| Biodiversity is the material basis for human survival and sustainable development,and it is also the basic element to maintain the balance and stability of ecosystems.Traditional marine benthic survey methods mainly rely on morphological identification,which is time-consuming and labor-intensive,destructive to the ecological environment,and requires appraisers to have a high level of benthic taxonomy.Environmental DNA refers to the interaction between organisms living in the environment and the environment,and the tissues or cells containing their own genetic information are released into the environment through skin shedding,mucus,feces,urine,etc,to form environmental DNA.At present,a large number of studies have shown that environmental DNA has important application value in the evaluation of biodiversity and ecological quality.In this paper,environmental DNA was used to monitor benthic biodiversity and evaluate ecological quality in the Yalu River Estuary,and compared with the results obtained from morphological identification,the main research results are as follows:The results of high-throughput sequencing of environmental DNA:the high-quality sequences of the 18 sites in the Yalu River Estuary ranged from 50559 to 85749,and the number of OTUs divided by cluster integration ranged from 112 to 504.High-quality annotation results of environmental DNA:A total of 2639 OTUs were obtained from 18 stations in the Yalu River Estuary,and 1099 OTUs(41.64%)were successfully annotated;A total of 71 OTUs were annotated with high quality,of which 22 OTUs(30.99%)were benthic organisms;The annotation rate of benthic organisms ranged from 0.95%to 4.73%,with an average of 2.45%.There are 18 stations in the Yalu River Estuary,and the environmental DNA identification of benthic organisms belongs to 10 classes,16 orders,19 families,20 genera,22 species.There are 27 stations in the Yalu River Estuary,and the morphological identification of benthic organisms belongs to 11 classes,30 orders,48 families,62 genera,64 species.Based on 17stations in the Yalu River Estuary:22 species of benthic organisms were identified by environmental DNA,57 species of benthic organisms were identified by morphology,and a total of 10 species of organisms,there is no significant correlation or difference between the number of biological species obtained by the two identification methods;The difference between the relative abundance percentage of the number of individuals identified by environmental DNA is much higher than that of morphological identification,and there is an extremely significant difference between the total number of individuals obtained by the two identification methods(Friedman:?~2=17.000,p<0.01);There are extremely significant differences between the Shannon Wiener indices obtained by the two identification methods(paired sample T test:t=-5.980,p<0.01);There are extremely significant differences between the Simpson indices obtained by t--he two identification methods(paired samples T test:t=-4.689,p<0.01);There is an extremely significant difference between the evenness indices obtained by the two identification methods(paired samples T test:t=-5.474,p<0.01);There was an extremely significant difference between the abundance indices obtained by the two identification methods(Friedman:?~2=13.235,p<0.01).The Cody indices obtained by the environmental DNA identification were all lower than those obtained by the morphological identification,indicating that the replacement rate of the biological species obtained by the environmental DNA identification was low;The Cody index obtained by the two identification methods gradually decreased with the increase of the distance from the coastline or port,and the change trend was basically the same.The Sorensen index obtained by environmental DNA identification is basically larger than that obtained by morphological identification,indicating that the biological species obtained by environmental DNA identification have a high degree of similarity;The Sorensen index obtained by the two identification methods gradually increased with the increase of the distance from the coastline or port,and the change trend was the same.The Jaccard index obtained by environmental DNA identification is greater than that obtained by morphological identification,which also shows that the biological species obtained by environmental DNA identification have a high degree of similarity;The Jaccard index obtained by the two identification methods increased gradually with the distance from the coastline or port,and the change trend was the same.The correlation between the evaluation indices obtained by environmental DNA identification was consistent with the correlation obtained by morphological identification,both of which were significant correlations between AMBI and BENTIX,H'and M-AMBI indices,and there is a significant correlation between the AMBI and BENTIX indices obtained by the two identification methods;According to the multi-dimensional analysis,the degree of distance between the same evaluation indices is relatively small,which can be roughly divided into three categories:AMBI1 AMBI2,BENTIX1 BENTIX2,H'1 H'2 M-AMBI1 M-AMBI2.The correlation between the evaluation grades obtained by environmental DNA identification was consistent with the correlation obtained by morphological identification,both of which were significantly correlated between AMBI and BENTIX,H'and M-AMBI grades,and the similarity between the AMBI and M-AMBI grades obtained by the two identification methods is relatively high;According to multi-dimensional analysis,the distance between the same evaluation grades is relatively small(except for the BENTIX grade),which can be roughly divided into three categories:AMBI1 AMBI2 M-AMBI1 M-AMBI2 BENTIX2,BENTIX1,H'1 H'2.According to the evaluation grades obtained by the two identification methods,combined with the actual ecological quality of the sea area near the Yalu River Estuary,it is concluded that the AMBI and M-AMBI grades are more in line with the actual situation,and the overall ecological quality of t--he Yalu River Estuary is evaluated as good.In summary:The annotation rate of benthic organisms at 18 stations in the Yalu River Estuary was between 0.95%and 4.73%,and 22 species of benthic organisms were identified by environmental DNA;There are extremely significant differences between the total number of individuals and the alpha diversity index obtained by environmental DNA and morphological identification;Both environmental DNA and morphological identification showed that the degree of habitat isolation between organisms gradually decreased as the distance from the coastline or port increased;Both the environmental DNA and morphological identification showed that the evaluation of the ecological quality of the sea area near the Yalu River Estuary by AMBI and M-AMBI index was more in line with the actual situation,and the overall ecological quality of the Yalu River Estuary was evaluated as good.The research shows that environmental DNA technology has good application prospects.Although it cannot completely replace the biological investigation method of morphological identification,it can be used as an important supplementary tool. |
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