Abstract:In recent years, environmental DNA (eDNA) metabarcoding has been widely used in the field of biological investigation, which includes species detection and biodiversity assessment. eDNA metabarcoding has the potential to rapidly assess species abundances in communities, making it a promising investigation tool in resource conservation and management. Although previous reports concerning eDNA metabarcoding found that the high-throughput sequencing (HTS) reads were related to the biomass in the natural environmental sample, a clear quantitative relationship was not found in this study. In the field and laboratory, the enrichment efficiency of eDNA is difficult to evaluate. Meanwhile, primer bias inevitably occurs in the eDNA amplification process, resulting in uncertainty in the eDNA HTS results, which restricts the application of eDNA metabarcoding for biological resource investigations. Assuming that the eDNA is completely recovered, and there is no primer bias during PCR amplification, an ideal state for deciphering whether there is a linear relationship between the eDNA and HTS reads is created. In this study, under controlled conditions in the laboratory, a sister group was selected (Penaeus vannamei and Penaeus merguiensis) and their DNA samples were mixed in different proportions to simulate eDNA samples enriched from natural waters. In this way, the recovery of the sample and primer bias was at optimal levels. Then, this eDNA template was used to explore the accuracy of eDNA metabarcoding in detecting species biomass. The results showed that when the concentration ratio of the DNA templates of two species was 1:1, the HTS ratio of the two species was 13/24 (P. merguiensis/ P. vannamei). Therefore, even between the closest relatives there is still a slight primer bias (primer migration rate: 1.5%). At the same time, the HTS results from the seven test groups showed an obvious linear relationship between the composition of eDNA in the water and the number of high-throughput sequencing reads, that is, y=0.0716x+0.7043 (r2=0.9824). In summary, this study provides direct evidence to verify the feasibility of eDNA metabarcoding in monitoring aquatic biological resources, and also provides ideas for the subsequent quantitative study of DNA metabarcoding.
