Spatial And Temporal Succession Characteristics Of Phytoplankton Functional Groups And Their Relationship With Environmental Factors In Dianshan Lake

The composition,community structure,and quantity of phytoplankton can reflect the changes of water environment.Dianshan Lake is one of the important water sources in Shanghai,the study of phytoplankton about it began earlier,and involved more contents,but there are few reports on the study of phytoplankton functional group in Dianshan Lake.Monthly phytoplankton and water samples collected from January 2015to December 2017.Through field surveys and laboratory experiments,explore the characteristics of the community structure of phytoplankton,and the classification method of phytoplankton functional groups were understood temporal and spatial succession of functional groups,and the cluster analysis and NMDS analysis were studied the similarity between functional groups,the significant spearman correlation analysis and canonical correspondence analysis were explored the relationships of phytoplankton functional groups?PFGs?with environmental factors.This study provide a theoretical basis for phytoplankton ecology,the protection and management of water resources in Dianshan Lake.The main results were as follows:1.There existed 332 species and 7 phyla in Dianshan Lake.Th e composition,abundance and biamass of community structures wer e dominated by Cyanophyta,Bacillariophyta and Chlorophyta,The c ommunity structure of phytoplankton was Cyanophyta-Bacillariophyta-Chlorophyta type.The species composition of phytoplankton was C-hlorophyta>Bacillariophyta>Cyanophyta>Euglenophyta>Other Phylu-m.The abundance of various seasons was summer>spring>winter>au--tumn and the abundance of various phylums was Cyanophyta>Bac-illariophyta>Chlorophyta>other Phylum.The biamass of various s-easons was summer>spring>autumn>winter and the biamass of various phylums was Bacillariophyta>Cyanophyta>Chlorophyta>Eu-glenophyta>Pyrrophyta>other Phylum.In addition,the abundance a-nd biamass of phytoplankton showed seasonal changes,and the suc-cession regulation of them were different in different years.2.29 phytoplankton functional groups?PFGs?were identified in Dianshan Lake,they were group P,X1,D,F,S1,MP,Lo,X2,C,W2,B,W1,M,K,E,T,Y,G,H1,TB,S2,WS,SN,A,NA,TC,X3 and Z.The group of J,P and X1 wrer very common groups;group D,MP,F,S1,C,X2,Lo,W2,E,W1,B,M,K and T were common groups;group G,H1,Y and TB only appear when conditions are suitablethe;group WS,A,S2,SN,TC,NA,X3 and Z were rare groups.Through ranking and screening the biomass of 29 functional groups,we got 18 dominant functional groups,they were group B,C,D,F,G,H1,J,Lo,M,MP,P,S1,S2,T,W1,W2,X1 and X2?3.The dominant functional groups of phytoplankton in Diansha n Lake were similar in different periods,but their succession rules were different.According to anniversary changes,In 2015,the grou p C/Lo/MP/J/P/D/W1 were dominant functional groups,and the ann ual succession regulation was C?Lo?C?MP/J/?P/W1?P?D.In2016,the group P/W2/Lo/M/H1were dominant functional groups,an d the annual succession regulation was P?W2/Lo?W2?M/H1?P.In 2017,the group P/Lo/W2/T/M/G/H1/B were dominant functional groups,and the annual succession regulation was P?Lo?W2?T?M?G/P/?H1/M?W2?B.According to seasonal changes,the su ccession rules of phytoplankton functional groups was spring?Lo/W2/P/MP??summer?M/MP/H1??autumn?P??winter?C/P/B?.According to the spatial distribution of functional groups,the phyto plankton functional groups in site St3 and St4,St5 and St6,St7,St8 and St9,St10 and St11 had high similarity,but on the whole,th e distribution and succession of the dominant functional groups in e ach site were different affected by geographical location,environme ntal factors and human activities.It is shown as follows:Sampling site St1 was dominated by groups MP and M;Sampling site St2 w as dominated by groups C,M and Lo;Sampling sites St3 and St4were dominated by groups W2 and C;Sampling sites St5 and St6were dominated by groups C/W2/MP/P/Lo;Sampling sites St7^St9were dominated by P2/W2/Lo,Sampling sites St10 and St11were dominated by groups M/P/J.4.The 11 environmental factors:Total Nitrogen?TN?,Total Phosphorus?TP?,Dissolved Oxygen?DO?,Transparency?SD?,Water Temperature?WT?,Electrical Conductivity?EC?,pH,Permanganate Index(COD_Mn),Chlorophyll a?Chl.a?precipitation?Pre?and Water level fluctuations?WLF?change regularly on the time scale,besides DO,WT,TN,TP,EC and COD_Mn showed obvious seasonal changes;SD is increasing year by year;pH in different month were closed to each other,and water was weakly alkaline;the precipitation concentrates from June to October in each year,and the water level fluctuations rise and fall regularly with precipitation.Affected by the geographical location of the sampling site and the environmental conditions of the water during the sampling period,the spatial changes of environmental factors at different sampling sites in Dianshan Lake.5.Canonical correspondence analysis?CCA?was conducted to analysis the relationship of Results showed that 18 phytoplankton functional groups?PFGs?and environmental factors.Results showed that water temperature?WT?,total phosphorus?TP?,transparency?SD?,pH,electrical conductivity?EC?and dissolved oxygen?DO?were the main impact factors associated with the composition and succession of PFGs in Dianshan Lake.Functional groups M/H1/S2/G were significantly positively correlated with TP and WT,and significantly negatively correlated with EC and DO;functional group C/D were significantly positively correlated with and DO,and significantly negatively correlated with WT,SD and pH;functional group B/Lo/T were positively correlated with EC and SD,and negatively correlated with TP.In addition,the main environmental factors that affected phytoplankton functional groups were different in each years.The Spearman correlation analysis of dominant phytoplankton functional groups and environmental factors showed that there were obvious correlations between most dominant functional groups and environmental factors,and the main impact factors of functional groups were different to each other.