DNA in waterways helps SCU researchers map spread of pest and endangered species

Australia Broadcast Center

30-05-2025

A project to map the diversity of life in NSW waterways has found pests, including cane toads, may be more widespread than previously thought.
Researchers from Southern Cross University (SCU) collected water samples from 234 locations across 33 estuaries, covering 1,000 kilometres of coastline.
They extracted environmental DNA to identify the "living beings" inhabiting the waterways and created unique biodiversity mapping for each one.
Lead researcher Maarten De Brauwer said the mapping could help control invasive species and protect endangered ones.
He said it revealed cane toads were living further south than previously thought.
"For the first survey we did in winter, we found them in the Sandon River," Dr De Brauwer said.
"Before that, the buffer zone was north of Yamba.
Dr De Brauwer said another surprising find was water buffalo DNA in the Richmond River.
"That was a bizarre one — a very strange occurrence," he said.
Water buffalo are not usually found in the Northern Rivers region, so the scientists initially thought there had been a sample contamination or a mistake.
"My colleague Kait [Harris] and I did a lot of sleuthing and we found out that a farmer there had used water buffalo to train draught horses, apparently," Dr De Brauwer said.
"I didn't know this was a thing.
"It was quite amazing as they were quite a distance away from the site."
Dr De Brauwer said eDNA surveys were a relatively new way to detect what lives in the environment.
"Environmental DNA is a term that refers to traces of DNA of any living being," he said.
"It can be casuarina trees, it can be rainbow lorikeets, it can be fish, it can be bacteria, or it can be COVID.
Dr De Brauwer said samples were collected in summer and winter and filtered for discarded genetic DNA, such as scales, faeces, fur or skin.
The DNA was then linked to animal or plant life and added to a digital map.
"We can detect threatened species as well," he said.
"For example, we found seahorses in quite a few estuaries. One of them was the white seahorse, which is endangered.
"So it can be a way of detecting threatened species and then knowing what areas to protect because endangered species are present."
The team detected 25 threatened species, from soft corals to fur seals and black cod.
In the Sandon River, east of Grafton, they found the DNA of a threatened bird — the varied sittella.
In the Richmond River, they found plants that did not yet have a common name.
Dr De Brauwer said the survey identified more than 10,000 species across New South Wales, and could be used to monitor changes after natural disasters.
"We can track how they recover and, ideally, what promotes recovery," he said.
"But … we are just at the start of discovering what we have in the estuaries."