Ciliates are globally distributed eukaryotic organisms inhabiting virtually all environments on Earth. Although ciliates range from 10 µm to a few millimetres in cell size, they are repeatedly reported in the pico‐sized fraction (<2–3 µm) of molecular surveys. Here, we used existing data sets (BioMarKs and Tara Oceans) with different size fractions to demonstrate that the ciliate pico‐sized signal, probably derived from cell breakage during filtration, is informative and reliable to study marine ciliate biodiversity and biogeography. We then used sequences from the pico‐eukaryotic fraction of two circumnavigation expeditions, Malaspina‐2010 and Tara Oceans, to give insights into the taxonomic composition and horizontal and vertical distribution of ciliates in the global ocean. The results suggested a high homogeneity of ciliate communities along the ocean surface from temperate to tropical waters, with ciliate assemblages dominated by a few abundant and widely distributed taxa. Very few taxa were found in a single oceanic region, therefore suggesting a high level of ciliate cosmopolitanism in the global ocean. In vertical profiles, ciliates were detected up to 4,000 m depth, and a clear vertical community structuring was observed. Our results provided evidence supporting ciliates as deeply integrated organisms in the deep‐sea trophic web, where they may play a relevant role as symbionts of metazoans and grazers of prokaryotes and small eukaryotes in the water column and in aggregates.

中文翻译：

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在公海中水平和垂直尺度上纤毛虫的多样性和分布。

纤毛虫是遍布地球上几乎所有环境的遍布全球的真核生物。尽管纤毛的细胞大小从10 µm到几毫米不等，但在分子调查的皮克级分数（<2-3 µm）中屡屡报道。在这里，我们使用了具有不同大小比例的现有数据集（BioMarKs和Tara Oceans）来证明纤毛皮克大小的信号（可能源自过滤过程中的细胞破裂）对于研究海洋纤毛生物的多样性和生物地理学是可靠而可靠的。然后，我们使用来自两次环游探险的Malaspina-2010和Tara Oceans的皮真核生物部分的序列，来深入了解纤毛虫在全球海洋中的分类学组成以及水平和垂直分布。结果表明，从温带到热带水域，沿海表面的纤毛虫群落具有高度的同质性，纤毛虫群落以一些丰富且分布广泛的类群为主导。在单个海洋区域中发现的分类单元很少，因此表明全球海洋中有高度的纤毛世界主义。在垂直剖面中，检出纤毛虫至4,000 m深，并观察到清晰的垂直群落结构。我们的结果提供了证据，证明纤毛虫是深海营养网中的深层整合生物，它们可能在水柱和聚集体中作为后生动物的共生体，原核生物和小型真核生物的放牧者的共生体。在单个海洋区域中发现的分类单元很少，因此表明全球海洋中有高度的纤毛世界主义。在垂直剖面中，检出纤毛虫至4,000 m深，并观察到清晰的垂直群落结构。我们的结果提供了证据，证明纤毛虫是深海营养网中的深层整合生物，它们可能在水柱和聚集体中作为后生动物的共生体，原核生物和小型真核生物的放牧者的共生体。在单个海洋区域中发现的分类单元很少，因此表明全球海洋中有高度的纤毛世界主义。在垂直剖面中，检出纤毛虫至4,000 m深，并观察到清晰的垂直群落结构。我们的结果提供了证据，证明纤毛虫是深海营养网中的深层整合生物，它们可能在水柱和聚集体中作为后生动物的共生体，原核生物和小型真核生物的放牧者的共生体。