Research On Structure Dynamic Characteristics Of Phytoplankton Community And Its Correlations With Water Environmental Factors In The Downstream Of Nenjiang River

The search established10sampling stations in the downstream of Nenjiang River and separately sampled in May,July,September and October of2011to conduct qualitative and the quantitative investigation to the phytoplankton.Simultaneously they have carried on the monitor and the analysis to the corresponding water environmental factors.By using the multi-dimensional scaling method,it analyzed phytoplankton biodiversity and the community structure in the biological statistics,and evaluated the water quality by using abundance,biomass and bio-diversity. Besides,through the Canonical Correspondence Analysis (CCA),it discussed the correlations between phytoplankton and environment factors in order to provide the scientific basis for the downstream of Nenjiang River protection and the governance as well as the ecology repair.In the investigation,there are totally7phyla,140species among which the majority were68kinds of Bacillariophyta and44kinds of Chlorophyta,11kinds of Chrysophyta,10kinds of Cyanophyta,4kinds of Euglenophyta,2kinds Cryptophyta and one kind of Pyrrophyta.In the period,it has found26common species in the downstream of Nenjiang in which there were mainly diatom and green alga and14dominant species,represented by diatom primarily and green alga following.The dominant species has been obviously affected,which is least in the summer and most in the autumn.Seeing from the superiority,Cyclotella meneghiniana has most superiority which achieved102.00×105ind./L in October in the summer.The abundance and biomass of phytoplankton were identical in the temporal and spatial distribution in the downstream of Nenjiang River.Analyzing from the seasonal variations,annual abundance and biomass from large to small sort:spring (May.)>winter(Oct.)>Autumn(Sep.)>summer(Jul.).Analyzing from the spatial distributions,average abundance of various sampling stations in the whole year from large to small sort:9#>10#>7#>8#>6#>5#>3#>4#>1#>2#.Annual average biomass from large to small sort:9#>10#>7#>8#>6#>3#>5#>1#>4#>2#.No matter if it was the abundance or the biomass,sample9#was the highest and sample2#was the lowest.In the investigation,Shannon-Weaver index of phytoplankton in the bio-diversity index was between1.87～4.45of the phytoplankton in the downstream of Nenjiang River’s;Pielou index between0.23～0.98;Margalef index between1.72～4.96.The temporal and spatial distributions of phytoplankton bio-diversity indexes were remarkable.Analyzed from the seasonal distributions,the Shannon-Weaver index was highest in the autumn(Sep.),the second one was in the summer(Jul.),and the lowest in the winter(Oct.);the Pielou index was highest in the summer(Jul.),the second was in the autumn(Sep.) and the lowest in the winter(Oct.);the Margalef index was highest in autumn(Sep.),the second one was in the spring(May.),and the lowest in the summer(Jul.).Analyzing from the spatial distributions of the whole year,the Shannon-Weaver index’s maximum and the minimum values appeared separately in the autumn(Sep.) the4#and winter (Oct.)10#;the Pielou index’s maximum and the minimum values appeared separately in the summer(Jul.)4#and the winter(Oct)10#;the Margalef index’s maximum values appeared in the autumn(Sep.)4#,and the minimum values in the summer(Jul.)4#and6#.The results of correlation analysis of the three indices can show phytoplankton bio-diversity well.From the results of Multidimensional scaling analysis to the phytoplankton community,it showed that phytoplankton bio-diversity in the upper,middle and lower parts in spring are remarkable. And in different seasons, the samples of phytoplankton are different in similarity.MDS distribution charts can demonstrate community’s distance-similarity of various samples and can also indicate that composition of various sites phytoplankton community existed different obviously.The results of Canonical Correspondence Analysis respected that water temperature is main driving factors phytoplankton’s community structure dynamic state in the downstream of Nenjiang River,which BOD5, CODMn, COND and DO follow in the second place.The ordination of main phytoplankton species abundance revealed an apparently dynamic character,which Chlorophyta,Eulenophyta and Cryptophyta are mainly under the impact of BOD5,CODMn,COND and DO.Water temperature is main environmental variable to influence the abundance of Cyanophyta,Chrysophyta and Bacillariophyta.