Shark Bay Australia
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SHARK BAY AUSTRALIA On the Indian Ocean coast at the westernmost point of Australia, Shark Bay’s waters, islands and peninsulas have three exceptional natural features: the largest, most diverse sea-grass beds in the world; a large population of dugongs; and the stromatolites of Hamelin Pool: colonies of algae in hard, dome-shaped deposits which are among the oldest life forms on earth. The Bay is also home to nine species of endangered mammals. COUNTRY Australia NAME Shark Bay NATURAL WORLD HERITAGE SERIAL SITE 1991: Inscribed on the World Heritage List under Natural Criteria vii, viii, ix and x. STATEMENT OF OUTSTANDING UNIVERSAL VALUE [pending] IUCN MANAGEMENT CATEGORY Shark Bay Marine Park: Ia Strict Nature Reserve Zuytdorp Nature Reserve: Ia Strict Nature Reserve Freycinet-Double Islands Nature Res: Ia Strict Nature Reserve Zuytdorp Historic Shipwreck: Ia Strict Nature Reserve Koks Island: Ia Strict Nature Reserve Charlie Island: Ia Strict Nature Reserve Friday Island: Ia Strict Nature Reserve Francois Peron National Park: II National Park Monkey Mia Conservation Reserve: II National Park Shell Beach Conservation Park: III Natural Monument Bernier & Dorre Is. Nature Reserve: IV Habitat/Species Management Area Hamelin Pool Marine Nature Reserve: VI Managed Resource Protected Area BIOGEOGRAPHICAL PROVINCE Western Sclerophyll / Western Mulga (6.04.06 / 6.08.08) GEOGRAPHICAL LOCATION Shark Bay is situated over 800 km north of Perth on the westernmost point of Australia. The western boundary of the World Heritage site extends three nautical miles (5.56 km) offshore for almost 300 km from the tip of Bernier Island to Zuytdorp cliffs in the south. The eastern boundary follows the mainland coast to the end of Hamlin Pool then drops south about 80 km to the end of Zuytdorp Nature Reserve, between 30 and 70 km inland. The town of Denham and the saltmines of Useless Loop and Useless Inlet, are within but excluded from the World Heritage property which lies between 24°44'S to 27°16'S by 112°49'E to 114°17'E. DATES AND HISTORY OF ESTABLISHMENT The component protected areas of the World Heritage site were established on the following dates: 1 1957: Bernier and Dorre Islands Nature Reserve; 1961: Freycinet-Double Islands Nature Reserve; 1976: Koks I.,Charlie I.,Friday I.; 1978: Zuytdorp Historic Shipwreck; 1988: Monkey Mia Conservation Reserve; 1990: Shark Bay Marine Park, Hamelin Pool Marine Nature Reserve; 1991: Zuytdorp Nature Reserve 1993: Francois Peron National Park; Shell Beach Conservation Park. LAND TENURE The state of Western Australia, the Federal Government and private ownership. Managed primarily by the Western Australian Department of Conservation and Land Management (CALM). AREA 2,197,300 ha. Protected areas - marine parks, marine nature reserves, terrestrial nature reserves and national park - cover 1,004,000 ha. Public land - marine areas 687,747 ha, vacant Crown Land 55,000 ha, pastoral land 450,000 ha, other reserves 2,500 ha plus private land 750 ha - covers 1,195.997 ha. Shark Bay Marine Park: 748,725ha Shell Beach Conservation Park: 518.00 ha Monkey Mia Conservation Reserve: 477.00 ha Freycinet-Double Islands Nature Reserve: 205.60 ha Hamelin Pool Marine Nature Reserve: 132,00 ha Zuytdorp Historic Shipwreck: 79.00 ha Zuytdorp Nature Reserve: 58,85 ha Francois Peron National Park: 52,529ha Bernier & Dorre Is. Nature Reserve: 9,72 ha Koks Island: 3.00 ha Charlie Island: 0.80 ha Friday Island: 0.80 ha ALTITUDE Sea-level to 20m. PHYSICAL FEATURES Shark Bay is a large divided semi-enclosed bay on the low-lying coast of the Indian Ocean lying behind a chain of barrier islands. It averages 100km wide from the mainland, is some 200km long from north to south, approximately 13,000 sq.km in area, and has an average depth of 9m with a maximum depth of 29m. The barrier is formed of the narrow Bernier, Dorre and Dirk Hartog islands, continued south in the equally narrow Edel peninsula. The Bay is split from the south by the 110km-long Peron-Nanga peninsula, dividing it into two very wide embayments - Denham Sound-Freycinet Harbour on the west, and L’haridon Bight and Hamelin Pool in the east. The Edel peninsula on the bayward side is fretted by four narrow inlets between four narrow north-south lesser peninsulas, one of which, Useless Inlet is given over to salt mining. The coastline of the property is 1,500km long, including the 200m high Zuytdorp cliffs well to the south, which are among the highest of the Australian coastline. The area has three distinct landscape types: the Gascoyne-Wooramel province along the eastern coast of the bay which is a low-lying plain with extensive supratidal flats, backed by a limestone escarpment; the Peron province, comprising the Peron-Nanga peninsula and Fauré Island, of low rolling sandy plains with salt and gypsum pans and ancient interdune gypsum-filled depressions (birridas), the seaward margin of which is a 3-30m-high scarp with narrow sand beaches; and the Edel province comprising Edel peninsula and the three barrier islands, a landscape of elongated north-trending dunes cemented to loose limestone which ends on the ocean in a series of spectacular cliffs (DASETT, 1990). The area basement rock is Late Cretaceous Toolonga limestone and chalk. The most extensive younger rocks are Peron sandstones and Tamala limestones which form the offshore islands. These are often overlaid by a series of longitudinal fossil dunes accumulated during the Middle to Late Pleistocene (described in DASETT, 1990). Gypsum has formed from the evaporation of saline 2 groundwater in ponds and broad tidal flats such as those bordering Hamelin Pool. Shell beaches at the southern end of L’haridon Bight form a rare 6 km long scientifically important deposit of organic shells Fragum erugatum, coquina limestone, ooid shoals and lithified sediments 8-9m deep. In Wooramel Bank the water currents and the build-up of sand banks and sills by seagrass beds, have created a vast mat of carbonate deposits and sediments. The outstanding marine feature of the Bay is the steep salinity gradient. Water exchange with the ocean is restricted but oceanic water from the south-flowing Leeuwin current flows through the wide northern Naturaliste Channel between Dorre and Dirk Hartog islands and the South Passage between Dirk Hartog Island and Steep Point, intruding warm low-salinity tropical water. The interaction of wind drift and tidal currents produces an anticlockwise circulation within the Bay, west to south-east, then east and finally north-west. Strong southerly summer winds push about 1-1.5m of water out of the Bay, exposing sandflats up to 2m wide. Tides vary between a spring range of 1.7m and a neap range of 0.6m. The salinity ranges from oceanic (35-40 ppt) in the northern and western parts of the Bay through metahaline (40-56 ppt) to hypersaline in Hamelin Pool and L’haridon Bight (56-70 ppt) which are partly blocked by sills each side of Fauré Island originating in the dense seagrass beds which have, with the low rainfall, high evaporation and low tidal flushing, produced the hypersaline conditions in which subsurface evaporite deposits, lithification and the formation of the ‘living fossil’ stromatolites occur. The three biotic zones resulting from the gradient have a marked influence on the distribution of marine organisms within the Bay (CALM,n.d.; DASETT,1990). Two intermittent rivers drain into the Bay from the east: the Gascoyne and Wooramel Rivers. There is very little surface run-off because of the low rainfall, high evaporation and permeable soils. There is active regional saline groundwater flow however, and some freshwater springs, as in the intertidal zone north of Monkey Mia (DASETT, 1990). There is a large quantity of artesian water approximately 300m below the ground surface, some of it hot. CLIMATE Shark Bay is at the meeting point of three major climatic regions but its climate is semi-arid to arid, characterised by hot dry summers and mild winters. Summer temperatures range between 20°C and 35°C; winter temperatures between 10°C and 20°C. Average annual precipitation is low, ranging from 200mm in the east to 400mm in the far southwest. Annual evaporation is high, between 2,000mm in the west to 3,000mm in the east. The Leeuwin Current greatly influences the temperature of the sea surface water in the bay. Seawater temperatures outside the bay vary from 20.9°C in August to 26°C in February. Within the bay water they vary: in the inner bay temperatures drop to 17°C in August but in February a maximum of 27°C has been recorded in Hamelin Pool, 26°C in Freycinet Harbour and 24°C in the oceanic salinity zone. VEGETATION The area is semi-desert where the flora is transitional between the South-west botanical province and the arid Eremaean botanical province found over much of central Australia. More than 620 species are recorded for the region, at least 51 being endemic. 283 species are at the limits of their range in Shark Bay about 80% at the northern limit of their range, and 20% at their southern limit. Many vegetation formations and species are found only in the interzone area. 25 species are considered nationally rare or threatened (DASETT, 1990). The South-west botanical province consists of vegetation rich in Eucalyptus species, forming woodland with diverse shrubby understories and heathlands poor in grasses. The Eremaean province is correspondingly rich in wattle Acacia species but has large areas dominated by grasses, especially spinifex and prickly hummock grasses of the genera Triodia and Plectrachne. The Province includes shrublands of Acacia ligulata, Pimelea microcephala and Stylobasium spathulatum.