Spatiotemporal Variability Of Phytoplankton Funtional Groups And Its Influencing Factors In Lake Ulansuhai

Water resources in lakes are one of the important components of global water resources.Lakes have multiple ecological functions.In recent years,the eutrophication status of lakes has been severe.Phytoplankton researching of aquatic vegetation in lakes can comprehensively reflect the eutrophication status of lakes.Algal bloom is the key indication of significant changes occurring in phytoplankton functional groups and is also an important manifestation of abrupt change in lake habitats.For a shallow lake in an arid region,the characteristics of an algal bloom outbreak are significantly different from those in a humid region in that a change in the color of a lake body is accompanied by the rapid growth of large algae.Although phytoplankton functional groups can effectively indicate lake habitats,the relationship between planktonic microalgae and large filamentous green algae and between large filamentous green algae and algae habitats is still not clear.In this study,we selected Ulansuhai,a shallow-water eutrophic lake of an arid area,located in Urad Front Banner,Inner Mongolia,China,as the study area.In April,August,and October of 2017 and January of 2018,we collected water samples and phytoplankton samples at 14 sampling sites.Based on the functional group classification method?FG?and the characteristics of the lake,we added functional group HT?Huangtai algae?and proposed a new functional group classification method suitable for Ulansuhai.We analyzed the dynamic change in phytoplankton functional groups and the characteristics of seasonal succession.Furthermore,we adopted the redundancy analysis?RDA?method to clarify the correlation relationship between dominant functional groups and environmental factors throughout the year and in dry and wet seasons.The main conclusions were as follows:?1?There were 125 species of phytoplankton,61 genera and 7 phytoplankton families in Ulansuhai,the temporal variation of species was small,Chlorophyta had the most species,followed by bacillariophyta and cyanophyta.The spatial distribution of species was quite different,which showed the characteristics of the middle part > the eastern entrance > the western entrance > the exit.?2?The cell density of phytoplankton showed obvious temporal variation.Which showed the characteristics of August>October>April>January.The eastern entrance was significantly higher than other regions.?3?The temporal variation of phytoplankton biomass in Ulansuhai was significantly different from that in other regions,which showed the characteristics of August> October> January > April.The temporal variation of Shannon-Wiener diversity index was small,belongs to ?-medium pollution?1?H?2?.But some areas were heavily polluted.?4?The phytoplankton in the Ulansuhai was divided into 23 different functional groups: C,D,N,P,MP,TC,S1,S2,SN,X3,X1,Y,F,J,K,H1,H2,Lo,LM,M,W1,W2,Wo,and according to the characteristics of the lake,a new functional group?HT?was added.According to the succession in April,August,October 2017 and January 2018.Temporal succession,the dominant functional group: N+X3+X1+F+J+M? MP+TC+Lo+M? D+MP+TC+S1+Lo+M? D+Y+W2.?5?This study found that when the biomass of functional group TC was larger than 0.0018 mg/L,it was correlated with the coverage of Huangtai algae?P<0.05?,and the correlation coefficient is r=0.810.Therefore,phytoplankton functional groups can be used as a link to indicate the lake habitat by identifying the coverage of Huangtai algae,thus providing a scientific basis for the early warning of an algal bloom.?6?The results of RDA analysis showed that TN,p H and TP were the main influencing factors for Spatiotemporal variability of phytoplankton functional groups in Ulansuhai,in wet season,TN,WD and TP were the main influencing factors,in dry season,Cond,COD_Mn and TP were the main influencing factors.