After years of pressure from mangrove encroachment, contaminated surface and ground waters as well as increased disturbance from public recreational usage, the rehabilitation and enhancement of Penrhyn Estuary is beginning to take shape. As part of the Port Botany Container Terminal Expansion Project, Sydney Ports has committed to securing Penrhyn Estuary for locally significant migratory shorebirds. The commitment will see $8 million spent to rehabilitate and expand Penrhyn Estuary. Due to decline or removal of other available habitat, Penrhyn Estuary has become the only viable feeding and roosting habitat site for locally significant shorebirds on the northern side of Botany Bay. As part of the habitat enhancement for the Estuary, 2.4 ha of additional saltmarsh habitat will be created and planted with a mix of saltmarsh species.
The past month saw the planting of 124,896 saltmarsh plants within Penrhyn Estuary. Saltmarsh is an Endangered Ecological Community within NSW and is protected under the Threatened Species Conservation Act 1995. It is an important component within the estuary as it plays a key role in stabilising banks, filtering surface run off, reducing nutrients and provides a habitat for shorebirds and other fauna that use the estuary. The saltmarsh species mix that was planted in the Estuary will have greater diversity than the existing community and will comprise the species Sarcocorina quinqueflora, Sporobolus virginicus, Isolepis nodosa, Suaeda australis, Samolus repens, Juncus kraussii and, Triglochin striatium.
The plants have been propagated from seed or stem pieces collected from within Penrhyn Estuary and Botany Bay. Saltmarsh seed/stem piece collection was undertaken between March and May 2008 and January and May 2009 with the seeds / pieces being propagated in two nurseries in Sydney, Toolijooa in Dural and Australian ECOFLORA in Ebenezer.
In addition to the propagation of new plants, an area of 0.2 ha of saltmarsh was located on the edge of the dune, west of Floodvale Drain and was removed to create intertidal habitat. 0.1ha of Sarcocornia and Sporobolus from this area has been transplanted into a 0.4ha area in the upper reaches of Penrhyn Estuary, to prevent it being lost as part of the landform changes. The transplanted Sarcocornia and Sporobolus species have shown initial success with the Sarcocornia seeding and the Sporobolus showing new growth.
The remaining saltmarsh on the western and eastern side of Floodvale Drain is being maintained as part of Dragonfly Environmental’s bush regeneration activities within Penrhyn Estuary.
Prior to construction, Penrhyn Estuary was dominated by mangroves that colonised the shorebird habitat, out-competing the saltmarsh species. Penrhyn Estuary contained about 1.4ha of Saltmarsh comprising of the species Sporobolus quinqueflora, Suaeda australis, Isolepis nodosa, Juncus Kraussii and Juncus acutus.