Instituto Tecnológico de Chascomús (INTECH), Universidad Nacional de San Martín-Consejo Nacional de Investigaciones Científicas y Técnicas, Av. Intendente Marino Km 8.200, (7130) Chascomús, Buenos Aires, Argentina.
University of Brest, CNRS, IRD, Ifremer, LEMAR, F-29280, Plouzané, France.
FEMS Microbiol Ecol. 2021 Aug 17;97(9). doi: 10.1093/femsec/fiab114.
East African Great Lakes are old and unique natural resources heavily utilized by their bordering countries. In those lakes, ecosystem functioning is dominated by pelagic processes, where microorganisms are key components; however, protistan diversity is barely known. We investigated the community composition of small eukaryotes (<10 µm) in surface waters of four African Lakes (Kivu, Edward, Albert and Victoria) by sequencing the 18S rRNA gene. Moreover, in the meromictic Lake Kivu, two stations were vertically studied. We found high protistan diversity distributed in 779 operational taxonomic units (OTUs), spanning in 11 high-rank lineages, being Alveolata (31%), Opisthokonta (20%) and Stramenopiles (17%) the most represented supergroups. Surface protistan assemblages were associated with conductivity and productivity gradients, whereas depth had a strong effect on protistan community in Kivu, with higher contribution of heterotrophic organisms. Approximately 40% of OTUs had low similarity (<90%) with reported sequences in public databases; these were mostly coming from deep anoxic waters of Kivu, suggesting a high extent of novel diversity. We also detected several taxa so far considered exclusive of marine ecosystems. Our results unveiled a complex and largely undescribed protistan community, in which several lineages have adapted to different niches after crossing the salinity boundary.
东非大湖是古老而独特的自然资源，被其周边国家广泛利用。在这些湖泊中，生态系统功能主要由浮游生物过程主导，其中微生物是关键组成部分；然而，原生生物多样性却鲜为人知。我们通过测序 18S rRNA 基因，研究了四个非洲湖泊（基伍、爱德华、阿尔伯特和维多利亚）表层水中的小型真核生物（<10μm）群落组成。此外，在分层的基伍湖中，我们对两个站位进行了垂直研究。我们发现了分布在 779 个操作分类单元（OTUs）中的高原生生物多样性，涵盖了 11 个高级分类群，其中最具代表性的超类群是纤毛门（31%）、后口动物（20%）和不等鞭毛类（17%）。表层原生生物群落与电导率和生产力梯度有关，而深度对基伍湖的原生生物群落有很强的影响，其中异养生物的贡献更高。约 40%的 OTUs 与公共数据库中报道的序列相似度较低（<90%）；这些 OTUs 主要来自基伍湖的深层缺氧水域，表明存在大量新颖的多样性。我们还检测到了一些迄今为止被认为是海洋生态系统所特有的分类群。我们的研究结果揭示了一个复杂且在很大程度上未被描述的原生生物群落，其中有几个类群在穿过盐度边界后，已经适应了不同的小生境。
