Effects Of Benthic Disturbances On Ammonia Oxidizing Bacteria And Ammonia Oxidation Processes In Lake Sediments

Nitrogen was one of the key elements of lake eutrophication,biogeochemic al cycle of nitrogen plays an important role in lake nutrient cycling.Nitrificati on(NH3?NO2-?NO3-)was a key step in the nitrogen cycle process,and the a mmonia oxidation process(NH3?NO2-)was the rate limiting step of nitrification.Ammonia oxidation which was driven by some microorganism,the community c omposition?abundance and activity of AOA and AOB will directly or in direct ly affect the ammonia oxidation process.AOA and AOB was the key driver o f global ammonia oxidation process.AOA and AOB had a very wide ecological location in the world,to date,the distributions of AOA and AOB had been w ell documented in soil and marine environments,while there was few studies co ncerned about their distribution and diversity in the lake ecosystem.In the lake Taihu ecosystem,the bioturbation of C fluminea and L.hoffmewasteri will ulti mately affect the ammonia oxidation process by influencing the community co mposition?abundance and activity of AOA and AOB.To better understand the e ffects of the two benthic animals bioturbation on the community composition a nd abundance of AOA and AOB in the surface sediment,reveal the effect on a mmonia oxidation process,sediment-water microcosms of different density and t emperature treatments of Corbicula fluminea and L.hoffmewasteri were construct ed.Clone libraries and real-time qPCR technologies were applied to analyze am monia oxidation process and the community composition and abundance of AO A and AOB in the surface sediments.The obtained results were as follows:1.Micricosms of density experiment(1)The addtion of benthic animals could release N elements into the water,promoted the nitrification process to a certain extent,and L.hoffmewaster was more effectively.The nitrification intensity ability of three density treatments was:low density,medium density,high density was the weakest.It showed that the right amount of biological disturbance provided a suitable niche forAOA and AOB.(2)qPCR results showed that the abundance of AOB amoA were significantly higher than AOA in the all surface sediments.In the system of C.fluminea,the abundance of AOB amoA showed negative correlations with the density.In the high density treatment,the abundance of AOA amoA was the lowest.In the system of L.hoffmeister,the abundance of AOA amoA did little change,the abundance of AOB amoA in medium density was the highest,of high density was the lowest.(3)The behavior of benthic bioturbation reduced significantly the diversity of AOA and AOB in the surface sediment,the community composition of AOA and AOB were more onefold.The diversity of AOA and AOB were lower than the control group.AOA clustered exclusively with Nitrosotalea?Nitrosopumilus?Nitrososphaera.All AOB fell within ?-Proteobacteria:Nitrosospira?Nitrosomonas,the former is superiority.In the system of C.fluminea,the diversity of AOA was:the low density was the highest.In the system of L.hoffmeister,the diversity of AOA had little difference,the diversity of AOB was:the high density was comparable for the medium density,which were higher than the low density.2.Micricosms of temperature experiment(1)Under the condition of 15?,22?,28?,the behavior of C.fluminea did little effect for nitrification process,L.hoffmeister promoted the nitrification process to a certain extent.The temperature variable affected the ability of nitrogen release significantly.(2)In all treatments,the abundance of AOB amoA was obviously higher than that of the rest treatments in 22?.In the system of C fluminea,the abundance of AOA and AOB had the same tendency,which were highest in 22?,28? lowest.In the system of L.hoffmeister,the abundance of AOA amoA had little difference in different treatments,the abundance of AOB amoA reached the highest value in 22?.(3)In all treatments,the community structure of AOA changed significantly.AOA clustered exclusively with Nitrosotalea?Nitrosopumilus?Nitrososphaera.All AOB fell within ?-Proteobacteri:Nitrosospira?Nitrosomonas,the former is superiority.In the system of C.fluminea,the phylogenetic analysis showed that the diversity of AOB was higher than AOA,which was higher than the control group.In the system of L.hoffmeiste,the diversity of AOA in 22? was lower than 15? and 28?,the diversity of AOB in 15? was higher than 22? and 28?.The community composition of AOB in C.fluminea treatment was higher than L.hoffmeister.These results would help to illustrate the inferences of environmental variables to the ammonia oxidation process,and found out the law of nitrogen cycle in the lake ecosystems.At the same time,these results also could provide benefical reference for nitrogen pollution abatement in lake Taihu.