Aquatic species and communities Wetlands

Several wetlands in the Sydney Basin bioregion (as defined for use in the Sydney Basin Bioregional Assessment) are regarded as being bioregionally significant. In the south of the bioregion, Swan Lake provides important breeding habitat for prawns and fish and is a key feeding and roosting area for waterfowl. Lake Conjola provides nesting habitat for a number of threatened shorebirds including the endangered little tern (Sterna albifrons) and hooded plover (Thinornis rubricollis) as well as the vulnerable pied oystercatcher (Haematopus longirostris). Both lakes also support significant areas of seagrass.

Narrabeen Lagoon and Deep Creek support the state-listed (TSC Act) threatened black bittern (Ixobrychus flavicollis), Australasian bittern (Botaurus poiciloptilus), osprey (Pandion haliaetus) and glossy black cockatoo (Calyptorhynchus lathami). The Australian bittern is also a nationally listed (EPBC Act) threatened species. Brundee Swamp also provides habitat for the Australasian bittern.

Bakers Lagoon, near Richmond, supports a range of important species listed under the TSC Act including the vulnerable freckled duck, Australasian bittern, black-tailed godwit (Limosa limosa), black bittern and the endangered black-necked stork (Ephippiorhynchus asiaticus). The black-tailed godwit is also listed as a threatened migratory species under the EPBC Act.

The Sydney Basin bioregion is densely populated and disturbances and threats to the wetlands are many and varied. They include impacts from urban, agricultural and industrial development such as decreased water quality resulting from runoff from urban areas, industrial areas, agricultural lands and rubbish tips, as well as stormwater and wet weather overflows. Potential spills from shipping and industries can also pose a serious risk to wetland health. Other threats include feral animals and exotic weeds, changed fire regimes, sedimentation, salinity, weir construction and mining development. Groundwater-dependent ecosystems

Within the Sydney Basin bioregion, flora and fauna species and communities are dependent on sources of water in addition to rainfall to survive. These sources might include surface water from streams and wetlands or groundwater either directly from subsurface aquifers, river baseflow or through springs. Such species and communities are referred to as groundwater-dependent ecosystems (Figure 49). Richardson et al. (2011) define groundwater-dependent ecosystems as ‘natural ecosystems that require access to groundwater to meet all or some of their water requirements on a permanent or intermittent basis so as to maintain their communities of plants and animals, ecosystem processes and ecosystem services’. The National Atlas of Groundwater Dependent Ecosystems (Bureau of Meteorology, 2012) highlights 125 rivers, 75 wetlands, two springs, one lake and 310 vegetation communities as groundwater-dependent ecosystems in the Sydney Basin bioregion.

Within the groundwater dependent ecosystems (GDEs), upland swamps are of particular interest because of their high vulnerability to impacts from longwall mining (Krogh, 2012). Upland swamps have high plant species diversity (Keith and Myerscough, 1993) and have an important role in catchment hydrodynamics and the maintenance of potable water supplies (Krogh, 2007). Upland swamps in the Sydney Basin bioregion generally develop on gentle slopes, within or adjacent to low-order streams where stream-power is relatively low (Tomkins and Humphreys, 2006). The swamp substrate consists of coarse-grained, quartzose sand and peat, often bound at the surface by a peaty mat (Keith and Myerscough 1993; Tomkins and Humphreys, 2006). Any activity that results in conversion of perched watertable flows into subsurface flows (including damage to confining aquicludes, aquitards and peat substrates as a result of longwall mining) will significantly change the water balance of upland swamps and may pose an irreversible threat to the integrity of the swamp ecosystems (Benson and Baird, 2012). Upland swamps in the Sydney Basin bioregion are listed in the EPBC Act as two threatened ecological communities (TEC).

The ‘Temperate Highland Peat Swamps on Sandstone’ TEC incorporates the ‘Montane Peatlands and Swamps of the New England Tableland, NSW North Coast, Sydney Basin, South East Corner, South Eastern Highlands and Australian Alps bioregions’, the ‘Newnes Plateau Shrub Swamp in the Sydney Basin Bioregion’, and the ‘Blue Mountains Swamps in the Sydney Basin Bioregion’ ecological communities (Table 22). Of the 3000 ha of this TEC, approximately 1300 ha are reserved in the Blue Mountains National Park, with the rest in a mix of freehold, state forests, and crown land (TSSC, 2005). Nationally threatened plant species and animal species known to inhabit this TEC include the Blue Mountains Water Skink (Eulamprus leuraensis), Giant Burrowing Frog (Heleioporus australiacus), Wingecarribee Leek Orchid (Prasophyllum uroglossum), and Wingecarribee Gentian (Gentiana wingecarribiensis). The swamps of this ecological community occur across a range of locations in the landscape, from ‘hanging swamps’ to depressions in the landscape, or along watercourses. Hanging swamps occur on sloping rock and/or cliff faces, and are particularly vulnerable to changes in water regime because they rely predominantly on groundwater discharge to sustain them. The discharging groundwater is most likely derived from perched watertables that develop over impervious geological layers. Water supply to hanging swamps is particularly vulnerable to fracturing caused by subsidence, which can reduce their water holding capacity or modify the groundwater flow paths that naturally replenish them. Hanging swamps have been identified in the Blue Mountains, on the Newnes Plateau and in the Bargo and Cataract gorges on the Woronora Plateau (Commonwealth of Australia, 2014). Blue Mountains and Newnes Plateau hanging swamps contain open heath vegetation communities that are dominated by shrubs or sedges (Commonwealth of Australia, 2014). Two threatened vegetation species, Epacris hamiltonii (endangered under the TSC Act and the EPBC Act) and Pherosphaera fitzgeraldii, are reported to depend on continual seepage from hanging swamps (Blue Mountains City Council, 2009). Hanging swamps provide unique habitat for the giant dragonfly (Petalura gigantea) and the red-crowned toadlet (Pseudophyrne australis), in addition to the giant burrowing frog and Blue Mountains Water Skink.

The ‘Coastal Upland Swamps in the Sydney Basin Bioregion’ TEC is listed under the same name on the New South Wales list of endangered ecological communities (Table 22). The community occurs primarily on poorly permeable sandstone plateaux in the low relief headwater valleys of streams and on sandstone benches with abundant seepage moisture, mainly at elevations of 200 to 450 mASL (Keith and Myerscough, 1993). In the south of the bioregion it primarily occurs on the Woronora Plateau, and in the north of the bioregion, it is mainly on the Somersby-Hornsby plateaux. Vegetation types include open graminoid heath, sedgeland and tall scrub (TSSC, 2014). Coastal Upland Swamp in the Sydney Basin bioregion provides habitat to a wide variety of birds, mammals, amphibians, reptiles and invertebrate species. Threatened species that have been recorded in the community include prickly bush-pea (Pultenaea aristata), giant burrowing frog, red-crowned toadlet, Rosenberg's goanna (Varanus rosenbergi), the green and golden bell frog (Litoria aurea), the eastern ground parrot (Pezoporus wallicus wallicus) and the giant dragonfly (NSW Environment and Heritage, 2012).

Figure 49

Figure 49 Surface and subsurface groundwater-dependent ecosystems within the Sydney Basin bioregion

As identified in The National Atlas of Groundwater Dependent Ecosystems (Bureau of Meteorology, 2013)

Data: Bioregional Assessment Programme (Dataset 2) Freshwater species

Three endangered, or critically endangered, freshwater species are listed under NSW’s Fisheries Management Act 1994. The Macquarie perch (Macquaria australasica) is present in both lake and river habitats in the Hawkesbury-Nepean region. The purple spotted gudgeon (Mogurnda adspersa) is a benthic species found in slow moving streams or billabongs and it is thought to be present in the Tweed, Richmond and Brunswick River catchments. The Fitzroy Falls spiny crayfish is restricted to a few locations along the Wildes Meadow Creek in the NSW Southern Highlands. It prefers flowing water and is threatened by reservoir construction and predation by the introduced yabbie (Cherax destructor).

Last updated:
21 January 2019
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