West-Central Australian Shelf large marine ecosystem
The West-Central Australia Large Marine Ecosystem (LME) extends from Cape Leeuwin, at Australia’s southwest edge, to NorthWest Cape. The LME owes its unity to the West Australia Current, a north-flowing current coming from the circulation pattern of the counter-clockwise Indian Ocean gyre and West Wind Drift. But it also has a southward-bound band of warm water]known as the Leeuwin Current, thanks to which tropical reefs flourish further south than anywhere else in the world. The LME has an extremely narrow shelf. It has cool, temperate waters and it includes seagrass beds and diverse and abundant algal communities.
For an analysis of the role of oceanic fronts as highly productive areas, see Menon, 1998. The West-Central Australian Shelf LME is considered a Class II, moderately high (150-300 gC/m2-yr) productivity ecosystem based on SeaWiFS global primary productivity estimates. Because of its latitudinal range it encompasses diverse pelagic and coastal ecosystems. The West Wind Drift carries water eastward to the coast of Australia, where it then flows north as the West Australia Current. The southbound warm water Leeuwin Current marks a boundary between this warm temperate LME and the tropical waters to the North, but this boundary is variable. See CSIRO for more information on the Leeuwin Current and its influence on this LME. Ocean current and wind systems along the coast of this LME inhibit the development of large, highly productive, Ekman-forced upwelling systems like those that occur along the western margins of North America, South America and Africa. Shark Bay along the coastline is an inverse estuary: along the arid coastline, the high evaporation rate from shallow embayments without significant freshwater inflows and with restricted tidal exchange creates an environment with a salinity that exceeds that of the seawater. For a general understanding of oceanographic processes affecting the nutrient dynamics and productivity of Australian marine ecosystems, read the State of the Environment Report. For more information on productivity, see Furnas. For information on Western Australian ocean surface environmental data (currents, temperatures, salinity, winds), as well as a study of ocean dispersal of Western rock lobster larvae, see a CSIRO report.
Fish and Fisheries
Australian waters are relatively nutrient-poor and unable to sustain large fish populations. This LME has a very narrow continental shelf. Production is limited by low levels of nutrient-rich upwellings. Fish stocks in the West-Central Australia LME are quite small. Many species are endemic to Australia. There are commercial fisheries for rock lobster, abalone, pink snapper, shark, crabs, pilchards, prawns and scallops. See the CSIRO report for the use of satellite altimetry in fisheries research on rock lobster larvae. Constantly changing ocean conditions affect the abundance and distribution of all species in the marine food chain (see CSIRO web site). The LME is a breeding ground for the Antarctica-feeding humpback whale. Dolphins, quokkas, sharks, sea lions and penguins can be found in this LME. Until recently, fisheries resources were usually managed in separate fishery units. Under the Environment Protection and Biodiversity Conservation Act 1999 (the EPBC Act), the Commonwealth Government has a framework that helps it to respond effectively to current and emerging environmental problems, and to ensure that any harvesting of marine species is managed for ecological sustainability. The Food and Agriculture Organization (FAO) website provides information on Australia’s fisheries and the characteristics of the industry. The University of British Columbia Fisheries Center uses FAO data to provide detailed fish catch statistics for this LME. Click on the graph for information on 12 groupings.
Pollution and Ecosystem Health
The LME is threatened by an increase in shipping. Ships empty of cargo that enter the ports of West-Central Australia are ballasted with water collected in the last port of call. This ballast water has been shown to contain organisms including bacteria, viruses, algal cells, plankton, and the larval forms of many invertebrates and fish. There are accidental discharges of contaminants, such as spills and shipping accidents. There is direct physical damage caused by port and industrial development, pipelines, mining and dredging. Tributyltin contamination (an ingredient of anti-fouling paint applied to ships and coastal vessels) is widespread throughout the Perth metropolitan region in areas near marinas and ports and is increasing. Another dominant pressure in the Perth area marine environment is excessive nutrient loads from industrial and agricultural sources, as well as from wastewater outfalls. To a lesser degree there are also contaminated groundwater and river and estuary discharges. There are environmental impacts caused by tourism. Large numbers of people are engaged in recreational fishing, SCUBA diving and boating. Activities associated with the use of this kind of equipment have the potential to affect the environment through the pollution of water by boats and the disturbance of species and habitats. A source of environmental impacts is the provision of infrastructure to support tourism (airports, power generation facilities, accommodation, sewage treatment and disposal facilities, moorings, and marine transport). For more information on marine and coastal pollution issues in this LME, see Pogonoski, 2002.
Thousands are involved in the fisheries, aquaculture and processing sectors of the economy. The FAO website provides information on the characteristics and socioeconomic benefits of Australia’s fishing industry. The LME also contains the city of Perth. Industry, shipping and tourism are major economic activities. There are several large-scale evaporative salt plants. The dry, hot climate of these areas makes them ideal for solar salt production. Marine and coastal-based tourism and cruises are important in this LME both in terms of domestic and international tourism. A significant proportion of the Australian population is involved in recreational fishing, surfing, wind surfing, diving, snorkeling, and boating. Tourists from overseas prize the coral reefs and the natural and unspoilt marine environment. Shark Bay is one of Six World Heritage Areas in Australia that have a marine component. There are, however, social, cultural, economic and environmental impacts caused by tourism. Tourism may affect the lifestyle of residents in ways they perceive as intrusive. Negative social impacts may include real or perceived increases in crowding, prices, or crime, as well as increase conflict between commercial, recreational and indigenous interests.
The West-Central Australia LME lies off the coast of the state of Western Australia. The main governance issues faced in this LME pertain to fisheries, tourism management and the establishment of marine reserves. The Department of Conservation and Land Management is responsible for the overall management of marine conservation reserves (the Shark Bay Marine Park). The aim is to preserve representative and special ecosystems in the marine environment. Australian fisheries resources are managed under both Commonwealth and State/Territory legislation. The demarcation of jurisdiction and responsibilities among these various governments has been agreed to under the Offshore Constitutional Settlement (OCS). Under OCS, the states and territories have jurisdiction over localized, inshore fisheries. The Commonwealth has jurisdiction over offshore fisheries or fisheries extending to waters adjacent to more than one state or territory. Each government has separate fisheries legislation and differing objectives. Transboundary fisheries and foreign fisheries are managed by the Commonwealth fishery agencies. Commercial fishing in Western Australia is managed by controlling the number and size of boats, the type of fishing gear, the length of the season or the amount of fish that can be caught. An important goal is to ensure that the exploitation of fisheries resources is conducted in a manner consistent with the principles of ecologically sustainable development. This includes the need to assess the impact of fishing activities on non-target species and the long-term sustainability of the marine environment. For more information on the governance of Australia’s fisheries, see the FAO website. The marine tourism industry has produced a code of conduct that covers issues such as anchoring, removal of rubbish, fish feeding and preservation of world heritage values. Australia declared a 200 nautical mile Exclusive Economic Zone in 1978. Australia is party to the following international agreements: Antarctic-Environmental Protocol, Antarctic Treaty, Biodiversity, Climate Change, Endangered Species, Environmental Modification, Hazardous Wastes, Law of the Sea, Marine Dumping, Marine Life Conservation, Nuclear Test Ban, Ozone Layer Protection, Ship Pollution, Tropical Timber 83, Wetlands, and Whaling.
Articles and LME Volumes
Menon, H.B., 1998. Role of Oceanic fronts in promoting productivity in the Southern Indian Ocean. In: Kenneth Sherman, E. Okemwa and M. Ntiba. (eds.), Large Marine Ecosystems of the Indian Ocean: Assessment, Sustainability, and Management (Cambridge, MA: Blackwell Science) pp. 175-191. ISBN: 0632043180.
- CSIRO marine research
- Furnas, Miles J., Land-sea interactions and oceanographic processes affecting the nutrient dynamics and productivity of Australian marine ecosystems.
- Pogonoski, J.J., D.A.Pollard and J.R.Paxton, 2002. Conservation Overview and Action Plan for Australian Threatened and Potentially Threatened Marine and Estuarine Fishes. Environment Australia.
- Sainsbury, K.J., 1988. The ecological basis of multispecies fisheries, and management of a demersal fishery in tropical Australia. In Fishery population dynamics: The implications for management. pp. 349-382. J.A. Gulland (Ed.). John Wiley and Sons, New York. ISBN: 0471911518.
Disclaimer: This article is taken wholly from, or contains information that was originally published by, the National Oceanic and Atmospheric Administration (NOAA). Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the National Oceanic and Atmospheric Administration (NOAA) should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.