The diverse physicochemical conditions prevailing in the Arabian Sea are expected to result in marked spatial variations in heterotrophic flagellate (HF) and ciliate communities. Here, we report the environmental association of heterotrophic micro-eukaryotes, particularly the heterotrophic flagellates and ciliates, based on 18S rRNA gene survey in the region. High-throughput next-generation sequencing, using the V4 eukaryotic-specific primer, was employed to study the composition of these communities associated with low-O₂ waters in both coastal and offshore settings. Canonical correspondence analysis (CCA) revealed a preference of the heterotrophic flagellates for nitrate- and nitrite-rich zones. Notably, the heterotrophic nanoflagellate genus Monosiga showed a strong positive correlation with NO₃⁻, which suggests its potential denitrifying capability. Shannon’s entropy analysis revealed a higher HF diversity in the hypoxic waters of the open ocean (depth 103 m), whereas ciliates were more diverse at oxygenated coastal stations. The estuarine waters exhibited a low diversity of both ciliates and flagellates. The UPGMA clusters of heterotrophic flagellates and ciliates in suboxic waters of the open ocean oxygen minimum zone were distinct from those found at other sites. Overall, CCA revealed the important relationship between nitrite, nitrate, salinity and chlorophyll a, which could be important factors for the partitioning of different ecological niches for specific HF and ciliate communities in the Arabian Sea. The community of heterotrophic protists that can adapt to varying biogeochemical regimes has been identified.

阿拉伯海普遍存在的各种理化条件有望导致异养鞭毛虫和纤毛虫群落的空间发生明显变化。在这里，我们根据该地区的18S rRNA基因调查报告了异养微真核生物，特别是异养鞭毛和纤毛的环境关联。使用V4真核生物特异性引物进行的高通量下一代测序被用于研究沿海和近海环境中与低O ₂水有关的这些群落的组成。典型对应分析（CCA）显示，异养鞭毛虫偏爱富含硝酸盐和亚硝酸盐的区域。值得注意的是，异养纳米鞭毛藻属Monosiga显示出与NO很强的正相关性₃ ^- ，这表明其潜在的反硝化能力。Shannon的熵分析表明，在公海低氧水域（深度103 m）中，HF的多样性更高，而在含氧海岸站，纤毛虫的多样性更高。河口水的纤毛和鞭毛多样性低。在开放氧最小区域的低氧水域中，异养鞭毛和纤毛虫的UPGMA团簇与其他地点的UPGMA团簇不同。总体而言，CCA揭示了亚硝酸盐，硝酸盐，盐度和叶绿素a之间的重要关系。，这可能是针对阿拉伯海特定的HF和纤毛虫群落划分不同生态位的重要因素。已经确定了可以适应不同生物地球化学方案的异养原生生物社区。