Public thesis defense of Douchan Hanuise

"Informing tropical seagrass recovery in the Great Barrier Reef using a biophysical modelling approach"

Summary

Seagrasses provide essential services for human well-being, including fisheries habitat, water filtration, coastal protection and carbon sequestration. 

Globally, these coastal ecosystems have been declining due to the cumulative and interactive effects of coastal development, pollution and climate change. Coastal and catchment management and restoration projects have been implemented to mitigate the impact of these threatening processes. 

However, the success rate of management interventions is highly variable. A comprehensive understanding of seagrass dynamics, particularly tropical seagrasses, is critical to protect and preserve these ecosystems. For example, dispersal and connectivity of seagrasses supports the replenishment and natural recovery of seagrasses. 

These processes can be assessed using biophysical models, combining ocean circulation simulations with biological traits. Yet, only few of them account for the interspecific and interannual variability inherent in tropical seagrass ecosystems, suggesting opportunities to improve the predicted dispersal patterns. These dispersal processes have not been assessed comprehensively in one of the world’s largest tropical seagrass ecosystems - the Great Barrier Reef World Heritage Area (GBRWHA) of Queensland, Australia. 

By using a biophysical modelling approach, this thesis assessed dispersal and connectivity processes of GBRWHA seagrasses to inform their management. 

Overall, this thesis underscores the importance of modelling parametrization and its impacts on seagrass dispersal predictions. It highlights the value of using robust biophysical models, built on well-considered assumptions including forcing choices, that integrate species-specific traits to accurately capture connectivity. 

This thesis highlights the drivers of seagrass dispersal in the GBRWHA, that include strong seasonal variations, complex coastal topography influencing wind patterns, and large dispersal variability between species. 

Broadly, this thesis advances the capacity to model and interpret connectivity in dynamic coastal ecosystems, providing a transferable framework to improve ecological forecasting and guide management strategies. 

Jury members

Prof. Emmanuel HANERT (UCLouvain), Supervisor
Prof. Alana GRECH (James Cook University, Australia), Supervisor
Prof. Marnik VANCLOOSTER (UCLouvain), Chairperson
Dr. Jonathan LAMBRECHTS (UCLouvain), Secretary
Dr. Severine CHOUKROUN (James Cook University, Australia)
Prof. Tom VAN DER STOCKEN (VUB, Belgium)
Dr. Eric TREML (Australian Institute of Marine Sciences, Australia)
Dr. Michael RASHEED (James Cook University, Australia)