This record provides an overview of the NESP Marine and Coastal Hub Research Plan 2024 project "Environmental DNA for measuring offshore marine biodiversity: what can DNA in water collected from the RV Investigator tell us?". For specific data outputs from this project, please see child records associated with this metadata. -------------------- Environmental DNA (eDNA) in seawater provides a non-extractive way to characterise marine biodiversity from genetic material shed by organisms, from microbes and plankton to invertebrates and fishes. It is an emerging tool for marine ecosystem monitoring, particularly in offshore areas where conventional sampling can be difficult, costly or environmentally disruptive. This project collected and analysed more than 500 eDNA samples from 91 sites during the South-east Australian Marine Ecosystem Survey (SEA-MES) on RV Investigator. Samples were collected along the continental shelf between Tasmania and southern New South Wales, including sites within the South-east Marine Parks Network, providing the first comprehensive eDNA baseline for this region. The project tested active eDNA sampling from CTD water samples and passive eDNA sampling from a deep-towed camera system. DNA metabarcoding and Tree of Life metabarcoding were used to identify biodiversity patterns across the water column and near the seafloor. Results were compared with conventional survey methods, including fish trawls, plankton sampling and deep-towed camera deployments, to assess how eDNA complements existing monitoring approaches. The dataset revealed clear biodiversity patterns by depth, latitude, and water-column position, including higher fish diversity near the seafloor than at the surface. Comparisons with trawl and plankton data showed that eDNA provided complementary biodiversity information, supporting its use alongside existing survey methods and highlighting its value as part of integrated monitoring programs. The outputs provide a new biodiversity baseline for south-eastern Australian waters, and practical guidance on future application of eDNA techniques for offshore monitoring of marine parks and fisheries. Outputs • eDNA sequences with associated collection metadata (x2 voyages x50 sites) [dataset] • Final project report [written]

This project generated a set of high-quality eDNA-based biodiversity datasets from samples collected at broadly distributed offshore sites across Southeast Australia. The data consists of processed data from eDNA metabarcoding assays (i.e. tables with sampling information, sequence read counts and taxonomy derived from the sequences). Raw sequence data (over 180 million sequences) is available from NCBI (https://www.ncbi.nlm.nih.gov/) under BioProject PRJNA1263580: Environmental DNA measuring offshore marine biodiversity in southeast Australia (https://www.ncbi.nlm.nih.gov/bioproject/PRJNA1263580/). The eDNA biodiversity information focussed on fish but includes sequence data from the full tree of life (from bacteria to vertebrates). Part of the purpose of data collection was to assess key technical aspects of eDNA data collection to refine sampling methods and provide guidance for best practices in future offshore eDNA research