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IMCRA mesoscale bioregions of Australia

We derived a number of physical and chemical (PC) stressor default guideline values (DGVs) using the Integrated Marine and Coastal Regionalisation of Australia (IMCRA 4.0) as the best possible representation of Australia’s inshore waters. When using these data, be mindful that jurisdictional derivations at even finer inshore scales will override these values.

Find physical and chemical stressor default guideline values for your IMCRA mesoscale bioregion​


Inclusion of IMCRA mesoscale bioregions

Australian jurisdictions involved in the revision of the Water Quality Guidelines sought guideline value derivations that were the best possible representation of inshore waters.

We used a review of bioregional classifications for Australia’s marine waters (Hale et al. 2012) to derive a number of PC stressors at IMCRA’s mesoscale (even though jurisdictional derivations at even finer inshore scales will override these values).

Our high-level guidance on management context, ecological descriptions, biological indicator selection and other advice is summarised for each of Australia’s 5 marine regions.

Great Barrier Reef Marine Park Authority (GBRMPA) provided separate guidance for the Great Barrier Reef Marine Park.

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Physical and chemical stressors not covered by this data

IMCRA mesoscale bioregions provide greater regional resolution for PC stressor DGVs than the ANZECC & ARMCANZ (2000) guidelines but the suite of DGVs differs between them.

For marine PC stressors not listed among the IMCRA mesoscale stressors, refer to Table 1. The data in Table 1 were supplied by Australian states and territories prior to 2000, and the resulting DGVs for those stressors were published in the ANZECC & ARMCANZ (2000) guidelines.

For stressors that cause problems at high values or concentrations (e.g. warm water releases from power stations, hypersaline brines from desalinisation plants, nutrients, SPM, biochemical oxygen demand (BOD), the 80th percentile of the reference distribution is used as the low-risk DGV. For stressors that cause problems at low levels (e.g. low dissolved oxygen in waterbodies), use the 20th percentile of the reference distribution as a low-risk DGV. For stressors that cause problems at both high and low values (e.g. temperature, salinity, pH), the desired range for the median concentration is defined by the 20th percentile and 80th percentile of the reference distribution.

Any available regional guideline values should be used in preference to DGVs provided in either Table 1 or through the IMCRA mesoscale bioregion search tool.

Table 1 Physical and chemical stressor default guideline values (DGVs) for Australian ecoregions for slightly disturbed marine ecosystems. DGVs are used to assess the risk of adverse effects due to nutrients, biodegradable organic matter and pH in the marine ecosystem.
Australian ecoregionEcosystemTP (µg P/L)FRP (µg P/L)TN (µg N/L)TAN (µg N/L)pH lower limitpH upper limit
South-westMarinebc–inshored20e 5e23058.08.4
South centralMarine100101,000508.08.5

TP = total phosphorus, FRP = filterable reactive phosphate, TN = total nitrogen, TAN = total ammonia nitrogen.
a. lower values are typical of clear coral dominated waters (e.g. Great Barrier Reef) and higher values are typical of turbid macrotidal systems (e.g. North West Shelf of Western Australia).
b. nutrient concentrations alone are poor indicators of marine trophic status.
c. these generic DGVs do not necessarily apply in all circumstances. For example, for some unprotected coastlines, such as Albany and Geographe Bay, it may be more appropriate to use offshore values for inshore waters.
d. inshore waters defined as coastal lagoons (excluding estuaries) and embayments and waters less than 20 m deep.
e. summer (low rainfall) values; values higher in winter for TP (40 µg P/L) and FRP (10 µg P/L).

​​About IMCRA 4.0

IMCRA 4.0 is a spatial framework for classifying Australia’s coasts and near shore marine environment into bioregions. It is derived from biological and physical data, including the distribution of demersal fishes, marine plants and invertebrates, sea floor geomorphology and sediments, and oceanographic data.

The IMCRA mesoscale bioregions were derived by jurisdictions at a finer scale than Australia’s marine planning regions. The seaward extent for over 50 mesoscale IMCRA bioregions is defined by the 200 m isobath except where this boundary extends beyond Australia’s Exclusive Economic Zone (EEZ).

IMCRA 4.0 is useful for regional planning with its ecological basis and appropriate scale (41 bioregions) — refer to map of IMCRA 4.0 provincial bioregions (PDF, 366KB).

Covering Australia’s waters from the coast to the edge of the EEZ, excluding Antarctica and Heard and Macdonald islands, IMCRA 4.0 combined two national-scale marine regionalisations: Interim Marine and Coastal Regionalisation of Australia (IMCRA 3.3), which provided a marine regionalisation of inshore waters, and the National Marine Bioregionalisation (NMB) of Australia for off-shelf waters.

See also:


ANZECC & ARMCANZ 2000, Australian and New Zealand Guidelines for Fresh and Marine Water Quality, Australian and New Zealand Environment and Conservation Council and Agriculture and Resource Management Council of Australia and New Zealand, Canberra.

Hale, J, Butcher, R, Collier, K & Snelder, T, 2012, ANZECC/ARMCANZ Water Quality Guidelines Revision: Ecoregionalisation and Ecosystem Types in Australian and New Zealand Marine, Coastal and Inland Water Systems, report prepared for the Department of Sustainability, Environment, Water, Population and Communities, Canberra.