Stream Transport and Retention of Environmental DNA Pulse Releases in Relation to Hydrogeomorphic Scaling Factors.

The DNA of aquatic organisms can be identified in water sampled from freshwater ecosystems to detect species presence. Because these DNA-based methods (termed environmental DNA, eDNA) confirm species presence by proxy of DNA in water, the processes influencing eDNA transport and removal from water are critical to the method's efficacy and interpretation of results. Previous studies of aquatic eDNA transport and fate have employed uncontrolled field experiments, controlled studies in experimental streams, and laboratory column tests. As a step toward understanding the processes controlling eDNA transport and retention, we released and tracked experimental pulses of white sturgeon eDNA (novel to the system) in five fourth-order stream reaches with varied hydrology and geomorphology. We found strong support that stream water transient storage controls eDNA areal uptake rate (or spiraling length). We calculated the median spiraling length to be ∼260 m. Down channel slope correlated with transient storage, suggesting that this slope could be used as a proximate measure of eDNA removal into the benthic zone. Our results suggest that sampling effort should be increased in reaches with longer transient storage (or lower slopes) to compensate for the increase in eDNA retention.