The ecological health of Buffalo Creek has been severely damaged by the sewage flowing into it, researchers have found after an intense week of sampling.
Tropical Rivers and Coastal Knowledge (TRaCK) researcher based at Griffith University, Dr Michele Burford said the results of the research had revealed extremely low oxygen levels in the creek which has a direct impact on aquatic life.
“Fortunately we have not had big fish kills from the lack of oxygen because the creek has big tides – up to eight metres – and the incoming tide brings more oxygen in. But on the outgoing tide these creek-dwellers run out of oxygen,” Dr Burford said.
The project has revealed nutrients from the sewage had formed a sediment pool in the creek that was much larger than that found in other creeks the researchers had sampled. The high level of nutrients is causing algal blooms in the water and sediment, with the nutrients also being released from the sediment pool at a rapid rate.
“The size of the sediment pool means that even if sewage outflows into the creek were stopped tomorrow, the nutrients from the sediment will be released into the creek for a very long time to come,” Dr Burford said.
The researchers found a chemical compound specific to sewage up and down the length of the creek, showing that the effects of the sewage extend throughout the whole system.
“If you find that compound in measurable levels in the water and mud you know that that area has been affected by sewage.”
Director of the Tropical Rivers and Coastal Knowledge program based at Charles Darwin University, Dr Michael Douglas said that any increase in sewage into Buffalo Creek was likely to damage ecological processes even further and affect the animals and plants living in the creek.
“We recommend monitoring oxygen levels as an early warning system and looking at better management of nutrient loads into Buffalo Creek as a priority,” he said.
Researchers also looked at sewage levels in Myrmidon Creek near Palmerston, and in this larger creek, did not find measurable impacts from sewage.
“This project is a good example of taking independent scientific evidence to the community and decision makers to help them make informed decisions for the future of our waterways,” Dr Douglas said.
“TRaCK provides independent advice to decision makers to help them manage our tropical rivers and coasts more effectively.
“We can use the approach taken in this project to help us improve the way we assess the health of estuaries and tidal waterways in the future.”
This collaborative project on the impacts of urbanisation on Darwin Harbour involved researchers from CSIRO, Griffith University, Geoscience Australia, Charles Darwin University and the Northern Territory Department of the Natural Resources, Environment, the Arts and Sport.