To understand the importance of picoeukaryotes in the biogeochemical cycle in the subtropical Kuroshio Current, a year‐round survey of the hydrography and the distribution of picoeukaryotes were conducted in four oceanographic cruises from October 2012 to July 2013. In comparison with other seasons, the highest abundancy of photosynthetic picoeukaryotes, with concentrations >10⁴ cells/ml, was observed around the eastern boundary of the Kuroshio in the winter. Accordingly, the composition of picoeukaryotes in this cold season was further studied by a metabarcoding analysis of the 18S rRNA gene. The majority of picoeukaryotes comprised Alveolata, followed by Haptophyta and Stramenopiles. Their composition was diverse in the waters affected by the Kuroshio and in the offshore province. For Haptophyta, in contrast to clade A prevailing in the Kuroshio waters, clade B1, which was considered the host of uncultivated diazotrophic cyanobacterium group A (UCYN‐A), appeared only in the offshore area. Similarly, in Stramenopiles, Pseudo‐nitzschia spp. and MAST‐1D, respectively, dominated in the Kuroshio‐influenced and offshore areas. While Alveolata was the most abundant group, the distributions of all lineages were similar. The association between picoeukaryote succession and hydrographic change is yet to be fully understood. Our results will assist future studies on the community composition of picoplankton and their relationship with marine ecology in the region.

中文翻译：

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冬季亚热带黑潮潮流中丰富的微核生物的空间变化

为了了解亚热带黑潮洋流中微生真核生物在生物地球化学循环中的重要性，于2012年10月至2013年7月进行了四次海洋航行，全年进行了水文学和微生真核生物分布的调查。与其他季节相比，最高浓度> 10 ⁴的光合微核生物的丰度 在冬季，在黑潮东边界附近观察到细胞数量/毫升。因此，通过对18S rRNA基因的元条形码分析，进一步研究了在这个寒冷季节中微核生物的组成。大部分的微核生物由小叶藻组成，其次是七叶植物和超大型变色龙。在受黑潮影响的水域和近海省份中，它们的成分各不相同。与黑潮水域盛行的进化枝A相反，对于七足植物而言，进化枝B1被认为是未经培养的重氮营养蓝藻群A（UCYN‐A）的宿主，仅出现在近海区域。同样，在Stramenopiles中，假性尼采spp。和MAST-1D分别在受黑潮影响的地区和近海地区占主导地位。Alveolata是最丰富的族群，但所有谱系的分布都相似。皮古真核生物演替与水文变化之间的联系尚待充分了解。我们的研究结果将有助于未来对浮游生物的群落组成及其与该地区海洋生态的关系的研究。