| As an important part of shallow water lake,sediment microorganism is of great importance for maintaining the function of lake ecosystem and promoting the material,energy and information flow in lake ecosystem.This study was financially supported by the State Key Project of National Natural Science Foundation of China(No.41230640),typical areas of different nutrient levels in Taihu lake(lightly eutrophicated,Xuhu;moderate eutrophicated,Gonghu,Meilianghu and West Taihu)were selected as the typical research areas.Monitoring of physical and chemical properties of overlying water and sediment and identification of microbial community were conducted for every season of successive three years.By means of high-throughput sequencing and method of molecular ecological network,spatiotemporal differences of sediments community structure and interspecific relationship in Taihu Lake were identified..In combination with the distribution characteristics of key elements,the influences of the factors on microbial community structure were discussed.The main conclusions are as follows:(1)Using Illumina high-throughput sequencing method to identify sediment microorganism,40149 reads on the average were obtained for every sample,and the coverage of the library was over 95%.65 phylums,153 classes,247 orders,264 families and 366 genera were identified in the Taihu sedimentary environment.The main phylums of Taihu sediment included Proteobacteria,Bacteroidetes,Firmicutes,Nitrospirae,Acidobacteria,Choroflexi and Verrucomicrobia.The main classes included Deltaproteobacteria,Betaproteobacteria,Gammaproteobacteria and Nitrospira.The main component species and diversity index are similar to other freshwater lake sediments.(2)The diversity of sediment microbial community was Gonghu>Meiliang>West Taihu>Xuhu,Shannon index was 6.17,6.10,6.01 and 5.96.respectively.Spatially,among the 25 dominant species,11 dominant species such as Gammaproteobacteria,Nitrospirae,Bacteroidetes showed significant differences between aeras of different nutrition levels.Temporally,17 species such as Gammaproteobacteria,Pseudomonadales,Acinetobacter showed significant differences between years.(3)Based on data of sediment microorganism operation taxon units(OTU)in first year of research,molecular ecological networks were constructed,and their topology was analyzed.Number of nodes,connections and average degree were moderate eutrophication lakes(359-389,1131-1679,5.86-9.35)>lightly eutrophic lake(254,721,5.68),so the networks of moderate eutrophication are more complicated and possess more interspecific interaction;ratio of positive connections was moderate eutrophication lakes(91.66%99.76%)>lightly eutrophic lake(87.70%),so lightly eutrophic lake possessed more competitive relationship;average path length was moderate eutrophication lakes(5.06-8.93)<lightly eutrophic lake(4.80)so transmission of material,information and energy in Xuhu molecular ecological network was more efficient.So environmental changes were more likely to affect Xuhu microbial community,so that moderate eutrophication lake area had higher resistance and stability compared with the lightly eutrophic lake area.(4)Correlation analysis of species abundance and environmental factors showed abundances were significantly correlated with environmental factors(P<0.01),temperature,S-NO3-,S-TN,S-TOM,S-TP in sediments,S-NO3-,S-TN were the most important factors affecting the abundance of dominant species(P<0.05);C,N and P were main factors influencing the molecular ecology network,for lakes of different nutrition level,the sediment microorganisms affected by different environmental factors,in lightly eutrophicated lakes,S-TP was main influence factors;in moderate eutrophicated areas,STOM,S-TN,S-NO3-,S-NH4+influences were greater.In conclusion,S-NO3-、S-TN were the most influential factors for microorganism species,microbial community structure and modules of ecological networks in Taihu. |
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