Rum Jungle Mine metals persist in Finniss River food web decades after closure

A new study from Charles Darwin University shows that metals from the Rum Jungle Mine continue to move through the Finniss River food web more than 50 years after the site shut down. The mine, located at the headwaters of the Finniss River in Australia's Top End, was the country's first large-scale uranium mine and supplied materials for U.S. and British nuclear programs until its closure in 1971.

CDU Ph.D. student Isabel Ely led the research, published in the Journal of Hazardous Materials Advances, which measured concentrations of copper, manganese, zinc, arsenic, lead and cadmium across various organisms in the river. While water quality and aquatic life in the Finniss have been monitored for decades, Ely's work is the first to examine metal accumulation across the entire food web.

The study found that filamentous algae, specifically Spirogyra, and detritus held particularly high metal concentrations. These components had not been included in previous monitoring. Freshwater mussels and prawns also showed elevated levels, while fish like barramundi had comparatively low concentrations of arsenic, lead and cadmium. Ely described this pattern as trophic dilution, where contamination is higher at the base of the food web and diminishes in predators.

Ely noted that including Spirogyra and detritus in future monitoring could help track whether metal exposure declines as rehabilitation efforts progress. She also said further research should investigate how metal accumulation affects the health, growth and reproduction of organisms, as the current study only confirms that exposure is occurring.