Role of parafluvial processes on the downstream transport of eDNA in lotic environments

Kush Paliwal
PhD student in the Lyles School of Civil Engineering
Purdue University

Tuesday, November 14, 2023
3:30 p.m.
HAMP 2123

Abstract

Traces of genetic material abound in the environment. The DNA extracted from field samples containing these ubiquitous biological remains (molecules, cells, or tissue) is called environmental DNA (eDNA). Measuring eDNA extracted from water samples is easy, sensitive, and non-intrusive and has emerged as a practical way to estimate species distribution. Because eDNA is transported in the environment, knowing where it originated remains a challenge, particularly in flowing waters. The interpretation of eDNA data gathered so far from experiments or surveys is hindered by a significant amount of unexplained variability. We propose a simple conceptual model to account for the seemingly erratic transport behavior: eDNA settles out of the water column and accumulates in the riverbed; continuous settling and resuspension events control the downstream transport and trigger the variable local concentrations. We conducted experiments in a laboratory channel to test our conceptual model. eDNA transport on a clean streambed (under limited and enhanced hyporheic exchange) resulted in a breakthrough curve without much noise, whereas experiments on an eDNA-loaded streambed resulted in obscured transport patterns. We were also able to measure eDNA retention (downstream transport length) for the clean bed. The exchange between the water column and the sediment bed could explain both the observed variability, attributed to bed accumulation and random ejections, and the average distance eDNA traveled under varying hyporheic fluxes. Our study demonstrates that para-fluvial processes control environmental-DNA transport in flowing systems and that we can thus tell where it came from.

Bio

Kush Paliwal is a PhD student at Purdue University in the Lyles School of Civil Engineering. He graduated from Purdue University in 2021 with an MS in Civil Engineering. His research focuses on the role of physical processes on the downstream transport of eDNA in lotic environments. Before joining Purdue, he worked as a research fellow at IIT Gandhinagar and a graduate engineer at Tata Projects Ltd.