Spatial Redistribution Characteristics of Bacterial Communities in a Micro-Tidal Influenced Estuary

Abstract

Microbial community variation in estuaries has been a research hotspot in recent years, but the effects of hydrodynamic forces on bacterial community redistribution have received less attention. This study conducted a fixed-point observation of bacterial community redistribution under hydrodynamic influence during both dry and wet seasons. Alpha diversity analysis revealed that the bacterial community in the dry season exhibited higher abundance and diversity than in the wet season, likely due to weaker hydrodynamics and lower temperatures. Specific taxa and co-occurrence networks differed between particle-associated (PA) and free-living (FL) bacterial communities, influenced by various hydrodynamic factors. The FL community was more affected by surface meridional flow, while the PA community was more influenced by bottom flow. It is speculated that FL community variation results from the mixing of seawater and river water bacteria, which are more affected by surface currents. While, PA community variation arises from sedimentation and bottom flow transportation of particles. Correlation analysis indicated more significant results between PA taxa and flow one hour ahead, suggesting that the redistribution of bacteria in the particle attachment state under water flow influence is not instantaneous. This study's analysis of the differential behavior of PA and FL communities driven by hydrodynamic forces enriches the understanding of factors influencing bacterial community variation in estuaries.

Keywords: amplicon sequencing, bacteria community, tidal redistribution, particle-associated, free-living, estuary