A self-preserving, partially biodegradable eDNA filter

eDNA studies often rely on water filtration in the field and immediate sample preservation to prevent DNA degradation during sample transport. However, filter membrane transfer steps for preservation can increase risk of sample contamination and the reliance on typical single-use filter housings produces significant plastic waste. We created a new eDNA filter housing (compatible with any suction pump) partially comprised of a biodegradable, hydrophilic material that functions to automatically preserve captured eDNA via desiccation-no filter membrane transfer steps, no chemical or cold storage required. We tested the self-preservation capabilities of the desiccating filter housings by filtering replicate samples in an eDNA mesocosm study and compared with ethanol preservation. Self-preserving filters were placed back into original packaging for storage, and samples for both preservation methods were kept at room temperature until extraction at prescribed time points (11 days, 18 days, 25 days, 32 days, 60 days, 88 days, 172 days) post-filtration. Paired field samples were also collected from six pond locations targeting an additional species to demonstrate field performance. Quantitative PCR results from the mesocosm study indicated that both methods effectively preserved eDNA over a 6-month storage period, with the self-preserving filters yielding slightly more target DNA on average (SQ = 329 copies) than ethanol-preserved samples (SQ = 288 copies) (F-1,F-38 = 4.050, p = 0.051). Neither method showed signs of degradation after 172 days. Results from field sampling indicated a larger difference between preservation methods, with the self-preserving filters containing approximately 2X the eDNA of ethanol-preserved samples on average (paired t test, p = 0.020). These data suggest that self-preserving eDNA filter housings are a viable alternative to standard ethanol preservation methods and may provide higher detection sensitivity in some circumstances. The new filter housings should also help in reducing the risk of sample contamination, minimize protocol steps and result in less plastic waste. Such innovations are important to assure eDNA data quality and to help in facilitating the inclusion of non-expert sample collectors (e.g. citizen scientists) in research programs.