Author(s): Longfei Wang; Yi Li; Jiaying Chen; Lihua Niu
Linked Author(s): Longfei Wang
Keywords: Intertidal zones Hyporheic exchange Prokaryotic community Assembly patterns
Abstract: Estuaries are experiencing intense tidal uplift and accumulation of nutrients, especially for those in mountainous rivers. The responses of prokaryotic communities to hydrodynamic disturbances and nutrient accumulation, and 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 superficial sediments than in deep 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.
Year: 2025