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The hot Q&As about eDNA
20th October 2017, Helen Barclay
In 2008 the first scientific paper came out about the concept of taking a water sample and isolating DNA. It highlighted the possibility that we could identify the organisms in waterways via DNA they have left behind - how very cool! Since this time, EnviroDNA scientists have been hard at work, refining processes for sample collection, DNA extraction and species detection tests. It's a science that industry is now taking note of, but there are still lots of questions.
A number of such questions were raised at the recent 'eDNA science meets industry catch up' - some are outlined below. You can also access a summary of the event takeaways here.
Q. The examples of eDNA application provided, target certain species, but, can you get a list of species?
Much of the eDNA work applied in industry has been single species focused but recently we have been looking at biodiversity suites of species using general DNA markers. So essentially this means pulling out all the fish or frogs or vertebrates for example from a single sample. Some ground breaking projects are just around the corner.
Q. Did eDNA give you an idea of density of platypus? (asked in the context of annual platypus monitoring work)
No, it didn’t in this instance because platypus are solitary. The amount of platypus DNA in the waterway doesn’t necessarily correlate with abundance, however, similarly, after 20 years of fyke net trapping this does not give data around abundance either.
Another way to think of it is - because you can do so many sites with eDNA to determine presence/absence you can look at site occupancy to give an indication of low/high density.
It’s valuable to use eDNA to look at trends over time such as is population increasing/decreasing.
Q. Can eDNA be used for vegetation?
We haven’t run any projects on vegetation yet, but certainly eDNA methods will pick up in-stream vegetation and quite possibly a lot of riparian vegetation as well. We haven’t come across anyone who wants to monitor that yet, but we imagine it could start to crop up more and more amongst CMAs.
Q. Is eDNA a loose assessment of abundance vs trapping? What is the comparison?
You can use eDNA as a tool for abundance if you are able to get a concentration of DNA. However, what could be more important is that eDNA allows you the opportunity to widen your sampling regime more then previously possible. You can also sample regularly to build an information database.
Q. Does eDNA tell you the difference between a live vs dead species?
One of the components of eDNA is how long it stays in the environment - does it stay in the environment for a long period of time? Once you remove target species from the environment the DNA is gone often within a week sometimes only a few days. There is a very rapid breakdown due to the type of material shedding or secreting into the environment. Fish species DNA is very quick to disappear other species it persists a little bit longer. You can determine whether something is alive or dead, but the techniques are very different and not as easy to use as what we are doing with eDNA.