Uranium mine contamination persists in Australian river food web

Isabel Ely, a doctoral student at Charles Darwin University, found that metals from a closed uranium and copper mine continue to affect the Finniss River ecosystem in Australia’s Top End region.

The Rum Jungle Mine closed in 1971 after supplying materials for British and U.S. nuclear programs. Although authorities have monitored the water quality and aquatic life for decades, Ely conducted the first study to track how metals move through the entire river food web.

She measured copper, manganese, zinc, arsenic, lead, and cadmium in various organisms to see how these elements travel from the bottom of the food chain to top predators. Ely discovered that filamentous algae called Spirogyra and detritus, which is decaying organic material, contain high concentrations of metals. These components were not included in previous monitoring efforts. Because these materials provide food for many other creatures, they act as a reservoir of contamination at the foundation of the river's ecosystem.

The research showed that freshwater mussels and prawns hold higher concentrations of metals than predatory fish like barramundi. This pattern, known as trophic dilution, suggests that metals are transferred from the base of the food web upward. Ely suggests that monitoring these specific organisms could help researchers track whether metal exposure decreases as rehabilitation efforts continue. Future research will look at how these metal levels affect the health, growth, and reproduction of the animals.