The Integrated Marine and Coastal Regionalisation of Australia (IMCRA), formerly the Interim Marine and Coastal Regionalisation for Australia, is a biogeographic regionalisation of the oceanic waters of Australia's exclusive economic zone (EEZ). As of 2008, the most recent version is IMCRA Version 4.0.[1][2]

IMCRA actually defines two bioregionalisations: a benthic bioregionalisation, based on biogeography of fish together with geophysical data; and a pelagic bioregionalisation, base on oceanographic characteristics.[2]

The benthic bioregionalisation incorporates three separate regionalisations:[2]

  1. A regionalisation of the EEZ into provincial bioregions, based on the biogeography of bottom dwelling fishes. In IMCRA 4.0, 41 provincial bioregions, consisting of 24 provinces and 17 transitions.
  2. A regionalisation of the continental shelf into meso-scale regions based on biological and physical characters, and the distance from the coast. In IMCRA 4.0 there are 60 meso-scale regions.
  3. A regionalisation of the EEZ into 14 geomorphic units, formed by grouping the 1,134 geomorphic units defined by Geoscience Australia.

The pelagic bioregionalisation divides the continental shelf into four provincial bioregions based on pelagic fish species biodiversity and richness. Offshore waters are divided into three-dimensional water masses, taking into account water properties, circulation patterns and energetics.[2]

List of provincial bioregions

This is a list of IMCRA 4.0 provincial bioregions:[3]

BioregioninformationIMCRA meso-scale bioregionsMarine Ecoregions of the World designation
Bass Strait Shelf Provincecold temperate watersCentral Victoria (CV) Victoria Embayment (VE), Central Bass Strait (CBS), Boags (BGS)Bassian (205)
Cape Provincenana
Central Eastern Shelf Provincewarm temperate watersManning Shelf (MAN), Hawkesbury Shelf (HAW)Manning-Hawkesbury (203)
Central Eastern Shelf Transitiontransition between the tropical Northeast Shelf and warm-temperate Central Eastern Shelf provincesTweed-Moreton (TM)Tweed-Moreton (202)
Central Eastern Provincenana
Central Eastern Transitionnana
Central Western Shelf Provincesubtropical watersShark Bay (SBY), Zuytdorp (ZUY)Shark Bay (210)
Central Western Shelf TransitiontransitionNingaloo (NIN)Ningaloo (145)
Central Western Provincesubtropical watersnana
Central Western Transitionnana
Christmas Island Provincetropical watersCocos-Keeling/Christmas Island (120)
Cocos (Keeling) Island Provincetropical watersCocos-Keeling/Christmas Island (120)
Great Australian Bight Shelf Transitiontransition between the warm-temperate Southwest Shelf and Spencer Gulf Shelf provincesEucla (EUC), Murat (MUR)Great Australian Bight (208)
Kenn Provincetropical watersnana
Kenn Transition
Lord Howe Provincewarm temperate watersLord Howe and Norfolk Islands (151)
Macquarie Island Provincecold temperate watersMacquarie Island (212)
Norfolk Island Provincewarm temperate watersLord Howe and Norfolk Islands (151)
Northeast Shelf Provincetropical watersWest Tropic Coast (WTC), Central Reef (CR), Lucinda-Mackay Coast (LMC), Shoalwater Coast (SC), Mackay-Capricorn (MC), Pompey-Swains (PS)Central and Southern Great Barrier Reef (143)
Northeast Shelf Transitiontransition between the tropical Northern Shelf and Northeast Shelf provincesTorres Strait (TS), East Cape York (ECY), Ribbons (RBN)Torres Strait and Northern Great Barrier Reef (142)
Northeast Provincetropical watersnana
Northeast Transitionnana
Northern Shelf Provincetropical watersVan Diemens Gulf (VDG), Cobourg (COB), Arafura (ARA), Arnhem Wessel (AWS), Carpentaria (CAR), Groote (GRO), Pellew (PEL), Wellesley (WLY), Karumba-Nassau (KAN), West Cape York (WCY)Arnhem Coast to Gulf of Carpentaria (140)
Northwest Provincetropical watersnana
Northwest Shelf Provincetropical watersPilbara (nearshore) (PIN), Pilbara (offshore) (PIO), Eighty Mile Beach (EMB), Canning (CAN), North West Shelf (NWS)Exmouth to Broome (144)
Northwest Shelf Transitiontransition between the tropical Northern Shelf and Northwest Shelf provincesKimberley (KIM), King Sound (KSD), Anson Beagle (ANB), Cambridge-Bonaparte (CAB), Bonaparte Gulf (BON), Tiwi (TWI)Bonaparte Coast (141)
Northwest Transitionnana
Southeast Shelf Transitiontransition between the warm-temperate Central Eastern Shelf and the cold-temperate Bass Strait Shelf provincesBatemans Shelf (BAT), Flinders (FLI), Twofold Shelf (TWO)Cape Howe (204)
Southeast Transitionnana
Southern Provincewarm temperate watersnana
Southwest Shelf Provincewarm temperate watersLeeuwin–Naturaliste (LNE), Western Australia South Coast (WSC)Leeuwin (209)
Southwest Shelf Transition transition between the subtropical Central West Province and the warm temperate Southwest Shelf Province Abrolhos Islands (ABR) and Central West Coast (CWC) Houtman (211)
Southwest Transitionnana
Spencer Gulf Shelf Provincewarm temperate watersCoorong (COR), Eyre (EYR), North Spencer Gulf (NSG), St Vincent Gulf (SVG), Spencer Gulf (SG)South Australian Gulfs (207)
Tasmania Provincecold temperate watersnana
Tasmanian Shelf Provincecold temperate watersBruny (BRU), Davey (DAV), Franklin (FRA), Freycinet (FRT)Bassian (205)
Timor Provincetropical watersnana
Timor Transitionnana
West Tasmania Transitionnana
Western Bass Strait Shelf Transitiontransition between the cold-temperate Bass Strait Shelf and Tasmanian Shelf provinces and the warm-temperate Spencer Gulf Shelf ProvinceOtway (OTW)Western Bassian (206)
IMCRA 4.0 provincial bioregions

List of Benthic meso-scale regions

  • Abrolhos Islands (ABR)
  • Anson Beagle (ANB)
  • Arafura (ARA)
  • Arnhem Wessel (AWS)
  • Batemans Shelf (BAT)
  • Boags (BGS)
  • Bonaparte Gulf (BON)
  • Bruny (BRU)
  • Cambridge-Bonaparte (CAB)
  • Canning (CAN)
  • Carpentaria (CAR)
  • Central Bass Strait (CBS)
  • Cobourg (COB)
  • Coorong (COR)
  • Central Reef (CR)
  • Central Victoria (CV)
  • Central West Coast (CWC)
  • Davey (DAV)
  • East Cape York (ECY)
  • Eighty Mile Beach (EMB)
  • Eucla (EUC)
  • Eyre (EYR)
  • Flinders (FLI)
  • Franklin (FRA)
  • Freycinet (FRT)
  • Groote (GRO)
  • Hawkesbury Shelf (HAW)
  • Karumba-Nassau (KAN)
  • Kimberley (KIM)
  • King Sound (KSD)
  • Leeuwin-Naturaliste (LNE)
  • Lucinda-Mackay Coast (LMC)
  • Mackay-Capricorn (MC)
  • Manning Shelf (MAN)
  • Murat (MUR)
  • Ningaloo (NIN)
  • North Spencer Gulf (NSG)
  • North West Shelf (NWS)
  • Oceanic Shoals (OSS)
  • Otway (OTW)
IMCRA 4.0 mesoscale bioregions

Geomorphic units

Map of geomorphic units of the ocean floor within the Australian EEZ

There are 1,334 separate geomorphic units in Australia’s waters, in 14 categories. The regions represent distinct areas of geomorphic features that have similar characteristics (e.g. areas of the continental slope that contain canyons, or flat plains).[2]

Geomorphic features are determined by bathymetric models (depth analysis) of the ocean floor and provide an important predictor of species assemblages at a large scale. For example, different species will occur on low-gradient terraces compared to those on the steep-walled submarine canyons.[4]

Categories

Nomenclature of geomorphic features are based on definitions endorsed by the International Hydrographic Organization (IHO, 2001).[5]

  • Apron:
    Gently dipping featureless surface, underlain primarily by sediment, at the base of any steeper slope.
  • Bank, sandbank:
    Shallow water or submerged bank of sand in a sea or river that may be exposed at low tide
  • Basin; terrace; plateau:
    Depression, characteristically in the deep sea floor, more or less equidimensional in plan and of variable extent;
    Relatively flat horizontal or gently inclined surface, sometimes long and narrow, which is bounded by a steeper ascending slope on one side and by a steeper descending slope on the opposite side;
    Flat or nearly flat area of considerable extent, dropping off abruptly on one or more sides.
  • Canyon:
    A relatively narrow, deep depression with steep sides, the bottom of which generally has a continuous slope, developed characteristically on some continental slopes.
  • Continental rise
  • Deep; escarpment:
    Generally depths greater than 6,000 m; Elongated and comparatively steep slope separating or gently sloping areas.
  • Knoll:
    Relatively small isolated elevation of a rounded shape.
  • Pinnacle:
    High tower or spire-shaped pillar of rock or coral, alone or cresting a summit. It may extend above the surface of the water. It may or may not be a hazard to surface navigation
  • Reef:
    Rock lying at or near the sea surface that may constitute a hazard to surface navigation
  • Ridge; sill:
    (a) Long, narrow elevation with steep sides. (b) Long, narrow elevation often separating ocean basins. (c) Linked major mid-oceanic mountain systems of global extent;
    Sea floor barrier of relatively shallow depth restricting water movement between basins.
  • Seamount:
    Large isolated elevation, greater than 1000 m in relief above the sea floor, characteristically of conical form.
  • Shelf; abyssal plain:
    A gently sloping, flatter region adjacent to a continent (or around an island) or at abyssal depths.
  • Slope:
    A sloped area seaward from the shelf edge to the upper edge of a continental rise or the point where there is a general reduction in slope.
  • Trench; saddle:
    Long narrow, characteristically very deep and asymmetrical depression of the sea floor, with relatively steep sides;
    Broad pass, resembling in shape a riding saddle, in a ridge or between contiguous seamounts.

See also

References

  1. IMCRA Technical Group. "Interim Marine and Coastal Regionalisation for Australia: an ecosystem-based classification for marine and coastal environments". Environment Australia, Department of the Environment, Australian Government. Retrieved 23 December 2013.
  2. 1 2 3 4 5 "A guide to the Integrated Marine and Coastal Biogeographic Regionalisation of Australia: IMCRA Version 4.0: June 2006". Department of the Environment, Australian Government. Retrieved 23 December 2013.
  3. IMCRA 4.0 data
  4. "Benthic Marine Bioregionalisation of Australia's Exclusive Economic Zone". environment.gov.au. Government of Australia. 2005. Retrieved 16 July 2017.
  5. "Geomorphic features of the continental margin of Australia". environment.gov.au. Commonwealth of Australia. 2005. Retrieved 16 July 2017.
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