| To study the diversity and distribution characteristics of protozoan with its dynamical relationship between water environments at Basumtso in the Tibetan region,a total of 254 water samples was collected by using 25# standard plankton net and the capped deep water sampler,where 9 sampling sites were selected and data were collected for 3 times from 3 seasons(spring,summer and autumn)separately during November 2017 to September 2018.The microscopic observation in vivo and fixed-staining methods were applied for species identification of protozoan,and the direct counting method was used for determining the number of individuals in each species of protozoan.The protozoan community and their relationship with water environment in Basumtso were analyzed using a biodiversity parameter of community,similarity and correlation analysis,the major results were showing follow.(1)The result of environmental factor analysis during spring,summer and autumn season in Basumtso showed that values of N,P and other factor were lower than the standard value,and it indicated that the Basumtso Lake had low levels of effect of external nutrition input.The vertical analysis of environmental factor showed that the lake had an obvious phenomenon of stratification,namely surface(stratification of temperature changing),which was from 0-30 m depth,the mid stratification(Thermocline)was identified from 30 m-60 m,and stratification of deep water(stratification of deep water)was determined that deeper than 60 m.This phenomenon was observed during spring and autumn seasons,but the mid stratification was does not much show during summer time.(2)A total of 277 species of protozoan was identified in this study(22 species were not identified),among them there were 168 species in spring,and they were belonged to 2 phylas,10 classes,23 orders,55 families and 76 generas,where the Tintinnida appeared as dominant group for the spring season and reach to 29.17% of total number of species,then the Amoebida was secondary dominant group and that reach to 10.71% of the total number of species,while the order of Arcellinda appeared as rare group and reach to 0.59% of the total number of species.137 species were found during the summer time,and they were belonged to 2 phylas,11 classes,28 orders,57 families and 75 generas,where the Tintinnida was dominant group and that reach to 24.09% of total number of species,the order of Arcellinda was secondary dominant group,and it reach to 12.41% of the total number of species,the Protostomatida was rare group and it reach to 0.73% of the total number of species.There were 124 species in autumn season,which belonged to 2 phylas,9 classes,23 orders,47 families and 69 generas.The Tintinnida has been dominant group and it reach to 32.26% of the total number of species,the Amoebida showed as a secondary dominant group,which reach to 12.90% of the total number of species,the Peritrichida showed a rare group for this season and it reach to 0.81% of the total number of species.Species of the Sarcomastigophora Phyla showed a dominant group for all three seasons and the dominance index was larger than 50%.As a whole,the structure of protozoan in this lake was presented a trend like so: spring>summer>autumn.(3)The Shannon community diversity index of protozoan was higher with the horizontal samples(3.38)than vertical samples(2.52)during the spring season in Basumtso,but the Margalef diversity index was higher in the vertical samples(6.73)than in horizontal samples(2.55),the Simpson dominance index was lower in horizontal samples(0.06)than in vertical samples(0.08),the Pielou evenness index was lower at the horizontal samples(0.89)than vertical samples(0.98).The Shannon community diversity index of protozoan was higher in the horizontal samples(2.97)than in vertical samples(2.44)during the period of summer,and the Margalef diversity index was higher at the horizontal samples(4.95)than vertical samples(2.70),the Simpson dominance index was lower in horizontal samples(0.07)than vertical samples(0.10),the Pielou evenness index was lower at horizontal samples(0.83)than in vertical samples(0.92).The Shannon community diversity index of protozoan in autumn was higher with horizontal samples(2.70)than vertical samples(2.60),the Margalef diversity index was higher in horizontal samples(4.07)than vertical samples(2.58),the Simpson dominance index was higher in horizontal samples(0.10)than in vertical samples(0.06),the Pielou evenness index was higher in horizontal samples(0.81)than in vertical samples(1.00).The result indicated that protozoan which distributed in horizontal samples had relatively lower community index and higher evenness,but the dominance index was not much different.Protozoan that distributed in vertical samples had extremely low community diversity index with low evenness index and simple community structure in Basumtso.(4)Analysis of nutritional functional groups of protozoan showed that BS groups higher than PA groups slightly in all three seasons,the saprophytic group and non-selective omnivorous groups had an increasing trend with increasing rate of water depth in Basumtso.(5)Analysis of community similarity index showed that the community similarity index between seasons were very different(0-0.17),which indicated that each sampling site had significant differences in both spatial and temporal level in Basumtso.(6)The correlation analysis between community parameter of protozoan and environmental factor showed that species richness and community distribution characteristics of the protozoan was co-influenced by multiples factors,but the water depth was major factor for influencing the community structure of protozoan in Basumtso. |
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