‘How low can you go’ with environmental DNA (eDNA) detection?

‘How low can you go’ with environmental DNA (eDNA) detection?

Environmental DNA (eDNA) methods can be used to detect species by analysing DNA present in environmental samples. These ‘environmental samples’ could be air, soil, faeces and water.

eDNA has been promoted as a particularly sensitive and cost‐effective way to detect species at low densities and to assist with confirming eradication success. However, to get an eDNA assay to a point where you are extremely confident in your answers, requires a lot of background research, testing and assay development.

The University of Canberra (UC) led EcoDNA team which is primarily funded through our Centre, have evaluated the sensitivity of their eDNA methods to better understand just how low the analysis will go with sensitivity detection rates – i.e. true species absence.

Using carp as a model species, Dr Elise Furlan from the UC EcoDNA team compared two lakes in Tasmania, one in which carp have been eradicated and a second in which carp are currently being eradicated. Her paper, published in the Journal of Applied Ecology, found that analysis of 100 water samples from each lake was sufficient to detect the low-density carp populations in Lake Sorell and supported the species’ absence from Lake Crescent.

As part of this project, the EcoDNA team did find that sensitivity of these surveys were low, so carp density decline over time may mean more survey effort is required to ensure confidence in the results.

While eDNA is currently being used as a detection tool for assisting with answering eradication efforts, it is important to note the immense amount of background work involved to get these tools validated.

The EcoDNA team thanks to funding through our Centre and the Australian Government is now working on developing real time assays, where the aim is to analyse samples within a 30-60 minute timeframe vs a couple of days of analysis in a lab – see https://invasives.com.au/news-events/finding-needle-haystack-new-portable-dna-device/

We’ll keep you posted on the progress of this exciting research.

Source paper:

Furlan, Elise M., et al. “eDNA surveys to detect species at very low densities: A case study of European carp eradication in Tasmania, Australia.” Journal of Applied Ecology 56.11 (2019): 2505-2517 – https://doi.org/10.1111/1365-2664.13485

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