Egge Elianne Sirnaes, Johannessen Torill Vik, Andersen Tom, Eikrem Wenche, Bittner Lucie, Larsen Aud, Sandaa Ruth-Anne, Edvardsen Bente
Department of Biosciences, University of Oslo, PO Box 1066, 0316, Oslo, Norway.
Marine Microbiology, Department of Biology, University of Bergen, PO Box 7803, 5006, Bergen, Norway.
Mol Ecol. 2015 Jun;24(12):3026-42. doi: 10.1111/mec.13160. Epub 2015 Apr 20.
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.
定鞭藻门的微藻在海洋生态系统和全球生物地球化学过程中发挥着关键作用。尽管它们具有生态重要性，但由于其细胞体积小且在光学显微镜下可见的形态特征较少，关于物种水平的季节动态、群落组成和丰度的知识仍然有限。在此，我们展示了来自两个年度周期的定鞭藻季节多样性和动态的独特数据，这些数据具有通过高通量测序获得的分类分辨率和采样深度。从挪威南部奥斯陆峡湾外海，每月采集纳米和微微型浮游生物样本，为期两年，并用定鞭藻门特异性18S rDNA V4引物扩增RNA/cDNA来靶向定鞭藻。经过严格的生物信息学过滤和99.5%的聚类后，我们从约400,000条454焦磷酸测序读数中获得了156个操作分类单元（OTU）。大多数OTU代表未培养和/或尚未进行18S rDNA测序的物种。定鞭藻OTU丰富度和群落组成表现出高度的时间变化和显著的年度周期性。丰富度在9月至10月（秋季）最高，在4月至5月（春季）最低。一些分类群全年都能检测到，如简单金藻、赫氏颗石藻和心形棕囊藻，而大多数钙化颗石藻仅在夏季至初冬出现。我们还揭示了代表假定新类群（HAP-3-5分支）或目（D、E、F分支）的OTU的季节动态。季节、光照和温度占OTU组成变化的29%。剩余的变化可能与生物因素有关，如竞争和病毒感染。本研究提供了关于北大西洋沿海水域定鞭藻季节多样性和动态的新的深入知识。
