Filter no more: a modified plankton sampler for rapid in-water eDNA capture
The combination of an efficient sampling method and high-throughput analysis of environmental DNA (eDNA) can be a powerful approach for characterizing biodiversity across aquatic ecosystems. Plankton net tows are one of the oldest, simplest, and least expensive methods for seston collection, but require laborious filtration steps which often lead to clogging and/or the introduction of contaminants.In this study, we used a novel Cruising Speed Net (CSN) device enabling the collection of seston-derived eDNA at 5 knots speed. We compared the performance of the CSN sampling protocol with conventional filtration of water sample versus a modified cod-end with 20 micron nylon mesh inserts enabling eDNA capture while towing, thus circumventing the active filtration step.Samples were collected in parallel horizontal tows along New Zealands North-Eastern coastline. Concentrated water was filtered on conventional 5 micron cellulose acetate membranes, while the 20 micron nylon mesh inserts were instantly isolated post-towing. Metabarcoding of bacterial 16S rRNA, eukaryotic nuclear 18S rRNA and mitochondrial COI genes, revealed no significant difference in alpha diversity between filtration techniques. In terms of community composition, a clear and significant shifts could be observed between sampling stations (R2>=0.46) and environments (R2>=0.32). Significant but marginal (R2<=0.07) differences could also be detected between filtration methods for 16S and COI. Nonetheless, each technique could detect dissimilarities associated to stations and environments with similar sensitivity.Our results demonstrate the promising potential of the modified cod-end to enable practical and cost-effective isolation of eDNA-derived biodiversity data from any vessel types (at <= 5 knots) across a large range of aquatic ecosystems and biogeographic scales.