Influence of Streambed Morphology on the Transport Dynamics of Environmental DNA in Lotic Systems

Abstract Submission: Environmental DNA (eDNA) refers to the DNA extracted from biological remnants found in samples collected from natural ecosystems. The analysis of eDNA derived from aquatic samples has gained prominence as an easy, sensitive, and non-invasive technique for species detection. However, ascertaining the origin of eDNA poses significant challenges, particularly in dynamic aquatic environments such as flowing waters. Understanding the role of stream-subsurface exchange processes in influencing the fate and transport of eDNA is critical to improving the method's efficacy. Controlled labo4ratory flume experiments were conducted under varying streambed conditions, including a smooth bed (no gravel), a gravel bed, and a gravel bed with periodic bedforms. The breakthrough curves obtained demonstrated distinct patterns of eDNA transport, revealing that lower removal and exchange rates were associated with smooth bed conditions. This observation underscores the enhanced exchange processes occurring between the water column and the sediment bed in the presence of undulating beds. Such exchanges significantly influence the accumulation and sporadic movement of eDNA, as well as their average downstream travel distances under varying hyporheic fluxes. Results indicate that eDNA tends to settle out of the water column and accumulate within the riverbed, with settling and resuspension events instigated by hyporheic exchange processes governing both the travel distances and local concentrations of eDNA. These results highlight the critical importance of parafluvial processes in the transport of eDNA within lotic environments.

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