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Key ecological features of the South-west Marine Region

The Bioregional Profile identifies a number of ecological features that are of conservation value because of the role they play in the environment of the South-west Marine Region. Key ecological features meet one or more of the following criteria:

1. a species, group of species or a community with a regionally important ecological role (e.g. a predator, prey that affects a large biomass or number of other marine species);
2. a species, group of species or a community that is nationally or regionally important for biodiversity;
3. an area or habitat that is nationally or regionally important for:
   1. enhanced or high productivity (such as predictable upwellings - an upwelling occurs when cold nutrient-rich waters from the bottom of the ocean rise to the surface);
   2. aggregations of marine life (such as feeding, resting, breeding or nursery areas);
   3. biodiversity and endemism (species which only occur in a specific area); or
4. a unique seafloor feature, with known or presumed ecological properties of regional significance.

Key ecological features have been identified by the Australian Government on the basis of advice from scientists about the ecological processes and characteristics of the area. A workshop held in Perth in September 2006 also contributed to this scientific advice and helped to underpin the identification of key ecological features. The report from that meeting is now available.

The table below identifies the key ecological features in the South-west Marine Region which were determined during the development of the Bioregional Profile. It summarises the rationale which was used to identify a specific feature as having a conservation value in the Region. So far, seventeen key ecological features have been identified within the South-west Marine Region.

Key ecological features in the South-west Marine Region

Key Ecological Features	Bioregion	Rationale
1. West Coast Canyons and adjacent shelf break	Central Western Province Southwest Transition	Enhanced productivity; feeding aggregations; unique seafloor feature The West Coast Canyons are believed to be associated with small periodic upwellings that locally enhance productivity and attract aggregations of marine life. The Perth Canyon is prominent among these canyons because of its magnitude and ecological importance. The Perth Canyon marks the southern boundary for a number of tropical species groups on the shelf, including sponges, corals, decapods and xanthid crabs. Deep ocean currents upwelling in the canyon create a nutrient-rich cold-water habitat that attracts deep diving mammals, such as pygmy blue whales and large predatory fish that feed on small fish, krill and squid.
2. Diamantina Fracture Zone	Southern Province	Unique seafloor feature The Diamantina Fracture Zone is a rugged, deep-water environment composed of numerous closely spaced troughs and ridges covering more than 100 000 km2. Marine experts point out that the size and physical complexity of the Diamantina Fracture Zone suggest that it is likely to support deep-water communities characterised by high species diversity and endemism.
3. Albany Canyons Group and adjacent shelf break	Southern Province	Enhanced productivity; feeding aggregations; unique seafloor feature The Albany Canyons, including 32 canyons along 700 km of continental slope, are believed to be associated with small periodic upwellings that enhance productivity and attract aggregations of marine life. Anecdotal evidence indicates that this area supports fish aggregations that attract large predatory fish, sharks and toothed, deep-diving whales such as the sperm whale.
4. Kangaroo Island Canyons and adjacent shelf break	Southern Province	Enhanced productivity; feeding and breeding aggregations; unique seafloor feature The Kangaroo Island Canyons - a small group of steep-sided, narrow canyons - are associated with enhanced productivity that attracts aggregations of marine life. Seasonal upwellings are believed to be an important factor enhancing production. These upwellings support aggregations of krill, small pelagic fish and squid that in turn attract marine mammals (e.g. pygmy blue whales, fin whales, sperm whales, dolphins and New Zealand fur seals), sharks, large predatory fish and seabirds. Anecdotal evidence indicates that orange roughy, blue grenadier and western gemfish aggregate here and are also thought to spawn in this area. Empirical evidence shows that orange roughy eggs occur in high densities. The canyons are also thought to be an important pupping area for school shark and the adjacent shelf break is known for high yields of giant crab and southern rock lobster.
5. Kangaroo Island pool and Eyre Peninsula upwellings	Spencer Gulf Shelf Province	Enhanced productivity; feeding aggregations The Kangaroo Island pool and Eyre Peninsula upwellings are known to be associated with seasonal aggregations of marine life. The nutrient-rich upwellings enhance the production of plankton communities supporting seasonal aggregations of krill, small pelagic fish and squid which in turn attract marine mammals (e.g. toothed whales, dolphins and New Zealand fur seals), sharks, large predatory fish and seabirds.
6. Meso-scale eddies (several locations)	Central Western Province Southwest Transition Southern Province	Enhanced productivity; feeding aggregations Eddies and eddy fields form at predictable locations off the western and south-western shelf break (south-west of Shark Bay, offshore of the Houtman Abrolhos Islands, south-west of Jurien Bay, Perth Canyon, south-west of Cape Leeuwin and south of Albany, Esperance and the Eyre Peninsula). The meso-scale eddies of this Region are important transporters of nutrients and plankton communities, taking them far offshore into the Indian Ocean where they are consumed by oceanic communities. Clockwise eddies are considered to play an important role in lifting deep water, which can be relatively cooler and richer in nutrients, toward the surface where it can enhance production of plankton communities that attract aggregations of marine life.
7. Naturaliste Plateau	Southwest Transition	Unique seafloor feature The Naturaliste Plateau is a complex and isolated seafloor feature that occurs in an area where numerous water bodies and currents converge. It is also the only seafloor feature in the Region that interacts with the sub-tropical convergence front. Although there is very little known about the marine life of this part of the Region, experts point out that the combination of its structural complexity, mixed water dynamics and relative isolation is highly likely to support deep-water communities characterised by high species diversity and endemism.
8. Commonwealth waters within and adjacent to the west coast inshore lagoons	Southwest Shelf Transition and Southwest Shelf Province	Enhanced productivity (benthic); breeding and nursery aggregations An extended chain of in-shore lagoons, extending from south of Mandurah to Kalbarri, is considered to be important for benthic productivity and recruitment for a range of marine species. Although macro-algae and seagrass appear to be the primary source of production, scientists suggest that ground water enrichment may supplement the supply of nutrients to the inshore lagoon. The in-shore lagoons are important areas for the recruitment of the commercially and recreationally important western rock lobster, dhufish, pink snapper, breaksea cod, baldchin and blue gropers, and many other reef species.
9. Commonwealth waters surrounding the Houtman Abrolhos Islands	Southwest Shelf Transition Central Western Province	High biodiversity The Houtman Abrolhos Islands and surrounding reefs have been relatively well studied and are noted for their high species diversity. The reefs are composed of 184 known species of corals that support about 400 known species of demersal fish, 492 known species of molluscs, 110 known species of sponges, 172 known species of echinoderms and 234 known species of benthic algae. The high biodiversity of the islands is attributed to the mix of temperate and tropical species resulting from the southward transport of species by the Leeuwin Current over thousands of years.
10. Commonwealth waters within and adjacent to Geographe Bay	Southwest Shelf Province	Enhanced productivity (benthic); high biodiversity; feeding, resting, breeding and nursery aggregations Geographe Bay is a large sheltered embayment with extensive beds of tropical and temperate seagrass that account for about 80 per cent of benthic primary production in the area. The seagrass beds are noted for their high species biodiversity and endemism. Similar to the lagoons to the north, Geographe Bay provides important nursery habitat for many shelf species (e.g. dusky whaler sharks use the shallow seagrass habitat as nursery grounds for several years, before ranging out over the shelf to adult feeding grounds along the shelf break). Geographe Bay is also an important resting area for migrating humpback whales.
11. Commonwealth waters surrounding the Recherche Archipelago	Southwest Shelf Province Southern Province	High biodiversity; breeding and resting aggregations The Recherche Archipelago is the most extensive area of reef in the South-west Marine Region (35 203 km2 of reef habitat). Its reef and seagrass habitat supports a high species diversity of warm temperate species including 263 known species of fish, 347 known species of molluscs, 300 known species of sponges, and 242 known species of macro-algae. The islands also provide haul-out (resting areas) and breeding sites for Australian sea lions and New Zealand fur seals.
12. Cape Mentelle upwelling	Southwest Shelf Province	Enhanced productivity (pelagic); feeding aggregations The Cape Mentelle upwelling draws relatively nutrient-rich water from the base of the Leeuwin Current, where nutrient levels are higher, up the continental slope and on to the continental shelf, where it results in blooms of phytoplankton at the surface. Higher densities of phytoplankton provide the basis of an extended food chain characterised by aggregations of small pelagic fish, larger predatory fish, seabirds, dolphins and sharks.
13. Commonwealth waters adjacent to the Head of Bight	Great Australian Bight Shelf Transition	Enhanced productivity (pelagic); high biodiversity; feeding and resting aggregations An ecologically important hotspot of higher productivity occurs on the inner shelf at the Head of Bight. Satellite images show higher concentrations of chlorophyll (an indicator for phytoplankton) in this area. This is supported by anecdotal observations of higher concentrations of a number of species that appear to use relatively sheltered areas of mixed seagrass, sand and limestone reef as nurseries and feeding grounds. These include juvenile Australian salmon, mulloway, King George whiting, school shark, sea lions, dolphins and southern right whales. Studies of benthic epifauna (animals such as crabs and molluscs which live on the seabed floor but don't burrow into it) have also found high biomass and species diversity at the Head of Bight.
14. Western rock lobster	Southwest Shelf Transition	Species with important ecological role This species is the dominant large benthic invertebrate in this bioregion. Western rock lobsters are an important part of the food web on the inner shelf, particularly when they are juveniles, as they are preyed upon by octopus, cuttlefish, baldchin groper, blue groper, dhufish, pink snapper, wirrah cod and breaksea cod. Western rock lobsters are also particularly vulnerable to predation during seasonal moults from November to December and to a lesser extent during April and May. The high biomass of western rock lobsters and their vulnerability to predation suggest that they are an important trophic pathway for a range of inshore species that prey upon lobster juveniles.
15. Small pelagic fish	Southwest Shelf Transition Southwest Shelf Province Great Australian Bight Shelf Transition Spencer Gulf Shelf Province	Species group with important ecological role Small pelagic fish are an extremely important component of pelagic ecosystems, providing a link between primary production and higher predators, such as other fish, sharks, seabirds, seals and cetaceans. Fluctuations in abundance of small pelagic fish have serious implications for the functioning of pelagic ecosystems. In the South-west Marine Region the small pelagic fish include ten species: sardine, scaly mackerel, Australian anchovy, round herring, sandy sprat, blue sprat, jack mackerel, blue or slimy mackerel, red bait and saury.
16. Demersal slope fish communities	Central Western Province	Communities with high species biodiversity Demersal slope fish in this bioregion are characterised by high species diversity. Scientists have described 480 species of demersal fish that inhabit the slope of this bioregion and 31 of these are considered endemic to the bioregion. Demersal fish on the slope in this bioregion in particular have high species diversity compared with other more intensively sampled oceanic regions of the world. Below 400 metres water depth, demersal fish communities are characterised by a diverse assemblage where relatively small, benthic species (grenadiers, dogfish and cucumber fish) dominate.
17. Benthic invertebrate communities of the eastern Great Australian Bight	Great Australian Bight Shelf Transition	Communities with high species biodiversity Soft-sediment benthic invertebrate communities of the eastern Great Australian Bight shelf, form some of the worlds most diverse soft sediment ecosystems. A 2002 survey of benthic marine life sampled 798 species, including 360 species of sponge, 138 ascidians and 93 bryozoans, many of which were new to science. The shelf in this area of the Region is part of the worlds largest cool-water carbonate province. Invertebrate skeletons and shells make up over 80 per cent of the shelf sediments.

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