From Fragments to Flow: Decoding eDNA States to Illuminate Hydrologic Processes

Environmental DNA (eDNA) analysis for rapid non-invasive species detection across the tree of life. Once the eDNA is released into the environment it can move through a landscape, aggregating as waterways converge. Thus, hydrological knowledge of a landscape benefits the interpretation of eDNA data. Simultaneously, eDNA may be utilized as a natural hydrologic tracer. To fully utilize eDNA as a tracer molecule, the ecology of eDNA i.e. its production, degradation, and transport have to be well understood. However, eDNA itself is a complex mixture comprising of different states, namely membrane-bound, dissolved, and adsorbed states with varying persistence times and transport potentials.

In this presentation, I will provide an overview of eDNA states, how they are formed and what we know about them. Then I will explore methods for sorting these eDNA states from a single sample. Lastly, I will show data from large study spanning eight lake watersheds comprising samples collected from 221 sites collected from the headwaters to lakes of 58 streams in eight Swiss watersheds. All the samples were state sorted and analyzed with board range metabarcoding assays for identifying metazoan diversity. The results show that while most biodiversity information is enveloped in the membrane-bound state, each eDNA state has a district diversity signature. Our results show that the metazoan diversity signals remain closely linked for samples within a given stream, they diverge significantly once the stream enters a lake, highlighting the use of natural eDNA input to track water movement.