 46(3), p. 229–248. doi: 10.1080/09670262.2011.554886. Full text in Research Archive Show summary

  A novel colonial prymnesiophyte from the inshore waters of South Africa, which is reminiscent of the genus Corymbellus, is described at light and electron microscope levels. It differs from the only species of this genus, Corymbellus aureus, in scale structure, cell shape and colony morphology and has a complement of unusual morphological features that link it most with members of the Prymnesiales. Phylogenetic analyses of the nuclear-encoded SSU and LSU ribosomal DNA sequences indicate that this organism is closely related to members of the genus Prymnesium sensu lato and it is thus considered as a novel species, here named P. radiatum. The closest relative to P. radiatum in the SSU rDNA phylogenetic tree was Prymnesium neolepis (formerly Hyalolithus neolepis). The reconfiguration of the cytoskeleton during cell division in this organism is also novel, with a progressive elaboration of existing elements, rather than the massive reorganization expected in the prymnesiophytes.

• Strand, David; Holst-Jensen, Arne; Viljugrein, Hildegunn; Edvardsen, Bente; Klaveness, Dag & Jussila, Japo [Show all 7 contributors for this article] (2011). Detection and quantification of the crayfish plague agent in natural waters: direct monitoring approach for aquatic environments. Diseases of Aquatic Organisms. ISSN 0177-5103. 95(1), p. 9–17. doi: 10.3354/dao02334. Full text in Research Archive Show summary

  Aphanomyces astaci, a specialised parasite of North American freshwater crayfish, is the disease agent of crayfish plague that is lethal to European freshwater crayfish. The life cycle of A. astaci has been inferred from experimental laboratory studies, but less is known about its natural sustainability and ecology. To address such questions, tools for monitoring of A. astaci directly in aquatic environments are needed. Here, we present an approach for detecting and quantifying A. astaci directly from water samples using species-specific TaqMan (R) minor groove binder real-time PCR. Samples of a 10-fold dilution series from similar to 10(4) to similar to 1 spore of A. astaci were repeatedly tested, and reliable detection down to 1 spore was demonstrated. Further, to simulate real-life samples from natural water bodies, water samples from lakes of various water qualities were spiked with spores. The results demonstrated that co-extracted humic acids inhibit detection significantly. However, use of bovine serum albumin or the TaqMan (R) Environmental Master Mix largely removes this problem. The practical application of the approach was successfully demonstrated on real-life water samples from crayfish farms in Finland hosting infected North American signal crayfish Pacifastacus leniusculus. Direct monitoring of A. astaci from aquatic environments may find application in the management of wild noble crayfish Astacus astacus stocks, improved aquaculture practices and more targeted conservation actions. The approach will further facilitate studies of A. astaci spore dynamics during plague outbreaks and in carrier crayfish populations, which will broaden our knowledge of the biology of this devastating crayfish pathogen.

• Oftedal, Linn Silje Wathne; Skjærven, Kaja Helvik; Coyne, Rosie Theresa; Edvardsen, Bente; Rohrlack, Thomas & Skulberg, Olav [Show all 8 contributors for this article] (2011). The apoptosis-inducing activity towards leukemia and lymphoma cells in a cyanobacterial culture collection is not associated with mouse bioassay toxicity. Journal of Industrial Microbiology & Biotechnology. ISSN 1367-5435. 38(4), p. 489–501. doi: 10.1007/s10295-010-0791-9. Full text in Research Archive Show summary

  Cyanobacteria (83 strains and seven natural populations) were screened for content of apoptosis (cell death)-inducing activity towards neoplastic cells of the immune (jurkat acute T-cell lymphoma) and hematopoetic (acute myelogenic leukemia) lineage. Apoptogenic activity was frequent, even in strains cultured for decades, and was unrelated to whether the cyanobacteria had been collected from polar, temperate, or tropic environments. The activity was more abundant in the genera Anabaena and Microcystis compared to Nostoc, Phormidium, Planktothrix, and Pseudanabaena. Whereas the T-cell lymphoma apoptogens were frequent in organic extracts, the cell death-inducing activity towards leukemia cells resided mainly in aqueous extracts. The cyanobacteria were from a culture collection established for public health purposes to detect toxic cyanobacterial blooms, and 54 of them were tested for toxicity by the mouse bioassay. We found no correlation between the apoptogenic activity in the cyanobacterial isolates with their content of microcystin, nor with their ability to elicit a positive standard mouse bioassay. Several strains produced more than one apoptogen, differing in biophysical or biological activity. In fact, two strains contained microcystin in addition to one apoptogen specific for the AML cells, and one apoptogen specific for the T-cell lymphoma. This study shows the potential of cyanobacterial culture collections as libraries for bioactive compounds, since strains kept in cultures for decades produced apoptogens unrelated to the mouse bioassay detectable bloom-associated toxins.

• Skjelbred, Birger; Horsberg, Tor Einar; Tollefsen, Knut-Erik; Andersen, Tom & Edvardsen, Bente (2011). Toxicity of the ichthyotoxic marine flagellate Pseudochattonella (Dictyochophyceae, Heterokonta) assessed by six bioassays. Harmful Algae. ISSN 1568-9883. 10(2), p. 144–154. doi: 10.1016/j.hal.2010.08.007. Full text in Research Archive
• Dittami, Simon; Aas, H.; Paulsen, B. Smestad; Boyen, Catherine; Edvardsen, Bente & Tonon, Thierry (2011). Mannitol in six autotrophic stramenopiles and Micromonas. Plant Signalling & Behavior. ISSN 1559-2316. 6(8), p. 1237–1239. doi: 10.4161/psb.6.8.16404. Full text in Research Archive
• Dittami, Simon; Aas, Hoai Thi Nguyen; Paulsen, Berit Smestad; Boyen, Catherine; Edvardsen, Bente & Tonon, Thierry (2011). Mannitol in six autitrophic stramenopiles and micromonas. Plant Signalling & Behavior. ISSN 1559-2316. 6(8), p. 1–3. doi: 10.4161/psb.6.8.16404. Full text in Research Archive
• Haande, Sigrid; Rohrlack, Thomas; Semyalo, Ronald Paul; Brettum, Pål; Edvardsen, Bente & Solheim, Anne Lyche [Show all 8 contributors for this article] (2011). Phytoplankton dynamics and cyanobacterial dominance in Murchison Bay of Lake Victoria (Uganda) in relation to environmental conditions. Limnologica. ISSN 0075-9511. 41(1), p. 20–29. doi: 10.1016/j.limno.2010.04.001. Full text in Research Archive
• Rounge, Trine Ballestad; Rohrlack, Thomas; Decenciere, Fernandiere Beatriz; Edvardsen, Bente; Kristensen, Tom & Jakobsen, Kjetill Sigurd (2010). SUBPOPULATION DIFFERENTIATION ASSOCIATED WITH NONRIBOSOMAL PEPTIDE SYNTHETASE GENE CLUSTER DYNAMICS IN THE CYANOBACTERIUM PLANKTOTHRIX SPP.1. Journal of Phycology. ISSN 0022-3646. 46(4), p. 645–652. doi: 10.1111/j.1529-8817.2010.00856.x. Full text in Research Archive

View all works in NVA

• Edvardsen, Bente (2025). Marine microalgae and other microbes. Full text in Research Archive
• Edvardsen, Bente; Fon, Mathias & Eikrem, Wenche (2025). Biology, toxicity and ecology of Chrysochromulina leadbeateri. Full text in Research Archive
• Assmy, Philipp Kurt Wolf; Bailey, Allison Michelle; Daase, Malin; Edvardsen, Bente; Eikrem, Wenche & Hopp, Clara J.M. [Show all 16 contributors for this article] (2025). Extensive summer blooms in fjords of West Spitsbergen triggered by run-off from land. Full text in Research Archive Show summary

  Primary production in Svalbard fjords is highly seasonal with the largest fraction of annual primary production traditionally associated with the phytoplankton spring bloom, usually peaking in May. The spring bloom is terminated when winter accumulated nutrients in surface waters are exhausted and typically followed by a post-bloom period characterized by low phytoplankton biomass. Here we report on extensive phytoplankton blooms in fjords of West Spitsbergen during late-June 2024 occurring four weeks after the peak of the spring bloom and coinciding with the snow freshet period. We focus on bloom development in Kongsfjorden and explore the environmental drivers that triggered this bloom. The bloom developed in the upper 5 – 15 m of the water column with exceptionally high chlorophyll-a concentrations of up to 25 µg L-1. Its species composition was distinctly different from the spring bloom, dominated by diatoms, and almost exclusively dominated by a pelagophyte species new to science. Surface currents, nutrient and chlorophyll-a profiles and satellite images indicate that the bloom developed inside the fjord and was subsequently advected onto the adjacent shelf. Since post-spring bloom nitrate concentrations in fjord surface waters were completely exhausted in the upper 25 m, we hypothesize that this bloom was triggered by land-derived nutrients associated with meltwater run-off, highlighting terrestrial drivers of marine primary production in fjord ecosystems. Such extensive blooms during early summer are unusual and could possibly be associated with the record melt on Svalbard in summer 2024.

• Solhaug, Anita; Fon, Mathias; Wang, Xinhui; Chen, An; Ghesquiere, Rosalie & Andersen, Aaron John Christian [Show all 15 contributors for this article] (2025). The cytotoxicity of the haptophyte Chrysochromulina leadbeateri towards gill cell lines. Full text in Research Archive
• Larsen, Thomas Ostenfeldi; Wang, Xinhui; Samdal, Ingunn Anita; Andersen, Aaron John Christian; Solhaug, Anita & Garrido, Bruno [Show all 12 contributors for this article] (2025). Structure elucidation of Leadbeaterin-1: The main fishkilling toxin from Chrysochromulina leadbeateri blooms in Northern Norwegian fjords. Full text in Research Archive
• Miles, Christopher Owen; Løvberg, Kjersti Eriksen; Rasmussen, Tone; Michelsen, Helena Kling; Rangel-Huerta, Oscar Daniel & Larsen, Thomas O. [Show all 11 contributors for this article] (2025). Sterolysin diversity during fish-killing Chrysochromulina leadbeateri blooms in northern Norway. Full text in Research Archive Show summary

  A major bloom of the haptophyte C. leadbeateri in 2019 killed 7.5 million farmed salmon, corresponding to a direct economic loss of €85 million, and indirect losses of €210–250 million. Very recently, we reported the isolation and structure elucidation by LC-HRMS/MS and NMR spectroscopy of a new fish-killing toxin, named leadbeaterin-1, in the ToxANoWa project.1,2 The presence of 5 other putative leadbeaterins was also revealed by LC–HRMS analyses of algal cultures.1 In May–June 2025, another C. leadbeateri bloom occurred in the same region, resulting in the deaths of ca. 2 million farmed salmon. LC–HRMS/MS analyses of extracts from passive samplers (SPATT disks) and SPE of water from stored and fresh samples from the two blooms, and samples from cultures (including a culture from 1991), were performed, including targeted metabolomics approaches. These revealed a rich array of related compounds, including putative precursors, metabolites, and degradation products. Here we report an update on findings from these studies and tentative structures for some of the major analogues. The implications of this sterolysin diversity for potential monitoring and early-warning strategies will also be discussed. References: 1. Wang X, Fon M, Andersen AJC, Solhaug A, Ingebrigtsen RA, Samdal IA, et al. Insights into the nature of ichthyotoxins from the Chrysochromulina leadbeateri blooms in northern Norwegian fjords. Harmful Algae. 2024;137:102681. 2. Wang X, Solhaug A, Mudge EM, Garrido BC, Fon M, Andersen AJC, et al. Structure elucidation of leadbeaterin-1: the main fish-killing toxin from Chrysochromulina leadbeateri blooms in northern Norwegian fjords. J. Agric. Food Chem. (manuscript in preparation).

• Samdal, Ingunn Anita; Miles, Christopher Owen; Solhaug, Anita; Edvardsen, Bente; Larsen, Thomas Ostenfeld & Michelsen, Helena Kling [Show all 7 contributors for this article] (2025). Chrysochromulina leadbeateri & toksinet – i prosjektet ToxANoWa. Full text in Research Archive
• Wang, Xinhui; Solhaug, Anita; Mudge, Elizabeth M.; Garrido, Bruno C.; Fon, Mathias & Andersen, Aaron [Show all 14 contributors for this article] (2025). Leadbeaterins, novel ichthyotoxic sterolysins from the haptophyte Chrysochromulina leadbeateri, responsible for massive fish kills in Norway. Full text in Research Archive
• Nygård, Elise; Kline, Simon Hasselø; Valestrand, Louise & Edvardsen, Bente (2024). Exploration of community dynamics of protists during the autumn season through metabarcoding and intensive sampling. Full text in Research Archive Show summary

  Increasing anthropogenic stressors and climate change are contributing to shifts in phytoplankton communities, which has significant consequences for marine ecosystems and biogeochemical cycles. Temperate regions, like Southern Norway, have distinct spring and autumn phytoplankton blooms which often differ in species composition due to variations in temperature, salinity, and light conditions, as well as nutrient availability. However, the autumn bloom is less explored than the spring bloom. Traditionally, phytoplankton monitoring programs collect samples once a month in the production period, this frequency may miss important aspects of population dynamics and species composition, especially during periods with rapid environmental and biological changes. This master’s project aims to get a better understanding of the phytoplankton autumn bloom in the Oslofjord. We intend to see if there is a difference in the composition and timing of the autumn bloom between the inner and outer Oslofjord, and whether frequent sampling reveals more of the changes over time and locality than traditional monthly sampling. This will be done through water sampling twice a week for about a month (mid-September to mid-October) in 2023 and 2024 from two marine sampling stations. The community diversity and composition will be examined by high throughput Illumina sequencing (using the V4 region of the 18S rRNA gene). Environmental factors, such as chlorophyll-a concentrations, along with nutrient and cDOM will be measured. Preliminary results from 2023 indicate differences in chlorophyll-levels between the stations, as well as temporal differences. Additionally, there appears to be weekly fluctuations in chlorophyll levels even with frequent sampling.

• Kline, Simon Hasselø; Saubrekka, Karoline; Eikrem, Wenche; Valestrand, Louise; Egge, Elianne Dunthorn & Eiler, Alexander [Show all 8 contributors for this article] (2024). Seasonal dynamics of the protist community in the Oslofjord and Skagerrak in a changing ocean. Full text in Research Archive Show summary

  Protists and prokaryotes compose approximately 90% of the biomass in the oceans, and any changes within this microbial community are likely to have reverberating effects throughout the ecosystem. Due to climate coastal marine systems are experiencing increased freshwater discharge from land and a darkening of the water column along with changes in nutrient concentrations. The phenology is also changing and in the inner Oslofjord the spring blooms starts on average 2 weeks later that 15 years ago. The causes for this delay in unclear. In this study we examine the diversity and seasonal dynamics of the protist community by metabarcoding in the inner and outer Oslofjord, and possible changes during 14 years. Monthly plankton samples were collected at two localities and two depths during 2023 and similar samples were collected in 2009-2011, to be sequenced by current high throughput technology (Illumina). Various environmental parameters have been measured including CDOM (colored dissolved organic matter). We ask whether browning or other physico-chemical conditions can explain the delayed spring bloom and other observed changes in the protist community in the Oslofjord and Skagerrak.

• Myrann, Olav; Kline, Simon Hasselø; Andersen, Tom & Edvardsen, Bente (2024). The effects of light and salinity on growth of spring bloom diatoms in the Oslofjord. Full text in Research Archive Show summary

  Diatoms dominate during the spring bloom in the Oslofjord, with members of the genera Skeletonema, Thalassiosira and Chaetoceros being among the most abundant. During the last 15 years there has been a recorded reduction in Skeletonema abundance during the spring bloom in the Inner Oslofjord, that may explain an overall reduction of diatom abundance. In comparison the concentration of other diatoms such as Chaetoceros spp. has remained stable in the same period. The concentration of dinoflagellates has remained stable in contrast to the decrease of diatom concentration since 2006. The main aim of this master’s project is to obtain further knowledge on the abiotic factors affecting the important spring bloom diatom genera Skeletonema, Chaetoceros and Thalassiosira, and how environmental changes may affect their growth. To reach these aims, two different growth experiments using diatom cultures isolated from the spring bloom in the Oslofjord will be employed: 1) growing strains of Skeletonema and Chaetoceros separately under a combination of varying salinity and light intensity, and 2) conducting a common garden growth experiment with cultures of two additional diatom cultures Chaetoceros and Thalassiosira resulting in 4 species in total. The common garden growth experiment will test various conditions of salinity. The project will give insight into the dynamics of the spring blooming diatoms in the Oslo fjord and how they are affected by changes in salinity along with their interactions.

• Eliassen, Sigurd, skaar; Kline, Simon Hasselø; Andersen, Tom & Edvardsen, Bente (2024). Investigating the phytoplankton spring bloom dynamics n the Oslofjord by single species and common garden growth experiments. Full text in Research Archive Show summary

  During the last 15 years there has been a gradual decrease of diatom concentration during the spring bloom in the inner Oslofjord. A part of this decrease may be explained by decrease of the concentration of the genus Skeletonema, while other important diatom genera such as Chaetoceros and Thalassiosira have maintained a stable concentration since 2006. The reason for this is unclear. Possible causes for these changes include changes of the physical or chemical conditions. One potential driver of the observed changes can be coastal darkening due to climate change leading to shifting phytoplankton dynamics in the inner Oslofjord. An increase of light absorbing molecules of dissolved coloured organic matter (cDOM) transferred to the fjord from river input could reduce the growth of phytoplankton and potentially also shift the spring bloom to a later date. Under conditions with limited light, the phytoplankton taxa with the ability to grow at the lowest light intensity may be able to outcompete other competitors for the available light. The aim of this master’s project is to get a better understanding of the dynamics of important spring bloom diatoms in the Oslofjord and possible explanations to the observed changes. By single-species growth experiments I will determine the compensation light intensity of strains of two diatom genera Chaetoceros and Thalassiosira grown at different salinities. In a common garden experiment strains of the two diatom genera will be grown together with a strain of Skeletonema under different light conditions, to determine their competitive ability to limiting irradiance. This may contribute to a better understanding of the changes in the spring bloom dynamic observed in the Oslofjord since 2006.

• Edvardsen, Bente (2024). History of haptophyte and other ichthyotoxic algal blooms in Scandinavia. Full text in Research Archive
• Wang, Xinhui; Fon, Mathias; Andersen, Aaron John Christian; Solhaug, Anita; Ingebrigtsen, Richard Andre & Samdal, Ingunn Anita [Show all 10 contributors for this article] (2024). Ichthyotoxins from the Chrysochromulina leadbeateri blooms in Northern Norwegian fjords. Full text in Research Archive
• Edvardsen, Bente; Fon, Mathias; Wang, Xinhui; Larsen, Thomas Ostenfeldt & Solhaug, Anita (2024). Chrysochromulina leadbeateri causing massive fish mortalities in Northern Norway – its growth, toxicity and toxins. Full text in Research Archive
• Samdal, Ingunn Anita; Uhlig, Silvio; Solhaug, Anita; Fon, Mathias; Miles, Christopher Owen & Rangel-Huerta, Oscar Daniel [Show all 12 contributors for this article] (2024). Ny forståelse rundt hvorfor millioner av oppdrettslaks døde av algegift i 2019. Full text in Research Archive
• Edvardsen, Bente; Fon, Mathias; Reitzel, Helene; Šupraha, Luka; Andersen, Tom & Uhlig, Silvio (2023). Growth preferences of the haptophyte Chrysochromulina leadbeateri forming ichthyotoxic blooms in fjords in N Norway. Full text in Research Archive Show summary

  Microalgal flagellates of the genera Chrysochromulina and Prymnesium may form extensive blooms in marine and brackish waters causing fish kills. Chrysochromulina leadbeateri blooms caused massive fish kills in fish farms in Northern Norway in May 1991 and 2019. More than 14 500 tons of farmed salmon died in 2019. Cultures from both blooms were used in physiological experiments to investigate possible causes for the blooms. Growth experiments with varying salinity, temperature and irradiance in a facultative design were performed. Highest growth rates were obtained at temperatures 11-15 oC and salinities 25-30, and the tolerance range for growth were between 4-15 oC and salinities 20-34. Under optimal conditions, growth rates increased with irradiance (up to 100 µmol photons m-2 s-1). During the bloom in 2019, highest C. leadbeateri concentrations were found in waters with slightly reduced salinity (32-33) and sea surface temperatures around 7oC. Strains from the blooms in 1991 and 2019 were identical in the 18S rRNA gene. This ribotype appears to have a cold water-Arctic geographical distribution based on the metaPR2 metabarcoding datasets, whereas other ribotypes of C. leadbeateri in this dataset show a cosmopolitan or temperate-warm water distribution. We suggest that C. leadbeateri consists of several ribotypes with different growth preferences and that the toxic blooms in Northern Norway were formed by a ribotype adapted to cold waters with slightly reduced salinity and can tolerate rather high irradiances. Possible causes for the ichthyotoxic blooms will be discussed.

• Edvardsen, Bente (2023). On the track of causes for fish-killing algal blooms. Full text in Research Archive Show summary

  Harmful algal blooms (HABs) in marine, brackish and fresh waters resulting in fish-kills occur worldwide and may lead to great economic and ecological losses, as well as suffering for the fish. Farmed fish in pens and ponds are especially prone as they cannot escape from the blooms. Many ichthyotoxic blooms are sporadic events and the causes and triggering factors of these HABs are often poorly understood. Knowledge on the responsible algae and their physiology, ecology and environmental factors promoting their growth are required to understand these events. Bloom formation may also be linked to their toxicity through a relaxation of the top-down control from grazers, pathogens or competitors. We thus also need to understand how toxin production or toxicity are affected by various environmental factors to be able to understand causes of HABs. Knowledge about the responsible toxin(s) and their mode of action may however be limited and difficult to quantify. In this presentation I will compare ichthyotoxic haptophytes and look at similarities and differences in their bloom formation, ecology, physiology and toxicity in order to better understand causes for some of these blooms, especially of the little studied species Chrysochromulina leadbeateri.

• Larsen, Thomas ostenfeld; Wang, Xinhui; Fon, Mathias; Andersen, Aaron John Christian; Hansen, Per Juel & Uhlig, Silvio [Show all 8 contributors for this article] (2023). Insights into the chemistry of microalgal toxins involved in recent northern European fish killing events. Full text in Research Archive
• Kwasniewski, Slawomir; Altenburger, Andreas; Assmy, Philipp Kurt Wolf; Bluhm, Bodil Annikki Ulla Barbro; Dabrowska, Anna Maria & Edvardsen, Bente [Show all 25 contributors for this article] (2023). Biodiversity in the northern Barents Sea and adjacent Nansen Basin – towards an updated inventory. Full text in Research Archive Show summary

  Biodiversity patterns shape and drive ecosystem processes and functions in the global ocean. Given the changing climate and recent agreements to protect ocean regions, current estimates of biodiversity must be assembled. Here, we present new estimates and spatial patters of taxon richness from microbes to mammals from a shelf-to-basin transect in the northern Barents Sea and southern Nansen Basin from seasonal sampling in 2018-2022 by the Nansen Legacy project. We find that estimates of taxon richness are higher on the shelf than in the basin for pelagic protists, zooplankton, and benthic macrobenthos, nematodes, and prokaryotes, but not for sympagic protists. Taxon richness varied seasonally for pelagic prokaryotes, protists, and zooplankton, but little for sympagic meiofauna, benthic prokaryotes and macrobenthos. Unsurprisingly, taxon richness was generally highest for single-celled taxa. Taxon-rich groups included: sympagic diatoms; pelagic prokaryotes (e.g., Alphaproteobacteria), diatoms, dinoflagellates, copepods; and benthic prokaryotes (with abundant taxa, e.g., Candidatus nitrosopumilus and Woesia), nematodes, and polychaetes. Unexpectedly absent - though known from earlier studies - were, for example, nematodes in sea ice. Ironically, at top (and perhaps other) trophic levels species richness is likely to be enhanced regionally for some time, while losses of Arctic (endemic) species will impact global biodiversity, and potentially Arctic ecosystem functioning

• Marquardt, Miriam; Goraguer, Lucie Hélène Marie; Assmy, Philipp Kurt Wolf; Bluhm, Bodil Annikki Ulla Barbro; Patrohay, Evan & Aaboe, Signe [Show all 12 contributors for this article] (2023). Seasonal dynamics of sea ice protists and meiofauna in the northwestern Barents Sea in relation to sea ice properties. Full text in Research Archive Show summary

  The rapid decline of Arctic sea-ice including that in the Barents Sea makes understanding sympagic biology an urgent task. Seasonal ice sampling (2019-2022) as part of the Nansen Legacy project focused on ice biota composition and abundance in the bottom 30cm of Barents Sea ice in relation to ice properties. In December and May we sampled growing first-year ice, while in July and August melting, older sea ice dominated, overall agreeing with ice trajectories. Abiotic ice conditions and Chla varied strongly seasonally, while POC values were unexpectedly homogenous. Low ice biota abundances in March could be related to late ice formation resulting in a short time for biota to build up biomass. Pennate diatoms dominated the bottom ice algal communities in all seasons, with highest biomass in May. Outside May, small-sized flagellates were co-dominant. Overall, ice meiofauna was comprised of harpacticoid copepods, copepod nauplii and rotifers, foraminiferans and highly abundant ciliates. While melting ice had released ice algal biomass in July, abundance of secondary producers remained high, indicating different life history traits. Unexpectedly abundant communities occurred in December, further strengthened the notion of an active biota in the dark Arctic winter. The data demonstrated a strong and partly unexpected seasonality in the ice biota, indicating that changing timing of ice formation and melt will significantly impact composition and phenology of sympagic communities.

• Fon, Mathias; Supraha, Luka; Andersen, Tom; Uhlig, Silvio & Edvardsen, Bente (2023). Using high-throughput techniques to understand the growth of the fish-killing haptophyte Chrysochromulina leadbeateri in northern Norway. Full text in Research Archive
• Samdal, Ingunn Anita; Uhlig, Silvio; Solhaug, Anita; Fon, Mathias; Gilbert, Dorothea & Ivanova, Lada [Show all 15 contributors for this article] (2023). Toxic microalgae in Norwegian waters - Uncovering fish-killing mechanisms of phytoplankton from Scandinavian waters. Full text in Research Archive
• Marquardt, Miriam; Goraguer, Lucie Hélène Marie; Assmy, Philipp; Bluhm, Bodil; Aaboe, Signe & Down, Emily [Show all 12 contributors for this article] (2023). Seasonal dynamics of sea ice protists and meiofauna in the Northern Barents Sea. Full text in Research Archive
• Marquardt, Miriam; Assmy, Philipp; Edvardsen, Bente; Goraguer, Lucie Hélène Marie; Gradinger, Rolf Rudolf & Patrohay, Evan [Show all 10 contributors for this article] (2023). Seasonal dynamics of sea ice protists and meiofauna in the northern Barents Sea. Full text in Research Archive Show summary

  The declining Arctic sea ice makes understanding sympagic biology a urgent task, including the Northern Barents Sea, which is highly influenced by ice loss and increased Atlantic inflow. A seasonal ice sampling effort (2019-2022) as part of the Nansen Legacy project focused on the poorly known ice biota composition and abundance in the bottom 30cm of Barents Sea ice in relation to season, hydrography and ice properties. We expected low abundances during the polar night and highest values during the spring prior to ice melt. From December and March, ice thickness increased while melting dominated in summer. Pennate diatoms, such as Navicula and Nitzschia spp., were dominating the bottom ice protist communities during all periods, while small-sized dinoflagellates were co-dominant. Ice meiofauna was comprised of harpacticoid copepods, copepod nauplii, rotifers, occasional visitors such as acoels and foraminiferans and highly abundant ciliates (50-90 %; total abundances). Surprisingly, active December communities occurred in higher than expected abundances. Low abundances in March could be related to later on-set of ice formation and reduced time for biota to establish. Maximum meiofauna abundances in May reflect a late spring bloom development. In August despite ice melting meiofauna abundances were still high. The data demonstrated a strong and partially unexpected seasonality in the ice biota, indicating that changing timing of ice formation and decay will significantly impact the current sea ice biology.

• Chen, An; Fon, Mathias; Edvardsen, Bente; Uhlig, Silvio & Solhaug, Anita (2023). Evaluation of toxicity of the microagla Chrysochromulina leadbeateri using the Atlantis salmon gill epithelial cell line ASG-10. Full text in Research Archive
• Saubrekka, Karoline; Vader, Anna; Supraha, Luka; Andersen, Tom & Edvardsen, Bente (2023). Diversity and Distribution of Arctic Protists in Pelagic and Sympagic Habitats in the Northern Barents Sea as Revealed by Metabarcoding. Full text in Research Archive
• Saubrekka, Karoline; Vader, Anna; Supraha, Luka & Edvardsen, Bente (2023). Diversity and distribution of Arctic protists in pelagic and sympagic habitats in the northern Barents Sea as revealed by metabarcoding. Full text in Research Archive Show summary

  Protists play crucial roles in the marine ecosystems and in a rapidly changing Arctic it is important to reveal who are there, when and where, for future research and management. The aim of this study was to describe and compare the composition of protist communities in sea ice and pelagic habitats from samples collected in the northern Barents Sea along a transect in August 2018 with low sea-ice extent and 2019 with high sea-ice extent. Metabarcoding targeting the 18S rRNA gene revealed 3682 unique amplicon sequence variants (ASVs), a proxy for species, and clear difference in ASV composition in ice and pelagic habitats. The pelagic community showed interannual differences. In 2018 the community was dominated by dinoflagellates and nano- and pico-plankton such as Micromonas polaris. In 2019 a community with more centric diatoms was observed at ice edge stations. Members of the class Chrysophyceae dominated in melt ponds, whereas communities within the ice were dominated by dinoflagellates and pennate diatoms. The community changed from top to bottom of the ice cores and the diversity was higher in thick than thin ice. Just below the ice, dinoflagellate ASVs dominated together with Phaeocystis. Our results indicate that protist communities are distinct and specialized by habitat. With further ocean warming, pelagic communities may shift towards smaller flagellates, and thinning of the sea ice may lead to a loss of habitats and diversity.

• Edvardsen, Bente; Supraha, Luka; Egge, Elianne Dunthorn & Saubrekka, Karoline (2023). Diversity and distribution of marine protists in the Arctic explored by a polyphasic approach. Full text in Research Archive
• Eikrem, Wenche; Vader, Anna; Hofgaard, Antje & Edvardsen, Bente (2023). Phytoplankton in the Arctic Ocean - Species Composition and Biomass during the Nansen Legacy Arctic basin cruise, 24 Aug-26 Sep 202. Full text in Research Archive Show summary

  At the southern-most station along the S-N transect, P7, the pelagic protist community was characterized by both high diversity and abundance. Large diatom species dominated the community, and large dinoflagellates and Phaeocystis pouchetii were also abundant. Moving north and into the ice, the protist community in the water column changed. Smaller organisms and heterotrophic species became more prominent. The larger diatom species became much scarcer but were still present. The community in the ice cores was dominated by pennate diatoms, but dinoflagellates and in particular the heterotrophic species were also abundant. In addition, green flagellates, cryptomonads, chrysophytes, and haptophytes were frequent. The sea-ice showed the highest chlorophyll-a values and had larger cells. In the melt ponds the salinity was low, but variable (2.8-5.7). The chlorophyll-a values there were low, and the species composition varied, and the taxa present were associated with brackish and freshwater as well as a benthic lifestyle.

• Edvardsen, Bente (2023). Biodiversity of microalgae in Scandinavian marine waters. Full text in Research Archive
• Edvardsen, Bente (2022). Exploration of protist diversity and distribution in the ocean by a polyphasic approach. Full text in Research Archive
• Edvardsen, Bente (2022). Metabarcoding and Systematics of Protists in the Ocean to Understand Ecosystem Functioning. Full text in Research Archive
• Edvardsen, Bente (2022). Mikroalger i Arktis - hvor unike er de? Full text in Research Archive
• Edvardsen, Bente (2022). Planteplankton i Oslofjorden, endringer og mulige årsaker. Full text in Research Archive
• Edvardsen, Bente (2022). DNA-strekkoding – et verktøy for gjennkjenning av arter. Full text in Research Archive
• Edvardsen, Bente; Supraha, Luka; Egge, Elianne Dunthorn & John, Uwe (2022). Harmful haptophyte blooms in Norway - bloom dynamics and ecology, with special focus on the Chrysochromulina leadbeateri blooms. Full text in Research Archive
• Edvardsen, Bente & Eikrem, Wenche (2022). Haptophyte taxonomy. Full text in Research Archive
• Edvardsen, Bente; Supraha, Luka & Egge, Elianne Dunthorn (2022). Diversity and distribution of marine protists in the Arctic explored by a polyphasic approach. Full text in Research Archive
• Vogt, Yngve & Edvardsen, Bente (2020). Varmere hav endrer algesamfunnet i Arktis. [Journal]. Apollon : Forskningsmagasin for Universitetet i Oslo. Full text in Research Archive
• Samdal, Ingunn Anita & Edvardsen, Bente (2020). Massive salmon mortalities during a Chrysochromulina leadbeateri bloom in Northern Norway. Harmful Algae News. ISSN 0020-7918. p. 4–5. Full text in Research Archive
• Edvardsen, Bente; Supraha, Luka; Gran-Stadniczeñko, Sandra; Eikrem, Wenche & John, Uwe (2020). An in-depth study of Chrysochromulina leadbeateri bloom in northern Norway during spring 2019. Full text in Research Archive Show summary

  The toxic algal bloom of the haptophyte Chrysochromulina leadbeateri in spring 2019 was the largest bloom of this species in Norwegian waters and worldwide ever recorded. Starting in the Vestfjorden area in northern Norway during early May and expanding north to Balsfjorden and Tromsø area, the bloom caused a major mortality of farmed salmon, with over 13 000 tonns of fish reported as lost during the outbreak. The C. leadbeateri bloom in northern Norway was studied in-depth in frame of a research cruise led by Alfred Wegener Institute (Germany) and in collaboration with the University of Oslo. The cruise focused on studies of phytoplankton diversity, distribution and functional ecology in several fjord systems along the northern Norwegian coast (Lofoten-Vesterålen area, Balsfjorden, Lyngen, Porsangerfjorden, Laksefjorden, Tanafjorden). Biological and environmental data collected during the cruise allowed for detailed analyses of the blooming organism, its distribution patterns in northern Norway, and its ecology. Cultures of C. leadbeateri isolated from the bloom were used to determine the morphology, taxonomic identity, and phylogenetic placement of the organism, and to compare it with a C. leadbeateri strain isolated from the previous major bloom in 1991. Metabarcoding data, light microscopy counts and flow cytometry data were used to map the distribution and abundance of the species along the coast of northern Norway, and correlate its distribution with biotic and abiotic parameters. Preliminary results show that the blooming organism is genetically identical in marker genes to the strain from the bloom in Vestfjorden in 1991. However, both strains and C. leadbeateri in field material exhibit significant intraspecific genetic variability. Biogeographic mapping shows that the bloom was most pronounced in the Balsfjorden area, with maximum cell concentration of over 27 million cells L-1. From an ecological perspective, C. leadbeateri abundance showed positive correlation with phosphate and nitrate, negative correlation with salinity and a slightly positive correlation with temperature. The results of our work provide a unique, in-depth insight into C. leadbeateri blooms, which may help in the monitoring, modelling and predicting similar events in the future. Ongoing work in our group focus on physiological and genetic profiling of the isolated C. leadbeateri strains with the aim to improve our understanding of factors triggering toxicity and bloom formation.

• Edvardsen, Bente (2020). Norsk algekultursamling (NORCCA) - en verdifull ressurs for innovasjon. Full text in Research Archive
• Edvardsen, Bente; Lundholm, Nina & Medlin, Linda K. (2018). Tribute to Professor Grethe Ryther Hasle. Diatom Research. ISSN 0269-249X. 33(1), p. 117–122. doi: 10.1080/0269249X.2018.1451392. Full text in Research Archive
• Edvardsen, Bente (2018). Endosymbiose hos alger i havet. Biolog. ISSN 0801-0722. 1, p. 14–20. Full text in Research Archive
• Edvardsen, Bente (2017). Planteplanktonet i havet og effekter av klimaforandringer. Full text in Research Archive Show summary

  Planteplanktonet i havet står for nesten halvparten av all fotosyntese og oksygenproduksjon på jorda, og er næringsgrunnlaget for det meste av livet i havet. Planteplanktonets sammensetning har betydelse for høyere trofiske nivåer. Et viktig spørsmål er derfor hvordan klimaforandringer vil påvirke produksjonen og sammensetningen av planteplanktonet i havet, og dermed produksjon av dyreplankton og fisk. Og vil endringer i planteplanktonsamfunnet kunne påvirke klimaet? For å kunne besvare disse spørsmålene trenger vi å kjenne artene som er til stede og hvordan planktonsammensetningen varierer i tid og rom. Og hvordan styrer ulike miljøfaktorer deres forekomst? I mitt foredrag vil jeg belyse disse spørsmålene og fortelle om vår forskning hvor vi undersøker planktonets mangfold og forekomst i Oslofjorden og Arktis med DNA-analyser av typen dypsekvensering, og med lys- og elektron-mikroskopi. Med dypsekvensering har vi oppdaget et stort mangfold av små encellede eukaryoter. Mange er nye registreringer for Norge og flere taksonomiske grupper er nye for vitenskapen. Noen er til stede året rundt, andre kun deler av året, noen har vid utbredelse, andre er kun funnet i Arktis. Kunnskap om deres sesongmessige og romlige forekomst, størrelse og taksonomiske tilhørighet bidrar til å forstå deres betydning i næringsnettet.

• Edvardsen, Bente (2017). Klimaendringer og effekter på planteplanktonet i havet. Full text in Research Archive
• Edvardsen, Bente; Egge, Elianne Dunthorn; Vaulot, Daniel; Larsen, Aud; Bratbak, Gunnar & Moreau, Hervé [Show all 7 contributors for this article] (2017). Protist community structure in Atlantic Arctic through the year as revealed by high throughput sequencing. Full text in Research Archive
• Eikrem, Wenche; Medlin, Linda K.; Henderiks, Jorijntje; Rokitta, Sebastian; Rost, Björn & Throndsen, Jahn [Show all 8 contributors for this article] (2017). Haptophyta. In Archibald, John M.; Simpson, Alastair G B & Slamovits, Claudio H (Ed.), Handbook of the Protists. Springer Publishing Company. ISSN 9783319281483. p. 1–61. doi: 10.1007/978-3-319-32669-6_38-1. Full text in Research Archive Show summary

  Haptophyta are predominantly planktonic and phototrophic organisms that have their main distribution in marine environments worldwide. They are a major component of the microbial ecosystem, some form massive blooms and some are toxic. Haptophytes are significant players in the global carbonate cycle through photosynthesis and calcification. They are characterized by the haptonema, a third appendage used for attachment and food handling, two similar flagella, two golden-brown chloroplasts, and organic body scales that serve in species identification. Coccolithophores have calcified scales termed coccoliths. Phylogenetically Haptophyta form a well-defined group and are divided into two classes Pavlovophyceae and Coccolithophyceae (Prymnesiophyceae). Currently, about 330 species are described. Environmental DNA sequencing shows high haptophyte diversity in the marine pico- and nanoplankton, of which many likely represent novel species and lineages. Haptophyte diversity is believed to have peaked in the past and their presence is documented in the fossil record back to the Triassic, approximately 225 million years ago. Some biomolecules of haptophyte origin are extraordinarily resistant to decay and are thus used by geologists as sedimentary proxies of past climatic conditions.

• Edvardsen, Bente (2017). Discovery of unknown microalgae and protozoa in the Ocean. Full text in Research Archive Show summary

  http://oiw.no/speakers/bente-edvardsen

• Edvardsen, Bente (2017). Symbiose og alger i havet. Full text in Research Archive
• Edvardsen, Bente (2017). Algal cultures for biotechnological innovation. Full text in Research Archive
• Egge, Elianne Dunthorn; Vaulot, Daniel; Larsen, Aud; Bratbak, Gunnar; Uwe, John & Edvardsen, Bente (2017). Protist community structure in Atlantic Arctic through the year as revealed by high throughput sequencing. Full text in Research Archive Show summary

  Unicellular protists, including microalgae are main suppliers of photosynthetic products that higher trophic levels depend upon. Yet, the Arctic protist community contains a vast unknown diversity and many of the described species are poorly known. Diversity and dynamics throughout the polar night and at great depths remains particularly understudied due to limited access. In the MicroPolar project we asked “Who are present and when during the year?”, “How is the community structured by depth and geography?” and “What are the environmental driving forces for the observed distribution?” Sampling cruises to North and West of Svalbard were carried out five times during 2014 (January, March, May, August and November). Samples were collected at 3-6 stations and four depths (1-1000m). Fifty litres were divided into four size fractions from micro- to picoplankton. The 18S V4 region of nuclear rDNA and the 16S V9 region of chloroplast rDNA and rRNA were high throughput sequenced with Illumina. We obtained c. 35 000 Operational Taxonomic Units (OTUs) clustered at 98% similarity. The protist community composition differed significantly between the dark and light seasons, and between surface water and beyond the photic zone. Also OTU richness varied significantly with depth and season. OTU richness was significantly higher in the deeper layers all months except March. The May samples had lowest richness, whereas August had highest. Both in terms of OTU richness and proportional read abundance Dinophyta was dominating in most samples, except in the May samples representing the spring bloom, where diatoms dominated. The 200 most frequent OTUs were detected all seasons and in both surface and deeper layers. The majority of these were assigned to defined clades consisting of environmental sequences only, such as MAST-clades and Dino-Group clades. This highlights the need for more reference DNA sequences from cultures. Several abundant and frequent OTUs matched well-known Arctic species, such as Chaetoceros gelidus (socialis), Phaeocystis pouchetii, Gyrodinium fusiforme and Micromonas pusilla. Interestingly, OTUs assigned to Picobiliphyta were also among the most ubiquitous OTUs. Picobiliphyta were first described in 2007 in particular from samples from the Arctic Ocean, and all are thought to be heterotrophic. As global climate change is expected to be most severe in the Arctic and may affect microbial communities and biogeochemical cycles more seriously in this region than anywhere else, this study is important to be able to assess the impact of climate change in the Arctic at the microbial level.

• Edvardsen, Bente; Vaulot, Daniel & Egge, Elianne Sirnæs (2016). A global haptophyte 18S rRNA gene phylogeny including potentially novel lineages, and a curated reference sequence database for taxonomic assignment of metabarcodes. Full text in Research Archive Show summary

  Microalgae of the division Haptophyta are a major component of the marine nanoplankton and present in all seas. They are important primary producers and grazers of picoplankton in the ocean, and their metabolic products can have an impact on global climate. Due to their small size, species are mostly difficult to distinguish by microscopy. Environmental sequencing studies have revealed a high marine haptophyte diversity. We have constructed a curated haptophyte 18S rRNA-gene reference database comprising c. 970 sequences, mostly >800 bp for taxonomic assignment of environmental sequences and metabarcoding reads. We have taxonomically assigned all sequences by phylogenetic analyses, removed chimeras, updated the taxonomy according to recent revisions, and defined clades without cultured and sequenced representatives. Haptophyta embrace numerous clades potentially representing novel lineages from genus to class level. Here we present current knowledge on their distribution based on available 18S rRNA gene sequences.

• Edvardsen, Bente; Egge, Elianne Dunthorn; John, Uwe & Vaulot, Daniel (2016). Protist diversity revealed by metabarcoding in Kongsfjorden, Svalbard mesocosm experiment. Full text in Research Archive Show summary

  As a part of the MicroPolar project a mesocosm experiment was conducted in Kongsfjorden, Svalbard in July 2015. The aim was to assess the effect of grazing pressure and levels of organic carbon on the microbial composition and relative abundance over time. In this part of the project we studied how the protist community composition and relative abundance were affected by these two factors. Water samples (2L) were harvested 5 times during a 10 days incubation, and DNA from the size fractions 0.2-3 and 3-50 µm were PCR amplified by eukaryote general V4 18 rRNA gene primers and tag sequenced by Illumina. Both composition and relative abundance differed significantly in response to the two factors.

• Edvardsen, Bente & Hessen, Dag Olav (2015). Genome size variation in microalgae”. Full text in Research Archive Show summary

  Genome size among eukaryotic microalgae vary with a factor of more than 17 000. The rRNA gene copy number similarly vary more than 12 000 times. The lowest genome size and rRNA gene copy number has been found in picoplanktonic chlorophytes (Ostreococcus, 12 Mb) and ochrophytes (Nannochloropsis, 25 Mb) and the highest in large dinoflagellate cells (e.g. c. 450 Gb in Prorocentrum micans and 12000 rDNA copies in Akashiwo sanguinea). For taxa analysed so far, the genome size is correlated with cell size and carbon-content both between and within species. Cell size is also generally positively correlated with growth rate within a taxonomic group, and smaller genome size thus corresponds to higher growth rate. A great diversity of life cycles is found among microalgae including diploid (diatoms), haplo-diploid (haptophytes), or haploid (dinoflagellates, many chlorophytes). The nutrient-sparing hypothesis implies selection for small cells and genomes under nutrient limited conditions, and may explain why some groups have retained a haploid or a haplo-diploid life cycle. A biphasic life cycle may be favorable under variable environmental conditions through niche partitioning or provide escape from biotic pressures such as pathogens and grazers, but may get lost under stable conditions. Nutrient scarcity may however also promote smaller cells due to their larger surface : volume ratio. Here we have compiled published data on eukaryotic microalgal genome size, cell size and growth rate and added own data for haptophytes to compare patterns among taxonomic groups, reveal driving forces and relate this to life cycle strategies.

• Edvardsen, Bente; Egge, Elianne Sirnæs; Stadniczenko, Sandra Gran; Johannessen, Torill Vik; Eikrem, Wenche & Sandaa, Ruth-Anne [Show all 10 contributors for this article] (2015). Diversity and seasonal dynamics of marine haptophytes and their viruses and the role of biotic interactions. Full text in Research Archive Show summary

  Members of the phytoplankton division Haptophyta are a major component in marine pico- and nanoplankton communities. They often occur in bloom concentrations that may have a major impact on the global carbon balance, on climate forcing and sometimes cause fish-kills. Because haptophytes are tiny and difficult to identify in the microscope little is known about their seasonal dynamics and ecological role at the species level. Virus may terminate haptophyte blooms and, according to the “killing the winner” concept, possibly prevent blooms by keeping them under constant control. The aim of this study within the HAPTODIV project was to reveal the diversity and dynamics of marine haptophytes to species level and how this relates to abiotic factors and viruses. We assessed the haptophyte and Phycodnaviridae/ Mimiviridae (algal viruses) taxonomic composition, OTU richness and relative abundance over time by high-throughput amplicon sequencing (metabarcoding) of monthly samples over 2 years from the outer Oslofjorden, Skagerrak, Southern Norway. Metabarcoding revealed higher haptophyte diversity (156 OTUs estimating species) than previously observed in the area with electron and light microscopy (85 spp), and most (84%) of this diversity remains to be cultured and sequenced. Many may represent novel lineages at the class to genus level, or species new for science. More than half of the OTUs (93) were affiliated with the order Prymnesiales such as members of e.g. Chrysochromulina and Prymnesium. Haptophyte richness and community composition showed high temporal variation and significant yearly periodicity correlating with light and temperature, with highest richness in autumn (Sep-Nov) and lowest in the spring (Apr-May). Our results indicated, however, that the abiotic factors only accounted for about 30% of the variation, and suggest that biotic factors explain some of the residual variation. Also algal virus diversity was high and showed temporal variations with highest richness in Sept-Oct. Biotic interactions between haptophytes and algal viruses were assessed by co-occurrence analyses. We detected 56 haptophyte-virus pairs with significant co-occurrence, of 49 000 possible pairs. The distribution patterns of these pairs may shed light on the role of virus infection on phytoplankton community composition and dynamics. We suggest that this approach may be a first step to test the “killing-the-winner” concept on haptophyte diversity and distribution.

• Edvardsen, Bente; Egge, Elianne Sirnæs; Stadniczenko, Sandra Gran; Johannessen, Torill Vik; Larsen, Aud & Sandaa, Ruth-Anne [Show all 7 contributors for this article] (2015). Diversity, seasonal dynamics and biotic interactions in marine phytoplankton and virus communities. Full text in Research Archive Show summary

  The taxonomic composition of phytoplankton communities and relative abundance of taxa in oceanic ecosystems undergo continuous change. This community reorganization is of major importance to higher trophic levels and biogeochemical cycles. This succession is partly accounted for by hydrographical and meteorological variations that select for different traits in time and space, but also by biological processes, such as pathogens. Virus may terminate haptophyte blooms and, according to the “killing the winner” concept, possibly prevent blooms by keeping them under constant control. We assessed the haptophyte (algal host) and Phycodnaviridae/Mimiviridae (virus) taxonomic composition and relative abundance by high-throughput amplicon sequencing of monthly samples over 2 years from the outer Oslofjorden. Haptophyte richness and community composition exhibited high temporal variation and significant yearly periodicity, with highest richness in autumn (Sept-Oct) and lowest in the spring (April-May). Also, algal virus diversity showed seasonal variations with highest richness in September-October and lowest in August. Biotic interactions between haptophytes and viruses and among haptophytes were evaluated to provide new insight in the role of biotic processes for phytoplankton community composition and dynamics.

• Le, Nhat Hao Tran; Tadesse, Margey; Edvardsen, Bente; Paulsen, Berit Smestad; Walker, S & Stokka, Anne Jorunn [Show all 7 contributors for this article] (2015). Marine bioprospecting of marine microalgae. Full text in Research Archive
• Edvardsen, Bente; Egge, Elianne Sirnæs; Johannessen, Torill Vik; Eikrem, Wenche; Sandaa, Ruth-Anne & Bittner, Lucie [Show all 10 contributors for this article] (2014). Diversity and seasonal dynamics of marine haptophytes and their viruses. Full text in Research Archive Show summary

  Members of the division Haptophyta are phytoplankton and a major component in marine pico- and nanoplankton communities. They often occur in bloom concentrations that may have a major impact on the global carbon balance, on climate forcing and sometimes cause fish-kills. Because haptophytes are small and difficult to identify in the microscope little is known about their seasonal dynamics and ecological role at the species level. We have studied the diversity and seasonal dynamics of marine haptophytes and their viruses, and how species composition and diversity are related to environmental factors using 454 pyrosequencing, complemented with electron microscopy and flow cytometry. This study revealed higher species richness of haptophytes than previously observed in the area with electron and light microscopy. The majority of the OTUs matched genetically uncharacterised taxa, most of which were affiliated with the order Prymnesiales. Several of the OTUs matched sequences forming deep-branching lineages, potentially representing novel classes of haptophytes. Haptophyte richness and community composition exhibited high temporal variation and significant yearly periodicity, with highest richness in autumn and lowest in the spring. Some taxa, such as some bloom forming species were present all year round, whereas most coccolithophores only appeared from summer to early winter. Also the algal virus (Phycodnaviridae) diversity was high and showed seasonal variations. Our results indicated that the abiotic factors only accounted for about 30% of the variation, and suggests that biotic factors may explain some of the residual variation.

• Edvardsen, Bente (2014). Minnetale over professor Grethe Rytter Hasle. Årbok / Det norske videnskaps-akademi. ISSN 0332-6209. Full text in Research Archive
• Edvardsen, Bente (2014). The diversity and dynamics of marine haptophytes. Projects Journal. 37, p. 39–41. Full text in Research Archive
• Edvardsen, Bente; Stadniczenko, Sandra Gran; Eikrem, Wenche; Hostyeva, Vladyslava; Logares, Ramiro & Egge, Elianne Sirnæs (2014). Diversity and seasonal dynamics of small dinoflagellates in the Skagerrak, Norway revealed by 454 pyrosequencing and microscopy. Full text in Research Archive Show summary

  Some dinoflagellates are small and difficult to identify under the light microscope and thus little is known about their seasonal dynamics at the species level. Here we combined high-throughput sequencing and microscopy to explore their diversity and seasonal dynamics, and relate this to environmental factors. We collected 21 monthly samples of nanoplankton (3-45 μm size fraction) from outer Oslofjorden, southern Norway over two years. The 18S V4 ribosomal DNA was amplified from RNA/cDNA and 454-pyrosequenced. The reads were cleaned, denoised and clustered to 99% in Qiime and assigned to taxon. From 46250 reads assigned to Dinoflagellata we detected 367 unique operational taxonomic units (OTUs) assessed to represent species or genera. The most OTU-rich orders were Gymnodiniales (32%), Syndiniales (22%), and Peridiniales (17%), followed by Dinophysiales (8%), Gonyaulacales (7%) and Suessiales (4%). Reads assigned to Gymnodiniales dominated in all samples except June and August 2010 when reads assigned to Suessiales dominated. We observed strong seasonal variation and significant yearly periodicity in dinoflagellate richness and species composition. OTU richness was highest in late autumn and lowest in winter-spring. Seasonal dynamics of potentially toxic taxa were examined. We also assess and discuss the ability to detect potentially toxic dinoflagellate species with 18S V4 high throughput sequencing and compare this with standard microscopical methods and electron microscopy. Potentially toxic species <45 μm observed under the microscope included e.g. Alexandrium pseudogonyaulax, A. ostenfeldii, Azadinium spinosum, Karenia mikimotoi, Karlodinium veneficum and Prorocentrum minimum.

• Henderiks, Jorijntje; Gerecht, Andrea; Hannisdal, Bjarte; Liow, Lee Hsiang; Reitan, Tore & Schweder, Tore [Show all 7 contributors for this article] (2013). PhytoSCALE project: calibrating phytoplankton cell size as a proxy for climatic adaptation. Full text in Research Archive
• Edvardsen, Bente; Egge, Elianne Sirnæs & Eikrem, Wenche (2013). Morphology, phylogeny and diversity of haptophytes. Full text in Research Archive
• Edvardsen, Bente (2013). Toxigenic marine microalgae in Norway and their toxins. Full text in Research Archive
• Edvardsen, Bente (2013). Biodiversity of microalgae -screening the potential. Full text in Research Archive Show summary

  Microalgae are a very diverse group of organisms, embracing single celled, filamentous or colony forming prokaryotic and eukaryotic microorganisms able to perform photosynthesis. Some lineages have however lost this ability, such as about half of the dinoflagellate species, and a number of heterokonts, which are heterotrophic. More than 20000 micro algal species have been described from marine and fresh waters. The application of molecular methods to environmental seawater samples show that there is a great hidden diversity, especially of the smallest nano- and pico-algae. It has been estimated that no more than 10% of the marine microalgal diversity is known and brought into culture. Microalgae produce a range of bioactive compounds, which are a potential resource for various applied purposes. They are the primary source of omega-3 long-chain polyunsaturated amino acids (LC-PUFA) in the marine food web, and fish obtain omega-3 LC-PUFA from microalgae through their diet. They are also a source of genes that regulate the biosynthetic pathways of these PUFAs. Members of kingdom Chromista and divisions Haptophyta, Ochrophyta and Dinophyta often show high content of fatty acids and a high proportion of the valuable LC-PUFA eicosapentaenoic (EPA) and/or docosahexaenoic acids (DHA). Members of Cyanophyta rarely contain these LC-PUFAs and members of Chlorophyta (green algae) usually contain no or low levels of DHA. However, there are large differences within groups and growth conditions are also of great importance. Only a small number of species are presently used as feed in aquaculture. In the search for new, potentially valuable micro-algal strains culture collections should be screened, and new strains isolated from habitats similar to the desired growth conditions. Dilution series may be the most efficient isolation technique for small, abundant and competitive microalgae, whereas capillary isolation may be the preferred method for isolation of larger and more rare organisms.

• Edvardsen, Bente; Egge, Elianne Sirnæs; Vik, Johannessen Torill; Sandaa, Ruth-Anne; Eikrem, Wenche & Larsen, Aud [Show all 12 contributors for this article] (2013). Diversity and dynamics of marine haptophytes and their viruses. Full text in Research Archive Show summary

  Haptophytes are nano- and picoplanktonic microalgae and important primary producers in the sea. They often form blooms that may impact on global carbon balance and climate forcing, and at times cause fish kills. Viruses may terminate these blooms. Knowledge on haptophyte diversity, quantitative distribution and dynamics at species level is limited because they are small and fragile, and species identification usually requires electron microscopy or molecular methods. In the project HAPTODIV we have developed methods to explore the diversity and dynamics of haptophytes and their viruses, using 454-pyrosequencing, environmental clone libraries, DNA-sequencing of new isolates, pulsed field gel electrophoresis, quantitative PCR, flow cytometry and microscopy. Plankton samples and environmental data were collected monthly from the Oslofjorden and Raunefjorden for two years. A high diversity of haptophytes was revealed, and a majority of the sequences represent unknown or uncultured species. Several taxa are recorded for the first time in Norwegian and North European waters and some may represent new taxonomic lineages (orders and class). In Oslofjorden and Raunefjorden, some taxa are present at all times, such as bloom-formers in the genera Emiliania, Phaeocystis, Chrysochromulina and Prymnesium, whereas the calcifying coccolithophorids were found mainly in summer-autumn, the period with highest diversity and temperature. The diversity of virus infecting algae (Phycodnaviridae), including haptophyte specific viruses, differed over time and with locality and was highest in spring and lowest in winter. We have isolated and characterised four new haptophyte specific viruses that differ more in genome size, DNA sequence or infection cycle than previously shown. Genetic characterisation of viruses and their haptophyte hosts have revealed their diversity, and also improved our understanding of virus-host interactions and fundamental biological processes in the ocean.

• Engesmo, Anette; Hostyeva, Vladyslava; Strand, David; Naustvoll, Lars Johan; Vrålstad, Trude & Edvardsen, Bente [Show all 7 contributors for this article] (2013). Assessing the abundance of the ichthyotoxic Karenia mikimotoi by quantitative PCR and microscopy. Full text in Research Archive Show summary

  The dinoflagellate Karenia mikimotoi may form blooms causing fish kills in coastal waters of the North East Atlantic region, including Norway and Sweden. A K. mikimotoi specific quantitative PCR (qPCR) assay was developed, based on the use of SYBR Green 1. The abundance of Karenia was assessed in samples from Outer Oslofjorden (Station OF2) collected monthly from August 2011 to June 2012, and 10 stations in Skagerrak collected during a cruise in April/May 2012. According to the qPCR assay, Karenia was present in all samples at station OF2, with a peak in August and September and with very low numbers in February, March, April and May. Karenia was also identified by light microscopy of net hauls (20 μm mesh) in both August and September. Cell counts were performed on the same samples and Karenia was only recorded in September (180 000 cells L-1). At the stations of the 2012 April/May Skagerrak cruise the abundance of Karenia was either very low or below the detection limit of our qPCR assay and Karenia was not observed by microscopy in any of the corresponding cell counts or net hauls. These results demonstrate that the qPCR assay was more sensitive than traditional counting methods using light microscopy in the detection of Karenia. In addition to traditional microscopy based methods, qPCR assays can be a powerful tool in the identification and quantification of Karenia and other harmful algae and may prove especially useful if applied in early warning programs.

• Brubak, Sissel Irene; Eikrem, Wenche; Fredriksen, Stein & Edvardsen, Bente (2013). Algal culture collection at the University of Oslo. Full text in Research Archive Show summary

  Algekultursamlingen ved Universitetet i Oslo ble startet på 1950-tallet ved avdeling for Marin botanikk til bruk i eksperimentelle og taksonomiske studier. Samlingen har gjennomgått stadige forandringer og vært preget av pågående forskningsprosjekter. I dag består samlingen av mer enn 200 stammer av eukaryote og prokaryote marine mikroalger innen algedivisjonene Haptophyta, Dinophyta, Chlorophyta, Ochrophyta, Cryptophyta, Cyanophyta, Euglenozoa og Chloraracniophyta. De fleste stammene er isolert fra norske kystfarvann og ved fortynningsserier eller kapillærisolering av ansatte ved instituttet. De dyrkes i ulike sjøvannsmedier med saltholdighet fra 10 til 40 PSU, i 7 klimarom med temperaturer fra 3 til 25 °C. Nåværende samling har blitt utviklet blandt annet for forskning relatert til alger innen divisjonen Haptophyta, og inkluderer 85 stammer av denne gruppen. Samlingen inneholder flere "type-kulturer" som representerer en ny art beskrevet av UiO-forskere, og flere toksiske stammer. Algekulturene er en sentral del av forskningen og undervisningen om mikroalgers taksonomi, fylogeni, økologi, fysiologi, kjemi, genomikk og evolusjon ved instituttet. Kulturer sendes også til andre forskere i inn- og utland. Algekultursamlingen er en verdifull ressurs som også kan utnyttes innen bioprospektering og bioteknologi.

• Edvardsen, Bente; Egge, Elianne Sirnæs; Bittner, Lucie; Eikrem, Wenche; Audic, Stéphane & Andersen, Tom [Show all 9 contributors for this article] (2012). Diversity and dynamics of marine haptophytes as revealed by 454 pyrosequencing. Full text in Research Archive Show summary

  Haptophytes are microalgae and a major component of marine plankton communities. Our aim is to provide new knowledge on the diversity and distribution of haptophytes below the genus-level, and how this is affected by environmental factors. We have developed and tested methods for analysing diversity using 454-pyrosequencing, We designed haptophyte-specific rDNA primers and constructed haptophyte databases and phylogenies for taxonomic assignation. We sequenced an artificial haptophyte community and compared the diversity and relative abundances from DNA and RNA/cDNA using various rDNA primers, and different programs to 18 remove errors from sequence data. We applied 454-pyrosequencing to samples from six European coastal sites and seasonal samples from Oslofjorden, and combined this with electron microscopy. We propose a strategy to more accurately depict the haptophyte diversity using 454-pyrosequencing and present results using this strategy.

• Edvardsen, Bente; Egge, Elianne Sirnæs; Bittner, Lucie; Audic, Stéphane & Vargas, Colomban de (2012). A strategy for 454-pyrosequencing of ribosomal SSU DNA and RNA to more accurately assess protist diversity and relative abundance. Full text in Research Archive Show summary

  Next generation sequencing of ribosomal DNA is increasingly used to assess the biodiversity and structure in microbial communities. Our aim was to develop a method to depict the diversity and community structure of marine planktonic haptophytes to species level. We used a mock community consisting of equal number of cells of 11 species representing all known haptophyte orders to investigate the ability to detect and assess the number of species present, and assess the relative abundance in terms of cell numbers and biomass by 454-pyrosequencing. We compared DNA to RNA/cDNA, 454-pyrosequencing to Sanger sequencing of clone libraries, and two different V4-SSU rDNA haptophyte biased primer pairs. Further, we tested 5 different strategies to clean the sequence data from errors. Up to 6000 unique tags per sample (with avg. 16500 reads) were obtained before sequence cleaning and clustering, and higher diversity was obtained from cDNA than DNA. The distribution of reads assigned to a species was significantly different from the initial proportions of cells or biomass in the culture mix, but cell numbers were better reflected by proportion of cDNA than DNA reads. Here we propose a strategy to more accurately depict the haptophyte diversity and assess relative abundance using 454-pyrosequencing.

• Hostyeva, Vladyslava; Dittami, Simon; Skylstad, Viljar Alain; Eikrem, Wenche & Edvardsen, Bente (2012). Seasonal dynamics of harmful algae in the outer Oslofjord monitored using microarrays, qPCR, and microscopy. Full text in Research Archive
• Edvardsen, Bente (2012). Diversity and dynamics of marine haptophytes and their viruses (HAPTODIV). Full text in Research Archive Show summary

  Haptophytes are microalgae and a major component in marine pico- and nanoplankton communities. They often occur in bloom concentrations that may have a major impact on the global carbon balance and climate forcing ,besides sometimes causing fish-kills. Because haptophytes are small and difficult to identify under the light microscope little is known about their seasonal dynamics and ecological role below the genus level. In the ongoing project HAPTODIV we aim at providing new knowledge about the diversity and dynamics of haptophytes, and how species composition, diversity and their abundances are affected by their viruses and environmental factors. We have developed, tested and applied a strategy for analysing diversity using 454-pyrosequencing, and combine this with environmental clone libraries, electron microscopy, qPCR and flow cytometry. We have used an artificial haptophyte community consisting of 11 cultured species to investigate the ability of 454-pyrosequencing in detection and assessment of the number of species present, and the assessment of relative abundance in terms of cell numbers and biomass. We compared DNA to RNA/cDNA, and 454-pyrosequencing to Sanger sequencing of clone libraries using two different V4-SSU rDNA haptophyte-specific primer pairs, and five different strategies to clean the sequence data from errors. I will further present some results on the diversity and dynamics of haptophytes and their viruses using this strategy.

• Gerecht, Andrea Cornelia; Hostyeva, Vladyslava; Edvardsen, Bente; Probert, Ian & Henderiks, Jorijntje (2012). How does phosphorus limitation impact coccolith size and morphology? Full text in Research Archive
• Gerecht, Andrea Cornelia; Hostyeva, Vladyslava; Edvardsen, Bente; Probert, Ian & Henderiks, Jorijntje (2012). How does phosphorus limitation impact coccolith size and morphology? Full text in Research Archive
• Egge, Elianne Sirnæs; Eikrem, Wenche; Hostyeva, Vladyslava; Andersen, Tom; Bittner, Lucie & Johannesen, Torill [Show all 9 contributors for this article] (2012). Diversity and seasonal dynamics of haptophytes in outer Oslofjorden revealed by 454 pyrosequencing. Full text in Research Archive
• Egge, Elianne Sirnæs; Eikrem, Wenche; Hostyeva, Vladyslava; Andersen, Tom; Bittner, Lucie & Johannesen, Torill [Show all 9 contributors for this article] (2012). Diversity and seasonal dynamics of haptophytes in outer Oslofjorden revealed by 454 pyrosequencing. Full text in Research Archive
• Egge, Elianne Sirnæs; Eikrem, Wenche; Andersen, Tom & Edvardsen, Bente (2012). HAPTODIV-Diversity and dynamics of marine haptophytes. Full text in Research Archive
• Vrålstad, Trude; Strand, David; Edsman, Lennart; Edvardsen, Bente; Engdahl, Fredrik & Fristad, Rosa Ferreira [Show all 14 contributors for this article] (2012). Hunting the crayfish plague disease agent in water sources – challenges and possibilities. Full text in Research Archive Show summary

  The specialized North American crayfish parasite and oomycete Aphanomyces astaci causes crayfish plague in European crayfish. Infectious A. astaci zoospores are released from American carrier crayfish and from diseased or dead European crayfish. The A. astaci spore quantity in the ambient water of crayfish will therefore largely reflect disease outbreaks in European crayfish or carrier status in American crayfish. During the past few years, molecular methods detecting A. astaci directly from crayfish tissues has become widely accepted. Now, the first studies employing A. astaci specific qPCR directly from water samples are approaching. Monitoring waterways could facilitate early warning of A. astaci infections, improve risk assessments, and reveal of infection reservoirs. It might also serve as a supplementary tool for declaring crayfish stocks and water bodies infection free in nature and aquaculture. Over the past three years, we have worked on this topic in a Nordic collaborative project. Here, we present methodological experiences e.g. sampling volumes, filtration methods, and subsequent molecular analyses. Possibilities and challenges connected to the transition from laboratory, via aquaria models, to natural environments are discussed. Furthermore, unknown diversity of oomycetes resembling A. astaci in the target DNA motif challenges the reliability of qPCR results, both from crayfish and natural environmental samples. We have therefore identified means that increase the probability of distinguishing between possibly true and false positives. These include qPCR optimizations, and use of a decision support tool that evaluates the qPCR result reliability on the basis of linearity (R2) and amplification efficiency of the PCRs.

• Egge, Elianne Sirnæs & Edvardsen, Bente (2011). QUANTIFICATION OF HAPTOPHYTE SPECIES BY PYROSEQUENCING: IS READ ABUNDANCE PROPORTIONAL TO CELL NUMBERS? Journal of Phycology. ISSN 0022-3646. 47, p. S63–S63. Full text in Research Archive
• Dittami, Simon; Riisberg, Ingvild; John, U.; Paulsen, B. Smestad; Tonon, Thierry & Jakobsen, Kjetill Sigurd [Show all 7 contributors for this article] (2011). DIVERSE ORIGINS OF HETEROKONT GENES - NEW INSIGHTS FROM A DICTYOCOPHYTE EST LIBRARY. Journal of Phycology. ISSN 0022-3646. 47, p. S17–S17. Full text in Research Archive
• Egge, Elianne Sirnæs & Edvardsen, Bente (2011). HAPTODIV - Diversity and dynamics of marine haptophytes. Full text in Research Archive
• Dittami, Simon; Medlin, Linda K. & Edvardsen, Bente (2011). Microarray detection of toxic algae. Full text in Research Archive
• Edvardsen, Bente & Eikrem, Wenche (2011). Fish-killing algal problems in Norway. Full text in Research Archive Show summary

  The aquaculture industry in Norway produced 940 000 metric tons salmon and trout to a value of 22 billion NOK in 2009 and is the world’s largest producer of farmed salmon. Ichthyotoxic algae may however cause large economic losses for fish farmers in Norway. Harmful algal blooms has been a threat to fish farms in Norway ever since its early era in the early70-ies. In the period 1974-1991 the dinoflagellate Karenia mikimotoi (=Gyrodinium aureolum) formed blooms almost yearly that at times discolored the water brown and caused recurrent fish kills in fish farms along the Skagerrak coast. In 1988 the haptophyte Chrysochromulina polylepis formed the possibly most extensive and toxic bloom ever recorded, killing not only farmed fish but also feral fauna and flora in the Skagerrak and Kattegat off the coasts of Norway, Sweden and Denmark. While this bloom appeared to be a unique event, the related haptophyte Prymnesium parvum formed recurrent blooms in a brackish-water fjord system in Ryfylke, W Norway that caused fish kills in the period 1989-1995. The fish farms were then moved from the most affected fjord arms and when they started up again in 2006 Prymnesium parvum again formed ichthyotoxic blooms. The haptophyte Chrysochromulina leadbeateri similarly killed farmed fish during several years (1991, 2000, 2003, and 2010) in the Lofoten area in N Norway. During the last decade another algal group has caused problems for fish farmers in Norwegian waters, the dictyochophytes, represented by Pseudochattonella and recently Dictyocha species. Pseudochattonella was for the first time recorded in bloom concentrations in N European waters in 1998, and it has been speculated whether it may have been introduced from Asia by ballast water. In 2001, Pseudochattonella formed a massive ichthyotoxic bloom in the Skagerrak and Kattegat, this time in cold waters (2-6 °C). Cultures were isolated, examined and found to represent a new species, Pseudochattonella farcimen, differing in rDNA sequence, ultrastructure and growth preferences from the previously known P. verruculosa (=Chattonella verruculosa), first reported from Japan. Since then Pseudochattonella has been recorded in the Kattegat and Skagerrak yearly and some years in bloom concentrations (e.g. 2006, 2011). The most recent ichthyotoxic algal flagellate to be recorded in Norwegian waters is the silicoflagellate Dictyocha fibula. It may occur in a naked form without the typical silica-skeleton (speculated to be identical to ‘Chattonella globosa’), in bloom concentrations together with the skeleton-bearing form. Fish-kills have occurred since 2007 along the W and S coast of Norway in waters dominated by this species. All these ichthyotoxic species have several features in common. They are nanoplanktonic (size range approx. 5-30 µm in diameter) flagellates with yellow-brown plastids of a haptophyte origin. They usually form blooms after the diatom spring bloom in stratified waters. Some have been shown to be mixotrophic. The toxin structure, production and toxicity are not well understood. Despite ample studies to elucidate factors influencing toxin production and growth we do still not fully understand what triggers the toxicity and bloom formation. Functional genomics may contribute to fill some of these gaps.

• Edvardsen, Bente & Egge, Elianne Sirnæs (2011). QUANTIFICATION OF HAPTOPHYTE SPECIES BY PYROSEQUENCING: IS READ ABUNDANCE PROPORTIONAL TO SPECIES BIOVOLUME? Full text in Research Archive Show summary

  Amplicon-sequencing of ribosomal RNA genes has become a standard for assessing microbial diversity in environmental samples. Abundance is of interest in addition to presence/absence of species to assess their ecological importance. The proportion of DNA sequences/reads from a particular species may, however, not reflect the proportion of the species in a sample in terms of cell number. We investigated the relationship between cell number and biovolume in an artificial community of haptophyte species, and the number of DNA sequences/reads appearing in libraries produced by cloning and 454-pyrosequencing nucleic acids extracted from this community. One million cells from each of 11 haptophyte species were pooled, and DNA and RNA extracted, and the V4 region of the small subunit ribosomal gene was amplified using haptophyte specific primers. The amplicons were sequenced by 454-pyrosequencing or Sanger sequencing. Pyrosequencing with 17000 reads per sample recovered all species in the culture mix, whereas clone libraries with 50-80 sequences per sample only recovered <50% of the species. Our results show that the proportion of reads from the different species in the 454-libraries were significantly different from the proportion of cells in the pool. There was a positive correlation between cell volume and read abundance, and thus cell size should be taken into account when interpreting 454-sequence data quantitatively.

• Bittner, Lucie; Gobet, Angelique; Egge, Elianne Sirnæs; Audic, Stéphane; Santini, Sebastien & Ogata, Hiroyuki [Show all 10 contributors for this article] (2011). Diversity of Haptophyta in the Bay of Naples as revealed by next generation sequencing (NGS): "anything new under the sea"? Full text in Research Archive
• Egge, Elianne Sirnæs & Edvardsen, Bente (2011). QUANTIFICATION OF HAPTOPHYTE SPECIES BY PYROSEQUENCING: IS READ ABUNDANCE PROPORTIONAL TO SPECIES BIOVOLUME? Full text in Research Archive
• Johansen, Renate; Miles, Christopher; Egaas, Eliann; Rundberget, Thomas & Edvardsen, Bente (2011). Are fish-killing algae a problem in Norwegian fish farming? Full text in Research Archive
• Edvardsen, Bente; Nersveen, Lars; Torgrimsby, Tonie Leonora; Engesmo, Anette; Egge, Elianne Sirnæs & Eikrem, Wenche (2011). Diversity and distribution of nano- and picoeukaryotes in the Southern Ocean as revealed by 454-pyrosequencing, clone libraries and microscopy. Full text in Research Archive Show summary

  In this study we explored the diversity and distribution of planktonic nano- and picoeukaryotes in Antarctic waters by combining 454-pyrosequencing, clone libraries and electron microscopy. Water samples were collected and physico-chemical parameters measured during summer 2008 with the Norwegian R/V G.O. Sars in the Atlantic sector of the Southern Ocean, at stations along a transect (15°E) between 45-67o S. Ribosomal DNA of plankton in the size range 0.8-35µm was amplified with universal eukaryotic and haptophyte specific primers followed by pyro- and Sanger sequencing. Most rDNA sequences could not be assigned to a cultured and sequenced species (at ≥99,3% identity level) indicating that a large fraction of the plankton community remains to be genetically characterized. Electron microscopy revealed some of this diversity, but more cultured strains are needed as reference for a precise identification. The taxonomic groups represented with highest number of clones/reads were dinoflagellates, stramenopiles and haptophytes. The species composition was significantly different at the northernmost station compared to further south, suggesting that nano- and picoeukaryote species composition and distribution may serve as indicators of climate change in polar waters.

• Dittami, Simon; Riisberg, Ingvild; John, Uwe; Paulsen, B. Smestad; Tonon, Thierry & Jakobsen, Kjetill Sigurd [Show all 7 contributors for this article] (2011). Diverse origins of heterokont genes – insights from a dictyocophyte est library. Full text in Research Archive
• Edvardsen, Bente & Eikrem, Wenche (2011). Species committee for microalgae in the Norwegian Artsdatabanken. Full text in Research Archive
• Miles, Christopher; Rundberget, Thomas; Egaas, Eliann; Johansen, Renate & Edvardsen, Bente (2011). Fish-killing algae—a chemical perspective. Full text in Research Archive
• Iversen, Svein Arnholt; Melle, Webjørn Raunsgård; Edvardsen, Bente; Krafft, Bjørn Arne; Skaret, Georg & Søiland, Henrik (2010). The Antarctic krill and ecosystem survey (AKES) with G.O. Sars in 2008. Full text in Research Archive
• Strand, David; Holst-Jensen, Arne; Viljugrein, Hildegunn; Edvardsen, Bente; Klaveness, Dag & Jussila, Japo [Show all 7 contributors for this article] (2010). Detection of crayfish plague (Aphanomyces astaci) directly from aquatic environments. Full text in Research Archive Show summary

  The oomycete Aphanomyces astaci is a specialized parasite on freshwater crayfish of North American origin, but also the causative agent for crayfish plague. A. astaci is ranked among the world’s top 100 invasive alien species, as it has caused (and still causes) large economical and ecological damage since its introduction into Europe, destroying indigenous European freshwater crayfish populations. Recently developed polymerase chain reaction (PCR) and real-time PCR assays for the specific detection of A. astaci in crayfish tissues have drastically improved crayfish plague diagnostics compared to earlier methods. However, little is known about the presence and dynamic of A. astaci spores in infected water systems. Here, we present an approach for detecting and quantifying A. astaci directly from water samples using a species specific TaqMan® MGB real-time PCR assay, thus providing new tools for further research, and for surveillance of crayfish plague in aquatic environments. Samples of a 10-fold dilution series from ~10000 to ~1 spore of A. astaci were repeatedly tested, demonstrating reliable detection down to one spore. Further, to simulate practical samples from natural water bodies, water samples from lakes with different water quality were spiked with spores. The results demonstrated that co-extracted impurities inhibit detection, but the use of bovine serum albumin (BSA) or the TaqMan® Environmental Master Mix largely removes this problem. Finally, we demonstrate the practical performance of the approach on samples from aquatic environments hosting infected North American signal crayfish (Pacifastacus leniusculus).

• Vrålstad, Trude; Strand, David; Edvardsen, Bente; Holst-Jensen, Arne; Jussila, Japo & Klaveness, Dag [Show all 7 contributors for this article] (2010). Molecular detection of crayfish plague (Aphanomyces astaci) in aquatic environments. Full text in Research Archive Show summary

  The oomycete Aphanomyces astaci (crayfish plague) is ranked among the world's 100 worst invasive alien species. This specialized parasite has caused large ecological and economical damage, killing off indigenous European freshwater crayfish. Recently developed polymerase chain reaction (PCR) and real-time PCR assays for detection of A. astaci in crayfish tissues have accelerated and improved crayfish plague diagnostics compared to earlier methods. A further step in the surveillance and management of crayfish and crayfish plague is direct monitoring of the oomycete in aquatic environments. We present an approach for detecting and quantifying A. astaci directly from water samples using species specific TaqMan® MGB real-time PCR. Samples of a 10-fold dilution series from ~10000 to ~1 spore of A. astaci were repeatedly tested, and reliable detection down to one spore was demonstrated. To simulate practical samples from natural water bodies, water samples from lakes with different water quality were spiked with spores. The results showed that co-extracted humic acids inhibit detection drastically. However, the use of bovine serum albumin (BSA) or the TaqMan® Environmental Master Mix largely removes this problem. Finally, we demonstrate the practical performance of the approach on samples from aquatic environments hosting infected North American signal crayfish (Pacifastacus leniusculus).

• Strand, David; Holst-Jensen, Arne; Viljugrein, Hildegunn; Klaveness, Dag; Edvardsen, Bente & Vrålstad, Trude (2010). Detection of crayfish plague in water and environment. Full text in Research Archive Show summary

  Den sopplignende organismen Aphanomyces astaci er kjent for å forårsake krepsepest. Denne patogene organismen kommer opprinnelig fra Nord Amerika, hvor den har evolvert sammen med nordamerikansk ferskvannskreps i et tett vert-parasitt forhold. Hyfer eller trådlignende strukturer av A. astaci vokser inn i skallet til krepsen. Arter av nordamerikansk kreps har utviklet et forsvar mot parasitten og hemmer dens vekst i skallet. Infeksjonen er dermed harmløs for disse krepsene. Ved infeksjon i europeisk kreps vil hyfene vokse igjennom skallet og videre inn i krepsen fordi denne ikke har utviklet et forsvar mot parasitten. Denne infeksjonen er dødelig for europeisk kreps. Når krepsen dør vil A. astaci produsere aseksuelle zoosporer som er i stand til å svømme; disse frigjøres i vannet for å finne ny kreps å leve på. Det er usikkert hvor lenge A. astaci klarer seg i naturen uten en krepsevert, og om parasitten klarer å overleve på andre organismer eller substrater. Da A. astaci ble introdusert til Europa for over hundre år siden, spredte den seg raskt igjennom Europa og forårsaket massedød av europeisk kreps. Etterfølgende introduksjoner av nordamerikansk kreps til Europa har økt frekvensen av krepsepestutbrudd dramatisk da disse er bærere av krepsepest. Nordamerikansk kreps utgjør derfor et konstant smittereservoar som truer europeisk kreps. Også i Norge har det vært gjentatte utbrudd av krepsepest, noe som truer de norske populasjonene av edelkreps. Siden 2006 har man ved tre tilfeller avslørt ulovlig introdusert signalkreps (en nordamerikansk ferskvannskreps) i Norge, og disse er bærere av krepsepest. Dette øker risikoen for nye krepspestutbrudd og utgjør en stor trussel mot edelkrepsen. Både signalkreps og A. astaci er oppført som høyrisiko arter på den norske svartelista over fremmede arter som ble første gang utgitt i 2007 og edelkreps står på internasjonal og nasjonal rødliste over truede arter. Norske myndigheter ønsker å ta vare på den sterkt truede edelkrepsen og jobber med strategier for bedre å kunne hindre spredning av krepsepest og signalkreps. Det er derfor essensielt å få økt kunnskap om økologien til A. astaci og utvikle gode verktøy for overvåking av krepsepest. Gjennom ”Miljø 2015” har Forskningsrådet bevilget midler til prosjektet ”Avansert overvåking av introdusert krepsepest for bedre forvaltning av truet freskvannskreps”. Det er nylig utviklet molekylære metoder som vesentlig forbedrer våre muligheter til å påvise krepsepest direkte i infisert kreps. Med dette verktøvet kan man detektere DNA’et (arvemassen) til A. astaci i krepsevev, noe som gjør det mulig å rask diagnostisere kreps for krepsepest. Ved å modifisere og videreutvikle disse metodene håper vi å kunne detektere krepsepest direkte i vann og miljøprøver, for å få økt kunnskap om økologien til A. astaci og for å få et raskt og effektivt verktøy overvåking av krepsepest. Prosjektet startet opp i slutten av 2008. Vi har så langt undersøk om det er mulig å påvise A. astaci sporer fra diverse vannprøver (kunstig tilsatt sporer). Prøvene har blitt filtrert og vi har analysert prøvene for A. astaci DNA. Vi har klart å påvise A. astaci i prøvene, men enkelte ferskvann inneholder stoffer (f.eks. humuspartikler) som er med på å blokkere påvisning av krepsepest DNA. Enkelte vann inneholder også mye partikler, noe som gjør det vanskelig å filtrere store mengder vann. Dette er utfordringer som vi jobber med for å løse. Vi har også vært ute i felt og tatt prøver fra vann og miljø, hvor vi vet det lever signalkreps infisert med krepsepest. Disse prøvene vil bli analysert når metoden er forbedret. Vi ønsker også å undersøke om A. astaci overlever på andre verter og substrater og å utvikle metoder for å undersøke ulike linjer (genotyper) av krepsepest og hvor aggressive/dødelige disse er.

• Torgrimsby, Tonie Leonora; Broms, Cecilie; Kaartvedt, Stein; Vestheim, Hege Finsås & Edvardsen, Bente (2010). Diet studies of Antarctic krill (Euphausia superba) using DNA as a biomarker. Full text in Research Archive Show summary

  Antarctic krill, Euphausia superba, is a major grazer on phytoplankton, and an important link between primary producers and organisms at higher trophic levels. The ability to determine krill feeding preferences is thus vital for the understanding of trophic interactions and processes that structure the Antarctic ecosystem. Microscopical analysis of stomach content can only identify prey with hard resistant parts. In this study, the diet of Antarctic krill was examined by using DNA as a biomarker. The diet was compared with potential food organisms present in the surrounding water. The material was collected during austral summer 2008 with the Norwegian research vessel G.O. Sars in the Atlantic sector of the Southern Ocean, at stations along two parallel N-S transects between 45-67o S, at ~15° and ~5°E. A station near the Bouvet Island with high abundance of krill and relatively high chlorophyll-a levels was compared with an open ocean station with low krill abundance and chlorophyll-a levels. To identify prey organisms in krill stomachs and surrounding water we constructed clone libraries based on SSU and LSU rDNA sequences, and compared these with observations under the light microscope. Upon analysis of krill stomachs we used a blocking oligos to inhibit the amplification of krill DNA, but not DNA from prey. Clone libraries of the surrounding water showed the presence of various diatoms (e.g. members of Chaetoceros, Fragilariopsis, Rhizosolenia, Corethron), dinoflagellates, haptophytes, prasinophytes, pelagophytes, bolidophytes, cryptophytes, dictyochophytes, ciliates, members of Telonemia, apicomplexans, radiolarians and copepods. Microscopical analysis of stomach content, revealed frustules of various diatoms and the dictyochophyte Dictyocha speculum. Presently, clone libraries of stomach content of krill are produced. This will give us new knowledge on preferences in the diet of Antarctic krill in parts of the Atlantic Southern Ocean with no previous studies of this kind.

• Nersveen, Lars; Eikrem, Wenche; Andersen, Tom & Edvardsen, Bente (2010). Diversity and distribution of nano- and picoplankton in Antarctic and Arctic waters. Full text in Research Archive Show summary

  Information on the diversity, distribution and abundance of pico- (0.2-2 µm) and nano-plankton (2-20 µm), that cannot be identified to species level under the light microscope, is still limited. The aim of this study is to explore the pico- and nano-eukaryotic diversity and distribution in Antarctic and Arctic waters by advanced microscopy and molecular biological techniques, such as environmental clone libraries and 454-pyrosequencing. Another aim is to obtain new information on the influence of environmental factors on the plankton biodiversity and species composition in polar waters. Water samples and net hauls were collected and physical and chemical parameters measured during austral summer 2008 with the Norwegian R/V G.O. Sars in the Atlantic sector of the Southern Ocean, at stations along a N-S transect between 45-67o S at 15°E. During summer 2009, stations were sampled with the R/V Lance along an E-W transect from Spitsbergen into the Fram Strait. The Antarctic transect was conducted in open ocean, while the Arctic took place in a fjord, open ocean and along the ice edge. Water samples were size fractioned (>3, 45-3 and 3-0.6 µm) by filtration on board, for DNA isolation and analysis in the laboratory. Clone libraries are under construction and massive parallel tag sequencing will be tried to explore the diversity of planktonic pico- and nanoeukaryotes and their distribution along the transects. Light and scanning electron microscopy will be used as a comparison. We have a focus on the algal division Haptophyta, an important component of the pico- and nano-plankton community in the ocean. The study may give new information on plankton diversity and distribution in polar waters, as well as on differences in ecosystem functioning between the Southern Ocean and Arctic waters.

• Engesmo, Anette; Eikrem, Wenche; Lundholm, Nina & Edvardsen, Bente (2010). Fragilariopsis and Pseudo-nitzschia species (Bacillariophyceae) in the Antarctic and Arctic: distribution, morphology and genetic variation. Full text in Research Archive Show summary

  The pennate diatom genera Pseudo-nitzschia and Fragilariopsis are common components of the phytoplankton community in Antarctic and Arctic waters and are important primary producers. Cryptic and pseudo-cryptic species of these genera occur, and electron microscopy and molecular methods are here required for a precise species identification. The aim of this study is to determine which species of Pseudo-nitzschia and Fragilariopsis that are present in different polar water masses, which species appear to be bipolar, and do strains from Antarctic and Arctic waters differ morphologically and genetically. The material from the Atlantic sector of the Southern Ocean was collected during a cruise with R/V G.O. Sars during summer 2008 along a N-S transect at 15°E between 45-67°S, while the material from the Arctic was collected along a E-W transect from Svalbard into Fram Strait summer 2009 with R/V Lance. Water samples, net hauls, and hydrographical data were collected and algal cultures started onboard on both cruises. More than 50 diatom strains from Antarctic and about 20 from Arctic waters have been established. Preserved and live algal material have been examined in the light and electron microscope, and 8 different Fragilariopsis species were observed from one Antarctic station. The cultured strains have been identified to species by electron microscopy (SEM and TEM) and analysed genetically, using coding (LSU) and non-coding (ITS) ribosomal DNA sequences as markers. Genetic examination of Fragilariopsis from the Antarctic shows that ITS, but not LSU rDNA can discriminate between closely related species. Our ITS rDNA sequence data suggests two genotypes in culture of the F. cylindrus and F. nana ‘species-complex’, differing from those previously reported. Our results will link morphology with genetic signature and geographic origin, and will give new knowledge on their genetic variability and distribution.

• Edvardsen, Bente (2010). Diversity and distribution of nano- and picoplankton in polar seas. Full text in Research Archive
• Hostyeva, Vladyslava; Eikrem, Wenche & Edvardsen, Bente (2010). Annual cycle of Pseudo-nitzschia species in the outer Oslofjord, Norway. Full text in Research Archive Show summary

  Monitoring of microalgae, including toxic species like Pseudo-nitzschia , is based on light microscopy; nevertheless precise identification of Pseudo-nitzschia at the species level requires verification by electron microscopy and/or molecular biological tools. Earlier investigations from Norwegian waters have shown a considerable variation in the species composition of the genus Pseudo-nitzschia, both geographically and seasonally. The genus contains more than 30 species and many of them are found in Norwegian waters (e.g. P. delicatissima, P. fraudulenta, P. granii, P. heimii, P. pungens, P. multiseries, P. calliantha. P. seriata and P. americana). Several species of Pseudo-nitzschia have been shown to be toxic, including P. seriata, P. callianta, P. delicatissima, P. multiseries and P. fraudulenta, which all may occur in Norwegian waters. Vertical net tows (0-20 m), quantitative water samples and hydrographical data have been collected monthly over one year, from June 2009 to June 2010, in the outer Oslofjord, southern Norway. The succession of Pseudo-nitzschia species have been recorded from acid cleaned samples viewed in the scanning electron microscope and transmission electron microscope. The abundance of Pseudo-nitzschia species has been determined and related to hydrographical conditions. The ability to produce domoic acid varies between species, thus a precise identification and knowledge about their geographical and seasonal occurrence at the species level is important to early warning systems serving the aquaculture industry.

• Sildever, Sirje; Edvardsen, Bente; Egge, Elianne Dunthorn; Engesmo, Anette; Harðardóttir, Sara & Jacobsen, Ása [Show all 25 contributors for this article] (2025). Reliable environmental DNA detection of planktonic biodiversity: Minimum sample volume for DNA metabarcoding. Nordic Council of Ministers. ISSN 9789289381468. doi: 10.6027/temanord2025-509. Full text in Research Archive Show summary

  Environmental DNA (eDNA)-based detection has become an attractive method for determining biodiversity as it can provide more detailed information compared to traditional morphology-based approaches. This is especially relevant for targeting overall biodiversity or screening for the presence of harmful algal bloom (HAB) species. However, despite the availability of several general guidelines, the workflow for marine environments has yet to be standardised. This lack of standardisation complicates the comparison between samples across different monitoring programmes and projects. This project focused on the first step of the workflow – determining and standardising the minimum reliable sample volume needed to detect phytoplankton diversity under various environmental and biological conditions. A study and a workshop were conducted to test different sample volumes (1000 mL, 500 mL, 200 mL, and 20 mL), using samples collected from the Baltic and North Seas and northwestern Atlantic Ocean under various environmental conditions. Across the studied samples, 200 mL was identified as a sufficient sample volume to detect various species across the different volumes tested. This result represents an important first step towards standardising the eDNA-based approach and incorporating it into routine monitoring. Furthermore, the results of this project are expected to contribute to reducing the time and resources required for monitoring.

• Fon, Mathias; Edvardsen, Bente; Solhaug, Anita; Uhlig, Silvio; Ivanova, Lada & Andersen, Tom (2025). Insight into the growth, toxicity and toxins of the fish-killing haptophyte Chrysochromulina leadbeateri. University of Oslo (UiO). Full text in Research Archive
• Reitzel, Helene; Edvardsen, Bente; Šupraha, Luka & Heuschele, Jan David (2023). The ichthyotoxic algae Chrysochromulina leadbeateri – an investigation into favorable conditions for growth and toxicity. Universitetet i Oslo. Full text in Research Archive Show summary

  Harmful algal blooms can be devastating to local ecosystems as well as have major impacts on economy and aquaculture. Chrysochromulina leadbeateri caused the death of an estimated seven and a half million farmed salmon in 2019, and the cause of this bloom is still unknown. While the growth and toxicity of other toxic prymnesiophytes have been examined, we still know little about optimal conditions for growth and toxicity of Chrysochromulina leadbeateri. In this thesis I have examined the growth of C. leadbeateri in controlled conditions, and how different salinities and temperatures affects the growth rate. I also examined the toxicity and whether or not I could induce it in a laboratory setting, and whether phosphorous limitation or other temperatures or salinities could play a role. I conducted three growth experiments. The first to establish a relationship between cell density and chlorophyll a fluorescence measurements. The second and third growth experiments were used to establish how different temperatures and salinities affected the strains of C. leadbeateri and how the different conditions affected growth rate as well as establish tolerance limits. Low temperatures and low salinities seemed to affect growth negatively, while optimum growth conditions were at 15°C and a salinity between 25 and 30. I recommend that the growth experiments are replicated with the inclusion of higher temperatures to establish where the upper temperature limit is, as well as repeat the temperatures used to get a better understanding of growth at 11°C as the equipment here had some flaws. I performed three Artemia bioassay experiments. The first showed that the cultures did not become more toxic after growing in phosphorous limited conditions compared to those that hadn’t. The second and third Artemia bioassay experiments were performed to see whether temperature or salinity played a role in inducing toxicity, as well as where in the growth phase the cultures were. Cultures that were in their stationary stage were toxic to Artemia nauplii, and this seemed to play a larger role in inducing toxicity than temperature or salinity.

• Tran, Jacquelynn Phuong-Vy; Edvardsen, Bente; Fon, Mathias; Heuschele, Jan David & Titelman, Josefin (2023). When hungry meets harmful: investigating the toxic relationship between haptophytes and copepods. Predatory induced defenses in Chrysochromulina leadbeateri. Universitetet i Oslo. Full text in Research Archive Show summary

  Harmful algal blooms are a recurring phenomenon all around the world, causing devastating effects including massive fish kills. A bloom of the toxic haptophyte, Chrysochromulina leadbeateri, in Northern Norway during May-June 2019 was the largest bloom ever recorded in that area causing massive mortalities of farmed salmon. While past C. leadbeateri blooms are known to cause such damage, relatively little is known about this toxic haptophyte, compared to other species. Some studies have investigated the bloom dynamics and abiotic factors influencing its toxicity, but little is known about the biotic influences. In particular, the predator-prey interactions with copepods. Past studies have found that when other species are directly exposed to predation threats (e.g. herbivorous copepods), the algae will respond by inducing and/or increasing toxicity potential as a defense mechanism. Those studies have focused on toxic diatoms and dinoflagellates producing shellfish toxins, but the potential for fish-killing algae to be influenced by predation pressure remains to be explored. In this thesis, I examined the biotic interactions between the toxic C. leadbeateri and the grazing Acartia sp. copepods. I first conducted a series of 3-day tolerance experiments, exposing Acartia sp. to different C. leadbeateri concentrations to answer: What is the threshold C. leadbeateri concentration that Acartia sp. can maintain survival and grazing? Then I conducted 3-day induction experiments, exposing C. leadbeateri to varying levels of grazing pressure, and in vitro tests using two fish cell lines to measure this potential grazing-induced toxicity to answer: Does the presence of copepod grazers affect toxicity in the ichthyotoxic haptophyte C. leadbeateri? Through the initial tolerance experiments, I determined that ca. 5 x 104 cells ml-1 of C. leadbeateri was the threshold concentration that enough Acartia sp. could survive and maintain feeding for the later toxicity induction experiments. Acartia sp. short-term tolerance to direct exposure to C. leadbeateri appeared to be concentration and time-dependent since the toxins need to be taken up by Acartia sp. to cause mortalities. Copepod grazing habits observed during the induction experiment appeared unaffected when C. leadbeateri was the only food source, as evidenced by fecal pellet production. However to accurately determine the effects of grazing on C. leadbeateri, future studies should observe grazing periodically with Acartia sp. exposed to different C. leadbeateri concentrations and non-toxic food alternatives. I examined whether the toxicity of C. leadbeateri was influenced by the presence of grazing copepods using in vitro tests on two fish (Rainbow trout and Atlantic salmon) cell lines to measure cell viability and light microscopy to look at morphological changes. I created different concentrations of algal extracts from crude C. leadbeateri material exposed to varying grazing levels. The different extracts were exposed to the gill cells in a microplate-based assay for 24 hours and at the endpoint, cell viability was measured using Alamar blue as an indicator dye. It seems that while increasing algal extract concentration decreases cell viability, extract made from C. leadbeateri exposed to increasing grazing pressure does not increase the negative effects on cell viability. The light micrographs of the gill cells suggest the same, but with some inclination that grazing pressure does affect some toxicity potential in C. leadbeateri. Unfortunately, with the lack of more independent trials, there is no statistical analyses to back up these claims. More experiments would allow for proper analyses and a potentially more conclusive statement about the relationship between copepod grazing and the toxicity potential of C. leadbeateri. This thesis can be used as a starting point for future research on the dynamics between toxic haptophytes and their copepod grazers.

• Walbækken, Hanna Myhre; Eikrem, Wenche; Edvardsen, Bente; Saubrekka, Karoline & Hofgaard, Antje (2023). Dinoflagellate diversity in the Barents Sea: a comparative identification analysis. Universitetet i Oslo. Full text in Research Archive
• Dankel, Eli; Supraha, Luka; Edvardsen, Bente; Eikrem, Wenche & Saubrekka, Karoline (2023). Arktiske kalkflagellater: et morfologisk og molekylært dypdykk i det nordlige Barentshavet. Universitetet i Oslo. Full text in Research Archive Show summary

  Oppblomstringer av kalkflagellater utgjør et viktig fundament for næringskjeden i Barentshavet. Fjernanalyse med satellittbilder har de siste tiårene dokumentert at denne oppblomstringen beveger seg nordover i takt med økende klimaendringer. Det er likevel fortsatt uvisst hva som skjer på artsnivå. Å forstå hvordan forekomsten til den enkelte art forandrer seg i møte med endrede miljøbetingelser, som redusert is og økende temperatur, gjør at man enklere kan forutse hvordan fytoplanktonsamfunnet vil respondere på et fremtidig, varmere Arktis. For denne oppgaven ble det hentet inn vannprøver fra syv stasjoner på et sør-nord-transekt i Barentshavet i august 2018 og 2019 under tokt i regi av forskningsprosjektet Arven etter Nansen (AeN). 2018 var globalt et av de varmeste årene på mange tiår, og Barentshavet var dermed isfritt den sommeren. I 2019 derimot var større deler av Barentshavet dekket av is. Prøver tatt for både svepeelektronmikroskopi (scanning electron microscopy, forkortet «SEM») og metastrekkoding (metabarcoding) ble brukt i oppgaven slik at resultatene fra metodene kunne sammenlignes. Formålet med SEM var å utføre både en kvalitativ og kvantitativ analyse av kalkflagellater. Metastrekkoding ble brukt til sekvensering av 18S rRNA-genet. I SEM fant jeg i prøvene fra 2018 Emiliania huxleyi, Coccolithus pelagicus, Papposphaera sarion, Papposphaera arctica, Wigwamma annulifera og Porsildia acerviphora. Utenom Coccolithus pelagicus og Wigwamma annulifera, ble de samme artene funnet i 2019. I tillegg ble Syracosphaera Marginiporata funnet i prøver fra et AeN-tokt i november-desember 2019. Artene fra 2018 var hovedsakelig til stede på den sørligste stasjonen i transektet, mens artene fra 2019 generelt ble funnet på flere forskjellige stasjoner. Fra metastrekkoding ble det registrert 13 OTUer (Operational Taxonomic Units) som er bestemt til kalkflagellat-taksa. Ettersom det stort sett mangler referansesekvenser for arktiske kalkflagellater, ble de fleste OTUene kun klassifisert til klasse eller orden. OTUene var for det meste til stede i prøvene fra den sørligste, og de to nordligste stasjonene. Det ble ikke observert et nevneverdig mønster i sammenheng med isdekket. Det ble derimot både for SEM og metastrekkoding observert at de fleste artene var til stede på stasjoner som i ulik grad ble påvirket av Den nordatlantiske havstrømmen. Resultatene er likevel ikke holdbare nok til å trekke en konklusjon om hvordan kalkflagellatsamfunnet i Barentshavet vil se ut i fremtiden. Ettersom de fleste OTUene viste lav taksonomisk oppløsning, og alle celler funnet i SEM ble bestemt til artsnivå, anbefaler jeg at SEM forblir den foretrukne metoden for kvalitativ og kvantitativ analyse av kalkflagellater.

• Edvardsen, Bente; Gryn, Khrystyna; Šupraha, Luka; Eikrem, Wenche & Saubrekka, Karoline (2023). Biodiversity and distribution of Arctic phytoplankton and ice algae. Universitetet i Oslo. Full text in Research Archive
• Røsbak, Silje K.; Edvardsen, Bente; Eiler, Alexander; Saubrekka, Karoline & Fon, Mathias (2023). Mikrobielt samfunn i kulturer av Chrysochromulina leadbeateri og relaterte svepeflagellater, undersøkt med metastrekkoding. Universitetet i Oslo. Full text in Research Archive Show summary

  Skadelige marine algeoppblomstringer er et tilbakevendende problem over hele verden, der skadene har en påvirkning på økosystemer og lokal økonomi. Chrysochromulina leadbeateri var årsak til en massiv fiskedød i 2019, men mekanismene bak denne oppblomstringen er fortsatt ukjent. Målet med oppgaven var å undersøke bakteriediversiteten i kulturer av den fiske-giftige Chrysochromulina leadbeateri, og sammenligne denne mot andre beslektede svepeflagellater, både hos potensielt giftige og ikke-giftige arter. I tillegg til dette ble bakteriediversiteten av mikrobiomet mellom fastsittende bakterier på algecellene og frittlevende bakterier i kultur undersøkt. I denne oppgaven ble det prokaryote mikrobiomet i kulturer av tre stammer av Chryochromulina leadbeateri og 6 stammer av beslektede svepeflagellatarter analysert. Dette ble gjort ved metastrekkoding av det ribosomale 16S rRNA-genet. Det ble påvist et mangfoldig mikrobiom der hele bakteriedatasettet inneholdt 3 rekker, 14 ordener og 53 slekter. Bakteriesamfunnets sammensetning bestod hovedsakelig av medlemmer i rekken Proteobacteria etterfulgt av medlemmer av rekken Bacteroidota, og kun noen få ASVer i rekken Actinobacteria. Av de 14 ordenene var Rhodobacterales, Flavobacteriales, Caulobacterales, Rhiszobiales og Cytophagales de mest vanlige. Av de 53 slektene var Marivita (Rhodobacterales) den mest abundante, etterfulgt av Roseovarius (Rhodobacterales), Jannaschia (Rhodobacterales), Hoefla (Rhizobiales), Seohaeicola (Rhodobacterales), Hyphomonas (Rhodobacterales) og Sulfitobacter (Rhodobacterales). Taksonomisk fordeling av bakterieslekter mellom de potensielt giftige og ikke-giftige svepeflagellatene viste forskjeller, der de potensielt giftige hadde flest unike identifiserte bakterieslekter. Når det gjelder alfadiversitet (forskjeller innad i et samfunn) viser de to gruppene derimot ingen store forskjeller i mikrobiomet. Det ble funnet en svak signifikant sammenheng i mikrobiomets betadiversitet (forskjeller mellom samfunn) mellom kulturer av potensielt giftige og ikke-giftige svepeflagellater, der svepeflagellatens giftighet innen slekt hadde en svak effekt i denne studien. I tillegg viste slekten til svepeflagellaten til å ha en signifikant betydning for hvilke bakteriearter som ble funnet i algekulturer. Ved en sammenligning av fordelingen av bakterieslekter som er fastsittende til algecellen og frittlevende i algekultur, deler de to gruppene 80 % av bakterieslektene, og har dermed høy likhet. De frittlevende bakteriene har høyest antall ASVer, noe som indikerer at de fleste bakterie-typene lever fritt i kultur. Dette vises også ved de statistiske analysene, der alfadiversiteten for de frittlevende bakteriene i kultur har et signifikant rikere mikrobiom i forhold til fastsittende bakterier til algecellen. Betadiversiteten mellom fastsittende og frittlevende bakterier viser derimot ingen signifikante forskjeller, som vil si at mikrobiom-sammensetningen ikke kan forklares ut ifra om det er fastsittende på algecellene eller frittlevende i kultur.

• Assmy, Philipp; Gradinger, Rolf Rudolf; Edvardsen, Bente; Wold, Anette; Goraguer, Lucie Hélène Marie & Wiktor, Józef [Show all 8 contributors for this article] (2022). Phytoplankton biodiversity Nansen Legacy Q3. Norwegian Polar Institute. Full text in Research Archive
• Assmy, Philipp; Gradinger, Rolf Rudolf; Edvardsen, Bente; Wold, Anette; Goraguer, Lucie Hélène Marie & Wiktor, Jozef [Show all 7 contributors for this article] (2022). Phytoplankton biodiversity Nansen Legacy JC1. Norwegian Polar Institute. Full text in Research Archive
• Assmy, Philipp; Gradinger, Rolf Rudolf; Edvardsen, Bente; Wold, Anette; Goraguer, Lucie Hélène Marie & Wiktor, Jozef (2022). Phytoplankton biodiversity Nansen Legacy Q1. Norwegian Polar Institute. Full text in Research Archive
• Assmy, Philipp; Gradinger, Rolf Rudolf; Edvardsen, Bente; Wold, Anette; Goraguer, Lucie Hélène Marie & Wiktor, Jozef [Show all 8 contributors for this article] (2022). Phytoplankton biodiversity Nansen Legacy JC2-1. Norwegian Polar Institute. Full text in Research Archive
• Assmy, Philipp; Wold, Anette; Gradinger, Rolf Rudolf; Edvardsen, Bente; Wiktor, Jozef & Tatarek, Agnieszka [Show all 7 contributors for this article] (2022). Ice algae biodiversity Nansen Legacy JC2-2. Norwegian Polar Institute. Full text in Research Archive
• Assmy, Philipp; Gradinger, Rolf Rudolf; Edvardsen, Bente; Wold, Anette; Goraguer, Lucie Hélène Marie & Wiktor, Jozef [Show all 8 contributors for this article] (2022). Ice algae biodiversity Nansen Legacy Q1. Norwegian Polar Institute. Full text in Research Archive
• Assmy, Philipp; Gradinger, Rolf Rudolf; Edvardsen, Bente; Goraguer, Lucie Hélène Marie; Wiktor, Józef & Tatarek, Agnieszka [Show all 7 contributors for this article] (2022). Ice algae biodiversity Nansen Legacy JC2-1. Norwegian Polar Institute. Full text in Research Archive
• Assmy, Philipp; Gradinger, Rolf Rudolf; Edvardsen, Bente; Wold, Anette; Goraguer, Lucie Hélène Marie & Wiktor, Jozef [Show all 7 contributors for this article] (2022). Ice algae biodiversity Nansen Legacy Q3. Norwegian Polar Institute. Full text in Research Archive
• Assmy, Philipp; Gradinger, Rolf Rudolf; Edvardsen, Bente; Wold, Anette; Goraguer, Lucie Hélène Marie & Wiktor, Jozef [Show all 7 contributors for this article] (2022). Ice algae biodiversity Nansen Legacy Q4. Norwegian Polar Institute. Full text in Research Archive
• Assmy, Philipp; Gradinger, Rolf Rudolf; Edvardsen, Bente; Wold, Anette; Goraguer, Lucie Hélène Marie & Wiktor, Jozef [Show all 7 contributors for this article] (2022). Ice algae biodiversity Nansen Legacy JC1. Norwegian Polar Institute. Full text in Research Archive
• Assmy, Philipp; Gradinger, Rolf Rudolf; Edvardsen, Bente; Wiktor, Józef; Tatarek, Agnieszka & Dabrowska, Anna Maria (2022). Phytoplankton biodiversity Nansen Legacy Q4. Norwegian Polar Institute. Full text in Research Archive
• Assmy, Philipp; Gradinger, Rolf Rudolf; Edvardsen, Bente; Wold, Anette; Wiktor, Jozef & Tatarek, Agnieszka [Show all 8 contributors for this article] (2022). Phytoplankton biodiversity Nansen Legacy JC2-2. Norwegian Polar Institute. Full text in Research Archive
• Assmy, Philipp; Gradinger, Rolf Rudolf; Edvardsen, Bente; Wold, Anette; Goraguer, Lucie Hélène Marie & Wiktor, Józef [Show all 8 contributors for this article] (2022). Phytoplankton biodiversity Nansen Legacy Q2. Norwegian Polar Institute. Full text in Research Archive
• 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. Full text in Research Archive 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.

• Strand, David; Vrålstad, Trude; Edvardsen, Bente & Klaveness, Dag (2013). Environmental DNA monitoring of the alien crayfish plague pathogen Aphanomyces astaci in freshwater systems - Sporulation dynamics, alternative hosts and improved management tools. Faculty of Mathematics and Natural Sciences. Full text in Research Archive

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