The mix of DNA floating in rivers聽and lakes will finally be聽used聽to monitor the state of聽aquatic ecosystems, after years聽of聽tests to show that the聽technique works.
Conventionally, aquatic life is聽monitored by capturing organisms, either by using nets or聽scraping under boulders, for examination. These techniques are time-consuming, can harm species and require skilled ecologists. Monitoring fish typically involves using electricity聽to stun them, which can聽sometimes prove fatal.
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But these techniques could be replaced by simply taking a water sample and analysing the DNA in聽it. This environmental DNA (eDNA) comes from the cells, waste and blood of organisms.
Thanks to advances in cheap, fast genetic sequencing and in our ability to identify which species the DNA comes from, England鈥檚 Environment Agency plans to start using eDNA to monitor fish next year. 鈥渆DNA is no longer a聽concept,鈥� says Kerry Walsh at the聽Environment Agency.
The agency has a responsibility to聽monitor the health of rivers and lakes, and the number of species living in these environments can indicate this. The agency began exploring the use of eDNA seven聽years ago in a bid to make efficiency savings, and now its proof of concept tests suggest that聽eDNA can be more accurate than established techniques.
In at Lake Windermere in Cumbria, eDNA analysis identified DNA from 14 of聽the 16 species of fish that have ever been recorded there. This is about three times as many species as are usually detected using conventional measures, and included pike and eel.
鈥淪ome fish become aware of nets and stay away. Whereas with eDNA it鈥檚 in the water, it鈥檚 mixed. Fish are great because they are slimy and releasing eDNA all the time,鈥� says Walsh.
The Environment Agency also hopes eDNA will provide an early warning system for the invasive species that rising temperatures are expected to help spread through UK waters. The group is developing procedures, expected to be ready by 2020, to spot four priority non-native species: the quagga mussel, zebra mussel, killer shrimp and demon shrimp. 鈥淚f we鈥檝e got the tools to detect them early before they鈥檙e established, it鈥檚 much easier to聽deal with them,鈥� says Walsh.
However, there are limitations to using eDNA for monitoring lakes and rivers, says Fran莽ois Edwards at the UK Centre for Ecology and Hydrology. While it is聽good at reflecting the diversity of species present, it is not so good at indicating their abundance.
It is also hard to know whether聽eDNA shows that an organism is present in a lake now, or was there a year ago but has since died off. And in rivers, the eDNA may have travelled a long way from where the species actually is. Nevertheless, eDNA holds potential, says Edwards.
