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Satellites Reveal a Flood of Information on the GBR

Researchers at James Cook University have proved that publicly available satellite imagery can be effectively used to map the extent, nutrient content and muddiness of flood plumes affecting the Great Barrier Reef (GBR).

Many important habitats in the GBR are in decline, and one important driver of this is poor water quality. Heavy rains and cyclones during the wet season scour mud and pollutants, such as fertilisers and pesticides, from the land. The resulting river flood plumes carry polluted water to the GBR.

Traditional methods of monitoring flood plumes require scientists to use submerged data loggers, or boats and helicopters to gather water samples. Such methods are expensive, labour-intensive and cannot be collected everywhere.

“Despite technical challenges, satellite time series provide the spatial and long-term window necessary for understanding water quality variability inside Great Barrier Reef coastal waters, and provide the baseline information to assess changes to important ecosystems, such as seagrass beds,” said Dr Caroline Petus from TropWATER at James Cook University.

Petus said these studies are the first steps toward the development of river plume risk maps for Great Barrier Reef seagrass and coral ecosystems. “Combined with ecological and in situ water quality data, these maps will help our understanding of the resilience of these ecosystems to water quality changes. In the near future they should help us predict ecosystems’ health changes associated with human activities or climate change,” Petus said.

Seagrass expert Dr Michael Rasheed of TropWATER says the information will help researchers understand the impact of flood plumes. “It is often difficult to determine whether declines in seagrass beds are due to polluted river run-off or coastal development such as dredging around a port. This new tool will allow us to better understand which activities are driving declines,” Rasheed said.