Sampling the river for eDNA

We looked for 'invisible' animals were in the River Great Ouse by taking an eDNA sample
10 August 2021

Interview with 

Kat Bruce, NatureMetrics


Kat Bruce eDNA sampling


Just 20 years ago, it would have taken months of work to get just one eDNA sample. Luckily, nowadays the process is so simple that even primary school kids are doing it. Sally Le Page met up with Kat Bruce, founder of NatureMetrics, to discover what animals had been visiting the river, Great Great Ouse, at Over in Cambridgeshire...

Kat - So we're going to collect an eDNA sample, so we are going to filter some water. And that filter will be sent back to the NatureMetrics lab and we will analyse it to see what species of animal we can find from the river.

Sally - It's so exciting. How do you collect eDNA? What are we going to be doing?

Kat - Over the years, we've designed this really simple kit. The first thing we ought to do is put gloves on. Again, this is to stop us from introducing our own DNA into the river. In reality, we actually are able to use human blockers in our analysis, and that really sort of reduces the amount of human DNA, because to be honest, this river is full of human DNA.

Sally - And out of this plastic bag with all of the different ingredients, I mean, that just looks like a sandwich bag to me. Have you just brought your packed lunch?

Kat - I have, this is a very sterile pack, so you can see it seals. So, we have to rip the top off to open it, take the top off this bag, reach down and scoop up some of the surface water. I'm going to hold it so the bags facing upstream and the water can just flow into it.

Sally - We now just basically have a very clean sandwich bag full of water.

Kat - I mean, so you can think of the water in here as a sort of soup of genetic material of all of the wildlife that's been in and around the river. So it will contain the DNA of the fish and things that are living in the river, but also a surprising amount of the land-based species that have been either drinking or swimming or whose DNA has been washed off the bank into the river as well. And then we've got a hundred mil syringe. We literally just go to use the syringe to pull up the water and then the syringe screws onto the filter housing with a filter membrane inside it, when we're dealing with eDNA, we're dealing with really tiny traces of DNA. That makes it very vulnerable to contamination either from ourselves or from sort of other things that we've brought in from the environment. So, the membrane is kept inside that housing.

Sally - It does just look like a plastic coin almost.

Kat - Yeah. It's about sort of twice the size of a 50 pence coin, I guess. So, then we just push the water through any traces of particles, sediments, DNA, cells, et cetera, that are all stuck inside the filter membrane now. So, we'll do this about 20 times. I think this is pretty much my last one and I'm just going to press the preservative liquid inside. I've got the cap on each end, he seems to have a yellowish colour on the inside.

Sally - That's the only thing that people have to post to your lab.

Kat - Exactly.

Sally - So we have just samples, potentially dozens of species just in like 10 minutes. That's just by sitting on a jetty and squirting some water through a glamorised water pistol with a filter on the end. That's it, that's it.

Kat - Yeah. Expedite that delivery back to the lab and see what we can find.

Sally - It was just unbelievably simple and because it's so simple, they can send these kits off to researchers wherever they are. They can stick them in their backpacks and they don't need a lab. And the company nature metrics is now working with the conservation organisation, the IUCN to sample water from around the globe to create eBioAtlas documenting all of the world's aquatic species.


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