Predicting seagrass connectivity in a disturbed environment

Connectivity between local populations of seagrass may strengthen regional seagrass population resilience by maintaining genetic exchange and allowing re-colonisation of disturbed patches. Therefore understanding the relative connectivity of different seagrass meadows allows management decisions on seagrass conservation and aids the identification of areas suitable for seagrass restoration efforts, but where initial colonisation may be impeded by issues related to connectivity. The dispersal of clonal seagrasses is achieved through asexual spreading (rhizome elongation), vegetative fragments and seed dispersal. Distances travelled very with seed and fragment settling velocities, and the strength and directions of wind and tidal driven currents. Retention and subsequent colonisation of a site depends on the bed shear stress climate, rugosities and suitable environmental factors for the germination and growth of the seagrass. In this study we examine the seed and fragment settlement rates of five subtropical seagrass species. Settlement rates and both biomass and distribution maps of seagrass in Port Curtis Bay, Queensland, were used in conjunction with erosive/depositional properties of seeds and fragments as inputs into an advection dispersion model. The numerical modelling was performed using BMT WBM's in house flexible mesh finite volume solver TUFLOW-FV to simulate the advection and dispersion of a mass of seeds/fragments within the hydrodynamic field where the rates of settling, deposition and erosion are specified by the modeller. Outputs of the models are discussed in terms of the persistence of seagrass distribution in Port Curtis Bay and in relation to the management and restoration of these important habitats