Spatial and temporal distribution of eDNA in fish ponds via metabarcoding

Environmental DNA (eDNA) metabarcoding is a promising tool for rapid, non-invasive biodiversity monitoring. In this study, eDNA metabarcoding was applied to explore the spatial and temporal community variances in ponds following the translocation and removal of two rare species that were new to the community. The highest community dissimilarity was observed on day D2 (43 hrs post-translocation of additional species) and decreased over time in both ponds. After day D6, there was no longer a significant difference in community dissimilarities between sampling events. These findings echo observed trends in eDNA concentration of added species, which peaked on day D2 then gradually declined and eventually stabilised by day D6. Notably, additional species were not detected at any sampling positions 48 hrs after their removal from ponds. Furthermore, eDNA signal of the additional species was the strongest at the original source position P1 and decreased as distance increased, although the signal increased slightly at position P4 located ~85 m from position P1. The highest community variances were observed at position P1, and community dissimilarities declined with increasing distance besides a slight fluctuation at position P4. Taken together, eDNA in static environments is highly localised in space and time. Therefore, rigorous and spatially standardised sampling designs are key to ensuring the reliability of eDNA surveillance. eDNA metabarcoding is a powerful tool for detection of rare species alongside more abundant species due to use of generic PCR primers and monitoring spatial and temporal community variances.