Research On The Construction Of And Symbiotic Relationship Between The Bacterial And Algal Community In Typical Water Bodies Of The Yellow River Basin

Bacteria and algae are important biological components of aquatic ecosystems.Although the two share similar habitats,they differ in their reproductive ability,response rate to environmental change,and diffusion capacity.Besides,the symbiotic system between bacteria and algae plays an important role in maintaining the balance of aquatic ecosystems.In recent years,progress was seen in numerous researches on the ecological dynamics of bacterial and algal communities;however,research on the construction mechanisms of bacterial and algal communities on a large watershed scale is still limited.The Yellow River basin provides a natural platform for studying the construction mechanisms of bacterial and algal com m unities with different lifestyles due to its diverse water types.Taking the mainstream of the Yellow River under the effects of the nature and human and the typical water bodies of the Baihe River Basin in the source region under the action of natural hydrologic and sediment processes as research region and bacteria and algae in water,suspended solids and sediment samples as research objects,this study made a systematic study on the distribution characteristics,community construction process,interaction relationships,and key environmental factors in typical water bodies in the Yellow River basin using high-throughput sequencing technology.The main conclusions of this study are summarized as follows:(1)The top three dominant bacterial phyla in the planktonic and suspended sedimentattached bacterial communities of the mainstream of the Yellow River are Proteobacteria,Bacteroidetes,and Actinobactcria,while the dominant bacterial phyla in the sediment bacterial commtunity are Proteohacteria,Bacteroidetes,and Chloroflexi.The environmental selection determines the biogeographical patterns of the planktonic and suspended sediment-attached bacterial communities,while the biogeographical pattern of the sedimentary bac-terial community is controlled by diffusion limitations.Based on the community coalescence and the analysis of community network,it can be inferred that the bacterial communities attached to suspended sediments may play an essential role in the construction process of bacterial communities in large sandy rivers.(2)The dominant algal groups in the planktonic community of the Yellow River mainstem are mainly composed of Cyanobacteria,Cryptophyta,and Bacillariophyta,while the algae communities attached in suspended sediment and in sediment are mainly Bacillariophyta,Cyanobacteria,and Chlorophyta.The suspended sediment-attached algal community is primarily affected by water quality,while the algae communities is planktonic and sediment are indirectly driven by altitude and land use.Compared with the planktonic and suspended sediment-attached algal communities,the lower diffusion capacity of the sedimentary algal community makes it more sursceptible to the diffusion limitations.The high sediment loads of the Yellow River mainstem has a restricting effect on algal growth,which offsets the promoting effects of nutrients on algal growth.(3)The top three dominant bacterial phyla in the planktonic bacterial communities of typical water bodies in the Baihe River watershed are Proteobacteria,Bacteroidetes,and Actinobacteria,while Proteobacteria,Bacteroidetes,and Acidobacteria are the dominant baccterial phyla in the sediment bacterial communities.Durinig spring(high water period),the connectivity of the mainstreams,tributaries and oxbow lakes of Baihe River promotes the vertical and horizontal coalescences of bacterial communities.Among them,the fusion among different water bodies in planktonic bacterial communities is higher than that of sediment bacterial communities.In addition,hydrological connectivity increases the complexity of bacterial networks and the competitiveness and diffusion capacity of bacterial communities.(4)The dominant algal groups in the planktonic and sedimentary algal communities of typical water bodies in the Baihe River watershed are mainly composed of Cyanobacteria,Bacillariophyta,and Chlorophyta.During spring(high water period),hydrological connectivity promotes the migration of algae,making stochastic process play a dominant role in the construction of planktonic and sedimentary algal communities in typical water bodies of the Baihe River watershed.Unlike the bacterial communities in typical water bodies of the Baihe River watershed,hydrological connectivity leads to a decrease in complexity and stability of the algal network.This may be because the adaptability of algal communities to disturbed environments is lower than that of bacterial communities.(5)The top two dominant bacterial phyla in the bacteria-algae symbiosis system of typical water bodies in the Yellow River watershed are Proteobacteria and Bacteroidetes,while the abundance of algal species varies with seasons and spatial distribution.The change in the species composition and OTU proportion of bacteria and algae systems will directly affect the complexity and stability of the bacteria-algae network.There are some differences between the networks of bacteria and algae with different lifestyles,with the highest similarity in the network between the planktonic and suspended sediment-attached bacteria and algae,followed the network between the attached and sedimentary groups,and the largest difference is between the planktonic and sedimentary groups.Hydrodynamics and suspended solids in the water are the major environmental factors that drive the symbiotic relationship between bacterial-algae communities in typical water bodies of the Yellow River watershed.This research provides scientific reference for a deeper understanding of the mechanisms of bacterial and algal community construction and symbiotic relationships in typical water bodies in the Yellow River watershed,and provides theoretical support for the formulation of ecological environmental protection and restoration of water bodies in the Yellow River watershed under natural and human interactions.