Environmental DNA (eDNA) refers to the DNA that is extracted from field samples containing various biological remnants such as molecules, cells, or tissues. Measuring eDNA obtained from water samples has emerged as a sensitive and non-invasive tool for estimating species distribution. However, determining the origin of eDNA remains challenging, particularly in lotic environments. The interpretation of collected eDNA data from experiments or surveys thus far has been hindered by a significant amount of unexplained variability. To explain this seemingly unpredictable transport behavior, a simple conceptual model is proposed where eDNA settles out of the water column and accumulates on riverbeds. Subsequent settling and resuspension events influence downstream transport patterns and contribute to variable local concentrations. Laboratory experiments of eDNA transport under both clean (limited and enhanced hyporheic exchange) and eDNA-loaded streambeds revealed distinct patterns of eDNA transport. On the clean streambed, there was a smooth breakthrough curve with little noise. However, on the eDNA-loaded streambed, transport patterns were more complex. Retention measurements of eDNA on the clean bed provided insights into exchange processes occurring between the water column and the sediment bed. These exchanges could account for variations in accumulation and random movement of eDNA particles as well as their average travel distance under different hyporheic fluxes. Experimental findings indicate para-fluvial processes play a crucial role in environmental-DNA transport within lotic environments, and a better understanding of the relevant transport processes will allow better source identification.
.jpg "Kush Paliwal, n/a (he/him/his) photo")