Study On The Spatial-Temporal Distribution Of Surface Sediment Bacterial Community Structure And Function In Poyang Lake

Environmental microbes play an important role in the process of material cycling and energy flow in lake ecosystems as decomposers.It is essential to elucidate the structure,function and development of lake ecosystems by reliably assessing the abundance,diversity and microbial activity of microorganisms.At present,the study of large freshwater lakes shows that,sediment bacterial communities may be influenced by a variety of physical-chemical parameters.Poyang Lake is complicated in the hydrological characteristics,with diverse lake form.In recent years,the establishment of the Three Gorges Dam and the anthropogenic activities brought potential ecological risks to the Poyang Lake.However,the spatial-temporal variation of the sediment bacterial community of Poyang Lake is still unclear,and it is also poorly aware about its response to the environmental changes.In this study,we selected four typical sampling sites to collected the surface sediment samples in April,July,October 2014 and January 2015.The sampling sites were: SM(main lake district),NJ(son lake),RH(tributary estuary)and BS(east basin).Sediment geochemical parameters such as pH,nitrate(NO3-N),ammonium nitrogen(NH4-N),total organic carbon(TOC),total nitrogen(TN),total phosphorus(TP),ash free dry mass(AFDM)and the contents of heavy metals(Cu,Cd,Pb,Zn).We adopted methods such as qPCR,16 S rDNA high throughput sequencing and Biolog-ECO plate analysis to determine the sediment bacterial abundance,bacterial community structure and function activity.The experimental results were as followed:The sediment environmental factors in Poyang Lake showed that the difference between sampling sites is larger than that between seasons.All parameters were significantly different between sites,except for TN and Pb,and only NO3-N?TP?TN?TOC and Pb were significantly different between seasons.Specifically,organic matter and nutrient parameters associated with carbon,nitrogen were higher at NJ than the other three sites,heavy metal contents were higher at RH than the other sites,but the all the nutrient and heavy metal contents showed lower level in SM sites.The bacterial community abundance in Poyang Lake showed significant difference between sites,but showed no difference between seasons,mainly performed as BS>RH>NJ>SM.The bacterial abundance mainly showed significant correlation with heavy metals.The bacterial community structure in Poyang Lake showed that the difference between sampling sites is larger than that between seasons,especially between SM sites and the others.The Shannon index in SM samples were higher than that from NJ and BS sites.All the high quality sequences fell into 50 phyla,129 classes,255 orders,463 families and 814 genera.Among the 50 phyla,Proteobacteria,Acidobacteria,Chloroflexi,Bacteroidetes,Nitrospira,Chlorobi were dominated in all samples.But in the family level,the predominant taxon was significantly different among samples.It was Nitrospiraceae,Anaerolineaceae,Xanthomonadaceae,Cystobacteraceae,FamilyI,BSV26,Xanthomonadales_Incertae_Sedis,Nitrosomonadacea,Sphingomonadaceae which played a major role in their differences.Cystobacteraceae,Anaerolineaceae,Nitrospiraceae and BSV26 were higher at NJ,RH and BS sites,but Xanthomonadaceae,Sphingomonadaceae and FamilyI were higher at SM sites.Redundancy analysis(RDA)revealed that water depth and environmental chemical characteristics(pH,heavy metals and nutrient parameters associated with carbon and nitrogen)were considered to be the key factors driving the spatial variation of bacterial community structure in Poyang Lake.Based on the results of 16 S rDNA sequencing,the METAGENassist function prediction analysis showed that the function of bacterial community was significant between sites.Among them,chitin degradation and aromatic hydrocarbon degradation function were particularly higher in SM than the other three sites.The microbial metabolic activity of surface sediments in Poyang Lake in April was significantly different among different samples with different anthropogenic disturbances,and all kinds of anthropogenic disturbance can reduce the microbial metabolic activity,mainly reflected that microbial carbon source utilization was higher in SM sites.Combined with Illumina Mi Seq high throughput sequencing,Verrucomicrobia and Firmicute,which contributed to the carbon metabolic pattern of RH area with industrial disturbance,showed negative correlation with polymer.Chloroflexi and Delta-proteobacteria,which contributed to the carbon metabolic pattern of NJ area with agricultural disturbance,showed negative correlation with carboxylic acids,amino acids,amine.Gamma-proteobacteria,Bacteroidetes and Beta-proteobacteria which contributed to the carbon metabolic pattern of SM sites,showed positive correlation with carboxylic acids,amino acids,amine.In conclusion,chemical factors of sediments in different types of habitats in Poyang Lake are the main factors affecting the bacterial community structure,which may be related to their human activities and disturbances.And different types of microbial metabolic function responsed differently to the environmental character,further research is needed to confirm this problem.