Examining Standard Environmental DNA Sample Extraction and Archival Methods

Using environmental DNA (eDNA) to detect rare or secretive species has become an important tool in biological research and monitoring. However, given the recent development of the field and the novelty of the methods employed, empirical testing of methods is needed. The goal of this research was to evaluate the handling of filters (used to concentrate DNA during field filtration) prior to and during the DNA extraction process. A common DNA extraction procedure involves splitting a filter sample into equal halves with one half processed and the other half archived by freezing (at -20°C or -80°C) in 200-proof molecular grade ethanol. Our objectives were to quantitatively evaluate the assumption that both filter halves have evenly distributed eDNA and the quantitative effects of freezing/archiving samples from 0 - 6 years on yield. We tested both objectives using samples collected annually in the Okanogan Basin as part of another study dating back to 2012. Preliminary results will be presented including statistical differences in the yield of halves of the filter and statistical differences in yield of stored filters across time. Results of this study could help improve eDNA laboratory methods and provide insight into proper sample archival procedures, helping to safeguard eDNA archives for future use