Heterotrophic flagellates are essential components of the marine microbial food web. However, how the changes in flagellate populations reflect environmental changes in marine ecosystems is still unclear, especially in polar regions. In this study, we used pyrosequencing to examine the community structure of heterotrophic flagellates (HFs) in the Powell Basin’s surface waters of the northern Antarctic Peninsula. OTUs (operational taxonomic units) of different taxa and the correlations between community structure and environmental factors were analysed. Eight taxa of HFs were selected for the principal analysis: Telonemia, Picozoa, Rhizaria, Amoebozoa, Apusomonas, Centrohelida, Choanomonada and marine stramenopiles (MASTs). The HFs were defined as heterotrophic picoflagellates (HPFs; <3 μm) and heterotrophic nanoflagellates (HNFs; >3 μm, <20 μm), which had similar dominant phyla (MASTs and Telonemia). However, their taxonomic composition differed. Environmental factors exerted similar effects on the community structure of both HPFs and HNPs. Compared with the correlation between HPF and environmental factors, the correlation between HNF and environmental factors was stronger. Salinity, bacterial biomass and the biological interactions amongst dominant taxa were the main variables to influence the diversity and community structure of HFs.

异养鞭毛虫是海洋微生物食物网的重要组成部分。然而，鞭毛虫种群的变化如何反映海洋生态系统的环境变化尚不清楚，尤其是在极地地区。在这项研究中，我们使用焦磷酸测序来检查南极半岛北部鲍威尔盆地地表水中异养鞭毛虫 (HF) 的群落结构。分析了不同分类群的OTU（操作分类单元）以及群落结构与环境因素之间的相关性。选择了 8 个 HF 分类群进行主要分析：端粒虫、皮角虫、根瘤菌、变形虫、  Apusomonas、Centrohelida、Choanomonada 和海洋原生藻菌 (MAST)。HFs 被定义为异养皮鞭毛虫（HPFs；<3 μm）和异养纳米鞭毛虫（HNFs；>3 μm，<20 μm），它们具有相似的优势门（MASTs 和 Telonemia）。然而，它们的分类组成不同。环境因素对 HPFs 和 HNPs 的群落结构产生了相似的影响。与HPF与环境因素的相关性相比，HNF与环境因素的相关性更强。盐度、细菌生物量和优势类群之间的生物相互作用是影响 HF 多样性和群落结构的主要变量。