Dynamic Changes Of Nutrient Elements And Their Effects On The Microbial Diversity Of Sediments During The Decaying Of Nelumb O Nucifera Detritus

Aquatic macrophytes are major part of lake ecosystem,they can maintain the stability of the entire lake ecosystem and the circulation of nutrients.When the plant enters the decline stage,stems,leaves and other tissues will gradually fall into the water body,and the nutrients of litters will be released into the water bod y and the sediment,which will cause secondary pollution in the lake water environment.Therefore,The study on decomposition of aquatic plants in freshwater ecology has been one of the hot issues in recent years.For this reason,we selected the emergent plant Nelumbo nucifera as the research object in this study.Through construct the field experiment systems and indoor systems,study the rate of decomposition,changes in biomass,release and migration of nutrients about stems?plus petiole?and leaves of Nelumbo nucifera in the entire decomposition process.To study the release of N,P,and other nutrients at different tissue under different environmental factors?DO,temperature?,and to analyze the effect on the quality of overlying water and nutrients in sediments during the decomposition.From the point of molecular biology,studythe effects on the community structure,abundance and diversity of sediment microorganisms during Nelumbo nucifera decomposition.The main research results are as follows:?1?The decomposition rate was difference at different tissues of Nelumbo nucifera,which has different effects on overlying water under different temperatures and DO conditions,and the distribution of sediment microbial species were divergence at different biomass densities.Stems need took 230.75 days to decompose 50%of dry biomass(t_0.5/d)from the decomposition,and 95%of dry biomass(t_0.95/d)required997.25 days,the leaves were decomposed 50%initial biomass(t_0.5/d)took 115.92 days,and the time to decompose 95%of initial biomass were 501 days.In the process of the decomposition,the TN content of overlying water under aeration conditions is lower than that without aeration,it can explain aeration conditions can reduce the water N concentration during decomposition.The biomass loss rate of Nelumbo nucifera leaves and stems?including petioles?was expressed as:T4>T3>T2>T1,which was proportional to the temperature.?2?During the decomposition process,the COD content in the overlying water body increased,and the order of concentration intensity was:150g>90g>30g>0g.The TN content in overlying water showed a rising-descending trend when the decomposition was 65 days,and this time TN concentration reached the maximum in the 150g group.The TP content in water rapidly increased at the early stage of the experiment and decreased slowly at the later stage of the experiment.The final TP concentration in the 150 g experimental group was the highest.The overall p H level of the sediments varied from 7.96 to 8.3,which was weakly alkaline.There was no significant difference between several density gradient groups.The S-OM content increases as the biomass density increases.When the biomass density of Nelumbo nucifera was 30g/m²,the pH of the sediments was significantly negatively correlated with the TP in overlying water?P<0.01?.There was a significant positive correlation between sediments conductivities and NH₄⁺-N in overlying water?P<0.05?when the biomass density was 90g/m²,there was a significant positive correlation between sediment TP and overlying water TP?P<0.05?.when the biomass density was 150g/m²,there was a significant positive correlation between S-OM and overlying water COD?P<0.05?,and a significant positive correlation between sediment NH₄⁺-N and overlying water COD?P<0.05?.?3?There were significant differences in the distribution,richness,and evenness of the microbial species in sediments under different biomass densities in the process of Nelumbo nucifera decomposition.The sediment microbial diversity was correlated with sediment NH₄⁺-N,TN,and TP.There was a significant positive correlation between sediment TN and OTUS?P<0.01?,and there was a significant positive correlation between NH₄⁺-N and Shannon index?P<0.01?,TN and Chao1index were significantly negatively correlated?P<0.01?,we could got conclusion,the impact on the physicochemical parameters of sedimentation will directly affect the ecological distribution of microorganisms in sediments during decomposition.Under high-density conditions,sediment species were abundantly distributed.The dominant species in each sediment sample were Proteobacteria,Acidobacteria,Chloroflexi,Nitrospira,Bacteroidetes,Nitrospina,Verrucomicrobia,Ignavibacteriae,Firmicutes.