Water contains fragments of DNA left behind by organisms. The eDNA method reads sequences of those fragments, letting ecologists like Christchurch-based Matt Best identify what’s been lurking.
It’s a relatively new and innovative way of measuring biodiversity. Sampling with eDNA is being used at WSP for initial freshwater surveys, reducing time, costs and health & safety risks for staff in the field.
Last year, an eDNA test on a tributary of a South Canterbury river saw water samples collected and run through a DNA filter. The samples were sent to Wilderlabs for sequencing. They were then compared against a database of DNA assigned to species.
Photo: WSP ecologist Matt Best taking a sample of water for eDNA analysis.
The test registered seven species of native fish, including torrentfish, longfin eel, bluegill bullies, and Canterbury galaxias. All are at risk of extinction. The test recorded introduced species such as brown trout, and an introduced freshwater jellyfish from Japan in what’s thought to be its southern-most location.
Matt says eDNA is an extremely useful tool for understanding more about biodiversity and aiding conservation and pest management strategies.
“It gives us a better understanding of what’s upstream and what’s interacted with the water in a cheaper, more efficient way.
“We recently had a job in Craigieburn in Arthur’s Pass where there was a significant fish barrier. By testing upstream, we could see if the fish were managing to get above that structure.”
eDNA results can be refined to species level if the sample contains enough fragments of DNA; or to genus level if there aren’t quite enough fragments. Matt says both are invaluable in narrowing down which species of creature have been in (or interacted with) a stretch of waterway.
Image: Wheel of species identified by eDNA from one of the water samples taken at the South Canterbury river.
As well as in-stream species, eDNA can pick up traces of terrestrial creatures like deer and possums. It also registers the presence of birds, vegetation, insects, and, recently, bats!
A single sample, taken by Styx Living Laboratory staff in Christchurch, detected long-tailed bat. While some believe this critically threatened species persists around Christchurch, no monitoring has confirmed their presence since the 1960s.
The eDNA record of long-tailed bat was small and doesn’t guarantee a present population within Christchurch, but WSP staff have been assisting Styx Living Laboratory with acoustic monitoring - as well as performing monitoring throughout Christchurch - in the hopes of confirming their presence.
Matt says at this stage eDNA is unable to quantify the number of species that inhabit an area. For this reason, initial eDNA surveys are often followed by more traditional survey methods like electric fishing, spotlighting or trapping. It is, however, a gamechanger in terms of accuracy.
“While eDNA is still relatively new technology, it’s a fast-moving field. It’s set to be the next big thing, and we’re pleased to be at the vanguard of using it to help better understand and protect Aotearoa’s biodiversity.”