Effects Of Anthropogenic Disturbance On The Rhizosphere Bacterial Community Structure And Diversity Of Aegiceras Corniculatum In The Mouths Of Maowei Sea In Qinzhou And Nanliu River Estuaries In Beihai

With the development of coastal industry,agriculture and aquaculture in Guangxi’s Beibu Gulf,human activities have significantly affected the health of mangrove wetland ecosystems.In order to explore the effects of different degrees of anthropogenic disturbance in Qinzhou and Beihai on the soil physicochemical properties,soil enzyme activity and rhizosphere bacterial community structure and diversity of rhizosphere bacterial community in Aegiceras corniculatum,this paper selected the rhizosphere soil of Jianxinwei mangrove forest and Xiandao Park mangrove forest in Qinzhou City and Nanliu River estuary mangrove forest in Beihai City.The effects of anthropogenic disturbance on soil physicochemical parameters(p H,seawater salinity),soil fertility(organic matter,organic carbon,alkali-hydrolyzable nitrogen,available phosphorus,available potassium,total nitrogen,total phosphorus and total potassium content)and soil enzyme activities(catalase,sucrase,urease,acid phosphatase)in the rhizosphere of Aegiceras corniculatum in Qinzhou Maowei Sea and Nanliu River estuaries in Beihai were discussed.On the other hand,as an important member of the mangrove ecosystem,the community structure of rhizosphere soil microorganisms will be affected by the type of ecological environment and the physical and chemical properties of the soil.In order to understand the effects of anthropogenic disturbance on the bacterial community structure and diversity of the rhizosphere soil of Aegiceras corniculatum,the variable region of bacterial 16 S r DNA V4 in the rhizosphere soil of Aegiceras corniculatum was sequenced by high-throughput sequencing technology.Through ASV annotation classification,alpha diversity analysis,beta diversity analysis principal component analysis(PCA),Pearson correlation analysis and redundancy analysis(RDA),the main bacterial community structure in the rhizosphere soil of Aegiceras corniculatum in Maowei Sea in Qinzhou and Nanliu River estuaries in Beihai and its relationship with soil physicochemical properties and soil enzyme activities were discussed.The main results of this study are as follows:1.Human disturbance can affect the soil p H of the rhizosphere of Paulownia trees.Compared with areas with less human activity,the soil p H of the rhizosphere of Aegiceras corniculatum in Xiandao Park next to Qinzhou residential area and Nanliu River estuaries duck farm in Beihai is higher.The change of salinity of the rhizosphere of the Aegiceras corniculatum is due to regional differences,and gradually decreases with the coastal to inland trend.2.Under human disturbance,the content of alkaline hydrolyzable nitrogen and available phosphorus decreased in the rhizosphere soil of Aegiceras corniculatum in Xiandao Park,and the total phosphorus content and C/N value of the surface rhizosphere soil increased,which had little effect on the organic carbon,organic matter,available potassium,total nitrogen,total potassium content and C/P value.Duck farm culture in Nanliu River estuaries in Beihai increased the contents of organic carbon,organic matter,alkalihydrolyzable nitrogen,available phosphorus,available potassium,total nitrogen and total potassium and C/P values in the rhizosphere soil of Tonghua trees,but decreased the soil C/N value,which had no significant effect on soil total phosphorus content.3.Catalase and acid phosphatase in the rhizosphere soil of Aegiceras corniculatum in Xiandao Park,which had more human disturbances,had higher enzymatic activities than those in the rhizosphere of Aegiceras corniculatum in Jianxinwei,while the sucrase activity was the opposite,which had little effect on urease activity in rhizosphere soil.Duck farm culture in the mouth of the Nanliu River estuaries in Beihai increased the activities of catalase,acid phosphatase,urease and sucrase in the rhizosphere soil of Paulownia trees,and duck farm culture had a great effect on the soil enzyme activity in the rhizosphere of Aegiceras corniculatum.Pearson correlation analysis showed that soil p H,organic carbon,alkali-hydrolyzable nitrogen,total nitrogen,total phosphorus content,C/N,C/P values and other physical and chemical properties became the main influencing factors of soil enzyme activity.4.The soil bacteria in the rhizosphere of the Aegiceras corniculatum in Jianxinwei and Xiandao Park mainly belong to 19 phyla,and the dominant phylums are Proteobacteria,Chloroflexi,Desulfobacterota,Actinobacteria,Acidobacteria,Bacteroidetes,Firmicutes,Nitrospirota,Cyanobacteria.Among them,the relative abundance of Proteobacteria,Chloroflexi and Desulfobacterota accounted for 47.45%-54.27%.There are mainly 15 phyla of soil bacteria in the rhizosphere of Aegiceras corniculatum in the mouth of the Nanliu River in Beihai,and the dominant phylum are Proteobacteria,Firmicutes,Chloroflexi,Actinomycetes,Dethiobacillus,Acidobacteria,Bacteroides,Nitrotrepira,and Gemmatimonadetes,among which the relative abundances of Proteobacteria,Firmicutes and Chloroflexi accounted for 49.04%-77.18%.Under human disturbance,the relative abundance of Proteobacteria in the rhizosphere soil of Aegiceras corniculatum in Xiandao Park was higher than that of Jianxinwei,while the relative abundance of phylum Chloroflexi,Desulfobacterota,Acidobacteria,Nitrospirota and Firmicutes decreased duck farm culture in the mouth of the Nanliu River in Beihai increased the relative abundance of soil bacteria Chlorobentomyce,Desulfobacillus and Bacteroides,and decreased the relative abundance of Proteobacteria,Firmicutes,Actinomycetes and Acidobacteria.5.The ACE index,Chao index and Shannon index of rhizosphere soil bacteria in the surface and deep layers of Xiandao Park decreased,and the Simpson index increased,and the diversity of bacterial species in the rhizosphere soil of Xiandao Park under human disturbance was lower than that of Jianxinwei duck farm culture at the mouth of the Nanliu River estuaries in Beihai reduced the bacterial alpha diversity of the rhizosphere soil of Aegiceras corniculatum in the region.6.Beta diversity analysis and PCA analysis showed that the bacterial community structure of the rhizosphere soil of Aegiceras corniculatum in Qinzhou Xiandao Park and Nanliu River estuaries duck Farm in Beihai changed under human disturbance.Pearson correlation analysis and RDA redundancy analysis showed that soil enzymes,p H,seawater salinity,organic carbon,organic matter alkaline hydrolyzable nitrogen,total nitrogen,available phosphorus content and C/P value significantly affected the alpha diversity and community structure of bacteria in rhizosphere soil.The decrease in bacterial community diversity and the change of community structure in the rhizosphere soil of Aegiceras corniculatum,which can be attributed to the change of physicochemical properties of the soil in the rhizosphere of Aegiceras corniculatum under anthropogenic disturbance.