DNA is the darling of the high-tech detective world, whether it’s used to solve murders or track what animals are nearby.
But what about it’s less famous relative, RNA? It turns out, this type of genetic material can also be a powerful tool for monitoring biodiversity, one that can do some things DNA can’t.
Its strength might be in what had previously been seen as a weakness: It breaks down much more quickly than DNA.
“That fragility turns out to be an advantage,” write scientists Wendy Morgado Gamero of McGill University in Canada and France’s Orianne Tournayre of the Université de Montpelier in a recent column in The Conversation. “It gives us a snapshot of what’s alive and active in the moment, offering a powerful new way of tracking living organisms in real time.”
In recent years, scientists have grown increasingly interested in the power of environmental surveillance using tiny bits of DNA that organisms shed into the air, water and soil. So-called eDNA has been used to track the intensity of COVID-19 outbreaks by testing for the SARS-CoV-2 virus in sewage, to estimate the size of fish populations in the ocean, and to see what species are living near air pollution monitors. One recent experiment showed that eDNA tests in the air at a park could reveal detailed information about people who had wandered nearby, as well as countless other organisms.
One problem, however, is that because eDNA can linger for weeks, it doesn’t offer a clear snapshot of when something was in the vicinity. Was the DNA from an invasive fish that just swam by yesterday? Was it dumped out of a ship’s ballast two weeks ago? Did it come from an upstream lake miles away? It can be tricky to say.
But RNA, which translates the genetic code in DNA to build proteins inside a cell, might be able to help, if it can be detected. Tournayre and Morgado Gamero were part of a team that wanted to see if they could harness short-lived RNA to track a species in the wild, and how that compared to using DNA.
To create a realistic scenario, they took water from Lake Hertel in Quebec and fed it into a string of large, 1,000-liter tanks. They then took a batch of laboratory water where they had raised a kind of water flea, Daphnia pulex, and poured some of it into the lakewater tanks.
This flea doesn’t live in the lake, so any Daphnia DNA or RNA that turned up in the experimental tanks came from the lab water. In some of the tanks the lab water was heavily diluted, at a ratio of 1 to 10,000.
The scientists then sampled water from each of the tanks many times over the course of 24 days, to see what they could detect.
The results were good news for the potential usefulness of RNA as a monitoring tool. In the first few hours, the flea’s RNA could be detected even in the most diluted tanks. But it also vanished from the water far faster than DNA. The RNA broke down to below detectable levels in between 6 and 12 hours, the scientists estimated. By contrast, DNA breakdown showed a pattern suggesting it could still be detected between two days and more than a month after the experiment began, the researchers reported in Molecular Ecology Resources.
The results show that “in particular, mRNA, the most fragile RNA, can provide a better snapshot of active life in aquatic systems,” the duo wrote. “This provides scientists and environmental managers with a faster means of detecting changes and taking action to protect freshwater ecosystems.”
It might even be able to tell us not just whether a species was living somewhere, but its health. That’s because RNA can tell you whether a part of an organism’s DNA has been “turned on” in reaction to something. Research involving the same senior scientist, McGill’s Melania Cristescu, showed that bits of eRNA associated with heat-stress could show whether water fleas had been exposed to water hot enough to cause physiological strain.
While none of this work has moved beyond experiments, in a world where species a moving around the globe and hot water is causing problems for everything from salmon to coral, such a tool might come in very handy.
Morgado Gamero, et. al. “Comparative Decay Dynamics and Detectability of eDNA and eRNA in Connected and Isolated Freshwater Mesocosms Using Digital PCR.” Molecular Ecology Resources. Aug. 13, 2025.
Image: ©Anthropocene Magazine
