Winter And Summer Succession And Impacts Of Planktonic Bacterial Communities In Dali-nor Lake

Bacterioplankton are the key components of lake ecosystem,which play important roles in the migration and transformation of elements and energy.To understand the change of bacterioplankton community in the cold-arid lakes,we had collected 89 water samples and 28 ice samples from the Dali-nor lake,which is an inland closed lake in Inner Mongolia Plateau.Coupling with comparisons of physicochemical proxies between "ice" and "water" samples,the phylum community characteristics of bacterioplankton had been analyzed in detail basing on the 16S rRNA gene-based high throughput sequencing technology.Here,our results show that:1.Because of the climatic and environmental differences of summer and winter,the relative content of typical physical and chemical indexes of the lake underwent a transition from non-frozen to frozen,and the spatial and temporal changes of different forms of N and P nutrients(such as TN,TP,DTP,DIP,etc)required for the growth of various aquatic organisms in the water were obvious,however,the change range of typical physical and chemical indexes such as EC,COD,DO was relatively small,on the whole,it was characterized by winter water higher than summer water and ice,reveals the indexes in water and ice are significantly affected by the seasonal changes and freezing process.2.In summer,the dominant phytoplankton is Proteobacteria,which accounts for the highest proportion(58.55%)in middle water,followed by bottom water(47.40%)and surface water(35.79%).In winter,the dominant phytoplankton is Actinobacteria has the highest proportion in bottom water(43.31%),followed by middle water(41.04%)and surface water(40.37%).And in ice,the dominant phytoplankton is Proteobacteria,which is 81.50%of surface ice and 62.90%of bottom ice.3.Basing on Alpha diversity analysis,the diversity and evenness is the highest in winter water,the lowest in ice,and the richness is the highest in ice,the lowest in winter water.Meanwhile,Beta diversity analysis shows that the significant differences in the seasons and freezing process of winter ice-water and summer water bacterioplankton communities structure.4.No mater summer or winter,ice or water,the dominant bacteria of Dali-nor Lake are mainly Proteobacteria,Actinobacteria and Cyanobacteria.However,the influencing factors of dominant bacterial community structure and the degree of impact are different.In summer water,Proteobacteria,Actinobacteria,Cyanobacteria,Bacteroides are mainly affected by the changes of indicators.In winter water,Actinobacteria,Proteobacteria,Cyanobacteria,Bacteroidetes are significant influenced.And in ice,Proteobacteria,Actinomycetes,Cyanobacteria,Bacteroidetes,and Verrucomicrobia have been impacted dramatically.5.Through redundancy analysis,in summer,the most obviously effect on bacterioplankton in surface water are DIP,EC,in middle water are DIP,DTP,TN,and in bottom water is TN,TP,DTP,EC.In winter,the most significant indicators are EC,DIP,DTP,pH,TP,TN in surface water,DTP,EC in middle water and TP,DIP in bottom water.And in ice,surface ice are most affected by DO,followed by TP,DIP,and bottom ice most affected by DTP,TP.Obviously,in different seasons,bacterioplankton community composition is diversely affected by physicochemical indexes.This difference is the response to the changes of main dominant class's relative content under the influence of seasonal change and icing process.