Environmental DNA (eDNA) has been shown to be an effective tool for detecting low abundance invasive or imperiled species. However, many unknowns related to the physical, chemical and biological aspects of the target organisms and their environment hinder the successful application of eDNA to detect new invasive or imperiled species. Here we used two local streams equipped with USGS flow gages to examine how stream flow and temperature over the course of a year might influence eDNA copy number of the invasive Asian clam (Corbicula fluminea). Next, we sampled eight central-Illinois streams to examine whether C. fluminea density was related to the amount of eDNA captured both at summer low-flow and during fall high-flow.
Results/Conclusions
Our results indicate that eDNA had a significant positive relationship with temperature, where eDNA copy number increased as temperature increased, which we attribute to biological activity and reproduction. Additionally, we found that as stream flow increased, eDNA copy number declined, indicating that sampling during high-flows could result in a decreased ability to detect a very abundant species (false negatives). We found no relationship between C. fluminea density and eDNA copy number and further, we found that sampling during fall high-flow also resulted in non-detections when C. fluminea were present (false negatives). Our study presents novel findings that stream flow dilutes eDNA, which may have serious implications for the detection of low abundance organisms. Further, we suggest that researchers seeking to use eDNA as a conservation tool should take into account knowledge of their biological organism and system prior to sampling efforts.