Didymo: Waikato researcher Dr Alexis Marshall close to solving Didymo's riddle after award

Rutherford Foundation Postdoctoral Fellowship recipient Dr Alexis Marshall is comparing samples of Didymo from New Zealand rivers with samples from around the world. Photo / Supplied

University of Waikato researcher Dr Alexis Marshall has been awarded the Rutherford Foundation Postdoctoral Fellowship from Royal Society Te Apārangi to investigate the algae species Didymo.

Didymo, also known as rock snot, grows in freshwater streams around the world. The algae is a unique organism growing under circumstances that other species struggle to survive.

Marshall said over the years Didymo became a biosecurity threat as it is an invasive species that quickly takes up the whole habitat.

The Rutherford Foundation Fellowship allows Marshall to focus on a large number of unanswered questions for the next two years.

New Zealand and Chile have the biggest problem with Didymo. However, it has not yet been found on the North Island.

"I'm trying to find out what keeps it away from the North Island so far and why it produces so much mass under bad, nutrient-poor circumstances – no plant does that. We also don't know whether the Didymo in New Zealand is the same type that grows in other parts of the world. If yes, how is New Zealand Didymo different," she says.

She also tries to establish why Didymo blooms and if the blooming occurs as the result of adaptation to climate change or a response to introduction to new environments.

In order to find answers, Marshall takes a genomic approach looking at Didymo's DNA.

"As the algae is so unique, we can't use the techniques we would normally use as they just don't work."

Deputy vice-chancellor research Professor Bryony James says: "Dr Marshall's work contributes to the freshwater expertise at the University of Waikato, and this Fellowship will help provide insights into a significant environmental challenge facing New Zealand that is still largely understood."

Historically, Didymo was an inconspicuous background organism found in nutrient-poor northern hemisphere rivers. Marshall says the algae is not toxic, however it deeply impacts how people use rivers as it gets caught on everything and sticks well.

"The problem is that no one wants to clean the Didymo out of the rivers, so all we can do at the moment is trying to stop it from spreading," she says.

University of Canterbury student Logan Williams found a method to turn Didymo into material for cups and plates.

Marshall says: "It is a great idea to make use of it so people might even want to clean the rivers of Didymo."