23 Oct 2019
23 Oct 2019
Status: this preprint was under review for the journal HESS but the revision was not accepted.

Water tracing with environmental DNA in a high-Alpine catchment

Elvira Mächler1,2, Anham Salyani3, Jean-Claude Walser4, Annegret Larsen3,5, Bettina Schaefli3,6, Florian Altermatt1,2, and Natalie Ceperley3 Elvira Mächler et al.
  • 1Eawag: Swiss Federal Institute of Aquatic Science and Technology, Department of Aquatic Ecology, Überlandstrasse 133, CH-8600 Dübendorf, Switzerland
  • 2Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
  • 3Faculty of Geosciences and Environment, Institute of Earth Surface Dynamics, University of Lausanne, 1015 Lausanne, Switzerland
  • 4Federal Institute of Technology (ETH), Zürich, Genetic Diversity Centre, CHN E 55 Universitätstrasse 16, 8092 Zürich, Switzerland
  • 5Soil Geography and Landscape Group, Wageningen University, Droevendaalsesteeg 3, 6708 PB Wageningen, The Netherlands
  • 6Geography Institute, University of Bern, 3012 Bern, Switzerland

Abstract. Alpine streams are particularly valuable for downstream water resources and for ecosystem conservation. However, the details of where and when water is stored and released in the heterogeneous mountain environment are rarely known. The use of physico-chemical flow path tracers is particularly challenging due to the temporary accumulation and storage of water in the form of snow and ice. Alternatively, biological tracers might complement information on flow and storage of water, especially as the different microhabitats in Alpine aquatic systems are inhabited by characteristic organismal communities. In this study, we explored the potential of particles of environmental DNA found in the water (eDNA) to characterize hydrological flow paths and connectivity in an Alpine catchment in Switzerland. Between March and September 2017, we sampled water at multiple time points at 11 sites distributed over the 13.4 km2 Vallon de Nant catchment for genetic species information based on naturally occurring eDNA. The sites correspond to three different water source types and habitats (main channel, tributaries, and springs).

Comparison of typical hydrological tracers and eDNA with temporal evolution of streamflow revealed that in the main channel and in the tributaries, the change in streamflow, dq/dt, is strongly correlated with biological richness. In springs, electrical conductivity was found to have a positive but not as strong correlation with biological richness. At the catchment scale, our results show that biological richness as indicated by the diversity detected by eDNA samples. When streamflow is increasing, transport of additional, and probably terrestrial, DNA into water storage or flow compartments is occurring. Such processes include overbank flow, stream network expansion and retraction, and hyporheic exchange. In general, our results highlight the importance of considering the at-site sampling habitat in combination with upstream connected habitats to understand how streams integrate eDNA over a catchment and to interpret spatially distributed eDNA samples, both for hydrological and biodiversity assessments. We identify next steps to be addressed to use eDNA as an independent tracer of Alpine water sources and we provide recommendations for future observation of eDNA in Alpine stream ecosystems.

Elvira Mächler et al.

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Status: closed
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Elvira Mächler et al.

Elvira Mächler et al.


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Short summary
We explored what genetic material collected from water (eDNA) tells us about the flow of mountain streams, which are particularly valuable for habitat and water resources, but highly variable. We saw that when flow increased, more diverse eDNA was transported, especially in the main channel and tributaries. Whereas in the springs, we saw more diverse eDNA when the electrical conductivity of the water increased, likely indicating more underground surface contact.