2025 CSDMS meeting-073
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Brandon Sansom, USGS Columbia Environmental , United States.
Katy Klymus, USGS Columbia Environmental Research Center , United States.
Diogo Bolster, University of Notre Dame , United States.
Advances in the measurement of environmental DNA (eDNA) have enhanced our ability to monitor both the occurrence and distribution of species in aquatic ecosystems. However, linking eDNA concentrations in streams and rivers with species abundance remains challenging due to the combination of unidirectional flow, streambed retention, and decay hindering identification of the source location. While numerous biotic and abiotic factors can cause reductions in eDNA concentration, their relative impact on overall concentration variations remains unclear. A mechanistic framework capturing the fate and transport of eDNA in the presence of both biological and physical heterogeneities still requires development. In this study, we use a continuous time random walk model to explore how eDNA removal is controlled by water column and hyporheic processes. We fit the model to concentration profiles produced from pulse conservative (Rhodamine WT) and continuous eDNA continuous tracer injections in the Big Piney river (Missouri), using multiple concentration profiles to capture evolving hydrodynamics across the reach. Regardless of location, modeled hyporheic removal rates are 2 to 4 orders of magnitude greater than laboratory based estimates of the water column reaction rate. This suggests that using only laboratory estimates of water column decay to predict eDNA concentrations with distance from the source may lead to significant prediction overestimates, as the hyporheic zone is likely the primary driver of eDNA removal in rivers.
