| Duliujiang River is an important river in southeast Guizhou,flowing through eight counties and districts of Qiandongnan Prefecture and Qiannan Prefecture,and water conservancy projects are currently under construction in the Duliujiang River Basin,which may have a certain impact on the ecological environment of the basin.The composition and community structure distribution of fish species can accurately reflect the ecosystem changes and environmental changes in the region.Therefore,this study uses environmental DNA(eDNA)technology to study the distribution characteristics of fish species α diversity,β diversity and spatial and temporal diversity in the Duliujiang River basin.In this study,a total of 10 sampling points were designed,mainly based on water sample collection and high-throughput sequencing,each sampling point was divided into 5L of water in the upper,middle and lower layers,and1 L was taken for DNA extraction after full mixing.Water samples were filtered using a 0.45 μm mixed cellulose ester(MCE)membrane,eDNA enrichment,and stored with liquid nitrogen.PCR amplification with 12 S r RNA as a molecular marker,high-throughput sequencing on the Illumina Nova Seq 6000 sequencing platform,and sequence alignment using Mitofish and NCBI resulted in the following:1.Based on eDNA technology,the species diversity of the dry period of the Duliujiang River was studied,and a total of 69 species of fish in 6 orders,18 families were obtained,of which 23 species appeared in the historical records compiled by Dai Yinggui.Compared with the original record,eDNA sequencing results increased by 46 fish species.According to the habitat and hydrological characteristics of each sampling point,it was divided into three groups: DF(pjw,blc),SR(bjx,dw,cj,njt)and SF(sdxc,dyx,rj,xjz),and the species diversity of DF group and other sampling points was quite different.The analysis of αdiversity index showed that cj had the highest community richness and the richest species diversity,and there was no significant difference in the analysis results of diversity index of each α(p>0.05).PCo A analysis of the above three groups shows that there are great differences between the DF group and the SR group on the x-axis.2.Based on the eDNA method,the species diversity of Duliujiang was studied during the flood period,and the results showed that a total of78 species of fish in 7 orders,17 families,were obtained,of which 34 species appeared in the historical records compiled by Dai Yinggui.Compared with the original record,eDNA sequencing results increased by 44 fish species.The species composition correlation heat map showed that the species composition of the two sampling points of xjz and cj did not achieve significant differences from those of other points(p>0.05),and the dominant species of xjz and cj was Siniperca undulata,while the dominant species of other sampling points was silver crucian carp.The analysis of α diversity index showed that the community diversity of pjw,dyx,dw and njt was high,while that of sdxc was low.One-way ANOVA analysis of the diversity index of α during the flood period showed that there was no difference in the analysis results of the indices(p>0.05).Taking the cj and xjz river sections as one group and other river sections as another group,the R and R Studio was used to analyze PCo A based on the distribution of sampling points and the presence-absence and abundance of species at sampling points,and there were large differences in the x-axis from the river sections and other river segments,and the dilution on the y-axis was small,and the cj river section was less different from other river segments.3.Based on the eDNA method Duliujiang,the spatiotemporal distribution characteristics were analyzed,and the eDNA of water samples collected from 10 samples in the waters of Duliujiang was sequenced with high-throughput sequencing,and a total of 1696708 reads and 4237 OTUs were obtained in the dry period,and 848636 reads and4601 OTUs were obtained in the flood period.Seasonal analysis of OTU and reads measured by Duliujiang showed that there was a significant difference in reads number(p<0.05)during the the dry period water period,and there was no difference in the OTU sequence number of the species interpreted(p>0.05).The results showed that the abundance of species in the flood period was higher than that of species in the dry period,and the cause of this phenomenon may be related to temperature,ultraviolet rays and sedimentation rate.Based on the "yes or not" and abundance of species in the the dry period flood period,the correlation heat map was drawn by Origin,and the results showed that the sampling points in the dry period were significantly different from the sampling points in the flood period(p<0.05),but the pjw sampling points in the dry period were only significantly different from the xjz sampling points in the flood period(p<0.05),and the xjz sampling points in the dry period were only significantly different from the xjz sampling points in the flood period(p<0.05).The results of α diversity analysis showed that the Chao1 index and Richness index showed significant differences in seasonal analysis(p<0.05),while the ACE index,Shannon index and Simpson index did not differ in seasonal analysis(p>0.05).In PCo A analysis,the sampling points in the dry period were clustered on the left side with a small aggregation range,and the sampling points in the flood period were clustered on the right side,but the aggregation range was large.A total of 48 species of fish were detected in both the flood period and dry period,and the species and abundance of fish in the flood period and dry period were quite different.Through PCo A analysis,the sampling points in the dry period were clustered on the left side,and the aggregation range was small,and the sampling points in the flood period were clustered on the right side,but the aggregation range was large.This phenomenon indicates that the species diversity of Duliujiang River is quite different from the the flood period and dry period,and the correlation heat map also reflects this status,and the concentration degree of sampling points in the dry period is higher than that in the flood period,indicating that the difference between the points in the flood period is greater than that in the dry period. |
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