Biodiversity Strategy - Gosford City Council - NSW Government
Biodiversity Strategy - Gosford City Council - NSW Government Biodiversity Strategy - Gosford City Council - NSW Government
A - 6.0 AQUATIC BIODIVERSITY This section describes aquatic habitats in the Gosford Local Government Area. It collates information from a variety of documents and reports prepared to address coastal resource management, locally and regionally. It highlights important gaps in our knowledge of local aquatic biodiversity and processes that impact it. Key points • Estuarine ecosystems contain critical habitats that require greater conservation effort. • There is little information available about the marine environments. • The coastal lagoons are suffering from urban development, which needs to be addressed with a review of management practices. • The major tributary creeks of Brisbane Water are polluted. • Smaller creeks are choking up with weeds and sediments. A - 6.1 Introduction Within the Gosford City Council local government area there is an incredible diversity of aquatic habitats. The area includes freshwater and marine wetlands, rivers, creeks, estuaries, lagoons, beaches, coastal reefs and rock platforms (Figure 6.1). The majority of these habitats are in relatively good condition and support a healthy diversity of aquatic flora and fauna. Other habitats, such as urban streams and particularly the coastal lagoons, are under huge presure from development. The Gosford LGA is located within the Hawkesbury Shelf Marine Bioregion, which extends south from the Hunter River at Newcastle to Shellharbour. This bioregion is one of 65 marine bioregions that cover the Australian coast (Breen et al. 2005). Brisbane Water and the Hawkesbury River are of particular importance because of their extensive stands of mangroves and saltmarsh, which are the second largest, within this bioregion, after Port Stephens. Brisbane Water is the major feature of the area with Gosford situated on the northern shore. This waterway includes many bays, islands and the large Kincumber Broadwater to the east. It has a fairly narrow and restricted channel to Broken Bay which provides limited tidal flushing. The Hawkesbury River meets Broken Bay near Lion Island and Mangrove, Popran, Mooney Mooney, Mullet and Patonga Creeks all flow into it. Coastal estuaries (or intermittently closed and open lakes and lagoons (ICOLLS)) are found at Wamberal, Terrigal, Bulbararing Lagoon and Avoca Lake and Cockrone Lagoon. These have restricted sea connection and would naturally, over considerable time, close completely. Major coastal creeks are Narara, Erina, Nunns, Egan, Kincumber, Saltwater, Cockrone and Kahibah Creeks. There are also some freshwater lagoons remaining, most notably the Lisarow Wetlands, Everglades Wetland and Illuka Lagoons on the Umina Sandplain. All have been modified and impacted by surrounding developments that has altered their natural hydrological regimes. More extensive freshwater wetlands would once have existed on much of the low lying areas of the eastern parts of the LGA. Rocky reefs and rock platforms occur along the coast and beaches stretch from Patonga, along the edges of Broken Bay to Forrester's Beach in the north. Biodiversity - Technical Report Page 129
A - 6.2 Aquatic Habitats A - 6.2.1 Estuaries An estuary is a semi-enclosed coastal water body within which seawater is measurably diluted with fresh water derived from land drainage. Estuaries are dynamic ecosystems, effectively open at either end and under the influence of a complexity of physical, chemical and biological processes. They are influenced by freshwater input from rivers, creeks, groundwater and stormwater runoff. These inflows vary in volume, rates of flow and chemical and biological content depending upon climate, geology, geography and land use within the drainage catchment. Marine processes, such as tidal and oceanic currents, as well as their associated chemical and biological content, also influence estuarine ecosystems. Estuarine processes are characterised by the diametrically opposed processes of stratification and mixing of freshwater and seawater. These processes in turn define the habitats and control recruitment and settlement through processes such as larval transport, salination, flocculation and sedimentation, eutrophication, deposition and scouring, pollutant accumulation and flushing, and bio-chemical processes such as de-oxygenation and reduction (Freewater, 2004). Estuaries support a variety of habitats and a brief description of these habitats and their importance to estuarine ecological integrity is provided below. Unvegetated soft sediments These habitats, which include shallow mud flats, sand flats and deeper soft substrate areas, are an important component of Gosford's estuaries, because they support a diversity of benthic (bottomdwelling) invertebrates. The most common are crustaceans (such as crabs and prawns), polychaetes (worms, generally hidden in the sediment) and molluscs (snails and shellfish). Invertebrates are an important prey item for many fish species of commercial and recreational fishing value. They are also important prey items for many birds. Marine invertebrates, like their terrestrial cousins, are the most abundant and diverse group of animals found in any habitat. They are also the most important group from an ecological perspective because of their importance as a food source for nearly all higher level predators. Yet, they are the least understood and many invertebrate species found in Gosford are still undescribed. Council is currently surveying the benthic invertebrates of Brisbane Water to partially address this data gap. Biodiversity - Technical Report Page 130
- Page 81 and 82: A - 3.4 References Australian Museu
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- Page 87 and 88: Mooney Mooney and Mangrove Creeks.
- Page 89 and 90: Aeolian Landscapes Beach Landscapes
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- Page 95 and 96: A - 4.9 Current Landuse Since the 1
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- Page 111 and 112: Figure 5.5 Endangered ecological co
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- Page 115 and 116: Figures 5.5 - 5.7 Waratah (Telopea
- Page 117 and 118: A - 5.4 A - 5.4.1 Terrestrial Fauna
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- Page 135 and 136: considered. This is true for all ri
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- Page 139 and 140: The Hawkesbury River The Hawkesbury
- Page 141 and 142: Gulls (Larus novaehollandiae); Pied
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- Page 149 and 150: Figure 6.11 Weedy Seadragon (Phyllo
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- Page 171 and 172: A - 7.14 References Anderson, C (20
A - 6.2<br />
Aquatic Habitats<br />
A - 6.2.1<br />
Estuaries<br />
An estuary is a semi-enclosed coastal water body within which seawater is measurably diluted<br />
with fresh water derived from land drainage.<br />
Estuaries are dynamic ecosystems, effectively open at either end and under the influence of a<br />
complexity of physical, chemical and biological processes. They are influenced by freshwater<br />
input from rivers, creeks, groundwater and stormwater runoff. These inflows vary in volume,<br />
rates of flow and chemical and biological content depending upon climate, geology, geography<br />
and land use within the drainage catchment. Marine processes, such as tidal and oceanic<br />
currents, as well as their associated chemical and biological content, also influence estuarine<br />
ecosystems. Estuarine processes are characterised by the diametrically opposed processes of<br />
stratification and mixing of freshwater and seawater. These processes in turn define the habitats<br />
and control recruitment and settlement through processes such as larval transport, salination,<br />
flocculation and sedimentation, eutrophication, deposition and scouring, pollutant accumulation<br />
and flushing, and bio-chemical processes such as de-oxygenation and reduction (Freewater,<br />
2004). Estuaries support a variety of habitats and a brief description of these habitats and their<br />
importance to estuarine ecological integrity is provided below.<br />
Unvegetated soft sediments<br />
These habitats, which include shallow mud flats, sand flats and deeper soft substrate areas, are<br />
an important component of <strong>Gosford</strong>'s estuaries, because they support a diversity of benthic<br />
(bottomdwelling) invertebrates. The most common are crustaceans (such as crabs and prawns),<br />
polychaetes (worms, generally hidden in the sediment) and molluscs (snails and shellfish).<br />
Invertebrates are an important prey item for many fish species of commercial and recreational<br />
fishing value. They are also important prey items for many birds.<br />
Marine invertebrates, like their terrestrial cousins, are the most abundant and diverse group of<br />
animals found in any habitat. They are also the most important group from an ecological<br />
perspective because of their importance as a food source for nearly all higher level predators.<br />
Yet, they are the least understood and many invertebrate species found in <strong>Gosford</strong> are still<br />
undescribed. <strong>Council</strong> is currently surveying the benthic invertebrates of Brisbane Water to<br />
partially address this data gap.<br />
<strong>Biodiversity</strong> - Technical Report Page 130