Transport distance of invertebrate environmental DNA in a natural river.

Kristy Deiner,Florian Altermatt,Tom Gilbert

doi:10.1371/journal.pone.0088786

Kristy Deiner, Florian Altermatt + Show 1 more

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https://doi.org/10.1371/journal.pone.0088786

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Abstract

Environmental DNA (eDNA) monitoring is a novel molecular technique to detect species in natural habitats. Many eDNA studies in aquatic systems have focused on lake or ponds, and/or on large vertebrate species, but applications to invertebrates in river systems are emerging. A challenge in applying eDNA monitoring in flowing waters is that a species' DNA can be transported downstream. Whether and how far eDNA can be detected due to downstream transport remains largely unknown. In this study we tested for downstream detection of eDNA for two invertebrate species, Daphnia longispina and Unio tumidus, which are lake dwelling species in our study area. The goal was to determine how far away from the source population in a lake their eDNA could be detected in an outflowing river. We sampled water from eleven river sites in regular intervals up to 12.3 km downstream of the lake, developed new eDNA probes for both species, and used a standard PCR and Sanger sequencing detection method to confirm presence of each species' eDNA in the river. We detected D. longispina at all locations and across two time points (July and October); whereas with U. tumidus, we observed a decreased detection rate and did not detect its eDNA after 9.1 km. We also observed a difference in detection for this species at different times of year. The observed movement of eDNA from the source amounting to nearly 10 km for these species indicates that the resolution of an eDNA sample can be large in river systems. Our results indicate that there may be species' specific transport distances for eDNA and demonstrate for the first time that invertebrate eDNA can persist over relatively large distances in a natural river system.

Highlights

In order to understand community dynamics and biodiversity patterns, to protect rare species, or to mitigate consequences of range shifts, information on the current and past distribution of species is needed [1]
Environmental DNA capture, extraction, and detection Daphnia longispina was detected at all sites and across the two time points (Fig. 3)
It may be relevant to the distribution and use of Environmental DNA (eDNA) as a monitoring tool in rivers

Summary

Introduction

In order to understand community dynamics and biodiversity patterns, to protect rare species, or to mitigate consequences of range shifts, information on the current and past distribution of species is needed [1]. Many techniques to directly or indirectly detect species have been developed and applied [3] These detection techniques range from visually observing the focal species (e.g., sightings of birds [4] or whales [5]), to collecting individuals through various kinds of trapping (e.g., emergence traps or kicknet-samplings [6]), or extrapolating presence from traces such as foot prints or feces [7]. Often, these detection techniques are very specific to the study organisms and cannot be applied across different taxonomic groups [2]. Many techniques depend on specific expertise that may be hard to learn or difficult to standardize, which can create unknown rates of false absences [8]

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