The Integrated Marine and Coastal Regionalisation of Australia (IMCRA), formerly the Interim Marine and Coastal Regionalisation for Australia, is a

biogeographic Biogeography is the study of the distribution of species and ecosystems in geographic space and through geological time. Organisms and biological communities often vary in a regular fashion along geographic gradients of latitude, elevation, ...

regionalisation of the oceanic waters of

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

's exclusive economic zone (EEZ). As of 2008, the most recent version is IMCRA Version 4.0. IMCRA actually defines two bioregionalisations: a benthic bioregionalisation, based on biogeography of fish together with

geophysical Geophysics () is a subject of natural science concerned with the physical processes and physical properties of the Earth and its surrounding space environment, and the use of quantitative methods for their analysis. The term ''geophysics'' som ...

data; and a pelagic bioregionalisation, base on

oceanographic Oceanography (), also known as oceanology and ocean science, is the scientific study of the oceans. It is an Earth science, which covers a wide range of topics, including ecosystem dynamics; ocean currents, waves, and geophysical fluid dynamics ...

characteristics. The benthic bioregionalisation incorporates three separate regionalisations: #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''. #A regionalisation of the

continental shelf 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 ...

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. #A regionalisation of the EEZ into 14 ''geomorphic units'', formed by grouping the 1,134 geomorphic units defined by

Geoscience Australia Geoscience Australia is an agency of the Australian Government. It carries out geoscientific research. The agency is the government's technical adviser on all aspects of geoscience, and custodian of the geographic and geological data and knowl ...

. The pelagic bioregionalisation divides the continental shelf into four provincial bioregions based on

pelagic fish Pelagic fish live in the pelagic zone of ocean or lake waters—being neither close to the bottom nor near the shore—in contrast with demersal fish that do live on or near the bottom, and reef fish that are associated with coral reef ...

species biodiversity and richness. Offshore waters are divided into three-dimensional water masses, taking into account water properties, circulation patterns and energetics.

List of provincial bioregions

This is a list of IMCRA 4.0 provincial bioregions:IMCRA 4.0 data

List of Benthic meso-scale regions

Geomorphic units

There are 1,334 separate

geomorphic Geomorphology (from Ancient Greek: , ', "earth"; , ', "form"; and , ', "study") is the scientific study of the origin and evolution of topographic and bathymetric features created by physical, chemical or biological processes operating at or n ...

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). Geomorphic features are determined by

bathymetric Bathymetry (; ) is the study of underwater depth of ocean floors (''seabed topography''), lake floors, or river floors. In other words, bathymetry is the underwater equivalent to hypsometry or topography. The first recorded evidence of water de ...

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.

Categories

Nomenclature of geomorphic features are based on definitions endorsed by the International Hydrographic Organization (IHO, 2001). * 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 canyon (from ; archaic British English spelling: ''cañon''), or gorge, is a deep cleft between escarpments or cliffs resulting from weathering and the erosion, erosive activity of a river over geologic time scales. Rivers have a natural tenden ...

:
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 The continental rise is a low-relief zone of accumulated sediments that lies between the continental slope and the abyssal plain. It is a major part of the continental margin, covering around 10% of the ocean floor. Formation This geologic str ...

* 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 A seamount is a large geologic landform that rises from the ocean floor that does not reach to the water's surface (sea level), and thus is not an island, islet or cliff-rock. Seamounts are typically formed from extinct volcanoes that rise abru ...

:
Large isolated elevation, greater than 1000 m in relief above the sea floor, characteristically of conical form. * Shelf;

abyssal plain An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between and . Lying generally between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth's surface. T ...

:
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 A trench is a type of excavation or in the ground that is generally deeper than it is wide (as opposed to a wider gully, or ditch), and narrow compared with its length (as opposed to a simple hole or pit). In geology, trenches result from eros ...

; 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.

External links

Interactive Map, Commonwealth marine reserves

References

{{reflist Biogeography of Australia Coastline of Australia