Field storage of water samples affects measured environmental DNA concentration and detection

Environmental DNA (eDNA) is an emerging approach for detecting species, yet numerous methodological questions remain unanswered. Here we examined how time to filtration (0-48 h after collection) and sample storage (open vs. chilled in the dark) influenced detection and measured eDNA concentration. Water samples kept in the dark and chilled had no significant decrease in detection or eDNA concentration relative to those filtered immediately upon return from the field. Water samples exposed to light and ambient air temperature had non-detections beginning at 1 h, the majority of these samples were below the limit of detection (LOD) by 6 h, and eDNA was undetectable in these samples by 24 h. These results have important implications for eDNA research where immediate access to refrigeration is not available, or for fieldwork that requires extended sampling time (e.g., canoeing a river). Further, we report faster eDNA degradation times under ambient conditions than some previous aquaria or mesocosm studies, suggesting an ongoing need to study mechanisms related to eDNA persistence and sample storage.