Controls on eDNA movement in streams: Transport, Retention, and Resuspension

Arial J Shogren,Elizabeth Andruszkiewicz,Andrew R Mahon,Diogo Bolster,Christopher L Jerde,Jennifer L Tank,Brett Olds

doi:10.1038/s41598-017-05223-1

Abstract

Advances in detection of genetic material from species in aquatic ecosystems, including environmental DNA (eDNA), have improved species monitoring and management. eDNA from target species can readily move in streams and rivers and the goal is to measure it, and with that infer where and how abundant species are, adding great value to delimiting species invasions, monitoring and protecting rare species, and estimating biodiversity. To date, we lack an integrated framework that identifies environmental factors that control eDNA movement in realistic, complex, and heterogeneous flowing waters. To this end, using an empirical approach and a simple conceptual model, we propose a framework of how eDNA is transported, retained, and resuspended in stream systems. Such an understanding of eDNA dispersal in streams will be essential for designing optimized sampling protocols and subsequently estimating biomass or organismal abundance. We also discuss guiding principles for more effective use of eDNA methods, highlighting the necessity of understanding these parameters for use in future predictive modeling of eDNA transport.

Highlights

Streams and rivers connect landscapes to oceans, moving natural and anthropogenic materials through extensive and heterogeneous network systems[1, 2]
We address three main processes controlling environmental DNA (eDNA) movement in streams: 1) Transport: How far does an average eDNA particle travel in streams with different hydrologic signatures and how might eDNA detection be used to infer where a species is located?; 2) Retention: Does surface-subsurface exchange trap eDNA in porous, benthic substrate interstices and does the presence of biofilms of organic matter play a role?; and 3) Resuspension: Can resuspension from the streambed result in eDNA detection after the source of eDNA has been removed, and does this depend on streambed characteristics? To answer these questions, we conducted a series of experimental eDNA additions into four experimental streams that varied only in the substrate lining the bottom
Our results show that eDNA movement is significantly more complicated than that of a conservative tracer or monodisperse solute of a particle, having both some level of apparently unpredictable behavior in the amount of eDNA recovered temporally downstream of the release and variability in retention across contrasting streambed substrates

Summary

Introduction

Streams and rivers connect landscapes to oceans, moving natural and anthropogenic materials through extensive and heterogeneous network systems[1, 2]. There remains a need for an improved understanding of interplay between critical variables controlling in-stream transport, retention, and resuspension of eDNA materials, which will facilitate quantitative interpretation, prediction, and modeling efforts of eDNA transport in fluvial systems to better predict the upstream presence of eDNA detected species. Parameterization of such mechanisms would move us from qualitative detection toward quantitative understanding and prediction of location and estimation of abundance, and will be critical in taking eDNA detection techniques to the level as a powerful diagnostic tool in ecology, conservation, and management

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