Following the completion of the final post-construction seagrass survey for the Penrhyn Estuary Habitat Enhancement Program (PEHEP) in 2017, results showed that seagrass distribution and species composition at Foreshore Beach had been highly variable throughout the monitoring period. However, these changes were attributed to natural factors rather than the Port Botany Expansion.
The 2017 survey also recorded a slight increase in the extent of Z. muelleri subsp. capricorni (Zostera), including the emergence of a new small patch at the south-eastern end of Foreshore Beach.
Researchers hypothesised that this new Zostera patch may have resulted from improved conditions following the construction of the three groynes at Foreshore Beach, particularly in terms of sediment stabilisation. Based on these findings, experts recommended three additional seagrass monitoring surveys to assess long-term trends following groyne construction.
Additional seagrass monitoring (2018-2020)
Aquatic ecology consultants (Cardno) conducted three additional seagrass monitoring surveys at Foreshore Beach from 2018 to 2020, with the final survey completed in April 2020.
Key findings
The most promising results were observed in the area between the southernmost groyne and the boat ramp, where:
- A patch of Halophila spp. doubled in size between 2019 and 2020, expanded seaward, and showed increased shoot density.
- The small Zostera patch first recorded in 2017 expanded tenfold since that time.
- These findings provide strong evidence that the groynes have stabilised sediments in this section of Foreshore Beach, creating conditions favourable for seagrass recolonisation in other areas once sediment stabilisation occurs.
Next steps
Port Authority is a research partner in an Australian Research Council (ARC) Linkage grant project with UNSW, the La Perouse Local Aboriginal Land Council and others: Restoring and future-proofing the biocultural values of endangered seagrasses.
The Project aim is to develop best-practice methods for the biocultural restoration of the endangered seagrass Posidonia australis. This project’s aims include:
- generating valuable new genetic information to guide restoration strategies including climate-adjusted genotypes.
- working with Indigenous groups to document and restore cultural values associated with Posidonia.
- working with industrial designers to develop cost effective techniques to scale-up seagrass restoration, which are to be trialed along two sites in Gamay Botany Bay: Foreshore Beach and Kurnell.