…a blog written by Sarah Hawkes, Buglife’s Natur am Byth! Scarce Yellow Sally Conservation Officer. (Gweld y dudalen hon yn Gymraeg)
The Scarce Yellow Sally is a secretive beast that spends more than 90% of its life at the bottom of UK rivers in the deepest part of the channel. At least it used to; in the UK the Scarce Yellow Sally was found in the lower reaches of major rivers across England and Wales. By the end of the 20th century, it could only be found in one UK river, the Welsh River Dee, and now it is labelled as Critically Endangered in Great Britain.
This year, during the Buglife commissioned kicksampling survey by John and Ollie Davy Bowker, the river was particularly deep following a winter of rain that began in November and was continuing through March. The survey was delayed as the rain kept coming and water levels stayed high. Conditions in a high fast flowing river are way too dangerous to work even if John had been able to keep his head above water, take samples and stand up against the pressure of the water flow. Even by adapting the sampling locations to the conditions the survey did not finally finish until 17th April instead of the planned late March.
Buglife’s project to highlight the plight of Scarce Yellow Sally is one of the Natur am Byth programmes across Wales to bring Nature to the forefront and talk about the incredible species we have, many of them rare and endangered like Sally, a tiny stonefly that spends just a month out of water as an adult and the rest of it’s one year life cycle underwater as a juvenile (or larva). This year, working round the difficult weather and the constant risk of our surveyor being washed away (he had to be roped to the bank just in case) we found nymphs at 3 sites and a little later, evidence of adults at each of those sites. But it is important too, to find out if there are smaller populations elsewhere in the river that were missed and also to find out what it is about those parts of the river that makes a good home for ‘Sally’.
To investigate what makes a river suitable, Hannah and Joe from Chester Zoo carried out detailed water quality testing at every one of the 12 survey sites, while John collected river data to the NRW standard for comparison with other rivers and used a Bathyscope to peer at the bottom of the river and check out the substrate.
Even so, were we finding Sally wherever it lived?
We don’t know, so with the help of Dr Alessia Bani from Derby University we sampled each of the 12 kick sampling sites for evidence within the water of ‘Sally’s’ DNA.
How is this done? Well, starting at the beginning with the easy bit, Alessia came down to give us a demonstration of the necessary procedure. We learnt how to ensure the samples were collected free of contamination and to sample 3 full litres of water per site. It was by that time late in the season and Sally would be actively moving towards the bank to emerge and become an adult. This was not the original plan, but in a way helpful because the more activity, the more DNA is shed and the more likely we are to pick up some of that DNA in our sample. Even so, it is a big river and one litre is a very small bit of the river!
Having got our litre, each sampler then had to push the water through a special filter which would collect the DNA and other small particles using a syringe, which got harder and harder to do as more of the litre was filtered and the filter itself became clogged. Look at the effort in Anna’s face as she pushes! To be fair to Anna, who is one of our volunteer helpers with the eDNA sampling, this picture is from the worst, most murky, sample site.
With each site sampled and the filters sealed and put in the freezer, they now had to get to Alessia at Derby University, two hours away. I used a tiny freezer plugged into the car so the samples could travel at -20C despite the day being really hot. We got them safely to the lab freezer in the University to be stored for when they can be processed and analysed.
Next, the samples will need to be ‘cooked and shaken’; brought up to 56 degrees Celsius over 24 hours. Once done, the samples can be made ready for analysis using chemicals to lift any DNA off the filters and get each sample ready for the final revealing analysis. Of course, this all takes days of laboratory time and has to be scheduled to fit in with quiet periods in the university. We expect our samples to be ready at the end of summer.
In the meantime I had a sneak preview of the method by which the liquid that hopefully contains the precious DNA, is made ready.
Visiting the Derby labs was really exciting in itself, seeing the fly labs where sometimes forensic work is carried out, the aquaria of water used for a range of experiments on seagrass to find what species can tolerate what conditions (another Natur am Byth Project from Anglesey) and more aquaria with corals in looking at how corals co-ordinate their spawning and what stimulates that but also what corals can withstand the high sea temperatures they are now exposed to in order to have the potential to help reefs recover. All of these are related to understanding how our changing climate will impact the natural world.
Now we wait for the results of our eDNA sampling. Until they are ready, we just don’t know if eDNA sampling will work for us and what we will find. There is so much hope riding on this.
If we do find DNA at each of the sites where there are known to be Scarce Yellow Sallies then any other positive results can probably be relied on and this is a tool we can use in the future. We do know it works for other species, like for example Great Crested Newts, but there are worries: We may have been too late with the sampling because of the unforeseen delays and the adults may already have emerged. Will we have sampled enough? Did we do it well enough?
So keeping my fingers firmly crossed, I have to finish this blog on a cliff hanger!
