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Seagrass Monitoring at Foreshore Beach

Following the completion of the final post-construction seagrass survey for the Penrhyn Estuary Habitat Enhancement Program (PEHEP) in 2017, it was concluded that overall seagrass distribution and species composition within Foreshore Beach had been highly variable over the monitoring period, but that these changes were due to factors other than construction for the Port Botany Expansion.

The 2017 seagrass survey also showed a slight increase in the extent of Z. muelleri subsp. Capricorni (Zostera), including the appearance of a new, small patch of Zostera at the south-eastern end of Foreshore Beach.

It was hypothesised that the establishment of this patch may have been a result of improved conditions related to the construction of the three groynes at Foreshore Beach, particularly in regards to stabilisation of sediment. It was therefore recommended that three additional surveys should be completed to assess long-term trends in seagrass beds following construction of the groynes.  

Aquatic ecology consultants (Cardno) were engaged to undertake three additional seagrass monitoring surveys at Foreshore Beach from 2018-2020.  The final of the three annual monitoring exercises was completed in April 2020.  All three reports can be found below. 

The most encouraging results relate to the improvement of the conditions for seagrass between the southernmost groyne and the boat ramp.  There, a patch of Halophila spp. doubled in extent between 2019 and 2020, expanded seaward and had increased shoot density.  Further, the small patch of Zostera noted in the 2017 survey has experienced rapid expansion with a tenfold increase in extent since 2017.  The report concludes that this presents strong evidence that the groynes have stabilised sediments in this part of Foreshore Beach and bodes well for future recolonisation of seagrass in other parts of Foreshore Beach once sediments stabilise.

Port Authority is currently exploring opportunities to implement the report’s recommendations regarding further seagrass monitoring and transplantation in partnership with a research institution.