Tackling Climate Change: Estuarine Seagrass Under Stress

As climate change progresses, coastal areas of NSW are likely to experience more frequent and intense rainfall.

This increase in freshwater runoff into estuaries poses a serious challenge to aquatic plants like the endangered seagrass, Posidonia australis.

Known for maintaining healthy estuarine ecosystems and providing vital habitats for marine life, Posidonia may now be under greater threat.

Floods can reduce salinity and make estuarine water murkier, making it difficult for Posidonia to photosynthesise.

Recent research led by Dr Tim Glasby, Principal Research Scientist at the Port Stephens Fisheries Institute, aimed to understand how well this seagrass species can withstand these stressful conditions.

He said by simulating extremely low salinity and reduced light over several months, the team observed Posidonia's response to repeated flood events.

"Initial findings reveal that after a single simulated flood, Posidonia lost a significant number of leaves and shoots, affecting its ability to photosynthesise," Dr Glasby said.

However, there was encouraging news: plants that survived one flood were better able to endure subsequent floods.

“The rhizomes and roots of Posidonia remained in reasonable condition even after enduring three simulated floods, suggesting potential for regrowth," he said.

Dr Glasby said this resilience is promising, given Posidonia's important role in keeping our estuaries healthy.

The next phase of the project will explore the resilience of Posidonia seedlings and investigate genetic differences among estuaries to understand how this species adapts to extreme environmental conditions.

"With ongoing research, we hope to secure the future of Posidonia australis, ensuring it continues to support biodiversity in our estuaries even as our climate changes," Dr Glasby added.

This project, ‘Impacts of future climate on the threatened seagrass Posidonia australis’ supports the delivery of the Marine Estate Management Strategy Initiative 3 ‘Estuarine habitat monitoring and threat assessment’. It is primarily funded by the NSW Environment Trust.