What is the eDNA?
eDNA sampling is a new survey technique where water samples are analysed to determine whether there is any environmental DNA from aquatic animals present in a particular pond. DNA fragments which aquatic animals leave in ponds comes in the form of skin, mucous or faeces. If DNA fragments are detected, then a great crested newt (Triturus cristatus) has been in contact with the pond.
What is the process?
eDNA sampling can be carried out between the 15th of April and the 30th of June. Water samples must be taken by a GCN licence holder with suitable training and experience and knowledge of correct protocol.
We take 20 water samples from sample sites evenly spaced around the pond using eDNA test kits, which include a sterilised pipette, mixing bag, sampler, pairs of gloves and tubes with preserving fluid. Following procedure set by Natural England, we then mix the samples.
The kits are sent to the lab by courier, where they are tested. The results are usually sent to us within 2 weeks.
What are the benefits?
Traditional methods require four surveys of the pond (or 6 if GCN are found) between mid-March to mid-June, with at least 2 of these (or 4 if GCN are found) between mid-April and mid-May. Three different survey techniques must be used each visit. Read on for details of how the eDNA improves upon traditional initial surveys.
Then eDNA can be used up till the end of June even if the survey window is missed. If the results are negative, the pond in question can then be ruled out.
An initial survey using eDNA is a cheaper alternative to traditional methods. However, if GCN presence is detected by the eDNA analysis, a full survey using the traditional methods is required to ascertain the population size which would be required to support a Natural England licence.
In a study of 35 ponds where GCN were known to be present, eDNA detected GCNs in 99.3% of cases compared with 95% of cases using the combination of bottle-trapping and torching. Although the 35 ponds were surveyed four times, this is a low sample, therefore more research is needed further understand the reliability of the methods.
For projects with a long lead-in time, carrying out eDNA analysis will give an early indication of constraints on the development. Any required mitigation schemes can be incorporated from the start of the project, minimising hassle at later stages.
What are the constraints and limitations?
In a study of 239 ponds, eDNA analysis correctly detected GCN in 91.2% of sites, but also returned 8.8% of ponds as a false negative. That is to say, when there were GCN present, the eDNA results indicated that they were not present.
More research is required to ascertain the robustness of this new technology and therefore a certain amount of caution is advised when using eDNA analysis.
eDNA cannot estimate the population size of GCN, and therefore traditional methods will still be required for work that requires a license.
If eDNA is carried out at the end of April and returned with a positive result, the window to use survey methods to carry out a population size assessment will have been missed and will have to be delayed till next year.
Does this mean the end of conventional survey methods?
No, it does not mean the end of traditional survey methods such as bottle trapping and torching. If a pond is thought to contain newts and any activities are to take place where a licence would be required, then a population count is needed in order to apply for the license.
Is an eDNA survey suitable for me?
This is very much dependent on the site, the development and the time of year. A suitably qualified ecological consultant will be able to talk through the options and advise you on the best course of action.
At the Ecology Partnership, all our members of staff have received training and certificates in collecting water samples for eDNA analysis in 2015 and have carried out a number of eDNA surveys since then.
If you have ponds on site, or within 500 metres of your development, we would be happy to have an initial informal chat!
1 Biggs J, Ewald N, Valentini A, Gaboriaud C, Griffiths RA, Foster J, Wilkinson J, Arnett A, Williams P and Dunn F 2014. Analytical and methodological development for improved surveillance of the Great Crested Newt. Appendix 5. Technical advice note for field and laboratory sampling of great crested newt (Triturus cristatus) environmental DNA. Freshwater Habitats Trust, Oxford.
To discuss great crested newt surveys, please email us or call us on 01372 364 133 or use our enquiry form below.