Effect Of Two Species Of Submerged Plants And Bellamya Aeruginosa And Their Combination On Water Purification

In order to solve the problem of eutrophication in shallow lakes,the paper selected two dominant submerged plants,Myriophyllum spicatum and Ceratophyllum demersum,and a species of snail,Bellamya aeruginosa to construct the microcosms,in Baiyangdian Lake on July to September of 2019,and explored the effect of different combinations on the purification of water quality,combining with high-throughput sequencing to study the composition and diversity of the attached bacterial communities,provide basic data and reference for the ecological protection and restoration of the Baiyangdian Lake.The four experimental groups divided:?1?Control group?CK?,Myriophyllum spicatum group?TM?,Bellamya aeruginosa group?TB?,and Myriophyllum spicatum+Bellamya aeruginosa group?TMB?;?2?Control group?CK?,Ceratophyllum demersum group?TC?,Bellamya aeruginosa group?TB?,and Ceratophyllum demersum+Bellamya aeruginosa group?TCB?;?3?Control group?CK?,Myriophyllum spicatum group?TM?,Ceratophyllum demersum group?TC?,and Myriophyllum spicatum+Ceratophyllum demersum group?TMC?;?4?Control group?CK?,Myriophyllum spicatum+Ceratophyllum demersum group?TMC?,and Myriophyllum spicatum+Ceratophyllum demersum+Bellamya aeruginosa group?TMCB?.The main results are as follows:1.Experiment of Myriophyllum spicatum and Bellamya aeruginosa and their combination:Myriophyllum spicatum?TM?can significantly increase DO and pH.The removal of NH₄⁺-N and COD by Bellamya aeruginosa?TB?was the best,and the removal of COD was significantly higher than other groups?P<0.05?,with a removal rate of 32.42%after 15 days.The removal of TN,TP,TUB in TMB group was the best,and the inhibition of algae was significant higher than other groups?P<0.05?.The addition of Myriophyllum spicatum compensated the increase of turbidity and chlorophyll caused by snail.The unique OTUs number increased after the addition of the Bellamya aeruginosa,that is,the diversity of attached bacteria increased.2.Experiment of Ceratophyllum demersum and Bellamya aeruginosa and their combination:the Ceratophyllum demersum?TC?can reduce NH₄⁺-N and COD and increase DO.Which were significantly higher than other groups?P<0.05?,COD removal rate reached59.31%and DO increase rate reached 85.99%at 60 days.The combination of Ceratophyllum demersum and Bellamya aeruginosa?TCB?had the best removal of TN,TP and TUB and the inhibition of Chl.a,which the addition of Ceratophyllum demersum compensated the increase of turbidity and chlorophyll caused by snail.The unique OTUs number of Ceratophyllum demersum increased after the addition of the Bellamya aeruginosa,that is,the diversity of attached bacteria increased.3.Experiment of Myriophyllum spicatum and Ceratophyllum demersum and their combination,Myriophyllum spicatum?TM?had the best removal effect on TN,with a removal rate of 30.48%after 15 days.Ceratophyllum demersum?TC?had the best removal effect on TP,NH₄⁺-N and COD,which the removal of COD was significantly higher than other groups?P<0.05?.The combination of Myriophyllum spicatum and Ceratophyllum demersum?TMC?had the best effect of increasing DO and decreasing TUB,and the inhibition of algae was significantly higher than other groups?P<0.05?.On the whole,the group containing Ceratophyllum demersum has better water purifying effects.The number of unique OTUs in the plant combination was higher than that of single species of plant.4.Experiment of two species of plant and sanil combination:both treatments group could improve water quality.The plant combination?TMC?has the best effect on the increase of DO,and the plant combination with snail?TMCB?has the best effect on the removal of TN,TP,NH₄⁺-N,COD,decrease of TUB and Chl.a,which the removal effect on COD is significantly higher than that of the plant combination?P<0.05?,and can significantly increase pH.5.A total of 29 phylum and 25 genus of the attached bacteria were found in all experimental groups.Among them,the bacteria to Myriophyllum spicatum belonged to 27phylum and 25 genus,and that attached bacteria belonging to the Ceratophyllum demersum belonged to 29 phylum and 18 genus.Proteobacteria was the most dominant phylum in each group,and Bacteroidetes,Fimicutes,Cyanobacteria were the subdominant phylum.Each group had different dominant genus in different periods.The RDA analysis of plant attached bacteria community and water physicchemical factors showed that Proteobacteria was positively correlated with NH₄⁺-N and TP,and negatively correlated with TN and pH.Among them,it was the most significant with NH₄⁺-N.Bacteroidetes was most significant with TN,TUB and T Positive correlation with NH₄⁺-N,TP and DO,negative correlation with NH₄⁺-N and TP was the strongest;Cyanobacteria positive correlation with pH,TN and T,negative correlation with NH₄⁺-N,TP and DO,among which NH₄⁺-N is the most negative correlation.Firmicutes was positively correlated with NH₄⁺-N,TP,and DO,and have the strongest positive correlation with NH₄⁺-N.Taken together,NH₄⁺-N,TP,pH and TN were the main influencing factors of the attached bacterial community structure.6.PICRUSt function prediction results showed that bacterial function mainly involved 6types of metabolic pathways,including 39 sub-functional groups such as Membrane Transport,Amino acid metabolism,Energy metabolism and Carbohydrate metabolism,showing functional richness.