Response Of Methane Functional Bacteria To Different C And N Environments In The Main Section Of The Yangtze River In Chongqing

The purpose of this study was to study the change of the number of methane functional bacteria with different organic carbon and organic nitrogen concentrations,and to clarify the correlation between them.In this study,the main stream of the Yangtze River and its tributaries in the main urban section of Chongqing were selected as the research area,Lijiatuo,Daxigou,Cuntan,Tangjiatuo,and Guojiatuo were selected as sampling points.Used high-throughput sequencing technique for the water samples of low water level and high water level,sediment samples for research,analyzed of three kinds methane bacteria community structure changes under different water level and the correlation with the physical and chemical indicators.At the same time,in order to study about the methane bacteria as well as the change of the methane release under the condition of different organic carbon and nitrogen,selected the sediment samples of high water level at Guojiatuo point to indoor simulation experiment,studied the post-experimental sediments by fluorescence quantitative PCR technology,after analyzing the change of the three kinds of methane bacteria number as well as the physical and chemical indicators of relevance.The conclusions were as follows:（1）The dominant species of methanogens in the main urban section of Chongqing during the low water level of water samples were Methanospirillum,Methanothermobacter,Methansaeta;during the high water level were Methanobacterium,Methanospirillum,Methanobrevibacter.The dominantspecies of methanogens during the low water level of sediment samples were Methanothermobacter,Methanobacterium;during the high water level were Methanothermobacter.The domin-ant species of MOB bacteria during the low water level of sediment samples were Methylocystis,Methylococcus,unclassified＿f＿Methylocystaceae,unclassified＿f＿Methylococcaceae;during the high water level were Methylococcus,Methylocystis,unclassified＿f＿Methylocystaceae,Methylosarcina.The dominant species of DAMO bacteria during the low water level of water samples were unclassified＿c＿Alphaproteobacteria,unclassified＿p＿Proteobacteriaand unclassified＿c＿Betaproteobacteria;during the high water level were unclassified＿p＿Proteobacteria,unclassified＿c＿Alphaproteobacteria.（2）The methanogens bacterial community in the main urban section of Chongqing during the low water level of water samples were positive correlation with NH₄⁺and CH₄,but with NO₃^-,NO₂^-and TN were negative correlation;during the high water level were positive correlation with CH₄,but negative correlation with NH₄⁺and NO₂^-.The methanogens bacterial community in the sediment samples were negatively correlated with NH₄⁺and NO₃^-,and positive correlation with NO₂^-and TN.The MOB bacterial community in the low water level of water samples showed positive correlation with NH₄⁺,NO₃^-and CH₄,but negative correlation with NO₂^-;during the high water level present positive correlation with NO₃^-and CH₄,but negative correlation with NO₂^-and TN.The MOB bacterial community in the sediment samples showed positive correlation with NH₄⁺and TN and negative correlation with NO₃^-.The DAMO bacterial community in the low water level of water samples were positive correlation with NO₂^-,TN,but negative correlation with NH₄⁺,NO₃^-and CH₄;during the high water level were negative correlation with NH₄⁺,NO₂^-and CH₄,and were positive correlation with NO₃^-and TN.The DAMO bacterial community in the sediment samples present positive correlation with NH₄⁺,NO₃^-and negative correlation with NO₂^-.（3）In the experiment of organic carbon concentration,nitrogen distributions in water were mainly includes NH₄⁺,NO₃^-and NO₂^-,among which CH₄ present negative correlation with NH₄⁺and positive correlation with NO₃^-,NO₂^-and TN.The number of methanogens,MOB bacteria and DAMO bacteria all decreased with the increase of organic carbon concentration.When the amount of organic carbon source was more than30mg/L,organic carbon had no effect on the number of methanogens,MOB bacteria,DAMO bacteria in the sediment samples and CH₄ concentration in the water samples.And the number of methanogens,MOB bacteria and DAMO bacteria were positively correlated with each other,in the meantime,the three species were negatively correlated withρ（C）,TN and organic nitrogen.In addition,the number of MOB bacteria present positive correlation with NO₃^-,the number of DAMO bacteria was positive correlation with NO₃^-and NO₂^-.（4）In the experiment of organic nitrogen concentration,nitrogen distributions in water were mainly includes NO₃^-and ON,among which CH₄ showed negative correlation with NO₃^-,ON and TN.The number of methanogens,MOB bacteria and DAMO bacteria increased first and then decreased with the increase of organic carbon concentration.When the amount of organic nitrogen source was more than 2mg/L,organic nitrogen had no effect on the number of MOB bacteria in the sediment samples.And the number of methanogens,MOB bacteria and DAMO bacteria were positively correlated with each other,in the meantime,the three species were positively correlated withρ（N）In addition,the number of methanogens showed positive correlation with NH₄⁺and NO₃^-,negatively correlated with ON,and the number of MOB bacteria and DAMO bacteria were positively correlated with NH₄⁺.