title: Seasonal diversity and dynamics of haptophytes in the Skagerrak, Norway, explored by high-throughput sequencing.
abstract: 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.
authors.affiliation: Department of Biosciences, University of Oslo, PO Box 1066, 0316, Oslo, Norway.
authors.forename: Elianne Sirnaes
authors.initials: ES
authors.lastname: Egge
authors.affiliation: Marine Microbiology, Department of Biology, University of Bergen, PO Box 7803, 5006, Bergen, Norway.
authors.forename: Torill Vik
authors.initials: TV
authors.lastname: Johannessen
authors.affiliation: Department of Biosciences, University of Oslo, PO Box 1066, 0316, Oslo, Norway.
authors.forename: Tom
authors.initials: T
authors.lastname: Andersen
authors.affiliation: Department of Biosciences, University of Oslo, PO Box 1066, 0316, Oslo, Norway.|Norwegian Institute for Water Research, Gaustadalléen 21, 0349, Oslo, Norway.
authors.forename: Wenche
authors.initials: W
authors.lastname: Eikrem
authors.affiliation: CNRS FR3631, Institut de Biologie Paris-Seine, F-75005, Paris, France.|Sorbonne Universités, UPMC Univ Paris 06, Institut de Biologie Paris-Seine (IBPS), F-75005, Paris, France.
authors.forename: Lucie
authors.initials: L
authors.lastname: Bittner
authors.affiliation: Uni Research Environment, Thormøhlensgate 49b, N-5006, Bergen, Norway.|Hjort Centre for Marine Ecosystem Dynamics, N-5006, Bergen, Norway.
authors.forename: Aud
authors.initials: A
authors.lastname: Larsen
authors.affiliation: Marine Microbiology, Department of Biology, University of Bergen, PO Box 7803, 5006, Bergen, Norway.
authors.forename: Ruth-Anne
authors.initials: RA
authors.lastname: Sandaa
authors.affiliation: Department of Biosciences, University of Oslo, PO Box 1066, 0316, Oslo, Norway.
authors.forename: Bente
authors.initials: B
authors.lastname: Edvardsen
mesh_terms: D044822:Biodiversity; D017931:DNA Primers; D004275:DNA, Ribosomal / Q000235:genetics; D004777:Environment; D058087:Haptophyta / Q000145:classification*; D059014:High-Throughput Nucleotide Sequencing; D008969:Molecular Sequence Data; D009664:Norway; D010802:Phylogeny; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D012621:Seasons; D012623:Seawater; D017422:Sequence Analysis, DNA
chemical_list: D017931:DNA Primers; D004275:DNA, Ribosomal; D012337:RNA, Ribosomal, 18S
keywords: Haptophyta; diversity; high-throughput sequencing; multivariate analysis; phytoplankton; seasonality