- Scientists at ETH Zurich launched a global project to gather biodiversity data from 500 lakes around the world.
- As part of LeDNA, citizen scientists from around the world collected environmental DNA samples from lakes to commemorate the U.N.’s International Day for Biological Diversity.
- With the samples, the team behind the project aims to understand more about how lakes could potentially serve as “sensors” detecting the richness of life in the catchments surrounding them.
What do lakes tell us about life on the land surrounding it?
When environmental DNA scientist Kristy Deiner and her team started thinking about this question, the answer seemed evident: probably a lot. Rivers flow through landscapes and end up in lakes or the oceans. Along the way, they collect and carry with them traces of the DNA, or environmental DNA (eDNA), of the biodiversity that lives in the catchment.
“It became clear that lakes are eDNA hotspots, and that we could go and get this large-scale information and understand more about biodiversity on Earth,” Deiner, assistant professor at the department of environmental systems science at ETH Zurich, told Mongabay in a video interview. The big question, she said, was, “Does the DNA that we expect on the landscape actually get into the lake?”
To test this hypothesis, Deiner and her team decided that it was imperative to get samples from lakes all over the world, spanning different types of ecosystems. “We realized we needed to rely on other people throughout the world,” she said. “So we came up with the idea of getting people to do it on a single day.”
They launched LeDNA, a project that worked with citizen scientists to gather environmental DNA samples from 500 lakes in 80 countries around the world. The samples were collected on May 22 to commemorate the United Nations-declared International Day for Biological Diversity. “People care about what’s going on,” Deiner said. “So let’s harness that. There’s no reason why that can’t be part of any solution that we have for conservation.”
Environmental DNA is increasingly being used to get a snapshot of the biodiversity living in a particular area. It hinges on the idea of identifying the presence of a species based on the genetic material it may have left behind via tissue or fluids such as fur, excreta and saliva. In recent years, scientists have gathered and analyzed eDNA samples collected from oceans, rivers, air, forests and even the world’s highest mountain. Scientists consider its noninvasive nature and ability to survey large areas a big plus. Its rising popularity has also prompted people to come up with creative ways to collect samples, including drones that collect water samples and robots that gather soil and leaves.
As part of the project, Deiner and her team sent out 515 sampling kits around the world. They’ve given participants until August to send the samples back to Switzerland, where the analysis process will take place.
Kristy Deiner spoke with Mongabay’s Abhishyant Kidangoor about what it took to get LeDNA off the ground and the power of using citizens for biodiversity monitoring. This interview has been edited for length and clarity.
Mongabay: How did you get into the field of environmental DNA? What about it fascinated you?
Kristy Deiner: I was working in alpine lake systems, and typically very remote places. I was always having to carry so much stuff just to study these places. When I was in there, I started thinking, “There has to be another way to be able to measure what’s in the place.” It was in these moments that I started thinking about DNA and if that would be a much easier way to sample things. Also, I am definitely somebody who has always felt guilty when we kill things just to study them. When it comes to the smaller species on our planet, the only way we can really study them is through killing them and looking at them under a microscope, and that always bothered me. So using DNA had a clear benefit. Then technology came in that allowed us to really advance.
Mongabay: How have you seen the field change over the years?
Kristy Deiner: In the beginning, the question was, “Can we do this?” Now it’s more about “How do we do this, how do we do it for different branches of the tree of life, does it work everywhere, and what is the context in which this works?” We have moved very far beyond, “Does this work?” There’s hundreds and hundreds of papers that show we can, and the geographic spread of those papers and their success demonstrate that it has reached a global scale now.
We are now at the point where we want to figure out how to make it more accurate. How do we use it for decision-making? How do we make it robust? How do we standardize it? How do we move it out of the frontier where scientists tend to work and move more into practice now? People see this as useful. They understand it’s not perfect, but have started thinking of where and when we can start applying this and use it for decision-making about biodiversity.
It advanced fast because we have forensic science and we have ancient DNA studies. Those fields are not so different from eDNA. There has been a lot of learning that happened with those other fields that the field of environmental DNA could learn from and implement at a much faster rate. It really benefits from standing on the shoulders of giants already out there.
Mongabay: Coming to the project you are leading, what gaps were you trying to fill with LeDNA?
Kristy Deiner: We have a hard time actually sampling our Earth. It’s very hard. When you want to sample all of life at the scale of our Earth, it’s very hard. We’ve been doing this since the beginning of scientific exploration for biodiversity, and we haven’t even scratched the surface. We haven’t described all the species we know, and we haven’t even been to most places on Earth for documentation.
Then, by around 2018-2019, it was starting to be known that DNA can be transported quite far from where the actual animals lived, and we were actually getting information from many locations. And we knew that the behavior of a molecule out in the environment gives us a powerful way to sample large areas with a very little amount of effort. That was the starting point.
Mongabay: Why the focus on lakes and water bodies in this project?
Kristy Deiner: It started with thinking about where we could sample on Earth. That should be places where all the DNA is moving to. If you think about rivers flowing through all the landscape, where do they go? They go to the lake, or they go to the ocean. All that DNA is getting collected, and these places are just like little sensors in the landscape, collecting all that DNA of everything living in its catchment. When I got to that idea, it became clear that lakes are like eDNA hotspots. They are on the surface of Earth, and we could go and get all this large-scale information and understand more about biodiversity on Earth. The big question was, “Does the DNA that we expect on the landscape actually get into the lake?” Then I was like, “What kind of experiment would I do to test that?” It became clear that we have to go global and take samples from lakes all over the world that have different environments, different chemistry, and different biodiversity.
We can’t fly all over the world and do that ourselves, although I would have loved to do that. We realized we need to rely on other people throughout the world. And so we came up with the idea of getting people to do it on a single day. People were sent these little kits and they took samples all over the world.
Mongabay: What did it take to coordinate that on a global scale?
Kristy Deiner: We have been working, more or less, since March of 2023 to plan everything for this one day. Step one was we had to pick a subset of lakes that would be interesting and where we could actually test some hypotheses. The main one that we’re testing is the surface area of a lake relative to the catchment area. One law in ecology is that the bigger the area, the more species there are. Basically, if it’s a very large catchment, but a small surface area of a lake, you would expect to find really high diversity in that lake from the DNA because it’s just summarizing a huge space. So we had to look at lakes all over the world.
We needed multiple samples from different places all over the world that have a small surface area and a large catchment. Nothing’s equivalent in nature, and it’s not like you will find a replicated experiment. So we had to go and look at what the biodiversity was there, and then try to find these units that would allow us to have enough replication with similar parameters to have a robust conclusion. It took us a long time. There’s a global database for that and we fished through this global database and came up with the potential lakes that could be sampled.
Mongabay: What happened next?
Kristy Deiner: We posted a map with lakes that people could sign up for. And we said, “Hey, would anybody like to sample these?” Then we allowed them a sign-up period of about three months. This ranged from grandpas taking their grandkids out, to other hard-core eDNA scientists. We had the full breadth of society. We had schoolkids. We had people participating in scientific conferences, making it part of their event. We also had all these legal compliance issues to look into. Once we knew who we could work with, we started figuring out a research agreement which is, essentially, “This is what we’re all agreeing to, here’s what you’re going to do, here’s what I’m going to do with these things.”
Then we had to train everybody on how to take a sample. We prepared training materials, videos and webinars. And then shipped the kits to 80 countries. Sadly, the state of sociopolitical affairs meant we couldn’t ship to Russia, Iran or North Korea, which is sad, because they are beautiful places that we can’t include. We spent some time understanding that kind of landscape and navigating that. And then, sending it out, which meant handling customs, which is different in every country.
Genetic resources are potentially regulated in many countries, and we had to navigate this and make sure we were in compliance with that for the project. This only gets triggered when the samples get sent back to us. There were some local collaborators that had to get permits and do things to ship it back.
What’s wonderful about it, though, is that the processing of the samples and the generation of the DNA information that we’ll be able to produce will go very fast. So that is where the efficiency is. It will be done by December. It’ll still take a long time for us to interpret and get a scientific paper out with all the collaborators in the world that are part of the project. We’re also sharing the data before it’s published with each partner. It’s not being held until one paper comes out where all the data will be. Each person will receive the data from their sample, and then they can choose what to do. All the collaborators in one country might want to do something specific to their country. Globally, we agreed on what we’re answering together. But the regional and individual samples also have tremendous value there. A local partner can use that for any kind of work that they have ongoing or have interest in. They can already use it and start doing things.
Mongabay: What questions are you hoping to get answered by the end of this?
Kristy Deiner: The main one is this area-catchment ratio. We want to test whether or not we see this pattern that we have predicted based on our understanding of ecology. If we can confirm that, it shows that lakes are accumulating DNA. If we show that, it becomes something that we can think about if we want to implement on a global scale. Could we imagine a global sampling network that would allow us to go out and collect on an annual basis, and then we have a way to measure the state of biodiversity? That’s the big dream. We could try to do it as a global monitoring system. And that was the motivation for me.
The other interesting questions are more about pushing the frontier. We’re interested in two things. One, as we’ve demonstrated, eDNA works kind of everywhere, and we can find DNA of species in the environment. But we have some of these global patterns that we have never been able to test with eDNA. There’s latitudinal gradient in species richness. As we move away from the tropics to the poles, you get less and less diversity. We want to demonstrate that we actually see this pattern because we’ll have samples from all over the world and across latitudes. Can we recover that pattern with eDNA as well?
When we talk about biodiversity, we know it’s not just species. It’s also about all the species interacting, the communities, how the ecosystem functions and its structure. What does it mean when you find species together in a landscape? Well, we know they’re not living in the lake together, but we know they’re in this watershed. This co-occurrence is something that we can detect from eDNA, and we can try to understand if that co-occurrence has information about how the ecosystems are functioning.
Those are the main things that we’ll be testing with the data set. Then, of course, there are a billion local questions, and that’s what we’re hoping our local collaborators will find value in the data to look at. Do we find invasive species? Do we find new species we’ve never detected in a lake or a region? It’ll be exciting because it’ll be a global sample, collected with the same methodology. It’ll be a pretty consistent data set. When we talk about implementation and standards and thinking about what it would take, this is a true test of if we can do this annually. It will also help us understand what we need to change if we were to do it again.
Mongabay: Now that you have done this, what is your advice to people who might want to do something similar in the future? What is your biggest learning experience?
Kristy Deiner: There are things that are difficult. When you have to understand regulation, you have to understand cultural differences. There were a lot of things we thought we understood, but it turns out it got interpreted a different way. We have language barriers. It’s complex, but it’s not unfeasible.
I think it’s also important to say that, from a scientific perspective, we’re always worried about accuracy and doing something to the best it can be done. But I think when you’re trying to do something that’s unfeasible to do any other way, you have to accept far more variance in what can occur. Relaxing our assumptions and demands is something that has been good. Maybe not everybody is going to sample exactly 30 liters [8 gallons], and this happened. But, you know, it’s important to design it in such a way that it’s still robust even if we have 10 liters or 20 [2.6 or 5.3 gal]. Having a good understanding of “Is this a 1% change? Or is this like night and day and it’s a no-go?”
I think understanding how to design something that’s robust to variation is what one must start from in designing crowdsourcing, and making sure that what comes in still has value. If you’ve designed it in a way that even if the minimum is met, you still have a way to move forward with that.
Mongabay: How did it feel to see this level of participation from all over the world?
Kristy Deiner: It has definitely been so positive to see the interest. You kind of assume that maybe 200 people will sign up. We had thousands interested in the beginning. When we got down to execution, it changed. But it’s just so beautiful to see that there’s that energy out there and people want to do something. People care about what’s going on. So let’s harness that. There’s no reason why that can’t be part of any solution that we have for conservation.
Banner image: A Eurasian otter (Lutra lutra) at a lake. Image by Cloudtail the Snow Leopard via Flickr (CC BY-NC-ND 2.0).
Abhishyant Kidangoor is a staff writer at Mongabay. Find him on 𝕏 @AbhishyantPK.
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