The Great Australian Bight is a large
ocean
The ocean is the body of salt water that covers approximately 70.8% of Earth. The ocean is conventionally divided into large bodies of water, which are also referred to as ''oceans'' (the Pacific, Atlantic, Indian Ocean, Indian, Southern Ocean ...
ic
bight, or open bay, off the central and western portions of the southern
coastline
A coast (coastline, shoreline, seashore) is the land next to the sea or the line that forms the boundary between the land and the ocean or a lake. Coasts are influenced by the topography of the surrounding landscape and by aquatic erosion, su ...
of
mainland Australia
Mainland Australia is the main landmass of the Australia (continent), Australian continent, excluding the Aru Islands Regency, Aru Islands, New Guinea, Tasmania, and other list of islands of Australia, Australian offshore islands. The landmass ...
.
There are two definitions for its extent—one by the
International Hydrographic Organization
The International Hydrographic Organization (IHO) (French: ''Organisation Hydrographique Internationale'') is an intergovernmental organization representing hydrography. the IHO comprised 102 member states.
A principal aim of the IHO is to ...
(IHO) and another by the
Australian Hydrographic Service (AHS). The bight is generally considered part of the
Indian Ocean
The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or approximately 20% of the water area of Earth#Surface, Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia (continent), ...
, although the AHS classifies it as part of the
Southern Ocean
The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the world ocean, generally taken to be south of 60th parallel south, 60° S latitude and encircling Antarctica. With a size of , it is the seco ...
. Its coastline is characterized by cliff faces and rocky capes, making it an ideal location for whale-watching.
This oceanic feature was first encountered by European explorers in 1627, and was accurately charted by English navigator
Matthew Flinders
Captain (Royal Navy), Captain Matthew Flinders (16 March 1774 – 19 July 1814) was a British Royal Navy officer, navigator and cartographer who led the first littoral zone, inshore circumnavigate, circumnavigation of mainland Australia, then ...
in 1802. The Great Australian Bight came into existence about 50 million years ago when the
supercontinent
In geology, a supercontinent is the assembly of most or all of Earth's continent, continental blocks or cratons to form a single large landmass. However, some geologists use a different definition, "a grouping of formerly dispersed continents", ...
Gondwana
Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...
broke apart, separating
Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...
from
Australia
Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
.
The Bight's waters are highly
biodiverse
Biodiversity is the variability of life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and phylogenetic diversity. Diversity is not distributed evenly on Earth ...
, especially in
zooplankton
Zooplankton are the heterotrophic component of the planktonic community (the " zoo-" prefix comes from ), having to consume other organisms to thrive. Plankton are aquatic organisms that are unable to swim effectively against currents. Consequent ...
, due to specific ocean currents. However, more research is needed to fully understand the region's complex ecosystems and the potential impacts of human activities, such as resource extraction.
Southern bluefin tuna are a popular fishing target in the Bight, and there have been attempts to explore the area for oil and gas since the 1960s. However, these proposals have faced significant opposition due to the potential environmental impacts.
Extent
Two definitions of the extent are in use – one used by the
International Hydrographic Organization
The International Hydrographic Organization (IHO) (French: ''Organisation Hydrographique Internationale'') is an intergovernmental organization representing hydrography. the IHO comprised 102 member states.
A principal aim of the IHO is to ...
(IHO) and the other used by the
Australian Hydrographic Service (AHS).
The IHO defines the Great Australian Bight as having the following limits:
''On the North.'' The south coast of the Australian mainland.
''On the South.'' A line joining West Cape Howe () Australia to South West Cape, Tasmania
Tasmania (; palawa kani: ''Lutruwita'') is an island States and territories of Australia, state of Australia. It is located to the south of the Mainland Australia, Australian mainland, and is separated from it by the Bass Strait. The sta ...
.
''On the East.'' A line from Cape Otway, Victoria to King Island and thence to Cape Grim, the northwest extreme of Tasmania.
The AHS defines the bight with a smaller area, from
Cape Pasley,
Western Australia
Western Australia (WA) is the westernmost state of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. Western Aust ...
, to
Cape Carnot,
South Australia
South Australia (commonly abbreviated as SA) is a States and territories of Australia, state in the southern central part of Australia. With a total land area of , it is the fourth-largest of Australia's states and territories by area, which in ...
- a distance of .
Much of the bight lies due south of the expansive
Nullarbor Plain
The Nullarbor Plain ( ; Latin: feminine of 'no' and 'tree') is part of the area of flat, almost treeless, arid or semi-arid country of southern Australia, located on the Great Australian Bight coast with the Great Victoria Desert to its no ...
, which straddles South Australia and Western Australia. The
Eyre Highway
Eyre Highway is a highway linking Western Australia and South Australia via the Nullarbor Plain. Signed as National Highways 1 and A1, it forms part of Highway 1 (Australia), Highway 1 and the National Highway (Australia), Australian Nat ...
passes close to the cliffs of the bight between the
Head of the Bight and
Eucla.
Outside of Australia, the Great Australian Bight is generally considered part of the
Indian Ocean
The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or approximately 20% of the water area of Earth#Surface, Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia (continent), ...
. The AHS considers it to be part of the
Southern Ocean
The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the world ocean, generally taken to be south of 60th parallel south, 60° S latitude and encircling Antarctica. With a size of , it is the seco ...
, using the expanded Australian definition used for this ocean.
[ The IHO in its Limits of Oceans and Seas (both the currently in-force 1953 edition][ and the 2002 never-approved draft) includes the bight with the Indian Ocean, while ]Bass Strait
Bass Strait () is a strait separating the island state of Tasmania from the Mainland Australia, Australian mainland (more specifically the coast of Victoria (Australia), Victoria, with the exception of the land border across Boundary Islet). The ...
and the Tasman Sea
The Tasman Sea is a marginal sea of the South Pacific Ocean, situated between Australia and New Zealand. It measures about across and about from north to south. The sea was named after the Dutch explorer Abel Janszoon Tasman, who in 1642 wa ...
are included by IHO with the South Pacific Ocean in the 2002 draft. In the 1953 edition, IHO includes Bass Strait as part of the Indian Ocean.
Coastline
The area around Cape Pasley is an eastern outcrop of the ancient crystalline rocks of the Yilgarn craton. From there the coast curves north-eastwards, with an escarpment parallel to the coast. The Israelite Plain lies between the escarpment, here called the Wylie Scarp, and the shore, with a chain of coastal lagoons behind coastal dunes. As the coast turns eastwards the escarpment meets the shore, creating the Baxter Cliffs which extend for . Near Cocklebiddy the escarpment curves inland again. Here the Roe Plains extends for about along the coast, reaching about inland at their widest point. There are extensive dunefields near the shore, some bare of vegetation, and others stabilized by coastal strand vegetation, shrubland, and mallee woodland. Near Eucla and the Western Australia–South Australia border the escarpment reaches the coast again, and the Bunda Cliffs or Nullarbor Cliffs extend for to Head of the Bight.[N. P. James, Y. Bone, R. M. Carter & C. V. Murray-Wallace (2006) Origin of the Late Neogene Roe Plains and their calcarenite veneer: implications for sedimentology and tectonics in the Great Australian Bight, Australian Journal of Earth Sciences, 53:3, 407–419, DOI: 10.1080/08120090500499289]
At Head of the Bight the escarpment turns inland to the northeast. The coastline of the western Eyre Peninsula
The Eyre Peninsula is a triangular peninsula in South Australia. It is bounded by the Spencer Gulf on the east, the Great Australian Bight on the west, and the Gawler Ranges to the north.
Earlier called Eyre's Peninsula, it was named after e ...
is characterised by rocky capes, bays, and islands, including Fowlers Bay, Smoky Bay, Streaky Bay, and the Nuyts Archipelago. The coastline is formed from aeolianite limestone. Waves and currents have formed beaches and dunes from eroded aeolianite sand. The southern Eyre peninsula is an outcrop of the granitic Gawler craton
The Gawler Craton covers approximately 440,000 square kilometres of central South Australia. Its Precambrian crystalline basement crustal block was cratonised ca. 1550–1450 Ma. Prior to 1550 Ma the craton comprised a number of active Protero ...
.[Bourman, Robert P., Colin V. Murray-Wallace, and Nick Harvey (2016). ''Coastal Landscapes of South Australia". University of Adelaide Press, 2016. DOI: http://dx.doi.org/10.20851/coast-sa]
History and exploration
The Great Australian Bight was first encountered by European explorers in 1627 when Dutch navigator François Thijssen sailed along its western margins. The coast was later first accurately charted by the English navigator Matthew Flinders
Captain (Royal Navy), Captain Matthew Flinders (16 March 1774 – 19 July 1814) was a British Royal Navy officer, navigator and cartographer who led the first littoral zone, inshore circumnavigate, circumnavigation of mainland Australia, then ...
in 1802, during his circumnavigation
Circumnavigation is the complete navigation around an entire island, continent, or astronomical object, astronomical body (e.g. a planet or natural satellite, moon). This article focuses on the circumnavigation of Earth.
The first circumnaviga ...
of the Australian continent. A later land-based survey was accomplished by the English explorer Edward John Eyre
Edward John Eyre (5 August 181530 November 1901) was an English land explorer of the Australian continent, colonial administrator, Lieutenant-Governor of New Zealand's New Munster province, and Governor of Jamaica.
Early life
Eyre was born in ...
.
Natural history
The bight came into existence when Gondwana
Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...
, along what is now Wilkes Land and Terre Adélie, broke apart and separated Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...
from Australia around 50 million years ago.
The coastline of the Great Australian Bight is characterised by cliff faces (up to high), surfing beaches and rock platforms, ideal for whale-watching. This is a popular activity during the southern hemisphere winter, when increasing numbers of southern right whale
The southern right whale (''Eubalaena australis'') is a baleen whale, one of three species classified as right whales belonging to the genus ''Eubalaena''. Southern right whales inhabit oceans south of the Equator, between the latitudes of 20� ...
s migrate to the region from their summer feeding grounds in the Antarctic. The whales come to the Bight region, especially to the Head of Bight, to calve and breed, and do not feed until they return to the Antarctic. Their numbers were severely depleted by whaling, particularly during the 19th century, but have since recovered to some extent.
The Nullarbor Plain
The Nullarbor Plain ( ; Latin: feminine of 'no' and 'tree') is part of the area of flat, almost treeless, arid or semi-arid country of southern Australia, located on the Great Australian Bight coast with the Great Victoria Desert to its no ...
, which borders much of the length of the Bight's coastline, is a former seabed, uplifted during the Miocene
The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
. Consisting of limestone, it is very flat, and has an arid or semi-arid climate with very little rainfall, and high summer temperatures and high evaporation rates. It has no surface drainage, but has a karst
Karst () is a topography formed from the dissolution of soluble carbonate rocks such as limestone and Dolomite (rock), dolomite. It is characterized by features like poljes above and drainage systems with sinkholes and caves underground. Ther ...
drainage system through cave formation in the underlying limestone. North of the Nullarbor lies the Great Victoria Desert
The Great Victoria Desert is a sparsely populated desert ecoregion and Interim Biogeographic Regionalisation for Australia, interim Australian bioregion in Western Australia and South Australia.
History
In 1875, British-born Australian explore ...
, which has an internal drainage system terminating in numerous small salt lake
A salt lake or saline lake is a landlocked body of water that has a concentration of salts (typically sodium chloride) and other dissolved minerals significantly higher than most lakes (often defined as at least three grams of salt per liter). I ...
s.
The lack of surface runoff
Surface runoff (also known as overland flow or terrestrial runoff) is the unconfined flow of water over the ground surface, in contrast to ''channel runoff'' (or ''stream flow''). It occurs when excess rainwater, stormwater, meltwater, or other ...
and terrestrial nutrients results in the relatively shallow waters of the Great Australian Bight being generally low in nutrients, and therefore oligotrophic, compared with many other continental shelves
A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...
which support major fisheries
Fishery can mean either the enterprise of raising or harvesting fish and other aquatic life or, more commonly, the site where such enterprise takes place ( a.k.a., fishing grounds). Commercial fisheries include wild fisheries and fish farm ...
. Seasonal upwelling of deep ocean water along the coast of the Eyre Peninsula
The Eyre Peninsula is a triangular peninsula in South Australia. It is bounded by the Spencer Gulf on the east, the Great Australian Bight on the west, and the Gawler Ranges to the north.
Earlier called Eyre's Peninsula, it was named after e ...
in the eastern part of the Bight brings nutrients to the surface waters, with the resulting fertility creating an important marine hotspot.
The waters of the Great Australian Bight are highly biodiverse, particularly in zooplankton, due to a particular series of ocean currents. A literature review undertaken by SARDI (South Australian Research and Development Institute) on the Benthic Protection Zone of the Great Australian Bight Marine Park in 2003 states: "Upwelling events during summer and autumn produce cool patches of surface water along the coast of the southern Eyre Peninsula. These patches contain elevated nutrient concentrations and support enhanced levels of primary productivity. High densities of zooplankton to the northwest of the patches indicate that the prevailing southeasterly winds transport the products of this enhanced biological production into the central GAB. These plankton communities support the highest densities of small planktivorous fishes, including sardine and anchovy, in Australian waters. Juvenile southern bluefin tuna (SBT) migrate into the GAB annually to feed on these rich pelagic resources."
As the nutrients are swept up from the deep water ocean floor and pushed in towards the coast, the food chain is injected with a massive influx of the bottom rung.
There is not enough known about the full scope of species that dwell in or migrate to the Great Australian Bight, so more studies are required. "The Interim Marine and Coastal Regionalisation of Australia (IMCRA) classification suggests that high biodiversity in the GAB may be explained by the presence of temperate species with eastern and western affinities, as well as “tropical stragglers” from northern regions. However, patterns of diversity vary between taxa. Mangroves are poorly represented due to the lack of estuaries. Seagrasses are confined mainly to sheltered bays and the lees of reefs and islands due to the frequent disturbance of inshore habitats by large swells. In contrast, the macroalgal assemblage of the GAB is one of the world's most diverse and includes >1200 species. Over 90% of species in most invertebrate groups are endemic to southern Australia, but the proportion that is confined to the GAB is unknown."
There is still much research needed to fully understand the complex ecosystems of the Great Australian Bight and how any resource extraction or other human activity may affect them. The Literature review also states: "Approximately 370 of the 600 fish species that occur in southern Australia have been recorded in SA. Several species, including the coastal stingaree (''Urolophus orarius'') and crested threefin (''Trinorfolkia cristata''), are restricted to South Australia and occur in the GAB. The patterns of distribution and abundance of fishes in the GAB are poorly understood."
There are some clear findings from the review, "The GAB provides critical habitat for two species of marine mammals that are recognised internationally as being priorities for conservation. The southern right whale
The southern right whale (''Eubalaena australis'') is a baleen whale, one of three species classified as right whales belonging to the genus ''Eubalaena''. Southern right whales inhabit oceans south of the Equator, between the latitudes of 20� ...
(''Eubalaena australis''), which is listed as ‘endangered’ under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999, breeds at the Head of Bight during winter. The Australian sea lion
The Australian sea lion (''Neophoca cinerea''), also known as the Australian sea-lion or Australian sealion, is a species of sea lion that is the only endemic pinniped in Australia. It is currently Monotypic taxon, monotypic in the genus ''Neopho ...
(''Neophoca cinerea''), which is endemic to Australia and is currently listed as “near threatened”, breeds in small colonies along the cliffs of the GAB." These marine mammals require this habitat to remain in existence, which has been recognised by Australian law.
One location on the bight that is specifically oriented towards the understanding of the natural history on its coastline is the Eyre Bird Observatory.
Current conditions
Economically, the Bight has been exploited over many years as part of the fishing, whaling and shellfish industries. Southern bluefin tuna have been a favoured target of fishing in the Bight.
Exploration for oil and gas in the Great Australian Bight first began in the late 1960s. Several oil majors — BP, Statoil/Equinor, and Chevron — proposed plans to drill exploration wells in the southern part of the area from 2017 onwards. On 11 October 2016, BP withdrew its plans to explore the area stating that it was not competitive and did not align with BP's strategic goals. The proposal to explore in the bight was the focus of community opposition. The Wilderness Society showed that a worst-case scenario leak of oil could have a catastrophic effect on the southern coastline of Australia. The Australian Senate commenced an inquiry into oil or gas production in the Great Australian Bight on 22 February 2016. The committee was reestablished on 13 September 2016 following the Australian Federal Election. In October 2017, Chevron withdrew from the project, but it returned alongside BP in 2019. Though the National Offshore Petroleum Safety and Environmental Management Authority approved exploration plans in late 2019, Equinor withdrew from the project in February 2020, citing profitability reasons.
The settlements existing along the coastline of the bight, such as Ceduna and Eucla have facilities to access the bight. Some other locations on the Eyre Highway or located on the Nullarbor do not have facilities or easy access.
See also
* Great Australian Bight Marine National Park
* Great Australian Bight Marine Park
* Great Australian Bight Marine Park (2017)
* Great Australian Bight Marine Park (Commonwealth waters)
* Great Australian Bight Marine Park Whale Sanctuary
* Great South Australian Coastal Upwelling System
* Great Southern Reef
* Western Australia–South Australia Border
* Great Australian Bight High
References
Further reading
* Edminds, Jack (1976) ''Panorama of Western Australia : the Great Australian Bight'' Perth,W.A. Periodicals Division, West Australian Newspapers. (ANB/PRECIS SIN 0140147)
External links
Great Australian Bight Marine Park - Eyre Peninsula
the South Australian portion of the park
Great Australian Bight Trawl Fishery
Wild Down Under Great Australian Bight
BBC
The British Broadcasting Corporation (BBC) is a British public service broadcaster headquartered at Broadcasting House in London, England. Originally established in 1922 as the British Broadcasting Company, it evolved into its current sta ...
Nature Documentary webpage for the fauna of the region
aerial video of the Great Australian Bight
{{Authority control
Bays of Australia
Bodies of water of the Indian Ocean
Bodies of water of the Southern Ocean
Coastline of Western Australia
Coastline of South Australia
Bights (geography)
Temperate Australasia
IMCRA provincial bioregions
Barwon South West (region)