water Review Towards the Optimization of eDNA/eRNA Sampling Technologies for Marine Biosecurity Surveillance Holly A. Bowers 1, *, Xavier Pochon 2,3 , Ulla von Ammon 2 , Neil Gemmell 4 , Jo-Ann L. Stanton 4 , Gert-Jan Jeunen 4 , Craig D. H. Sherman 5 and Anastasija Zaiko 2,3   Citation: Bowers, H.A.; Pochon, X.; von Ammon, U.; Gemmell, N.; Stanton, J.-A.L.; Jeunen, G.-J.; Sherman, C.D.H.; Zaiko, A. Towards the Optimization of eDNA/eRNA Sampling Technologies for Marine Biosecurity Surveillance. Water 2021, 13, 1113. https://doi.org/10.3390/ w13081113 Academic Editor: Lorenzo Mari Received: 25 November 2020 Accepted: 10 April 2021 Published: 18 April 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039, USA 2 Coastal and Freshwater Group, Cawthron Institute, 98 Halifax Street East, Nelson 7010, New Zealand; Xavier.Pochon@cawthron.org.nz (X.P.); Ulla.vonAmmon@cawthron.org.nz (U.v.A.); Anastasija.Zaiko@cawthron.org.nz (A.Z.) 3 Institute of Marine Science, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand 4 Department of Anatomy, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand; neil.gemmell@otago.ac.nz (N.G.); jo.stanton@otago.ac.nz (J.-A.L.S.); gert-jan.jeunen@otago.ac.nz (G.-J.J.) 5 Queenscliff Marine Research Facility, School of Life and Environmental Sciences, Deakin University, Queenscliff 3225, Australia; craig.sherman@deakin.edu.au * Correspondence: hbowers@mlml.calstate.edu; Tel.: +1-831-771-4138 Abstract: The field of eDNA is growing exponentially in response to the need for detecting rare and invasive species for management and conservation decisions. Developing technologies and standard protocols within the biosecurity sector must address myriad challenges associated with marine environments, including salinity, temperature, advective and deposition processes, hydrochemistry and pH, and contaminating agents. These approaches must also provide a robust framework that meets the need for biosecurity management decisions regarding threats to human health, environmental resources, and economic interests, especially in areas with limited clean-laboratory resources and experienced personnel. This contribution aims to facilitate dialogue and innovation within this sector by reviewing current approaches for sample collection, post-sampling capture and concentration of eDNA, preservation, and extraction, all through a biosecurity monitoring lens. Keywords: eDNA; eRNA; marine biosecurity; invasive species 1. Introduction Biological invasions have followed human activities for centuries [1], with cross- regional transfer of non-indigenous species (NIS) having amplified rapidly over the last few decades [2,3]. In the marine realm, this is largely attributed to the massive increase in seaborne trade beginning in the 1950s [4,5], which has served as the major pathway for marine biological invasions [1,6,7]. Continued growth in global maritime traffic and an associated 3- to 20-fold increase in global invasion risk is predicted for the next few decades [8]. Disrupting a potential invasion at the earliest stage of propagation is key, since downstream eradication in highly dynamic marine environments is difficult at best. Although managing the spread of unwanted organisms remains a high priority for re- gional, national, and international jurisdictions (e.g., Marine Strategy Framework Directive; European Union (EU) Invasive Species Regulation; New Zealand Biosecurity Act), a lack of operational tools and technologies for early detection has been a long-term hurdle [9]. Molecular methods have been used for decades to aid environmental monitoring [10]. The use of tissue or blood samples from an individual to obtain a genetic signal alleviates issues surrounding taxonomic identification, while still relying on visual detection and collection of specimens at the sampled area [11]. More recently, the application of DNA and RNA (collectively termed nucleic acids (NAs)), recovered from environmental samples and referred to as environmental DNA (eDNA) and RNA (eRNA), is increasingly advocated for to be used in biodiversity assessments (e.g., [12–14]). The non-invasive manner of sampling Water 2021, 13, 1113. https://doi.org/10.3390/w13081113 https://www.mdpi.com/journal/water