Analysis Of The Fish And Phytoplankton Diversity In Poyang Lake Basin Using Environmental DNA Metabarcoding

Environmental DNA metabarcoding technology has been paid more and more attention,and it has been widely used in many research fields such as biodiversity monitoring.The emerging environmental DNA metabarcoding technology can accurately identify the target species by directly extracting DNA from environmental samples,using general primers for specific groups for PCR amplification,combined with next-generation sequencing.There is no need to collect target organisms in the operation process.Environmental DNA metabarcoding technology has the characteristics of non-destructive sampling,easy operation and high sensitivity,which makes up for the deficiency of traditional morphological monitoring.Under the comprehensive implementation of the “a decade fishing ban” measure in the Yangtze River,many traditional aquatic biological monitoring methods are difficult to adapt to the new monitoring requirements.Environmental DNA metabarcoding technology has great application potential in biodiversity assessment.In this study,the temporal and spatial pattern of fish diversity in Nanchang section of the lower reaches of Ganjiang River,the diversity of eukaryotic phytoplankton,and the genetic diversity of Hypophthalmichthys nobilis(bighead carp)in Poyang Lake basin were studied using environmental DNA metabarcoding technology.It’s provide a practical example for the application of this technology in biodiversity monitoring,and provide a basis and reference for the research on biodiversity in the Poyang Lake.The results are as follows:1.The species and community characteristics of fish in the Nanchang section of the lower reaches of the Ganjiang River were studied based on environmental DNA metabarcoding technology.In terms of species composition,a total of 114 fish species were detected by environmental DNA metabarcoding technology,consisting of 88 species of fish on history recorded and 26 species of fish on history unrecorded.Most fish species belong to Cyprinidae.The living habits of fish were mainly lake resident species.The demersal fishes were the most in ecotype.The fish diversity and community structure of this research area showed significant seasonal differences(p <0.01),and there were 103 species at most in spring.Using this technology,we also found that more fish species were detected in the surface water samples,and more species were detected inshore than farshore.The diversity of fish detected in the different locations was not obvious differences(p>0.05),but differences in fish community structure(p<0.05).2.Based on the environmental DNA technology,a total of 166 genera of phytoplankton from 10 phyla,24 classes,54 orders and 101 families were identified.Chlorophyta and Bacillariophyta had abundant species.There are 89 genera of Chlorophyta and 28 genera of Bacillariophyta.At the genus level,Chlorophyta and Bacillariophyta account for 70.5% of phytoplankton in Poyang Lake.Judging from the obtained OTUs,OTU2 has the greatest dominance,with absolute dominance in the middle and southern regions.The diversity and evenness of phytoplankton communities in the middle region were higher.Based on the OTU analysis of the diversity index of different regions in Poyang Lake,the diversity index was not significantly different among the three regions in the northern,southern and middle regions(p>0.05).The NMDS analysis showed that the phytoplankton communities in the southern,middle and northern of Poyang Lake were significantly different(p <0.01).The RDA analysis and Heatmap analysis also showed that chlorophyll a,p H,and waterflow velocity were important factors affecting the characteristics of the phytoplankton community.3.The feasibility of studying fish genetic diversity based on environmental DNA metabarcoding technology was discussed.Eight haplotypes of Hypophthalmichthys nobilis(bighead carp)in Poyang Lake area were obtained.Among them,haplotype H8 had the largest number of sequences,and haplotype H4 had the least number of sequences.The haplotypes of the bighead carp population in the Poyang Lake area also showed spatial and temporal differences.The haplotype richness of the population in Nanjishan Nature Reserve in the south of Poyang Lake was high,and seven haplotypes were detected.Only one haplotype was detected in Shahu Lake,Jiangxi section of the mainstream of the Yangtze River and Qinglan Lake.The number of sequences in spring is the largest,accounting for 60.20% of the total number of sequences.Common haplotype H3 was detected in all four seasons.At the same time,the population of Nanjishan Nature Reserve also showed high haplotype diversity and nucleotide diversity;the genetic differentiation coefficient Fst showed that there was significant differentiation among collection locations in hydrologically independent lake basins in dry season(Shahu Lake and Nanjishan Nature Reserve)and other populations.As a relatively frontier biodiversity monitoring method,environmental DNA metabarcoding technology can be used to efficiently detect the biodiversity and spatial distribution of fish and phytoplankton in Nanchang section of the lower reaches of Ganjiang River and Poyang Lake.The survey of resources and the formulation of protection policies by relevant departments play an important role,and also provide new technical means for Poyang Lake biodiversity monitoring and ecosystem assessment.In addition,environmental DNA metabarcoding appears promising in monitoring the genetic diversity of species,especially endangered and commercial species.