The effluents of wastewater treatment plants (WWTPs) represent a complex mixture of nutrients and toxic substances, thus, the potential exists for the effluents to significantly impact the biochemical characteristics and bacterial communities of the receiving water. We examined spatial and seasonal patterns, and the impact of effluents on microbial biomass, bacterial community structure, and metabolic diversity on a fourth-order stream. We took triplicate sediment samples at five different locations along a 5000 m transect over three sampling periods. We quantified bacterial community structure as community-level physiological profiles and microbial biomass with phospholipid phosphate analysis. Our findings highlight the worrisome impacts of effluents on microbial biomass and bacterial metabolic diversity on the receiving water. Microbial biomass was significantly higher at the WWTP outfall compared to upstream and downstream sites and correlated positively with sediment physicochemical parameters. Furthermore, our data revealed significant spatial differences in bacterial community structure in the context of WWTP impact. High nutrient availability (lower carbon/nitrogen ratios) at the outfall increased site-specific bacterial metabolic diversity in winter but decreased the same in fall. Seasonal changes in the sedimentary microbial biomass and bacterial carbon substrate utilization were evident regardless of the spatial variations or impacts of the wastewater effluents. Communities in fall showed more versatile substrate utilization patterns than the winter communities. These results suggest that WWTP effluents significantly increased microbial biomass and highlight its mixed effects on bacterial community structure and metabolic diversity. Also, our data underscore a close association between sedimentary physicochemical parameters and the associated microbial functional activities.

污水处理厂 (WWTP) 的出水是营养物质和有毒物质的复杂混合物，因此，出水可能会显着影响接收水的生化特征和细菌群落。我们研究了空间和季节模式，以及污水对微生物生物量、细菌群落结构和四阶流代谢多样性的影响。我们在三个采样周期内沿着 5000 m 横断面的五个不同位置采集了三次重复的沉积物样本。我们通过磷脂磷酸盐分析将细菌群落结构量化为群落水平的生理特征和微生物生物量。我们的研究结果强调了污水对受纳水体的微生物生物量和细菌代谢多样性的令人担忧的影响。与上游和下游站点相比，污水处理厂排放口的微生物生物量显着更高，并且与沉积物物理化学参数呈正相关。此外，我们的数据揭示了在污水处理厂影响背景下细菌群落结构的显着空间差异。排污口处的高养分利用率（较低的碳/氮比）在冬季增加了特定地点的细菌代谢多样性，但在秋季则减少了。无论废水排放的空间变化或影响如何，沉积微生物生物量和细菌碳底物利用的季节性变化都很明显。秋季群落显示出比冬季群落更多样化的基质利用模式。这些结果表明，污水处理厂出水显着增加了微生物生物量，并突出了其对细菌群落结构和代谢多样性的混合影响。此外，我们的数据强调了沉积物理化参数与相关微生物功能活动之间的密切关联。