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The air is full of DNA

Airborne DNA falls to the earth's surface, where it blends with existing DNA deposits from the area's animals and plants. New research emphasizes the need for ongoing control and separation of airborne DNA when collecting environmental DNA samples. Furthermore, the discovery calls for new methods for nature monitoring.

24 bowls of sterile water were set up in Mols Bjerge and at Aarhus Harbour. The content of DNA was analysed at regular intervals during a 24-hour period. The results showed that the diversity of DNA in the water increased over time, because DNA from the air "fell" into the water and accumulated. Photographer: Martin Johannesen Klepke

Environmental DNA is increasingly used to monitor biodiversity across ecosystems, where samples from e.g. water and soil reflects the presence of various species in the area. In this way, researchers and authorities get an up-to-date picture of biodiversity in an efficient and non-destructive manner.

Environmental DNA is a growing field of research, which continuously makes new discoveries, for example when researchers from the University of Copenhagen recently were able to document that the air in the Copenhagen ZOO is filled with DNA from the ZOO-animals.

Adding to this, researchers from the Department of Biology at Aarhus University have recently shown that airborne DNA from nearby birds, fish and insects can also be found in the wild. Consequently, airborne DNA challenges existing environmental DNA methods as it can contaminate environmental DNA samples taken in an ecosystem. The results have great significance for researchers’ continuous focus on ensuring the quality of environmental DNA as a monitoring tool when they set up experiments and analyze the data.

24 bowls of water were filled with DNA

To investigate whether there was airborne DNA in the wild, the researchers sat up 24 bowls of sterile water in Mols Bjerge and at Aarhus Harbour. Then, they analyzed the content of DNA at regular intervals during a 24-hour period. The results showed that the diversity of DNA in the water increased over time, because DNA from the air "fell" into the water and accumulated.

"We found that the DNA reflected the species in the immediate area, even if they had not been in physical contact with the water. So, it had to come from the air. The bowls in Mols Bjerge contained DNA from insects, while the bowls from Aarhus Harbor contained DNA from fish, just as we expected. In addition, we also found DNA from birds and dogs," says Martin Johannesen Klepke, who is the author of the thesis on airborne environmental DNA on which the results are based.

Improving methods for nature monitoring

Associate professor Philip Francis Thomsen is head of the research group, and he is not too concerned that the airborne DNA hinder the use of environmental DNA for monitoring biodiversity.

"Airborne DNA probably breaks down quickly, just as it does in water. Consequently, there will be relatively less airborne DNA from species living further away. However, I expect that our discovery can improve nature monitoring methods that are using environmental DNA, as our study has shown that airborne DNA originates from the local environment. But airborne DNA can also contaminate other environmental samples such as water samples, and we must take that into account in our work," he says.

The study is supported by the Velux foundation and the Carlsberg foundation.

Read more weekendavisen.dk (in Danish): https://www.weekendavisen.dk/2022-36/ideer/en-cocktail-af-egern-og-musvit

Read the original research article that has just been published in the journal Environmental DNA: https://onlinelibrary.wiley.com/doi/full/10.1002/edn3.340