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Key departmental publications, e.g. annual reports, budget papers and program guidelines are available in our online archive.

Much of the material listed on these archived web pages has been superseded, or served a particular purpose at a particular time. It may contain references to activities or policies that have no current application. Many archived documents may link to web pages that have moved or no longer exist, or may refer to other documents that are no longer available.

Our Sea, Our Future
Major findings of the State of the Marine Environment Report for Australia

Compiled by Leon P. Zann
Great Barrier Reef Marine Park Authority, Townsville Queensland

Department of the Environment, Sport and Territories, Canberra (1995)
ISBN 0 642 17391 5

1. Description of Australia's marine environment and its status

Figure 2

Figure 2: A generalised schematic view of Australia's coastal zone and ecosystems, from temperate to tropical regions.

Australia's 200 nautical mile Fishing Zone, which excludes the Australian Antarctic Territory, is 8.94 million square kilometres in area and is the third largest in the world. The total area of the continental shelf around Australia, as defined by the 1982 United Nations Convention on the Law of the Sea, is 14.8 million square kilometres.(1),(58)

Australian waters span almost 60 degrees in latitude from Torres Strait in the north, to Antarctica in the south, and 72 degrees in longitude from Norfolk Island in the east to Cocos (Keeling) Island in the west. They include a great range of geographic, geologic and oceanographic features, and around 12,000 islands. The length of the coastline of the mainland and that of the larger islands is estimated to be 69,630 kilometres at a 0.1 kilometre scale, or 30,270 kilometres at a 10 kilometre scale.(1)

But sea boundaries exist only on maps. Australia's marine domain is essentially a part of the interconnected world ocean which covers 71% of our planet. Many marine species are migratory, travelling across many nations' boundaries. Currents may carry marine organisms and pollutants great distances through the sea, necessitating a regional, national and international approach to marine environmental management.(2),(93),(95),(96)

THE OCEAN

The waters surrounding Australia and its external territories are part of three large, interconnected ocean basins of the Southern Hemisphere: the Pacific, Indian and Southern Oceans.

Oceanography

Australia's seas encompass all five of the world's ocean temperature zones: tropical (25 to 31oC); subtropical (15 to 27oC); temperate (10 to 25oC); subpolar (5 to 10oC); and polar (-2 to 5oC). The main ocean currents affecting the marine environment around the continent are the East Australian Current which brings warm equatorial and Coral Sea water down the east coast, and the Leeuwin Current bringing warm, low salinity water down the west coast. These are not major currents by world standards. Other major ocean features are the sub-tropical and antarctic convergences. The periodic influence of the El Nino/Southern Oscillation has a great effect on ocean temperature and biological productivity, and on Australia's terrestrial climate and agriculture.(2) Similarly there are the periodic influences of strong winds and storm surges associated with tropical cyclones and mid-latitude low pressure systems(84).

Figure 3

Figure 3: Australia's waters encompass all five of the ocean's climatic zones. These images, produced from satellite data, show average surface temperatures for summer (a) and winter (b) between 1982 and 1988.

Figure 4: Satellite image of eastern Australia showing the meandering east current.This current brings warm equatorial and Coral Sea water down Australia's eastern coast. Around the Sydney area it turns east into the Tasman Sea where it forms giant loops and eddies.

Figure 5: Satellite image of western Australia showing the Leeuwin Current. This curent brings warm, low salinity water masses from the North West Shelf region down the western and south-western coasts. It sometimes reaches the Eyre Peninsula in South Australia.

Figure 6: Satellite image of South Australia's gulfs showing marked changes in surface sea temperatures. The gulfs are 'reverse estuaries' which become warm and more salty in their upper reaches.

Figure 6
ocean nutrients and productivity

Australian waters are generally low in nutrients and therefore have a relatively low biological productivity. This is because they are largely dominated around the continent by low-nutrient tropical water masses; there are no major upwellings of nutrient-rich deep water in the region; and the run-off from our ancient, leached land is naturally low in nutrients. Paradoxically, some inshore areas tend to be dominated by highly productive mangroves, seagrass and coral communities which are adapted to low-nutrient waters. The generally low nutrient status also contributes to the relatively low fisheries production of Australian waters.(2),(30)

sea floor

The mainland of Australia is surrounded by a continental shelf between 15 and 400 kilometres wide, and 2.5 million square kilometres in area. The shelf is connected to Papua New Guinea in the north, and to Tasmania in the south. With the exception of the complex Great Barrier Reef in the north-east, and the undersea cliffs and pinnacles off Tasmania, the sea floor is generally rather featureless but is broken by occasional reefs, terraces and plateaus.(3)

Figure 7

Figure 7: Spectacular volcanic cones recently discovered around 100 kilometres south of Tasmania. The cones which lie in 1,000 metres of water and average 200metres in height, are the fishing grounds for Tasmania's lucrative orange roughy fishery. This image, which covers an area of around 35 kilometres square was produced by multibeam sonar in 1994.