Abstract：
Microbial communities assemble stochastically and deterministically, but how different assembly processes shape diatom community structure across riverine habitats is unclear, especially in sediment-laden environments. In this study, we deciphered the mechanisms of riverine diatom community assembly in the water column and riverbed substrate with varying sediment concentrations. Water and sediment samples were collected from 44 sampling sites along the Yellow River mainstream during two seasons. Diatom communities were characterized based on high-throughput sequencing of the 18S ribosomal RNA genes coupled with multivariate statistical analyses. A total of 198 diatom species were taxonomically assigned, including 182 free-living and particle-attached species and 184 surface-sediment species. Planktonic communities were structurally different from benthic communities, with Cyclotella being dominant mainly in the middle and lower reaches of the river with higher sediment concentrations. Both stochastic and deterministic processes affected diatom community assembly in different habitats. Species dispersal was more important in the water than in the substrate, and this process was strengthened by increased sediment concentration across habitats. Diatom communities exhibited lower network complexity and enhanced antagonistic or competitive interactions between species in response to higher sediment concentrations compared with lower sediment concentrations mainly in the source region of the river. Differences in the species composition and community diversity of planktonic diatoms were closely correlated with the proportion of bare land area, nitrogen nutrients, precipitation, and sediment concentration. In particular, particle-attached diatoms responded sensitively to environmental factors. These findings provide strong evidence for sediment-mediated assembly and interactions of riverine diatom communities.
摘要：
微生物群落随机和确定性地聚集，但是不同的组装过程如何塑造河流栖息地的硅藻群落结构尚不清楚，尤其是在充满沉积物的环境中。在这项研究中,我们破译了不同沉积物浓度的水柱和河床基质中河流硅藻群落聚集的机制。在两个季节中，从黄河干流的44个采样点收集了水和沉积物样本。硅藻群落的特征是基于18S核糖体RNA基因的高通量测序和多变量统计分析。总共对198种硅藻物种进行了分类分配，包括182种自由生活和颗粒附着物种和184种地表沉积物物种。浮游群落在结构上与底栖群落不同，Cyclotella主要在河流的中下游占主导地位，沉积物浓度较高。随机和确定性过程都会影响不同栖息地的硅藻群落组装。物种在水中的扩散比在基质中更重要，整个栖息地的沉积物浓度增加，加强了这一过程。与主要在河流源区的较低沉积物浓度相比，硅藻群落表现出较低的网络复杂性，并且物种之间的拮抗或竞争性相互作用增强，以响应较高的沉积物浓度。浮游硅藻物种组成和群落多样性的差异与裸露土地面积的比例密切相关，氮素养分，降水,和沉积物浓度。特别是,颗粒附着的硅藻对环境因素反应敏感。这些发现为沉积物介导的河流硅藻群落的组装和相互作用提供了有力的证据。
