Automated collection of airborne eDNA from the UK and its impact on the environmental monitoring community: From disjoint sampling to regular, repeated data collection through an air quality monitoring network
Eily Allan, a molecular biologist and chief scientist of the eDNA Collaborative, a research programme at the University of Washington in Seattle, says the automated collection of airborne eDNA using existing networks of air-monitoring stations could “push environmental monitoring into the twenty-first century”. It moves the research community from disjointed sampling to regular, repeated, long-term data collection, she adds.
James Allerton, a scientist at the UK’s National Physical Laboratory, read about the experiment and came up with one of those wait just a minute ideas. The UK has a heavy metal network that the laboratory operates. At these monitoring stations, air passes through filters, which are then analyzed to measure levels of toxic metals. We had not sat at NPL wondering if there were any recovered fragments on these filters. Allerton remembers. The idea was too interesting to ignore. “When you read a report about people who’ve successfully managed to capture animal DNA out of the air—and there we are, working in particulate measurements—then you have the light-bulb moment.”
In the latest research, Clare and her colleagues ran a pilot study in which they got access to existing UK air-quality monitoring stations in London and near Edinburgh, to see whether they could trap airborne eDNA from the local flora and fauna. The devices can be used to monitor atmospheric pollutants such as lead that gets trapped in the filters. A UK-wide network is run by the National Physical Laboratory in Teddington, and includes the Edinburgh station.
It wasn’t considered, either by air quality scientists. “We’ve had a lot of these conversations with scientists the last couple of weeks and people who run these networks,” says Clare. Did you know it does this as well? They all looked a bit shocked on their face. And then they go, ‘Oh, but of course it must.’ It really seems obvious once you’re told about it, but it isn’t obvious, because the people operating them aren’t biologists.”
The method can monitor a large amount of eDNA in the air, but it is unknown how far it travels. Study co-author Joanne Littlefair, a molecular ecologist at Queen Mary University of London, says the team is also still working out what ecological information eDNA can provide beyond identifying species. She believes it is unlikely that the method will be able to measure abundance. It could keep an eye on how birds are changing in response to climate change.
But before the monitoring method can be rolled out widely, researchers need to work out some details, including the optimal sampling time to ensure broad eDNA collection. The team said it’s best to keep the DNA for so long that it degrades, even if a day is too short.
Air monitoring stations and biodiversity monitoring: how long can we keep tabs on taxa, wrens, ants, Soleirolia and Septoriella fungi?
Many countries around the globe have already established an air-monitoring infrastructure thanks to the advantage of using existing stations. They urge monitoring-station operators to preserve filters after air-quality analysis so ecologists can use them.
The researchers were surprised to find many group of organisms on the filters. These included 34 species of bird, such as wrens (Troglodytes troglodytes) and great tits (Parus major), as well as ash trees (of the genus Fraximus), nettles (of the genus Soleirolia) and pathogenic Septoriella fungi (see ‘Keeping tabs on taxa’).
The research team took out eDNA from one quarter of the filters. Scientists compared the sequences of those in the GenBank with those available in other databases.
To test whether sampling time is important, the researchers set up a London station which is next to a deer park, and took samples over different time periods. They explored how long the samples could be held for, after the filters on the Edinburgh stations had collected the sample for a week.
Global biodiversity is plummeting — some estimates suggest a 69% drop in wildlife populations since 1970. The scientists don’t have the infrastructure to measure the rate of decline of organisms on large scales. Typically, researchers or volunteers in the field monitor a few species in small regions using labour-intensive processes such as camera surveilling and in-person observations. Over large scales, only very general measurements are possible, such as assessments of forest cover.