Study On Ecological Distribution Characteristic Of Nitrogen Cycling Bacteria In Epiphytic Biofilms Attached On The Aquatic Plants And Abio-substrates

Aquatic plants,especially submerged macrophytes,as the primary productivity of lake ecosystems,play a pivotal role in the structure and function of lake ecosystems and the maintenance of biodiversity.For submerged macrophytes,the body of plant is below the water surface,and its roots,stems,leaves and other body surfaces are often attached to a large number of various substances such as algae,microorganisms,micelles,silt and debris,and form special organisms-water micro boundary layer(MBL),the body surface of which becomes one of the key MBL hot spots for the attachment of water pollutants and the migration and transformation of nutrients.In addition,various non-living substrates floating in the water body can provide a micro-habitat site for the migration and transformation of pollutants as a biofilm attachment carrier,thereby realizing the degradation of pollutants.Therefore,the attachment of aquatic plants/abio-substrates to biofilms is an important way to control and regulate the material transport and exchange between organisms and water bodies.It is also a key interface that affects the transformation of elements in freshwater ecosystems,and improves the material circulation of freshwater ecosystems and the improvement of water environment quality has an important impact.Based on this,in order to compare and study the distribution of AOA and its nir S denitrifying microorganisms on the surface of aquatic plants and abio-substrates under different types and different habitat conditions,this paper constructed a combined ecological floating bed system(IEFBs)and Field cultivation was carried out,and the differences in the distribution characteristics of aquatic plant roots(Ipomoea aquatica Forsk)and three abio-substrates attached to the surface of biofilm microorganisms under the same habitat conditions were obtained;at the same time,four field lakes were selected in Zhenjiang City to collect aquatic plants(Ceratophyllum demersum and Potamogeton pectinatus),Potamogeton pectinatus,and samples of non-living bodies(inanimate characteristic samples such as floating plastic bags on water),to study the effects of different habitat conditions on the distribution of microorganisms attached to the surface of aquatic plants and the surface of abio-substrates.influences.The main findings are as follows:(1)The biological and abio-substrates of the ecological floating bed system have a significant impact on the diversity and community structure of ammonia oxidizing microorganisms attached to biofilms.The four different substrates in IEFBs have good adsorption and filtration capabilities for suspended organic particles,algae and other substances,and can provide ideal habitats and richer nutrients for the growth of microorganisms.There are differences in the composition and microhabitats of different substrates,that is,the ability to provide biologically active substrates(C,N,and P)for microorganisms.Therefore,the community structure and the relative abundance of nitrogen-related functional genes vary with substrates.And a significant change.The results of cluster analysis and principal component analysis showed that the types and numbers of nir S-type denitrifying bacteria in the same non-biological matrix were obviously similar.The comparison within the biological matrix group is quite different,which may be related to the physiological characteristics of the biological matrix itself.However,AOA showed similarity in group F only,indicating that the surface of other groups had more complex microbial communities.The predominant phyla of AOA and nir S denitrifying bacteria accounted for a large difference in the proportion of each sample group,and other relatively less abundant phyla and genera also had specific microbial communities on the surface of different substrates.It can be seen that there are many factors that affect the community structure and the relationship is more complicated.(2)The biofilm ammonia oxidizing microorganisms attached to the surface of submerged macrophytes are significantly affected by the habitat,plant species,and the growth stage of the plant itself.Submerged plant surface attachments can sensitively respond to changes in the water environment micro-habitat.In this study,there are significant differences in the dry weight of plant surface attachments at four points(P<0.05).Plant attachments at some sampling points It is strongly affected by COD,temperature,C/N and Ec(P<0.05),indicating that the attachments are significantly affected by the water environment in the water area.The difference in the nitrogen content of attachments between aquatic plant substrates and abio-substrates at the same point is It mainly reflects the dual effects of the difference between plant and non-biological substrate materials and the characteristics of plant life on nitrogen transformation.The difference in the content of attached elements will further affect the composition of the attached biological community,and ultimately directly or indirectly participate in the cycle of nutrients.The dry weight of the attachments of the samples collected in the same lake is expressed as aquatic plants>non-biological substrate,and between different species is expressed as hornwort>pumpkins,and it changes dynamically with the growth stage of the plant.The results of the Alpha diversity index of ammonia oxidizing archaea showed that the richness and diversity of the biofilm community attached to the surface of aquatic plants/abio-substrates was much higher than that of water bodies.The diversity and richness of abio-substrates attachments is greater than that of aquatic plants.The community structure and dominant bacteria(phyla and genus)of ammonia-oxidizing archaea in the attached biofilm are more stable than those in water,indicating that the biological matrix/abiotic matrix can provide a favorable microenvironment for the growth and reproduction of microorganisms.In general,this study found that the diversity and community structure of attached microorganisms are significantly affected by habitat conditions such as the physical and chemical properties of attachments,the nature of the substrate,and the nutrient load of the water body.Both biological and abio-substrates can be nitrogen-related microorganisms.Provides a good growth surface and abundant nutrients,and has the potential to increase the diversity of nitrogen-related microorganisms and regulate the community structure.The results of the study have a great significance for the understand the nitrogen cycle process in the surface MBL attached on bio-substrates and abio-substrates in freshwater waters.