尾水排放对受纳水体底栖生物膜细菌群落和水溶性有机质的影响机制

底栖生物膜是河流生态系统重要的初级生产者,能够对外界环境变化做出迅速响应,在河流碳循环过程中扮演重要角色.然而,人们对于污水处理厂尾水受纳河流底栖生物膜细菌群落与水溶性有机质(water-soluble organic matter,WSOM)的特征及内在联系的认识还十分有限.本研究使用16S rRNA高通量测序、紫外可见光谱和三维荧光-平行因子分析解析代表性污水处理厂尾水受纳区底栖生物膜细菌群落和WSOM的特征.结果表明,底栖生物膜WSOM中识别出两种类腐殖质组分和一种色氨酸类蛋白组分,其中大分子类腐殖质在底栖生物膜WSOM中占据优势地位.尾水区底栖生物膜细菌群落的均匀度及多样性沿程提高,相较于未受污染的上游区,污染源头区和污染下游区生物膜细菌群落结构更加稳定.发色水溶性有机质(colored water-soluble organic matter,CWSOM)、有机质芳香性和分子量是影响尾水区底栖生物膜细菌群落变化的主要因素,其中芳香性色氨酸类蛋白对生物膜细菌群落变化的解释度最高(34％).共现网络揭示了细菌群落与WSOM组分之间复杂的相互关系,Proteobacteria和Halobacterota通过碳循环过程参与生物膜WSOM的新陈代谢,生物膜细菌群落与WSOM的组成将以一种动态变化的模式对尾水排放做出响应.本研究为探寻尾水受纳区水生态变化的指示标志提供了新的思路.

Impacts of Wastewater Effluent Discharge on Bacteria Community and Water-soluble Organic Matter in Benthic Biofilm in Receiving River

Benthic biofilms, which respond rapidly to environmental alterations, are important primary producers and play an important role in the carbon cycle in riverine ecosystems. However, there is limited knowledge on the characteristics and linkages between water-soluble organic matter (WSOM) and bacterial communities in the benthic biofilm along the effluent-receiving river. In this study, an integrated use of 16S rRNA high-throughput sequencing, UV-vis spectroscopy, and EEM-PARAFAC analysis were employed to characterize WSOM and bacterial communities in benthic biofilm, and their relationships were investigated through a co-occurrence network. Two humic-like fractions and one tryptophan-like protein fraction were identified, with macromolecular humic fractions dominating the benthic WSOM. The uniformity and diversity of the benthic biofilm bacterial community increased along the effluent-receiving river, and the biofilm bacterial community structure in the downstream area of WWTP was more stable compared to that in the upstream area. Colored water-soluble organic matter, aromaticity, and molecular weight of organic matter were proven predominant factors influencing the benthic biofilm bacterial community, with aromatic tryptophan-like proteins explaining the highest change (34%) in the biofilm bacterial community. The co-occurrence network shows the complex relationships in the bacterial communities. The phylum of Proteobacteria and Halobacterota participate in the metabolism of biofilm WSOM through carbon cycling. The composition of the biofilm bacterial community and WSOM respond to effluent discharge in a dynamically changing pattern. This study provides a new insight for exploring ecological indicators responding to effluent discharge.