| With the rapid development of urbanization and industrialization,a large number of toxic heavy metals are discharged into aquatic ecological environment system through industrial and agricultural waste water and domestic sewage and mainly stored in sediments,posing a great threat to aquatic environment and human health.The microorganisms gathered in sediments play an important driving role in the material circulation and element transfer of the ecosystem.In recent years,many studies have shown that sediment microorganisms are more susceptible to heavy metal pollution than other pollutants.Heavy metal pollution can affect ecological function by affecting microbial community structure and function.Therefore,by studying the effects of heavy metals in sediments on the structure and function of microbial community,it has been paid more and more attention to provide enhanced strategies for pollution control and ecological restoration of water environment.In this experiment,samples were collected from sediments at the estuary of Nanfei River,Paihe River and Hangbu River in level season and wet season,and the concentrations of heavy metals Cu,Zn,Pb,Cr,Ni and Cd were determined.The high-throughput sequencing platform was used to analyze the distribution characteristics of microbial community structure and the PICRUSt2 technology was used to predict the function of microbial community.Spearman correlation analysis and Redundancy analysis were used to explore the effects of heavy metals on microbial community structure and function in different seasons and in different lake entrance sediments,which provided a theoretical basis for further understanding of the effects of heavy metals on microbial community structure and function in lake sediments.The study’s main conclusions are as follows:(1)The average concentration of metal elements in sediment samples is in the order of Zn>Cr>Pb>Ni>Cu>Cd,and the concentration of all elements exceeds the background value of Anhui soil elements.The enrichment factor method shows that Zn and Cd are moderately enriched,and the potential ecological risk assessment method shows that Cu,Zn,Pb,Cr and Ni are all low ecological risk.Cd is the moderate ecological risk level.From the perspective of different seasons,the average concentration of heavy metals in level season is higher than that in wet season,and the ecological risk level of heavy metals in level season is higher than that in wet season.The comprehensive potential ecological risk of the two seasons is slight risk.From the perspective of different estuarys,except for Cd at the estuary of the Hangbu River,the concentration of metal elements at the other estuarys exceeded the background values of soil elements in Anhui Province.Heavy metal enrichment was the highest at the estuary of the Nanfei River,while Zn and Cd were moderately enriched.The metal elements at the estuary of the Paihe River and the Hangbu River are not enriched at all.The comprehensive potential ecological risks of heavy metals at the three estuarys were all slight risks.The analysis of NMDS showed that the Ming Dynasty had a certain effect on the heavy metal concentration,and the heavy metal concentration at the estuary of the Nanfei River was more affected by heavy metal emission in the surrounding areas than that at the estuary of the Paihe River and Hangbu River.(2)High throughput sequencing results showed that the number of OTUs in wet period was significantly higher than that in level season,and there was little difference in the mean values of OTUs at different inlets,as follows: the estuary of the Paihe River >the estuary of the Hangbu River > the estuary of the Nanfei River.The dominant bacteria in the sediment samples were Proteobacteria,Acidobacteriota,Chloroflexi and Bacteroidota.Proteobacteria was the absolute dominant phylum,which had a significant difference in wet season but no significant difference in different lake inlets.The dominant bacteria classes were Gammaproteobacteria,Bacteroidia,Anaerolineae,Vicinamibacteria and Alphaproteobacteria,Gammaproteobacteria was the absolute dominant class,and Alphaproteobacteria had a significant difference in different water seasons.Prediction of microbial community function based on PICRUSt2 technique,The results showed that Metabolism,Genetic Information Processing and Environmental Information Processing had the highest relative abundance.The predicted functional abundance of microbial communities at different seasons and inlets was almost unchanged.Although there were significant differences in microbial community structure at different seasons and inlets,their functions were consistent,suggesting that different microbial groups may have overlapping functions.(3)Spearman correlation analysis was used to analyze the effects of heavy metals on α-diversity of microbial community.The results showed that heavy metals were negatively correlated with α-diversity index of microbial community in level seson,and Zn and Cd had the most negative effects on α-diversity of microbial community.Zn,Pb and Cd had the greatest negative effect on α-diversity of microbial community in wet season,and Pb and Cr were positively correlated with community richness.The influence of heavy metals on α-diversity of microbial community was different in different lacustrine inlets.Heavy metal was negatively correlated with α-diversity index of microbial community at the estuary of Nanfei River,and Cr had the greatest negative effect on α-diversity index of microbial community.at the estuary of Paihe River,heavy metals in sediments had positive effects on α-diversity of microbial community,and Pb and Cr had the most positive effects on α-diversity of microbial community.The heavy metals in the sediments from the inlet of the Hangbu River have a positive effect onα-diversity of the microbial community,and Cu and Cr have the most positive effect onα-diversity of the microbial community.Redundancy analysis was used to analyze the effect of heavy metals on microbial community composition.The results showed that Cr had the greatest effect on microbial community composition in both level and wet seasons.The effect of heavy metals on the composition of microbial community was different at different estuarys of the lake.Cr was the most significant influence on the composition of microbial community at the estuary of the Nanfei River,while Pb was the most significant influence on the composition of microbial community at the estuarys of the Paihe River and Hangbu River.Spearman correlation analysis was used to analyze the effects of heavy metals on microbial community functions.The results showed that the community functions of sediments in level season were significantly negatively affected by Cr and Ni,and were negatively correlated with some second-order functions of metabolic functions,genetic information process functions and some second-order functions of environmental information process functions.The effect of heavy metals on microbial community function was not significant in wet season.The effect of heavy metals on microbial community function at the estuary of the Nanfei River was significantly different from that at the estuarys of the Paihe River and Hangbu River.There was a significant negative correlation between heavy metal and microbial community metabolism and genetic information process function at the estuary of the Nanfei River.The effects of heavy metals on microbial community metabolism,genetic information process and environmental information process were small.The effects of heavy metals on the genetic information process and environmental information process of microbial community were not significant,but they had significant positive and negative effects on some level 2 metabolic functions,respectively.Figure [24] Table [8] Reference [121]... |
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