Intense tidal uplift and accumulation of multiple nutrients are defining characteristics of estuaries, especially for those in mountainous rivers. Though previous contributions have been conducted to explore the microbial community structure in estuarine sediments, the responses of prokaryotic communities to hydrodynamic disturbances and nutrient accumulation, as well as the depth-dependent assembly patterns in intertidal sediments remain largely unknown. Taking a small mountainous river estuary as an example, the bacterial and archaeal community compositions, assembly patterns and driving factors were profiled from four sites varying in hydrodynamic forcing and nutrient levels. Frequent alterations in hyporheic exchange directions were detected, with upwelling and downwelling flow dominated when tide receded and upon tidal inundation, respectively. The average exchange flux in seaward region was signally higher (P < 0.05) than in riverward area. The contents of TOC, TN, TP and NH4+ in seaward sediments were substantially higher than those from riverward area (P < 0.05). The hydrodynamic perturbation facilitated the species dispersal in seaward sediments, with nutrient accumulation simultaneously increasing the α diversity therein. Consequently, the amplified environmental filtering led to the decline in β diversity. Homogeneous selection (HoS) within deterministic processes (26.4 ∼ 42.5 %) in the seaward sediments were signally higher than those from riverward regions (20.6 ∼ 27.5 %). Hyporheic flux is proven key driving factor (P < 0.001) governing HoS and diffusion limitation in riverward sediments. While NH4+ dominantly controlled the HoS and drift in seaward samples (P < 0.001). More complex co-occurrence network and reinforced inter/intraspecies interactions were observed in seaward sediments compared with riverward samples. Similar patterns were also witnessed in deep sediments than in superficial layers. We firstly explained how hydrodynamic and nutrients co-shape the depth-dependent prokaryotic community assembly patterns in the intertidal zone, benefiting for the proposal of targeted ecological restoration measurements for nutrient reduction and habitat rehabilitation.

中文翻译：

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水动力学扰动和营养物质积累共同塑造了山区河流河口潮间带沉积物中深度依赖性原核生物群落组装


强烈的潮汐上升和多种营养物质的积累是河口的决定性特征，尤其是山区河流中的河口。尽管之前已经为探索河口沉积物中的微生物群落结构做出了贡献，但原核生物群落对水动力干扰和营养积累的响应，以及潮间带沉积物中深度依赖性的组装模式在很大程度上仍然未知。以一个小山区河流河口为例，从流体动力学强迫和营养水平不同的 4 个地点分析了细菌和古细菌群落的组成、组装模式和驱动因素。检测到低流交换方向的频繁变化，分别在潮汐退去和潮汐泛滥时，上升流和占主导地位。向海区的平均交换通量明显高于向江区 （P < 0.05）。向海沉积物中 TOC、TN、TP 和 NH4+ 含量显著高于沿江区（P < 0.05）。水动力扰动促进了物种在向海沉积物中的扩散，养分积累同时增加了其中α多样性。因此，放大的环境过滤导致β多样性下降。向海沉积物中确定性过程 （26.4 ∼ 42.5 %） 内的均质选择 （HoS） 明显高于河流区域的均质选择 （HoS） （20.6 ∼ 27.5 %）。事实证明，低流通量是控制河流沉积物中 HoS 和扩散限制的关键驱动因素 （P < 0.001）。而 NH4+ 主要控制向海样品的 HoS 和漂移 （P < 0.001）。 与河流样本相比，在向海沉积物中观察到更复杂的共现网络和增强的种间/种内相互作用。在深层沉积物中也观察到了与表层类似的模式。我们首先解释了水动力学和营养物质如何共同塑造潮间带深度依赖性原核生物群落组装模式，有利于提出有针对性的生态恢复测量以减少营养物和栖息地恢复。