Studies On Effect Of Submerged Macrophytes On Eutrophication Water Restoration And Its Correlation With Macrophyte Bacteria

In this paper,8 submerged macrophytes such as Vallisneria natans,Vallisneria denseserrulata,Hydrilla verticillata,Elodea canadensis,Ceratophyllum demersum,Potamogeton malaianus,Potamogeton pectinatus,and Potamogeton maackianus from Zhejiang Province were selected to study their purification ability under indoor static water conditions,and Illuminal6S rRNA was used to determine the community composition of bacteria associated with submerged macrophytes,and the submerged macrophytes with better purification effect were selected according to analysis of the decontamination ability of submerged macrophytes and the structural diversity of plant flora.On this basis,in order to screen out the highly efficient submerged macrophytes combinations with strong pollution function,the experiment of different submerged macrophytes combinations was carried out by simulating eutrophication water.The test results showed,the removal efficiency of eight submerged macrophytes to TN and TP in water mainly depended on plant synergism,plants had a lower removal efficiency through absorption and enrichment,the nitrogen and phosphorus’enrichment and absorption rates were 1.65%～15.69%and 1.51%～17.95%respectively.Among them,Vallisneria denseserrulata had the highest removal rate of TN,TP and NH4+-N in water;they were 91.58%,96.81%and 96.68%respectively.The purification effects of Ceratophyllum demersum,Hydrilla verticillata and Elodea canadensis ranked second,and the purification effects of Potamogeton pectinatus and Potamogeton maackianus were the worst.The purification effect of each treatment on CODMn was not obvious during the experiment.Proteobacteria was the absolute dominant phylum of the associated bacteria of 8 submerged macrophytes(Abundance values were more than 40%).The common dominant genera of various submerged macrophytes were Cupriavidus,Rhodobacter and Gemmatimonas.The reason that different submerged macrophytes could enhance the purification ability of water quality through synergism might be that most of the associated bacteria of plants had degradation effect.Taking into account the above factors,it was concluded that:Vallisneria denseserrulata,Ceratophyllum demersum,Hydrilla verticillata,and Elodea canadensis had a good effect on the purification of pollutants in water,so it should be selected as the preferential species for the remediation of eutrophic water.The removal effect of the combination with various submerged macrophytes on pollutants in water was better.The growth trend of C1 combination(Vallisneria denseserrulata+Ceratophyllum demersum+Hydrilla verticillata+Elodea canadensis)was the best,which had the net increased biomass of 3.89g.The combination B4(Vallisneria denseserrulata+Hydrilla verticillata + Elodea canadensis)and combination C1 had the best effect on the purification of nitrogen and phosphorus in water.Their TN and TP removal rates were 86.14%,83.52%,85.59%and 81.26%respectively.The removal rate of NH4+-N of each combination was more than 70%,and the C1 combination and B1 combination(Vallisneria denseserrulata+Ceratophyllum demersum+Hydrilla verticillata)had best purification effect.The combination C1 and the combination B2(Vallisneria denseserrulata+Ceratophyllum demersum+ Elodea canadensis)had the best removal rates of 89.63%and 88.96%to CODMn.At the end of the experiment,DO concentrations in the water bodys of all combinations were higher than 7 mg·L-1.The conclusion of the comprehensive evaluation was that:In terms of the restoration of eutrophic water,combination B4 and combination C1 could be used as the optimal plant combination.