Data from: Seasonal diversity and dynamics of haptophytes in the Skagerrak, Norway, explored by high-throughput sequencing

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（Haptophyta）的微藻在海洋生态系统及全球生物地球化学循环中发挥着关键作用。尽管其生态重要性显著，但由于细胞体型微小且光学显微镜下可观测的形态特征有限，学界对其物种层级的季节动态、群落组成与丰度的认知仍较为匮乏。
本研究依托高通量测序获得的分类学分辨率与采样深度，呈现了基于两个年度周期的定鞭藻门季节多样性与动态的独有数据。研究于挪威南部奥斯陆峡湾外海域，以月度为间隔采集了为期两年的纳米级与皮克级浮游生物样本，通过定鞭藻门特异性18S rDNA V4引物对RNA/cDNA进行扩增以靶向富集定鞭藻门类群。经严格的生物信息学过滤与99.5%相似度聚类后，我们从约40万条454焦磷酸测序读段中获得了156个操作分类单元（operational taxonomic units，OTUs）。其中绝大多数OTU所代表的是尚未完成纯培养或未进行18S rDNA测序的物种。
定鞭藻门OTU的丰富度与群落组成呈现出较强的时间变异性与显著的年周期性：物种丰富度峰值出现在9月至10月（秋季），谷值则见于4月至5月（春季）。部分类群可全年被检测到，如简单定鞭金藻（Chrysochromulina simplex）、赫氏球石藻（Emiliania huxleyi）与囊状棕囊藻（Phaeocystis cordata）；而多数钙化颗石藻类仅在夏季至初冬时段出现。本研究同时揭示了代表疑似新纲（HAP-3~5演化支）或新目（D、E、F演化支）的OTU的季节动态模式。
季节、光照与温度可解释29%的OTU群落组成变异，剩余变异或与生物相互作用（如种间竞争与病毒感染）相关。本研究为北大西洋近岸海域定鞭藻门的季节多样性与动态提供了全新的深度认知。