Zooplankton Diversity And Community Characteristics In Poyang Lake Based On DNA Metabarcoding And Morphology

Poyang Lake is the largest freshwater lake in China,and its ecosystem function and biodiversity have been extensive concerned.Zooplankton is one of the main groups in the lake ecosystem,and it is an important link in the food chain,which plays a vital role in maintaining the stability and function of the ecosystem.In recent decades,DNA metabarcoding technology has shown great potential and advantages in biodiversity monitoring and assessment.The technique is characterized by operation without separating the target organism,non-destructive,simple and sensitive,which makes up the shortage of time and energy consumption of traditional morphological method in aquatic biological monitoring.It is necessary to further understand the zooplankton community structure and the evolution of biodiversity in Poyang Lake,particularly in the context of increasing climate change and human activities.In order to provide a basis for the scientific management of Poyang Lake,we used DNA metabarcoding and morphological method to monitor and evaluate zooplankton diversity in Poyang Lake from 2019 to 2021.The main results are as follows:1.Zooplankton community characteristics in Poyang Lake and its connected waters(Hukou section of the Yangtze River,Tongjiang Waterway,main lake of Poyang Lake,Nanjishan Protected Area,Junshan Lake and Qinglan Lake).The results showed that 165 species of zooplankton were detected by DNA metabarcoding in Poyang Lake,including 96 species of rotifers in 46 genera,50 species of copepods in 30 genera,and19 species of cladoceran in 11 genera.There were 128 zooplankton species in Poyang Lake detected by morphology,including 88 species in 34 genera,16 species in 14 genera of copepods,and 24 species in 15 genera of cladoceran.The α diversity of zooplankton detected by the two methods in different seasons showed the same trend,and NMDS analysis showed that the species composition of summer and winter had the biggest difference.The results also showed that DNA metabarcoding had better species detection ability,which was similar to the traditional morphological results.2.The zooplankton community characteristics of Poyang Lake basin(Hukou section of the Yangtze River,Tongjiang Waterway and main lake of Poyang Lake)from2019 to 2021 were studied based on morphological methods.The results showed that143 species of zooplankton belonged to 64 genera and 26 families,and rotifers were the dominant group.There were significant differences in the number of zooplankton species in different seasons.The number of zooplankton species in spring and summer was more than that in autumn and winter.There were 28 dominant species,including24 rotifers,1 cladoceran and 3 copepods.The dominant species showed significant spatio-temporal differences.The α diversity index showed significant spatio-temporal differences,and the Shannon-wiener index showed significant differences between spring and winter,spring and autumn.Spatially,there are significant differences in Shannon-wiener index,Pielou evenness index and Simpson index between Yangtze River and Tongjiang Waterway and the main lake of Poyang Lake.The zooplankton community structure showed obvious spatial and temporal differences,especially between the Hukou section of Yangtze River and other regions.The main environmental factors affecting the zooplankton community in different seasons is different.The main environmental factors affecting zooplankton community in spring were total nitrogen(TN),dissolved oxygen(DO)and temperature(T).In summer,it is temperature(T),total nitrogen(TN),and flow velocity(V).In autumn,it is velocity(V),transparency(Dia)and depth(WD).The main environmental factors in winter were total phosphorus(TP)and dissolved oxygen(DO).3.Shahu lake is one of the important butterfly shaped lake in Poyang Lake nature reserve for migratory birds,and the main lakes have different hydrologic features,analysis of the zooplankton diversity and community features can offer reference for scientific control reserve level.Zooplankton diversity and community characteristics in Shahu lake were studied based on 18 S metabarcoding(MBC)and morphology(MOI).MBC detected 98 species of zooplankton,and MOI detected 90 species of zooplankton.Both of the two methods showed a lower number of species in spring and a higher number in summer,and both were dominated by rotifers.The α diversity index analyzed by the two methods showed the same trend.The α diversity index was higher in summer,followed by autumn and lower in winter.NMDS and community cluster analysis showed that there were significant seasonal differences in zooplankton community composition detected by the two methods.4.Based on the existing public database information,we organized the species of zooplankton COI and 18 S barcode information database.Total 27679 of zooplankton COI and 18 S barcode sequences were screened from NCBI database and BOLD database,including 808 zooplankton morphological species.Copepods had more COI and 18 S barcode sequences,while cladoceran 18 S barcode sequences were less.As a new technology,DNA metabarcoding has been paid more and more attention and has been widely used in many fields,including biodiversity monitoring.Especially in the context of the "10-year fishing ban" in the Yangtze River,this technology provides a new method for the protection and monitoring of aquatic ecosystem diversity.In this study,the zooplankton diversity and its driving factors in Poyang Lake were analyzed by combining the traditional morphological identification method and DNA metabarcoding method.The results showed that the DNA metabarcoding method had a good ability to detect species,and the results were similar to the traditional morphological method.These results can provide reference for monitoring biodiversity in Poyang Lake Basin and other watersheds by using DNA metabarcoding technology in the future.In spite of this,the DNA metabarcoding technology still need further perfect and standardize,for example,sample collection and handling process,choice of molecular markers,primer design,PCR’s preferences,in particular to improve reference database or regional database.