What is eDNA?

What is eDNA?

Environmental DNA (eDNA) is nuclear or mitochondrial DNA that is released from an organism into the environment. Sources of eDNA include secreted faeces, mucous, gametes, shed skin, hair and carcasses. Recent research has shown that the DNA of a range of aquatic organisms can be detected in water samples at very low concentrations using qPCR (quantitative Polymerase Chain Reaction) methods.

How long does environmental DNA persists in the water?

In aquatic environments, eDNA is diluted and distributed in the water where it persists for 7–21 days, depending on the conditions. However, the DNA of organisms once trapped in sediments can be preserved for thousands of years.

For a guide on how to collect eDNA, please click here!

How sensitive is the method?

It is actually quite difficult to answer this question because, although it is clear that the method can detect very small amounts of DNA it is much harder to say what the minimum number of newts is that can be detected. This is because it is difficult even using conventional survey methods to say how many newts there are in a pond without very intensive mark and recapture studies. In this project (as in much newt survey work) we counted the newts seen at night with torches or caught in bottle traps. Such counts are themselves only rough approximations of the actual number of newts. Added to this the amount of DNA in the water (its concentration) depends on other factors like how much DNA the newts produce, the volume of the pond and how fast DNA breaks down.

In practice, during the breeding season, we were able to detect newts with DNA in ponds with torch or bottle trap counts of just 1 or 2 animals, and sometimes when no animals were recorded.

When can you use the method?

Our research was confined to the newt breeding season: from late April to late June. We are confident the method worked well at that time but know very little about how well it will work at other times. We resurveyed three New Forest ponds in October, November and December 2013and found that eDNA did not always detect newts when they were known to be present by torch counting.

Where can you use the method?

At the moment we know it works for Great Crested Newts in ponds. In Britain eDNA methods have not yet been tested in any other habitats, although some researchers are using DNA from mashed up diatom samples to identify species in river algal samples – but this is not the same methods, as the DNA comes from organisms themselves rather than the water they lived in. In other parts of the world eDNA has been collected in water samples from a range of amphibians, from a water snail and a mussel, from a water flea and from fish, otters and water birds.

For a guide on how to collect eDNA, please click here!

What we’ve found out so far

Read the report