Study On The Protozoa Diversity In Qinghai Lake Watershed

As the largest inland saltwater lake in China,Qinghai Lake is a typical representative of the world's plateau inland lake wetland types.Protozoa is a kind of single-celled eukaryotic organisms,which have strong fecundity and fast growth rate.It is an important part of the natural water body ecological group.In addition,protozoa are very sensitive to environmental changes and are good indicator organisms for environmental monitoring.We collected water samples from 32 sample sites of four types of water bodies,i.e.inflow river,lakeside,main lake and sub-lake of the Qinghai Lake Watershed in August 2020(high water period),and a total of 95 water samples were obtained,using metagenomic sequencing technology and bioinformatics methods to carry out from the molecular level.Research on the diversity and community structure of protozoa and their influencing factors in this watershed.The main results are as follows:(1)A total of 176 protozoa operational taxonomic units(OTUs)in the Qinghai Lake Watershed were obtained by high-throughput sequencing belonging to 12 phyla,19 classes,43 orders,61 families and 72 genera,mainly including Ciliophoran,Euglenozoa and Cercozoa.Among them,there are 170 protozoa OTUs in inflow river,belonging to12 phyla,19 classes,42 orders,61 families,72 genera,and are mainly Ciliophoran,Cercozoa and Euglenozoa;175 protozoa OTUs in lakeside belong to 12 phyla,19 classes,43 orders,61 families,72 genera,and are dominated by the Ciliophoran and Cercozoa.There are 173 protozoa OTUs in main lake area,belonging to 12 phyla,19 classes,43 orders,60 families,71 genera,and are mainly Ciliophoran and Cercozoa;170 protozoa OTUs in sub-lake belong to 11 phyla,19 classes,43 orders,61 families and 69 genera,and are mainly Ciliophoran and Cercozoa.(2)Based on the analysis results of the Pielou index,Shannon index,Richness index and Simpson index,the protozoa diversity of the four types of water environment in the Qinghai Lake Watershed is inflow river > lakeside > main lake area > sub-lake;the NMDS and Pco A analysis,there were significant differences in the protozoa community structure among the four types of water environments.(3)The results of RDA analysis showed that the protozoa community in the Qinghai Lake Watershed is affected by p H,salinity,water temperature,total dissolved solids,turbidity,total nitrogen and total phosphorus;The protozoan community in inflow river is related to dissolved total solids,total nitrogen,salinity and p H;the protozoan community in the lakeside is related to dissolved oxygen,temperature,turbidity,and total phosphorus;the protozoan community in the main lake area is related to p H,salinity,dissolved oxygen,temperature,turbidity,and total phosphorus are related;the protozoan communities in sub-lake are related to dissolved oxygen,temperature,turbidity,and total phosphorus.(4)Based on the relative abundance >0.02,the protozoa dominant taxa is calculated,and a total of 25 dominant OTUs are obtained.Among them,there are 12 OTUs in inflow river,12 OTUs in the lakeside,10 OTUs in the main lake area,and 11 OTUs in the sublake.Mataza hastifera?Pseudodifflugia sp.?Protaspa longipes?Vorticella sp.?Korotnevella stella?Metanophrys sp.?Paraphelidium sp.etc.play an important role in the protozoa community in the Qinghai Lake Watershed.(5)Based on the R software indicspecies package.A total of 16 indicator OTUs of protozoa were obtained for the four types of water environments.Among them,there are12 protozoa OTUs in inflow river,7 protozoa OTUs in the lakeside,3 protozoan OTUs in the main lake area,7 protozoa OTUs in sub-lake.Mesodinium sp.is an indicator species with relatively high relative abundance,and is a common indicator species in the main lake area and sub-lakes.(6)Analysis of the co-occurrence networks of protozoa and other plankton in inflow river,lakeside,sub-lake and main lake have gradually become less modular,and the interaction networks among taxonomic groups have gradually become fragmented.The co-occurrence network shows the interaction of protozoa and algae,protozoa and algae,copepods,rotifers,protozoa and algae,cladocerans,rotifers,protozoa and algae,copepods,cladocerans,rotifers.In this study,high-throughput sequencing technology was used to analyze the protozoa species diversity,dominant groups,indicator groups,community structure and their correlation with environmental factors in inflow river,lakeside,main lake area,and sub-lake main lake areas of the Qinghai Lake Watershed.The purpose is to deeply understand the protozoa community characteristics of the water ecosystem of the plateau saltwater lakes,and to provide basic data and scientific basis for the research of water ecology and biological monitoring of the water environment in the Qinghai Lake Watershed.