Scientists have combined environmental DNA (eDNA) samples and hydrological methods to accurately determine the biodiversity of a river in northeast Switzerland. They hope to extend their approach to the country’s entire network of rivers and streams.

Rivers and streams contain DNA belonging to organisms such as fish, vertebrae and plants, so-called environmental DNA (eDNA). By collecting water samples and extracting and sequencing eDNA, the biodiversity of freshwater ecosystems can be accurately determined in a faster, less invasive process.

And since the DNA in rivers can be transported downstream for many kilometres, information on the numbers and density of organisms in an upstream catchment area can also be calculated.

Using mathematical models, scientists from the University of Zurich (UZH) and the Swiss Federal Institute of Aquatic Science and Technology (Eawag) reconstructed in detail the biodiversity patterns for 740 km2 of the Thur River in northeast Switzerland. Their research was published in Nature Communications journal on July 17.External link

Around one-third of all species are under threat in Switzerland. Freshwater ecosystems are particularly at risk due to changes to their habitat, pesticides and the spread of non-native species.

The researchers say their biodiversity monitoring technique is extremely accurate.

“Our model matches the direct observation of aquatic insects’ local occurrence with an unprecedented accuracy of 57-100%,” said lead author of the study, Luca Carraro.

The approach allows researchers to identify biodiversity hotspots that could be otherwise overlooked, and thus enable targeted conservation strategies, said Florian Altermatt, professor at the Department of Evolutionary Biology and Environmental Studies of the University of Zurich.

Switzerland is playing a leading role in this field, he added.

The team is finalising guidelines for the Federal Office for the Environment on how to use eDNA in standard biodiversity monitoring. In the years ahead, they hope to see their techniques being deployed to better detail and monitor biodiversity for Switzerland’s entire 65,000-km network of rivers and streams.