Study On The Driving Mechanism Of Bacterial Community In The Middle And Lower Reaches Of The Yellow River

The mudflat wetland ecosystem in the middle and lower Reaches of the Yellow River provides nutrients and habitats for diverse and active bacterial communities.However,the basic data of bacterial community structure and environmental preference in coexisting water and sediment in this system are not systematic.In this study,16 Sr RNA gene sequencing technology was used to study the bacterial communities in water and sediment of typical plant communities in the middle and lower Reaches of the Yellow River.The main research results are as follows:(1)There were significant differences in bacterial community structure,co-occurrence network and community assembly between water body and sediment,indicating that the interaction between water body and sediment was limited.Proteobacteria,Actinobacteria,Firmicutes and Cyanobacteria are the dominant phyla in water bodies.Proteobacteria,Acidobacteria,Chloroflexi and Gemmatimonadetes were the dominant phyla in the sediments.The abundance and diversity of bacterial communities in water were more sensitive to nitrogen compounds and electrical conductivity,and the bacterial communities in sediment were more sensitive to nitrogen compounds,p H and TP.The relative contribution of random process and deterministic process to bacterial community construction in water body and sediment was quantitatively studied.It was found that both random process and deterministic process acted on bacterial community construction in wetland ecosystem of the middle and lower Yellow River,but there were differences in bacterial community construction between water body and sediment.The contribution of homogenous selection is the highest in water body,while the contribution of heterogenous selection is the highest in sediment.In terms of co-occurrence network,there are more key species in water than in sediment,and the complexity and stability of bacterial community network in water is higher than that in sediment.(2)In terms of interannual effect,Proteobacteria,Actinobacteria and Cyanbacteria were the dominant phyla in the first year of this study,among which Actinobacteria accounted for the highest proportion(34.85%).In the second year,Proteobacteria,Actinobacteria and Firmicutes were the dominant phyla,and Firmicutes had the highest abundance(32.58%).In the first year,Proteobacteria,Acidobacteria,Chloroflexi and Gemmatimonadetes were the dominant phyla,of which Proteobacteria accounted for the highest proportion(39.47%).In the second year,the composition of the dominant bacterial communities was consistent with that in the first year,and Proteobacteria accounted for the highest proportion(38.18%).The Chao1 index,Shannon index and Simpson index of water and sediment bacterial communities in the first year were higher than those in the second year.In terms of microbial co-occurrence network,the negative correlation coefficients of sediment and water bacterial network in the second year were higher than those in the first year.The proportion of key species in the water network in the first year was higher than that in the second year,while the sediment showed the opposite state.In the second year,the water body and sediment bacterial networks have stronger natural connectivity and higher network stability.(3)In terms of the influence of typical plant communities on bacterial communities,there was little difference in the composition and abundance of the bacterial communities in the water between The Plant communities of Conyza canadensis and the plant communities of Phragmites australis,and the dominant phyla were as follows: Proteobacteria,Actinobacteria,Firmicutes and Cyanobacteria,among which the Actinobacteria with the highest abundance accounted for 32.75% and 33.1% respectively.There were no significant differences in the composition and abundance of sediment and water bacterial communities between the two plant communities.The dominant phyla were Proteobacteria,Acidobacteria,Chloroflexi and Gemmatimonadetes.Proteobacteria with the highest abundance accounted for 38.16% and 39.13% in the two plant communities,respectively.Compared with Phragmites australis community,Chao1 index,Shannon index and Simpson index were lower in water body and higher in sediment,but the difference was not significant.In terms of co-occurrence network,the negative correlation coefficient of water body in Conyza canadensis community was higher than that in Phragmites australis community,while the negative correlation coefficient of sediment was opposite.Compared with Phragmites australis community,there were more key species and higher natural connectivity and stability in the co-occurrence network of Conyza canadensis community.(4)There were no significant differences in bacterial community composition and abundance between the surface sediments and the underlying sediments.Chao1 index,Shannon index and Simpson index of bacterial community in surface sediments were higher than those in lower sediments,but the differences were not significant.The negative correlation coefficient of bacterial community co-occurrence network in the lower sediments is higher than that in the surface sediments,and the bacterial community in the surface sediments has higher average path length,key species and natural connectivity,and the stability of microbial network in the surface sediments is higher than that in the lower sediments.In general,the differences of bacterial communities between water body and sediment are greater than those of different plant community types,interannual effects and different sediment profiles,and the interactions between water body and sediment bacterial communities are limited.This study expanded the understanding of bacterial communities in water and sediment of the floating tender beach in the middle and lower Reaches of the Yellow River,and also provided scientific basis for ecological protection of the Yellow River wetland.