Harnessing eDNA for reef monitoring: a continental scale comparison with visual surveys in AustraliaNovel Approaches

Lara Denis-Roy¹, Katrina West², Graham Edgar¹, Bruce Deagle², Priscila Goncalves³, Yann Herrera Fuchs¹, Tyson Jones¹, Matthew Rose¹, Olivia Johnson¹, Laura Missen³, Marcelle Ayad³, Craig Johnson¹

¹University of Tasmania, Australia - ²Commonwealth Scientific and Industrial Research Organization, Australia - ³University of Western Australia, Australia

Biodiversity is declining on a global scale and monitoring efforts that inform better management can benefit from the use of environmental DNA (eDNA). This developing method boasts several advantages for rapid marine biodiversity assessment but requires further standardization and validation at a continental scale for macro-organisms’ biomonitoring.

The present study aims to compare the use of eDNA against visual surveys in studying reefs and to determine the value of its application to assess ecological change in reef ecosystems at the scale of the Australian continent. It analyses reef communities through two metabarcoding assays (16S Fish and COI Leray) as well as underwater visual surveys (UVS) following the Reef Life Survey method. Water sampling and UVS were done synchronously across six Australian states, both during the day and at night. The sensitivity of eDNA is measured against the ‘conventional’ UVS method for biomonitoring, in terms of taxonomic composition and species detectability at a local and continental scale, including for rare and threatened species. The surveys identified 1096 species using eDNA and 1576 species for UVC, post-curation. Additionally, the study investigates how diel changes affect understanding of marine communities using eDNA and UVS, including the detection of nocturnal species.