Biodiversity is declining on a global scale and monitoring efforts that inform better management can benefit from the use of eDNA1,2. A powerful and relatively recent method boasting several advantages for rapid marine biodiversity assessment3,4 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 applying environmental DNA (eDNA) 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 method5. Water sampling and UVS were done synchronously across six Australian states, both during the day and at night at over thirty sites. The sensibility of eDNA is measured against a ‘traditional’ method for biomonitoring, in terms of taxonomic composition and species detectability at a local and continental scale, including for rare and threatened species. Additionally, the study investigates how diel changes affect understanding of marine communities using eDNA and UVS, including the detection of nocturnal species.