Coastal Saltmarsh

Coastal Saltmarsh is an ‘endangered ecological community’ of the intertidal zone of estuaries and lagoons. Sydney Olympic Park supports 20 hectares of remnant and regenerating Coastal Saltmarsh, across the Parklands precincts of Newington Nature Reserve wetland, Badu Mangroves, Haslams Reach, Haslams Creek Flats, Nuwi Wetland, Newington Armory, Blaxland Common and Wilson Park.

The term ‘Coastal Saltmarsh’ refers to the integrated assemblage of succulents, sedges, grasses, fauna and other organisms that form the ecological community. Saltmarsh provides habitat and food for invertebrates such as crabs, insects including mosquitoes, molluscs and spiders, as well as for fish, birds and bats. It is a breeding and nursery ground for marine life, and filters nutrients that would otherwise enter estuarine waters. Saltmarsh at Sydney Olympic Park provides habitat for migratory shorebirds protected under international treaties, and for one of the two known remaining Sydney populations of the White-fronted Chat.

Plants of the Coastal Saltmarsh community at Sydney Olympic Park include:

• Sarcocornia quinqueflora
• Suaeda australis
• Triglochin striata
• Sporobolus virginicus
• Wilsonia backhousei
• Lampranthus tegens
• Halosarcia pergranulata
• Juncus kraussii
• Samolus repens

Elevation and hydrology affects species composition at particular locations – Sarcocornia quinqueflora dominates at lower, and hence more frequently inundated levels, whereas Wilsonia backhousei and Juncus kraussii prefer less frequent inundation.

Conservation significance

Coastal Saltmarsh communities are undergoing widespread global and local decline. Coastal Saltmarsh in NSW was listed as an ‘endangered ecological community’ under the NSW Threatened Species Conservation Act 1995. An endangered ecological community is one that is likely to become extinct in nature in NSW unless the circumstances and factors threatening its survival cease to operate. The Coastal Saltmarsh of Sydney Olympic Park contains Wilsonia backhousei, a saltmarsh plant that was listed as ‘vulnerable’ under the NSW Threatened Species Conservation Act 1995 in 2000. A vulnerable species is one that is considered likely to become endangered in NSW unless the circumstances and factors threatening its survival or evolutionary development cease to operate.

Large areas of Coastal Saltmarsh have been lost from Homebush Bay and elsewhere along the Parramatta River as a result of land reclamation and development. The community has regenerated to some extent at Sydney Olympic Park, which now supports the largest remaining Coastal Saltmarsh community on the Parramatta River, and the second largest within the Sydney Basin. The Coastal Saltmarsh community contains the largest Sydney population of Wilsonia backhousei, and two species of restricted distribution and local conservation significance – Halosarcia pergranulata and Lampranthus tegens. The latter is thought to have been introduced from South Africa, but has naturalised in Australia and is now only known from the Sydney region and the Victorian coast. It is regarded as part of the cultural heritage of Sydney Olympic Park.

The Coastal Saltmarsh at Sydney Olympic Park also forms part of a rare example of complete estuarine zonation of Mangrove forest, Coastal Saltmarsh, Casuarina forest and Eucalypt forest.

Management

Sydney Olympic Park has been identified as a ‘threatened species demonstration site’ for work to conserve and enhance saltmarsh communities. Coastal Saltmarsh generally, and Wilsonia backhousei in particular, were identified as being of conservation significance in the early stages of Sydney Olympic Park’s redevelopment, many years prior to the legal protection that came with their listing under threatened species legislation.

Remediation works in the 1990s included several major estuary restoration projects. Remnant Coastal Saltmarsh was conserved and a nursery established to provide local provenance seed and cuttings used in replanting programs. The concrete-lined channel of Haslams Creek was replaced with a new creek-bed and newly-built tidal mudflats were planted with Coastal Saltmarsh. Tidal flushing was restored to the wetlands of Newington Nature Reserve to improve the health of the wetland communities, and Coastal Saltmarsh was planted along a newly-built Fishway in Bicentennial Park.

Remnant and planted Coastal Saltmarsh has been under active management since the 1990s. Current management actions within Coastal Saltmarsh communities include:

• Staged removal of the weed Juncus acutus
• Removal of mangrove and casuarina seedlings that threaten saltmarsh stands
• Management of water levels within Newington Nature Reserve and Badu Mangroves
• Saltmarsh planting and establishment trials along Haslams Creek

Restoration of tidal flushing within Newington Nature Reserve has resulted in a significant expansion of the saltmarsh community across Main Lagoon, at the expense of tidal mudflats. The Authority is seeking to achieve a balance between these two habitats through adaptive management of weir settings.

Various monitoring and research projects have been undertaken in the Coastal Saltmarsh of Sydney Olympic Park, aimed at improving understanding of the ecology of the community and guiding its management. These include a Sydney Olympic Park Authority (the Authority) funded PhD study of the ecology of Wilsonia backhousei and Lampranthus tegens.

The Authority undertakes strategic mosquito management across many of the Park’s estuarine wetlands, by aerial and ground-based application of a biological larvicide.

Where to see saltmarsh

The saltmarshes of Sydney Olympic Park can be seen at:

• River Walk at Newington Armory
• Fishway at Bicentennial Park
• pathways at Badu Mangroves

Help to protect and conserve the saltmarsh by staying on the paths and do not pick saltmarsh plants.