The Comparison Of Microbial Community Structure Within The Rhizosphere Of Typical Wetland Plants Between Two Types Of Polluted Rivers

Compared with other natural wetlands,river wetlands are characterized by strong fluidity,large catchment area and complex pollution sources.The sources of pollution in river wetlands mainly due to the different seasonal of agricultural production activities and urban living activities.The dynamic characteristics of organic matter,nitrogen,phosphorus and other pollutants in agricultural source-contaminated wetlands and domestic polluted river wetlands among seasons are different.The removal of organic matter,nitrogen and phosphorus from river wetlands mainly through microbial degradation and transformation,plant absorption,sediment adsorption and other processes,in which the microorganisms play an important role in all processes.The microbial community structure and diversity in river wetlands are affected by river pollution characteristics,seasonal dynamics,plant species and so on.However,both the relationship between microbes and the factors above and the extent of their impacts need to be further explored.In this research,the microbial community structure and diversity in rhizospheree of Phragmites australis and Typha orientalis,which are widely distributed in wetlands were analysed.Seasonal dynamics of water quality indicators and sediment carbon,nitrogen and phosphorus in the rhizospheres of Phragmites australis and Typha orientalis in rivers of domestic and agricultural pollution were also determined.The main conclusions are as follows:?1?The average values of organic carbon,total nitrogen,ammonium nitrogen and total phosphorus in the sendiments of rhizosphere of Phragmites australis in the domestic sewage polluted stream were 7.86 g·kg^-1,2.50 g·kg^-1,101.89 mg·kg^-1,0.91 g·kg^-1,respectively,were higher than the agricultural polluted stream.The organic carbon,ammonium nitrogen,nitrate nitrogen and total phosphorus in Typha orientalis were 7.23 g·kg^-1,2.06 g·kg^-1,101.05mg·kg^-1,47.82 mg·kg^-1,0.91 g·kg^-1,which were were higher than the agricultural polluted stream,too.The seasonal dynamics of pH,DO,COD,NH₄⁺,TP and organic carbon,total nitrogen,nitrate nitrogen were changed significantly in the domestic sewage polluted stream.And the pH?DO?COD?TN?NH₄⁺?NO₃^-and pH,organic carbon,total nitrogen,were changed significantly in the agricultural polluted stream.?2?The contents of PLFAs in P.australis ranged was 7.46-41.80 nmol·g^-1,T.orientalis was4.97-28.48 nmol·g^-1 in the domestic sewage polluted stream.The contents of PLFAs in P.australis ranged was 4.35-26.72 nmol·g^-1,T.orientalis weas 7.29-20.86 nmol·g^-1 in the domestic sewage polluted stream.The ratios of B:F were the highest in summer,while the ratio of G⁺:G^-were the lowest in summer.The Shannon diversity index of reed root bacteria were higher than that of cattail root.The two plants root bacteria were mainly Proteobacteria,Firmicutes,Chlorofloxi and Exiguobacterium,Acetobacter and Smithella.The difference of dominant phylum and dominant genera of reed root bacteria were large.The contents of PLFAs and bacteria PLFAs markers in reed roots were lower than those in cattail roots,and the ratios of PLFAs markers B:F,G⁺:G,cy:pre,S:M,i:a in reed roots were lower than those in cattail roots,but the ratios of aerobic and anaerobic bacteria were higher than those in cattail roots.Shannon diversity indexs of Typha root system bacteria were higher.The main root system bacteria were Proteobacteria,Firmicutes,Bacteroidetes and Exiguobacterium,Thiobacillus and Povalibater.The dominant phylum and dominant genera of reed root bacteria vary greatly in seasons.?3?The concentrations of COD had great influence on microbial community in the domestic sewage polluted stream,and positively correlated with cy:pre and i:a of reed and cattail roots,negatively correlated with total PLFAs of reed roots,but positively correlated with PLFAs of cattail roots,positively correlated with Pseudomonas of reed roots,and negatively correlated with TN and TP of Pseudomonas of reed roots,and positively correlated with TN and TP of Azotobater and Dechloromonas of reed roots However,COD,TN and BOD₅ had great influence on microbial community,and positively correlated with Dechloromonas,Acinetobacter,Bacillus and Clostridium,and negatively correlated with Pseudomonas.In addition,DO had great influence on microbial community,and positively correlated with aerobic and anaerobic bacteria.There was a positive correlation between organic carbon and cy:pre,i:a,B:F,ammonium nitrogen and S:M,aerobic bacteria:anaerobe,Typha root organic carbon,total nitrogen,total phosphorus and cy:pre,i:a,etc.,and a negative correlation between total phosphorus and Acinetobacter,Bacillus,etc.The concentrations of DO,pH had great influence on microbial community in the agricultural polluted stream,and positively correlated with total PLFAs,B:F,S:M,i:a,TN,and negatively with total PLFAs,while TN was negatively correlated with total PLFAs,pH,DO were positively correlated with Azotobacter,COD,TN were positively correlated with Acinetobater,Dechloromonas,etc.Organic carbon,total phosphorus and total nitrogen in reed root sedimentS were positively correlated with cy:pre,i:a,S:M,aerobic:anaerobic bacteria,etc.,while organic carbon,total phosphorus and total nitrogen were negatively correlated with total PLFAs,etc.;ammonium nitrogen,nitrate nitrogen and pH of reed root were positively correlated with Acinetobacter,Pseudomonas,Clostridium,etc.,organic carbon and total phosphorus were positively correlated with Azotobacter,and total phosphorus was positively correlated with Pseudomonas,etc was negatively correlated.?4?The microbial communities structure and bacterial diversity in the rhizosphere of P.australis and T.orientalis in the two pollution types of streams were different:In the rhizosphere of P.Australis,total PLFAs,bacteria,fungi,actinomycetes,protozoa,AMF,ethane oxidizing bacteria,and the ratios of B:F in the domestic sewage polluted stream were higher;while the ratios of G⁺:G^-,aerobicand bacteria:anaerobic bacteria,cy:pre,S:M and i:a were lower than those in the agricultural polluted stream.AMF PLFAs and the ratios of G⁺:G^-,B:F,bacteria:anaerobic bacteria,cy:pre,S:M,i:a the domestic sewage polluted stream were lower.The diversity of bacteria in the rhizosphere of both P.Australis and T.orientalis in the domestic sewage polluted stream was higher.