DNA Detectives: New ways to spot Southern Ocean hitchhikers

10 July 2023

How do you spot an invader you can’t see in a harsh and unforgiving environment?

Scientists at the Australian Antarctic Division are looking for new methods to defend the frozen continent from alien invasion.

Every living organism sheds its DNA into the environment, leaving an invisible record of its presence.

Now a new paper has examined how this environmental DNA (eDNA) could be used to bolster biosecurity surveillance in East Antarctica.

An Adelie penguin sitting on its pebbly nest surrounded by poo squirts — Every living organism sheds its DNA into the environment, leaving a record of its presence. Photo: Matt Low

Ocean-going aliens

Co-Lead author Dr Anna MacDonald said the first task was for a panel of scientists to rank non-native species that posed potential risk to East Antarctica.

“The question we asked was, ‘what plants and animals do you think are the biggest concerns, based on species that have a capacity to reach Antarctica and potential to become established once there?’” Dr MacDonald said.

“We didn’t identify specific species but instead, broader groups, such as mussels and grasses. Now we can use this information to develop new genetic tools for biosecurity monitoring for those groups of concern.”

Strict biosecurity screenings are already in place in Australia and at research stations.

But sea stars, mussels, springtails and ascidians (sea squirts) could gain a foothold in East Antarctica due to climate change and human activity.

Scanning a barcode

Co-lead author Dr Laurence Clarke said for eDNA surveillance to work, better DNA data or ‘barcodes’ would be needed to tell the difference between the locals and the gate crashers.

“It’s quite possible there are some Antarctic plants or animals that have a similar DNA sequence or barcode to non-native things we’re trying to stop,” Dr Clarke said.

“If we don’t know what’s down there, we run the risk of getting a DNA sequence that could end up being a false alarm.

“So having reference barcode sequences of native Antarctic species on file is important.”

How it works?

For marine environments, scientists can detect eDNA in water samples.

On ice-free areas of land, scientists can identify eDNA in soil samples, or screen food and station supplies.

Importantly, eDNA could also be used to detect ‘biofouling’ on ships’ hulls in Australia, and potentially Antarctica, where species could cling to the hulls of vessels. It could also detect species transported via footwear or in plane or ship cargo.

What lies beneath?

The paper highlights the need for more research to understand terrestrial and ‘benthic’ (seabed) life along the East Antarctic coast.

Co-author Dr Jonny Stark said most knowledge on coastal ecosystems had been gathered around Davis and Casey stations.

“These areas have developed very special or unique communities the likes of which aren't found anywhere else on Earth,” Dr Stark said.

“There are around 36 ice free coastal areas in the Australian Antarctic Territory and most of these we’ve never visited, let alone studied.

“This is a priority for future research to address this knowledge gap.”

Cataloguing the plants and animals that make up the biodiversity of Antarctica and its surrounding waters and understanding how these unique communities are changing in response to threats, including from invasive species, will be a critical element of monitoring undertaken by the Australian Antarctic Division and others in East Antarctica.