Like a naughty pet labrador, the Australian lungfish has little restraint when it comes to food.
"We had 360sqm of aquatic plants growing inside enclosures; but, once the fences were removed, lungfish and other aquatic animals feasted on the plants, and most of the vegetation was gone within 21 days."
Colin Burke, a PhD Candidate within Griffith University's Australian Rivers Institute, is leading a study to restore and reestablish critical aquatic vegetative habitat in the Brisbane River downstream of Wivenhoe Dam for the federally threatened Australian lungfish, while also supporting broader native freshwater fauna communities.
Funded by Seqwater, with support from the National Environmental Science Program (NESP) Resilient Landscapes Hub, restoration trials of underwater aquatic plants, particularly Vallisneria nana (ribbon plant) has been underway since 2020 in an area that historically supported extensive aquatic plant habitat before the 2011 floods.
Seqwater's Chief Executive Officer, Emma Thomas, said the study was critical to supporting native floral and fauna in South East Queensland rivers.
"Protecting our native fauna and flora is essential to the long‑term resilience of our rivers and the water quality our communities rely on. Strengthening our understanding of these ecosystems helps us to take action to protect them and support healthy, sustainable and thriving natural systems for future generations," she said.
The Australian lungfish is one of Australia's most ancient and unique freshwater species, and survives in only a few rivers in South East Queensland.
Lungfish are extremely long-lived, with individuals known to survive for decades. This means populations recover very slowly when numbers decline.
"Repeated flooding without sufficient habitat recovery can reduce recruitment of young lungfish to adulthood, increasing long-term risks for already vulnerable populations," Burke said.
"When aquatic plants are removed by floods, recovery downstream of major dams can be slow. That loss of habitat can become self-reinforcing, with plants taking years to naturally re-establish. Well established plants are also crucial for lungfish as they are not only a food source, but they use them to lay eggs."
PhD Candidate Colin Burke
Early aquatic plant restoration trials led by Seqwater used natural fibre mats to hold underwater plants in place, helping them establish, but were unfortunately grazed upon.
The proceeding trial, which was documented in a study published in the Journal of Environmental Management, saw initial success in establishing 360sqm of ribbon plant using fenced enclosures which was grazed upon when the fences were removed.
"And managing fences in flowing rivers is logistically complex and time-intensive, and there is always a risk they could be damaged or lost if flooding occurs," Burke said.
Despite these initial trial-and-error setbacks, Burke and the team's recent efforts - essentially distributing clumps of ribbon plant propagules by throwing them downstream and allowing them to establish in shallow parts of the riverbed - were showing promising results.
"This is called 'managed hydrochory', which focuses on restoring the natural process of plant dispersal by water rather than planting large beds all at once," Burke said.
"So far, we've released about 150kg of plant material, equivalent to roughly 40,000 individual propagules, allowing plants to spread naturally through the river.
"This approach helps spread grazing pressure along the river reach. We have also installed wooden stakes throughout a 1.5km reach where these stakes should enhance retention of the released propagules. Another benefit of this method is that the aquatic plant propagules might be able to settle and establish further downstream.
"It's a low-cost, scalable method that has strong potential to help rivers recover after severe floods that scour the riverbed.
"To our knowledge, this is one of the first process-based restoration trials for submerged aquatic plants in rivers anywhere in the world.
"The research being undertaken by Griffith University, is provides valuable insights that strengthens our understanding of how large dams influence the ecology of South East Queensland's rivers," said Dr David Roberts, Seqwater Senior Research Scientist.
"It is helping to fill critical knowledge gaps and improve how we protect and enhance river health. For example, we did not previously understand that large dams could delay the natural recovery cycle of aquatic plants after major flood events like those in 2011 and 2022.
"This research is equipping Seqwater with powerful new tools to better mitigate these impacts, support river health and help restore the natural balance of aquatic plants that, in turn, will support diverse river ecosystems and improve water quality."
Burke and the team will continue to monitor the how released aquatic plant propagules establish and spread through the river over time, then trial this method at multiple sites downstream and gradually scale up the amount of plant material released.
"We are hoping to see self-sustaining aquatic plant communities that can persist and naturally recover following large flood events," Burke said.
"Having collaborators means the research is grounded in real-world river management, not just theory. Working closely with Seqwater allows us to test ideas in the river, learn quickly from what works and what doesn't, and apply those lessons directly to restoring lungfish habitat."
