A brighter future for the Swan River
How mussel power is reviving our mighty river
For generations, the Swan River has been a place where simple memories have been made. So, when decades of agricultural and urban runoff brought it close to collapse, Murdoch scientists turned to nature to save it.
Under the surface of Derbarl Yerrigan – the Noongar name for the Swan River – thousands of mussels are silently pumping water. Each shell-full that passes through their fine rack of filters improves the quality and chemistry of this ancient river.
“This is nature healing itself,” Dr Alan Cottingham said.
“While we’ve stepped in to repopulate the river with these amazing little creatures, it’s a totally natural process that’s bringing Derbarl Yerrigan back to life.”
Dr Cottingham is an aquatic scientist at the Harry Butler Institute and has been working with local schools, communities and non-profits for over a decade to revive the river.
Mussels cleaning a tank of water full of algae in just three hours.
The expansive river restoration program has helped develop reefs able to filter over a third of the estuary in a single season and drawn the community in to help restore the place they remember, for the future.
“Shellfish provide an incredible range of ecosystem services for coastal environments and communities,” Dr Cottingham explained.
“They provide habitat and prey for fish and crustaceans, enhance the biodiversity of marine ecosystems, and improve water quality through filter feeding.
“It’s all really important – but that last contribution is what’s most impressive.”
Reefs in the river
The team at the Harry Butler Institute worked with The Nature Conservancy Australia (TNC) to explore how limestone mussel reefs could clean up the river. The results were astonishing.
“What we discovered is the tremendous potential for these bivalves to improve water quality in the river, with a single reef able to filter 35% of the total volume of the estuary over winter,” Dr Cottingham said.
“In doing so, the mussels absorbed more than 42 tonnes of organic matter into tissue – a huge amount of the agricultural and urban runoff coming in the waterway upstream.”
Swan-Canning Estuary is home to many wildlife
The research was the first of its kind undertaken in Western Australia, paving the way for more informed estuary conservation efforts across the country.
This will not only benefit our rivers, but entire ecosystems as shellfish reefs are among the most threatened of all marine habitats worldwide.
The limestone reef established in the Swan River is one of 13 sites across the country developed as part of Reef Builder, Australia’s largest marine restoration program, led by TNC in partnership with the Australian Government.
It’s one of several projects Murdoch scientists are involved in that are bringing mussel power to bear on restoring the health of the river.
Pygmies return to their patch
Another shellfish that once maintained Derbarl Yerrigan en masse was the black pygmy mussel, which not only acted as the kidneys of the river helping clean water but also as a crucial food source for the famous black bream.
“The nutrients from domestic and agricultural runoff over the past few decades have encouraged algae to grow on the surfaces that these little mussels would otherwise attach themselves to,” Andrew Bossie, Murdoch alumni and now Seascapes Conservation Officer at TNC said.
Murdoch scientists have worked with TNC and local community volunteers to create new habitat for the native shellfish – and they have come strolling back.
“We’ve seen pygmy mussels naturally populate the habitats that community members have put in the river, with, in some cases, over three thousand mussels populating each square metre of matting.”
“On a large scale, 1,000 square metres of deployed habitat over the course of summer could filter up to 34% of the volume of water that runs through the Swan River.”
“This is a tremendous opportunity to build natures capacity to clean the river.”
Spies under the surface
Fish kills are often the first visible signs that a river is under stress, pointing to larger problems that can impact plant and animal health, as well as drinking water quality.
Dr Cottingham has harnessed mussels to get early warning of these events so we can more effectively monitor river health.
Mussels are sensitive to changes in their environment and close their shells at the first sign of stress brought on by water quality issues.
By fitting tiny remote sensors to their shells, Dr Cottingham is alerted to when they are closing up.
“We are using a ‘canary in a coal mine’ theory and applying technology to help us identify ecosystem changes that may result in far greater issues such as fish kills and toxic algal blooms.”
The water monitoring work aims to understand the impacts and causes of fish kills and discover how to reduce their frequency and severity.
“Finding ways to support much earlier intervention is critical to maintain healthy river ecosystems, so we hope to bring these little tech workers into the Swan soon.”
Protecting our waterways takes a village. Learn how scientists, Indigenous leaders, students and industry are working together to protect this precious resource now - and for future generations
Hope for a brighter future
The Swan River is the state’s most important river and is of immense recreational and cultural significance.
“Despite all the anthropogenic impacts to the estuary and its catchment since European settlement the river still functions as a ‘healthy’ environment containing a huge diversity of fauna,” Dr Cottingham said.
“If we continue to care for it, we’ll be able to continue enjoying it and making memories here for generations to come.”
Thank you to The Nature Conservancy Australia and the Harry Butler Institute for generously providing the footage and photography that made this story possible. Your support has been invaluable, and we truly appreciate your contribution to this project.
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