Coral reef–influenced air masses promote new particle formation over the Great Barrier Reef

Abstract. Coral reefs are among the most biologically important ecosystems on Earth and are highly sensitive to climate change. The Great Barrier Reef (GBR) is the largest coral reef system globally, yet the extent to which it contributes to local atmospheric particle loading remains poorly understood. Here, we present a case study focusing on particle formation processes observed during a six-week measurement campaign at Heron Island on the GBR. Our results show that when air masses spent considerable time over the reef itself, we observed a number of new particle formation events. These events were preceded by an increase in dimethylsulfoxide (DMSO) concentrations and led to increased sulfate and ammonium in the resulting particle population. Importantly, DMSO concentrations were not higher during event days in comparison to other days, suggesting that both precursor availability and favorable photochemical conditions such as increased solar irradiance played a role in initiating particle formation over the reef. These findings provide evidence that the GBR ecosystem can influence local aerosol formation processes, with implications for regional cloud formation and climate feedbacks in marine ecosystems.