Towards a System of Ecologically Representative Marine Protected
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Table of Contents Table of Figures ____________________________________________________________ 2 8 Ecological Attributes of Each Area Recommended for the Representative System ___ 3 8.1 Nuyts Archipelago, St Francis Isles & Coastal Embayments (Murat Bioregion) _____________3 8.2 Baird Bay to Cape Bauer (including nearshore islands) (Murat / Eyre Bioregions Boundary)_34 8.3 Venus Bay and Surrounds (Eyre Bioregion)__________________________________________47 8.4 Investigator Group of Islands (Eyre Bioregion) _______________________________________58 8.5 Thorny Passage (Eyre Bioregion)___________________________________________________70 8.6 Sir Joseph Banks Group & Dangerous Reef (including Tumby Bay) (Eyre Bioregion)_______81 8.7 Neptune Islands Group (Eyre Bioregion) ____________________________________________98 8.8 Gambier Islands Group (Eyre Bioregion)___________________________________________105 8.9 Franklin Harbour and surrounding waters (Spencer Gulf / North Spencer Gulf Bioregions Boundary) ___________________________________________________________________________112 8.10 Upper Spencer Gulf (North Spencer Gulf Bioregion) _________________________________121 8.11 South-Eastern Spencer Gulf (Spencer Gulf Bioregion) ________________________________148 8.12 Western Investigator Strait (between the “Toe” of Yorke Peninsula and Northern Kangaroo Island) (Eyre/Gulf St Vincent Bioregions Boundary) ________________________________________167 8.13 North-Western, Western and South-Western Kangaroo Island (Eyre Bioregion) __________183 8.14 Southern Eyre (Eyre Bioregion)___________________________________________________195 8.15 The “Heel” of Yorke Peninsula (Gulf St Vincent Bioregion) ___________________________217 8.16 Upper Gulf St Vincent (Gulf St Vincent Bioregion)___________________________________230 8.17 Southern Fleurieu / North-East Kangaroo Island / Backstairs Passage / Encounter Bay / Upper Coorong (Gulf St Vincent Bioregion) _____________________________________________________252 8.18 Upper South-East (Coorong / Otway Bioregions Boundary) ___________________________300 8.19 Lower South-East (Otway Bioregion) ______________________________________________318 1 An Ecologically Representative System of Marine Protected Areas in S.A. Technical Report 2004 Table of Figures FIGURE 3: NUYTS ARCHIPELAGO, ST FRANCIS ISLES & COASTAL EMBAYMENTS 3 FIGURE 4: BAIRD BAY TO CAPE BAUER (INCLUDING NEARSHORE ISLANDS) 34 FIGURE 5: VENUS BAY AND SURROUNDS 47 FIGURE 6: INVESTIGATOR GROUP OF ISLANDS 58 FIGURE 7: THORNY PASSAGE 70 FIGURE 8: SIR JOSEPH BANKS GROUP & DANGEROUS REEF 81 FIGURE 9: NEPTUNE ISLANDS GROUP 99 FIGURE 10: GAMBIER ISLANDS GROUP 105 FIGURE 11: FRANKLIN HARBOUR AND SURROUNDING WATERS 112 FIGURE 12: UPPER SPENCER GULF 121 FIGURE 13: SOUTH-EASTERN SPENCER GULF 148 FIGURE 14: WESTERN INVESTIGATOR STRAIT 167 FIGURE 15: NORTH-WESTERN, WESTERN AND SOUTH-WESTERN KANGAROO ISLAND183 FIGURE 16: SOUTHERN EYRE 195 FIGURE 17: THE “HEEL” OF YORKE PENINSULA 217 FIGURE 18: UPPER GULF ST VINCENT 230 FIGURE 19: SOUTHERN FLEURIEU / NORTH-EAST KI / BACKSTAIRS PASSAGE / ENCOUNTER BAY / UPPER COORONG 252 FIGURE 20: UPPER SOUTH EAST 300 FIGURE 21: LOWER SOUTH EAST 318 2 An Ecologically Representative System of Marine Protected Areas in S.A. Technical Report 2004 8 Ecological Attributes of Each Area Recommended for the Representative System 8.1 Nuyts Archipelago, St Francis Isles & Coastal Embayments (Murat Bioregion) Figure 3 shows the location of this area. Figure 3: Nuyts Archipelago, St Francis Isles & Coastal Embayments 3 An Ecologically Representative System of Marine Protected Areas in S.A. Technical Report 2004 1. Biogeographic Tourville Bay / Davenport Creek Significance Mangroves at the Tourville Bay / Davenport Creek area are reported to be the largest stand on Eyre Peninsula, and represent the westernmost extent of mangroves in South Australia, and the largest stand of mangroves between Spencer Gulf in South Australia and Exmouth Gulf in Western Australia. Mangroves at Davenport Creek grow on a sandier substrate than is usual for mangroves in South Australia (Morelli and de Jong, 1995; Edyvane, 1995c; Ashman, 1996b; South Australian Coast and Marine Atlas, 2001). Tourville Bay The bay is one of only three estuarine areas in South Australia to be rated as near pristine by participants at a national workshop for the National Land and Water Resources Audit, in 1999. Tourville Bay is therefore listed in the Australian Estuaries database under the category of near pristine (see GeoScience Australia, 2001). Previously Tourville Bay was listed in a national inventory of Australian estuaries (Bucher and Saenger, 1989) as one of the three South Australian estuaries of outstanding conservation significance, due to its undeveloped nature and relatively pristine catchment area. Streaky Bay, Smoky Bay and smaller bays in the region Collectively form the largest area of seagrass on the West Coast of S.A. Seagrass is estimated to cover a total area of approximately 86,160 ha in Streaky and Smoky Bay. Seagrasses of the Far West Coast represent approximately 15% of the total area of seagrasses recorded in South Australia (Edyvane, 1999b). Eastern Great Australian Bight Subject to seasonal warm water masses (see Rochford, 1986 and Herzfeld, 1996,1997), which may influence the “Indo-Pacific” element in the invertebrate fauna (e.g. various species of hydroid, sea cucumber and basket star) (Maxwell and Cresswell, 1981, cited by Edyvane and Baker, 1999b); part of the fish fauna (species of Western and other warmer region affinity – see section below on Taxonomic Diversity); the abundance and diversity of some marine macroalgae (e.g. species of Sargassum); and the seasonal presence of migratory species, such as turtles (Edyvane and Baker, 1999b). 2. Major Physical Major physical influences include variable wave and swell climate (see Hames Sharley Influences, and Australia, 1989; Shepherd and Womersley, 1976; Edyvane and Baker, 1999b; Relative GeoScience Australia, 2001; Shepherd and Brook, 2003), ranging from: Productivity Level strong south-westerly swell (e.g. St Francis Isles and some of the exposed Far West Coast headlands) and large waves (from strong south-easterly winds) on the exposed outer island areas (e.g. West Island, Hart Island); moderately wave-exposed headlands (e.g. Point Peter, Point James); less exposed waters in the more protected lee of the Nuyts Archipelago inner islands, and broad bays of the Far West Coast; and low wave energy, low swell conditions of the inner bays (Smoky, Tourville, Murat, and others), which are protected by islands and sand spits. Wave exposure is low in the bay areas. For example, mean wave height is around 0.8m in the Blanche Port area, and 0.3m in Smoky Bay. The seasonal warmer water currents, which characterise the Great Australian Bight area, also extend to the islands and bays of the Murat Bioregion (see bioregion description below). Warm water masses in the region are likely to influence the type of macroflora, sessile invertebrates, fish species and migratory taxa (such as marine turtles), that occur in the region (Maxwell and Cresswell, 1981; Edyvane and Baker, 1999b). Warm waters in the eastern Great Australian Bight were previously considered to be due solely to the influence of the Leeuwin current from W.A. (Rochford, 1986). However, more recent oceanographic work (e.g. Herzfeld, 1996,1997; Herzfeld and Tomczak, 1997) has indicated that some of the warm water masses that influence the eastern 4 An Ecologically Representative System of Marine Protected Areas in S.A. Technical Report 2004 GAB region, may form locally, at the Head of the Bight, and travel eastwards towards Eyre Peninsula. It is evident that the cooler water seasonal upwelling that characterises the lower Eyre Peninsula, is also periodically present along parts of the Far West Coast. For example, Ward et al. (2002, Figure 3) showed that sea surface temperatures are periodically lower in inshore waters of the Far West Coast (e.g. Streaky Bay region), compared with offshore waters. Cooler bottom waters occur during upwelling periods, for example at the St Francis Isles (Shepherd and Brook, 2003). The habitats and biota of the area are influenced by all a combination of the oceanographic features listed above. For example, the St Francis Isles lie in the path of several water masses. In winter, warm waters from the Leeuwin Current and warm Great Australian Bight plumes flow easterly, maintaining mild sea temperatures, whilst during summer to autumn, the same warm plumes, heated on the shallow shelf of the northern GAB, mingle with cooler upwelling water off eastern Eyre peninsula, 2-3oC lower than surface temperatures (Griffin et. al., 1997; Herzfeld, 1997; Herzfeld and Tomczak, 1997). The large, shallow bays, such as Murat, Denial, Smoky and Streaky have broad depth contours. For example, depths of 20 m or more do not occur until at least 20 km seaward of these bays. Most of the area in these large bays is less than 5m deep. The bays are less wind-exposed than other parts the West Coast that face into the Great Australian Bight, and are protected oceanographically from waves and swell, by islands of the Nuyts group, submerged reefs, sand barriers closer to shore (e.g. near Tourville Bay), and the shallow bay gradients. At St Peter Island, currents from the south-west of the island deposit eroded sands and other sediments on the north-eastern side, and new habitats are being created in this way. Due to variation in erosion