COS 102-4 - Environmental DNA (eDNA)-based assessment of the longitudinal connectivity for fish community in two river systems from South Korea

Background/Question/Methods

Environmental DNA (eDNA) is the extracellular DNAs in environments (e.g. sediment, water, air), which are originated from skin, mucous, saliva, sperm, secretions, eggs, and etc. of many different organisms. NGS (next generation sequencing)-based metabarcoding using eDNA now becomes an emerging approach for efficiently detecting unperceivable species such as rare, endangered, and also invasive species currently expanding the geographic distribution. Because of less environmental disturbances entailed, eDNA approach has largely been employed to assess and monitor biodiversity in a diverse array of ecosystems. In the present study, we analyzed and compared the fish community structure and species diversity between traditional and eDNA surveys to assess the longitudinal connectivity of the fish community among artificial barriers (e.g. fish ladder and weirs) along down-, middle- and upstream in two river systems. We collected eDNA water samples at nine and 14 sites from the Yeongok Stream in East-flowing river and the Seomjin River, respectively from South Korea. All freshwater samples were collected from the waterside and central areas at each site during spring and fall in 2020-2021. We used mitochondrial DNA 12S rRNA (MiFish primer, ~240 bp) as a genetic marker for metabarcoding.

Results/Conclusions

The eDNA fish communities at every site slightly differed from those from the field traditional surveys and species diversity generally decreased from down- to upstream in both river systems. Results of non-metric multidimensional scaling (nMDS) analysis showed a higher similarity for three clusters representing down, middle and upstream in both rivers, while the most upstream sites showed the most divergent fish community structure compared to others. The fish community similarity tended to increase as distances between sites decrease, based on results of heatmap analysis. We found that particular fish species predominantly represent each of the three down, middle and upstream groups (e.g. the Yeongok Stream for spring, downstream; Plecoglossus altivelis, middlestream; Zacco koreanus, upstream; Rhynchocypris kumgangensis). The findings of this study highlight the versatility and power of eDNA metabarcoding for monitoring native fish community, determining a barrier for the dispersal range of migrating fishes, and further evaluating the longitudinal connectivity of river ecosystems.