"I had been asked to write a document on how environmental DNA can be used to monitor biodiversity in the future," says lead study author Dr. Elizabeth Clare, an ecologist at York University in Toronto, Canada, by email. "I listed soil, snow, rain, honey even spraying foliage and collecting the water that runs off. I then said "and air" and went looking for a case study I could describe. I was very surprised that there really were none."
She learned that Queen Mary University of London (where Clare was affiliated at the time) had a funding source for high-risk, high-reward ideas and proposed a project on sampling environment DNA (eDNA) in the air. "We were surprised to see that people were talking about it, but it had not been tried ... so we decided we should do it ourselves," she says.
At the same time as Clare's study, a similar study was being carried out at the University of Copenhagen in Denmark. Dr. Christina Lynggaard, study author and a researcher at the University of Copenhagen, says her fellow University of Copenhagen researcher Kristine Bohmann came up with the idea.
"She wanted to apply for a Danish research grant called 'Villum Experiment' which supports 'crazy' projects that may not work, but if they do work they will revolutionize the research area. She then thought, and I quote: 'This project has to be totally crazy, like trying to detect animal DNA by vacuuming air.' She got the money for the project and we were able to try it out," says Lynggaard by email.
Don't worry — this isn't a case where one team is fighting the other for credit. Indeed, the fact that they independently were successful validates both studies. It turns out there's more than oxygen and allergens floating around in the air we breathe. Animal DNA is all over the place and knowing this can be a helpful conservation measure, especially where endangered and invasive species are concerned.
How the Animal DNA Was Collected
Clare's team collected the animal eDNA in the Hamerton Zoo Park, U.K., using a low-powered pump fitted with a filter "It's a bit like making coffee," she says, noting that with a coffee maker the water goes through the filter and the grounds are caught. In this circumstance, "We hope the air goes through and the DNA is caught." The team detected 25 different species of animals such as tigers, lemurs and dingoes. They even collected eDNA from animals hundreds of meters from their testing site.
The Copenhagen team also used filters attached to blower fans, at the Copenhagen Zoo in Denmark, but in another sample opted for a water-based vacuum that sucked up the air particles. "This water is filtered using special filters used for retaining DNA in water," says Lynggaard. Through these methods, the team found 49 animal species in the area, including fish, birds, reptiles, amphibians and mammals.
Both the English and the Danish teams also picked up the eDNA of chickens, cows, horses and fish, which are used as food for the zoo animals, as well as eDNA from animals that lived outside the zoo, like squirrels and hedgehogs. The results of both studies were published separately in Cell Biology.
Why eDNA Is a Big Deal
At this point, you might be asking yourself if this is more than just a cool party trick. But the potential is huge for animal conservation efforts. "By having a new method that allows us to monitor vertebrates in a non-invasive way, we can hopefully help monitor invasive species, and even endangered species that are sometimes difficult to monitor due to their low population density," explains Lynggaard.
Both studies, Lynggaard says, "have pushed the boundaries for what can be done with eDNA but also demonstrated a novel and non-invasive tool to complement existing methods for monitoring terrestrial animals — something of great importance to inform conservation efforts."
It'll be a minute before this really takes off in conservation circles, since eDNA research is still in its relative infancy. First, the Copenhagen team wants to repeat the experiment in different areas, since their initial experiment was done inside a zoo. "We expect that it will also be possible to do it everywhere, but that is the next thing to do. We want to know what happens in nature," she says.
At this point, it's unclear how animal DNA gets into the air. "It may be any source of biological material. Sloughed-off skin cells, bits of hair, feces, urine, even from breathing out potentially? We simply do not know. [EDNA] is only defined as any DNA we collect that is not directly from a tissue source," says Clare.
"We have no idea how far it can travel, how quickly it accumulates, how fast it degrades and what weather or location factors might alter this," she adds. Further tests, she says, will flesh out the concept to a much greater degree. "This will help us figure out how we can actually deploy this method in the real world to sample biodiversity."