Spatial And Temporal Distribution Characteristics Of Algae Communities In Typical Areas "one River And Two Streams" Basin Of Tibet And Their Relationship With Environmental Factors

The Qinghai-Tibet Plateau has a unique niche.As the political,economic,cultural and transportation center of the Tibet Autonomous region,sufficient attention should be paid to its aquatic environment.A seasonal survey on the community structure of planktonic and epiphyticalgae of the typical section of“One River and Two Streams”Basin wasconducted in June?summer?,October?autumn?,December?winter?2018and April?spring?2019,the physical and chemical parameters of water body were monitored simultaneously.Water quality evaluation was carried out with information from both hydrochemistry and aquatic algology,and the relationship between algae community and water environmental factors was discussed.The main results were as follows:During the survey,6 phyla,78 genera and 130 species of planktonicalgae were detected at 7 stations in the“One River and Two Streams”Basin,including 53 species of Bacillariophyta from 28 genera that with an annual average abundance of 72.2%,16 species of Cyanophyta from12 genera with annual average abundance of 9.7%,and 50 species of Chlorophyta from 32 genera with annual average abundance of 11.8%.A total of 97 species of epiphytic algae from 5 phyla and 60 genera were detected,including 48 species of Bacillariophyta from 25 genera with an annual average relative abundance of 88.5%,17 species of Cyanophyta from 13 genera with an annual average relative abundance of 6.7%,and26 species of Chlorophyta from 18 genera with annual average relative abundance of 3.6%.Bacillariophyta,Chlorophyta and Cyanophyta were the dominant phyla in both planktonic and epiphytic algae species,and Nitzschia sp.was the main dominant species.The variance analysis of water environmental factors showed that the water temperature?WT?in summer was significantly higher than that of other seasons,while the pH was lower than other seasons.The water turbidity in autumn was significantly higher than other seasons,the concentration of ammonia nitrogen?NH₃-N?in winter was significantly higher than that in other seasons,and the concentration of total phosphorus?TP?was less affected by seasonal change.The concentrations of Turbidity,NH₃-N and TP were significantly affected by site changes,while WT and pH had no spatial heterogeneity.Based on the analysis of hydrochemical parameters:the water quality evaluated with single factor analysis indicated by NH₃-N and TP were mostly in type?and?.The calculated comprehensive pollution index?CPI?ranged from 0.41 to 0.50,0.33 to 0.64,0.37 to 0.69 and 0.42to 0.83 in spring,summer,autumn and winter season respectively,and with an average of 0.49 in the whole year,which indicated the water quality was between type?and??mostly in type??.Based on the analysis of algae biological parameters:the Simpson index of planktonic algae varied from 0.75 to 0.94 and averaged at 0.87,the Shannon index ranged from 2.11 to 3.19 and averaged at 2.66,the Pielou index ranged from 0.55 to 0.82 and averaged at 0.70,the Margalef index ranged from2.49 to 5.11 and averaged at 3.20.Across the epiphytic algae,the Simpson index averaged at 0.87?ranged from 0.71 to 0.93?,the Shannon index averaged at 2.54?ranged from 1.84 to 2.97?,and the Pielou index averaged at 0.71?ranged from 0.53 to 0.90?.Based on the indication from calculated diversity index,generally,the water quality of“One River and Two Streams”Basin was under light or medium pollution condition.The pollution indicator algae also indicated that the studied areas were in?mesosaprobic zone.The biological integrity index?IBI?of planktonic algae was averaged at 2.91?ranged from 1.80 to 4.64?,while the epiphytic algae was averaged at 2.17?ranged:0.98-3.14?.The water quality was mostly under moderate and good condition based on IBI evaluation.The water quality evaluation results showed good consistency between hydrochemical method and aquatic algology method.The redundancy analysis?RDA?of the relationship between environmental factors and key biological parameters showed that WT had significant effects on both the abundance and the pollution indicator species of planktonic algae,that with increased abundance and pollution indicator species with WT rising.Photosynthetically active radiation?PAR?had significant effects on the dominant species of both planktonic and epiphytic algae,and the dominant species of epiphytic algae were significantly affected by UVA.The abundance of most dominant species in planktonic and epiphytic algae were stimulated with increasing of PAR and UVA.Turbidity had a significant effect on the species number of epiphytic algae,except in Dinophyta that was not significantly affected by Turbidity,species from other four phyla decreased with increase of Turbidity.In conclusion,Bacillariophyta,Chlorophyta and Cyanophyta were in dominant position in the study area of“One River and Two Streams”Basin,and Nitzschia sp.was always the main dominant species.Water quality evaluation from both the hydrochemical parameters?single factor analysis and CPI?and the index from planktonic and epiphytic algae?diversity index,pollution indicator algae and IBI?showed good consistency and indicated the water quality are mostly in good or medium condition.Community structure of planktonic and epiphytic algae in the basin mainly modulated by WT,PAR,UVA and turbidity based on the analysis of the relationship between number of algae species,abundance and water environmental factors.