Dynamic Changes And Influencing Factors Of Phytoplankton Community Structure In Reservoirs With Different Nutritional Status In Guizhou

The phytoplankton community structure could quickly reflect changes in the water environment,and has important guiding significance for the protection of reservoir water resources and water ecosystems.Guizhou is located in the Yunnan-Guizhou Plateau.The territory is a typical karst landform with complex topography.Compared with other regions,the eutrophication status and phytoplankton structure distribution in Guizhou reservoirs are unique.To study the changes and influencing factors of phytoplankton community structure under different nutritional states in Guizhou,27 sampling points were set up for stratified sampling of water environmental factors and phytoplankton in Hailong Reservoir(HL),Goupitan Reservoir(GPT),Chayuan Reservoir(CY),Langou Reservoir(LG),Huaxi Reservoir(HX),Puding Reservoir(PD),Guijiahu Reservoir(GJH)and Wanfeng Reservoir(WF)from October 2020 to August 2021.The main results were as follows:1.The comprehensive nutritional status index(TLI)showed that Hailong Reservoir(52.19)and Langou Reservoir(50.43)were in eutrophic state,Chayuan Reservoir(35.48)and Wanfeng Reservoir(39.46)were in mesotrophic state,and Guijiahu Reservoir(47.23),Puding Reservoir(46.52),Goupitan Reservoir(45.31)and Huaxi Reservoir(44.43)were medium-eutrophic reservoirs.2.76 species(genera)in 7 phyla of phytoplankton were identified,mainly dominated by Chlorophyta(40.79%),Bacillariophyta(23.68%)and Cyanobacteria(22.37%).26 functional groups were classified,namely A,B,C,D,E,F,G,H1,J,K,L_M,Lo,M,MP,N,P,S1,S2,S_N,T,TC,W1,W2,X1,X2,Y.Among them,the functional groups MP,Y,and D were the dominant functional groups shared by the 8 reservoirs,and the representative species were Achnanthes sp.,Synedra acusvar and Cryptomons erosa Ehr.3.The average biomass ranged from 282.76 to 5175.36?g/L,and the variation of the average biomass was as follows:HL>LG>GPT>PD>GJH>HX>WF>CY,showing that the eutrophic reservoir biomass(HL and LG)was significantly greater than the trend in mesotrophic reservoirs(n=265,P<0.05).The phytoplankton community composition of the same reservoir samples was significantly similar,and the phytoplankton community composition of the eutrophic reservoir was significantly different from that of other trophic state reservoirs(n=265,P<0.05),indicating that the phytoplankton community had obvious response to changes of nutrient environment in reservoir.4.Redundancy analysis(RDA)and variance decomposition analysis(VPA)indicated that total phosphorus(TP),total nitrogen(TN),dissolved inorganic nitrogen(DIN),water temperature(WT),p H and transparency(SD)were the main factors affecting the changes of phytoplankton functional groups(n=265,P<0.05).Eutrophic reservoirs were less affected by nutrients than mesotrophic reservoirs,SD had a greater impact on eutrophic reservoirs than other trophic state reservoirs,WT and p H were important environmental factors that affect the dynamic changes of phytoplankton functional groups.The results indicated that environmental factors affect the dynamic changes of phytoplankton functional groups mutually.5.The results of 23s rRNA gene sequencing showed that the number of OTUs shared by 8 reservoirs was 297,and the diversity index showed HL>LG>PD>GJH>HX>GPT>WF>CY,indicating that the microbial diversity in the low nutrient state reservoirs was greater than that in high nutrient.20 genera of cyanobacteria were obtained from 8reservoirs,of which Synechococcus(Synechococcus?sp.?PCC?7920)had the highest relative abundance,ranging from 26.41%to 93.25%.