A jewel on the edge of the Royal National Park – the marine habitats of Port Hacking
Creese, R., Glasby, T., Williams, R. and West, R., 2011. A jewel on the edge of the Royal National Park – the marine habitats of Port Hacking. Presentation given at the Linnean Society of NSW and National Parks & Wildlife Service symposium on 'Natural History of the First National Park', 29 September – 1 October 2011, Botany Bay National Park, Sydney, Australia.
Port Hacking is an extensive estuary that interdigitates with Royal National Park on its northern edge. A small part of the estuary is a Marine Protected Area because the National Park Boundary includes a section of one of its southern arms. It has many unique features, and is often considered the most pristine estuary in the Sydney region. Never-the-less, it has been subject to numerous pressures since European settlement, although commercial fishing has been banned for many years. In particular, land clearing in parts of the catchment and extensive urbanisation along much of its shoreline has resulted in changes to its sedimentary regime, water flow and habitat features. Aerial photographs have been used to document the extent of the key biotic habitats – mangroves, saltmarsh and seagrass at several intervals from the 1940s to the present time. These analyses show that seagrass suffered greatly during the 1960s and 1970s, but that the extent of seagrass beds has recovered slowly since then, although periodic dredging of the main channels continues to pose a threat. A more recent threat to these seagrass beds has been the establishment of an introduced green seaweed, Caulerpa taxifolia, which was first recorded in Port Hacking in 2000. This seaweed has the potential to overgrow and replace seagrass, change the composition of the associated fauna and alter the sediment chemistry in the area. Regular monitoring of Caulerpa taxifolia over the past decade has shown that, while it has spread to several parts of the estuary, it has not had a major impact on the seagrass. Ongoing monitoring of the marine habitats in Port Hacking and efforts to enhance the health of the estuarine environment will continue to complement terrestrial conservation efforts in the Royal National Park itself.