What’s happening?
QUT researchers, working with Southern Cross University’s National Marine Science Centre, have advanced the science behind seawater mist spraying, a potential tool to shield coral reefs from bleaching. Their high-resolution modelling has revealed how high-pressure spray systems split seawater into tiny droplets, forming sun-reflecting mist plumes.
Why it matters
Coral bleaching, driven by rising sea temperatures, poses one of the greatest threats to reef survival. This new research into droplet dynamics offers a path to optimise fogging technology, providing reefs with temporary protection during dangerous periods of extreme heat and calm weather. Beyond reefs, the findings could also improve spray technology in agriculture, medicine and industry.
Local impact
The breakthrough supports the Reef Restoration and Adaptation Program (RRAP), funded by the Australian Government’s Reef Trust and the Great Barrier Reef Foundation. For high-priority reefs along Queensland’s coast, this technology could serve as a frontline defence to buy time while longer-term climate measures take effect.
By the numbers
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Coral bleaching is one of the biggest threats facing the Great Barrier Reef, which supports an estimated $6.4 billion tourism economy annually.
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Over 2,900 reefs make up the Great Barrier Reef system, making targeted protection crucial during extreme heatwaves.
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The RRAP Cooling and Shading team has already been testing misting technologies, with this research fine-tuning how droplet sprays form and behave.
Zoom in
PhD researcher Saima Bukhat Khan, lead author of the study, said the findings shed light on a process called secondary droplet break up, where droplets fragment into smaller ones after spraying.
“Our findings provide a deeper understanding of how these fine droplets form, move, and change in size after being sprayed,” Ms Khan said.
She explained that the team used wind tunnel experiments and computer simulations to study how filtered seawater droplets behave when sprayed through impaction-pin nozzles. “These experiments and computer simulations enabled us to model the droplet sizes and spray patterns with high accuracy.”
Ms Khan added that the spray produced “a wide and even mist of droplets at sizes consistent across experiments and simulations,” leading the way to better nozzle design.
Zoom out
Co-researcher Dr Joel Alroe from QUT said the applications of this research extend well beyond reef protection.
“Spray technologies are used in agriculture, medicine and industrial settings,” he said.
“The more we understand about droplet dynamics, the more efficient and precise systems we can design.”
The project team also included Professor Zoran Ristovski, Professor Emilie Sauret, Dr Chris Medcraft and Associate Professor Daniel Harrison.
What to look for next
The findings, published in the Journal of Aerosol Science, provide a scientific foundation for future trials of mist spraying over the Great Barrier Reef. Researchers will now look to optimise nozzle design and spray systems to maximise sun reflection, with the long-term goal of shielding coral during the hottest, calmest days.
