Study On The Ecological Distribution Characteristics Of Aerobic Ammonia Oxidizing Microorganisms In River And Lake Sediments In Zhenjiang City

With the rapid development of urbanization and industrialization and the increasing human activities,excessive nitrogen discharges into the natural water,and the nitrogen content in the water environment increases sharply,which not only damages the water ecological environment,but also seriously threatens the survival and development of human beings.As the first and rate limiting step of nitrification,aerobic ammonia oxidation driven by ammonia oxidizing bacteria and ammonia oxidizing archaea is the central link of global nitrogen cycle.As an important parti cipant in the process of aerobic ammonia oxidation,the key roles of AOA and AOB in nitrogen biogeochemical cycle have been paid more and more attention.Zhenjiang City is located at the intersection of the Yangtze River and the "cross golden waterway" of the Beijing Hangzhou Grand Canal.In this area,one lake and nine rivers interweave vertically and horizontally with dense river network and abundant water.In recent years,with.the rapid econom ic development and the expansion of urbanization scale in Zhenjiang City,water pollution in different degrees has appeared in one lake and nine rivers.Therefore,water environment quality control and ecological environment restoration of rivers and lakes have become an important mission for the construction of w aterfront and "landscape garden city" in the north of Zhenjiang city.Based on this,this paper takes "one lake and nine livers" in Zhenjiang City as the research area,studies the ecological distribution of aerobic ammonia oxidizing microorganisms in sediments through molecular biology technology,explores the response rule of the relationship between ammonia oxidizing microorganisms and environmental factors in sediments,and clarifies the relative contribution of AO A and AOB on nitrification process in sediments.The research results are expected to know the key process of nitrogen migration and transformation and the microbiological mechanism driving this process,so as to provide a theoretical basis for the comprehensive management and ecological construction of urban rivers and landscape lakes.The main results are as follows:(1)The total nitrogen pollution of rivers and lakes in Zhenjiang City is serious.The nitrogen pollution degree of river water is higher than that of Jinshan Lake,and the nitrogen pollution degree in winter is higher than that in summer.Ammonia is the main inorganic nitrogen in the overlying water of Jinshan Lake.Nitrate is the main inorganic nitrogen in winter and ammonia in summer.(2)The contents of nutrient elements in the sediments of rivers and lakes in Zhenjiang City changed significantly with space and season.The order of nitrogen content in river and lake sediments was Org-N>NH4+>NO3-.The degree of nitrogen pollution in lake sediments in winter is higher than that in summer,but the change of the distribution of nitrogen content in river sediments with season is not obvious.The pollution degree of nitrate nitrogen in lake sediments is higher than that in rivers,while the pollution degree of ammonia nitrogen is lower than that in rivers.The pollution degree of TP in winter is higher than that in summer.The average C/N ratios of river and lake sediments in winter and summer were 5.89 and 4.64 respectively,indicating that endogenous pollution was the main source.(3)The diversity of ammonia oxidizing microorganisms in river and lake sediments of Zhenjiang City has obvious changes in space and season.In terms of alpha diversity,the abundance and diversity of ammonia oxidizing archaea and ammonia oxidizing bacteria in rivers are higher than those in lakes,and their seasonal change rule is more complex.From the perspective of beta diversity,the community structure of ammonia oxidizing archaea in lake sediments is not related to seasonal variation,but has a great relationship with spatial variation,while the community structure of ammonia oxidizing archaea in river sediments has obvious seasonal and spatial variation.(4)The composition of ammonia oxidizing microbial community in Zhenjiang River and lake sediments change significantly in space and season.At genus level,Nitrosorchaeum is the main ammonia oxidizing archaea in lake sediments,and Candida_Nitrosocaldus in river sediments,Candida_Nitrosotenuis only exists in lake sediments;Proteobacteria is the main phylum in river and lake sediments,Thaumarchaeota only exists in a small amount in lake sediments.Nitrosomonas is the main ammonia oxidizing bacteria in lake sediments and nitrosovibrio in river sediments.(5)There is a response mechanism between ammonia oxidizing microorganisms and environmental factors in Zhenjiang River and lake sediments.Candidatus_Nitrosocaldus in Lake Sediments was positively correlated with Cu content in winter and negatively correlated with Cu content in summer Candidatus Nitrosocaldus and Nitrososphaera in River Sediments were positively correlated with Cr,TN,TP and Zn,Candidatus_Nitrosotalea was positively correlated with Pb.C renarchaeota was negatively correlated with nitrate in lake sediments and positively correlated with TN,Cu and O.M in river sediments.(6)The dominant relationship between ammonia oxidizing microorganisms and nitrification is still unclear.The potential nitrification rate of AOA in winter is higher than that in summerg while that of AOB is lower,than that in summer,indicating that AOA may play a dominant role in winter,while AOB plays a maj or role in summer.The relative contribution of AOA on nitrification is higher than that of AOB.AOB abundance is correlated with PNR.In conclusion,the dominant relationship between ammonia oxidizing microorganisms and nitrification is not clear.