Pochon X1,2, Laroche O1, von Ammon U1, Zaiko A1,2
1Cawthron Institute, Nelson, New Zealand; 2Institute of Marine Science, University of Auckland, Auckland, New Zealand;
The efficient collection and high-throughput analysis of environmental DNA (eDNA) is 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 are impractical in exposed environments, and require 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 built-in 20 mm nylon mesh enabling eDNA capture while towing, thus circumventing the filtration step. Samples were collected in parallel horizontal tows along New Zealand’s Eastern coastline. Concentrated waters were filtered on 5 mm membranes, while the built-in filters were instantly isolated post-towing. Metabarcoding of bacterial 16S rRNA, eukaryotic nuclear 18S rRNA and mitochondrial COI genes, revealed clear community shifts between sampling stations but no statistically significant differences in alpha diversity among sample types. Some fine-scale differences in community composition were observed using 16S and COI markers at turbid sites without affecting biodiversity estimates at regional scale. Our results validate the future use of the modified cod-end, revolutionising our ability to easily and rapidly isolate eDNA-derived biodiversity data in aquatic ecosystems from any vessel types and across much larger spatio-temporal scales than currently possible.
Biography:
Xavier is a marine molecular ecologist in the Coastal & Freshwater group at Cawthron Institute and an Associate Professor at the Institute of Marine Science of the University of Auckland. His research expertise focuses on developing multi-trophic molecular detection tools to analyse environmental DNA (eDNA) and measure biodiversity changes associated with natural and human-induced stressors in aquatic ecosystems. Xavier is involved in multiple research programmes using DNA and RNA proxies for monitoring New Zealand’s aquatic health (e.g. Lakes380), emerging contaminants such as organics and microplastics, non-indigenous marine species (Marine Biosecurity Toolbox), and benthic impacts associated with aquaculture. Xavier is very passionate about his research and particularly enjoys interacting with the general public as well as regulators and industry partners, to find better ways of protecting our aquatic ecosystems.