An environmental DNA approach to informing restoration of the functionally extinct oyster, Ostrea angasi

Abstract

1. The success of oyster reef restoration can be enhanced by data on the distribution of remnant populations to inform the selection of suitable restoration locations. A quantitative polymerase chain reaction-based environmental DNA (eDNA) assay was designed to provide distribution data for the oyster, Ostrea angasi, whose reefs are functionally extinct in Port Phillip Bay, Australia.2. Ostrea angasi eDNA accumulation and decay was measured in aquaria containing oysters in low and high densities, prior to testing the efficacy of the eDNA approach for detection of oysters at 15 field sites. Ostrea angasi eDNA accumulated significantly faster in aquaria where more individuals were present, while eDNA became undetectable 2-6 days after oysters were removed in lowdensity treatments.3. The eDNA samples were successful at detecting O. angasi in the field when taken in close proximity of an oyster population. Increasing the sample number and volume could maximize oyster detection, demonstrating the potential of eDNA to identify suitable sites for the restoration of functionally extinct marine ecosystems.

An environmental DNA assay for the detection of Critically Endangered angel sharks (Squatina spp.)

“…eDNA barcoding is a promising approach to provide important information for the conservation of rare species (Coutts et al, 2022), especially when used with an appropriate sampling design. Although the developed qPCR assay can amplify DNA of 13 other species of fish (Appendix S6), none overlap with the ranges of the three Squatina species in this study.…”

I aha ki ngā toheroa nō Horowhenua, what happened to the toheroa of the Horowhenua?

“…However, the assay shows promise as a tool for non-invasive detection of this taonga, with potential for the initial sensitivity level to be refined and potentially improved through further optimisation and transfer to a more sensitive droplet-digital PCR system (ddPCR). Further optimisation of this eDNA protocol for the toheroa will help inform future restoration of toheroa species, by indicating areas where toheroa may be in limited numbers, as was shown in Coutts et al, (2022).…”

“…In cases where species are in very low population numbers, sampling eDNA is considered a cost-effective, non-invasive, simple, and fast survey method, compared to conventional methods (Ferris, 2020;Evans et al, 2017). Environmental DNA (eDNA) is genetic material such as faeces, urine, saliva, or shed cells and tissues which has been left behind as the trace of an organism (Coutts et al, 2022;Steiner et al, 2022). eDNA is shed from organisms, and can be extracted from environmental samples such as water or sediment, and amplified to target specific species using polymerase chain reaction (PCR) (Ferris, 2020;Steiner et al, 2022).…”

“…Examples of where eDNA analysis is currently being used in Aotearoa include coastal investigations of pāua (Adams et al, 2022), kākahi [freshwater mussel;Echyridella menziesii] in New Zealand lakes (Steiner et al, 2022), and general surveying of biodiversity (Adams, 2021). Overseas, eDNA has also been used to inform the restoration of the oyster Ostrea angasi in Port Phillip Bay, Australia (Coutts et al, 2022), and for locating populations of freshwater pearly mussel species (family Unionidae) in southern Ontario, Canada, where it was found to be a valuable complement to traditional methods of locating the species (Currier et al 2018). Wee et al, (2023) also reviewed the potential for eDNA in mangrove restoration in Southeast Asia, and Levy et al, (2023) conducted similar investigations for coral reef reformation.…”