Mr Jason Alexander1, Mr Michael Marnane2, Mr Justin McDonald3, Mrs Sherralee Lukehurst1, Mr Travis Elsdon2, Mrs Tiffany Simpson1,4, Mr Shawn Hinz5, Mr Michael Bunce1,6, Mr Euan Harvey7
1TrEnD Laboratory, Curtin University, Bentley, Australia, 2Chevron Technical Center, Perth, Australia, 3Sustainability and Biosecurity, Department of Primary Industries and Regional Development , Hillarys, Australia, 4Ascension Island Government Conservation and Fisheries Directorate, Georgetown, UK, 5Gravity Marine, Fall City, USA, 6Institute of Environmental Science and Research, Wellington, New Zealand, 7Fish Ecology Laboratory, Curtin University, Bentley, Australia
Broad scale monitoring of marine diversity is challenging, with many methods limited to sampling only a small portion of the actual diversity present. As such, eDNA metabarcoding is becoming increasingly applied, particularly in logistically challenging locations such as ports and other marine infrastructure. eDNA studies have predominantly focused on the collection and isolation of DNA from bulk seawater, however literature suggests this approach may not detect as broadly from adjacent epibenthic substrates. In this study we compare three eDNA collection methods targeting the water column and four methods targeting the epibenthos, with samples taken at two depths. All methods revealed significantly different detection compositions, with only 2.8% of families found across all methods, and all but one scraping method were able to detect fine scale community shifts associated with sampling depths. Epibenthic methods ranged from 50 to 117 families detected, with methods that collected bulk DNA material (scraping methods) detecting considerably lower diversity. Those methods targeting the water column detected between 78 to 154 families, with sponge materials yielding a higher diversity, indicating that the physical matrix may be better at retaining low DNA concentrations. This study provides the base toolkit for the broad characterisation of vertical diversity at both natural and man-made marine structures, such as oil and gas platforms. Additionally, these highly varied results demonstrate the importance of the correct selection of substrate and method in broad diversity studies, and indicate that multiple sampling methods may be required to adequately characterise diversity.
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