Scientists have found a previously unknown source of nitrogen and phosphorous pollution impacting the Great Barrier Reef. 

New research, published in Environmental Science and Technology, suggests that efforts to safeguard the iconic ecosystem may need a significant rethink.

Using natural tracers, the research team, which included experts from CSIRO, AIMS, and Gothenburg University (Sweden), collected data spanning from south of Rockhampton to north of Cairns. Radium isotopes enabled them to trace nutrient transport from land and shelf sediments via unseen groundwater flows.

The study's standout discovery was that groundwater discharge surpassed river inputs by a factor of 10 to 15, an aspect previously overlooked. 

Groundwater discharge accounted for about one-third of the newly introduced nitrogen and two-thirds of phosphorous, indicating that nearly twice as much nitrogen enters the Reef from groundwater in comparison to river sources.

Southern Cross University’s Dr Douglas Tait says there is a need for a strategic shift in management approaches to protect the Great Barrier Reef from nutrient excess. 

Unlike river outflows, nutrients in groundwater can remain underground for decades before discharging into coastal waters, highlighting the necessity for long-term research and protection strategies.