Coasts and Oceans Theme Report

Australia State of the Environment Report 2001 (Theme Report)
Australian State of the Environment Committee, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06751 5

Water Quality

  • Key pollutants of marine and estuarine waters
  • Impacts on marine and estuarine waters
  • Responses to marine and estuarine water pollution
  • Conclusions and implications
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    Environmental indicators reported in this section:

    Environmental Indicator
    CO 6.3 Turbidity
    CO 6.4 Water nutrients (nitrogen)
    CO 7.5 Coastal discharges

    Marine and estuarine waters are valued by the community for a range of purposes or environmental values (ANZECC/ARMCANZ 2000). Those environmental values are:

    • aquatic ecosystem maintenance,
    • primary industry, and
    • recreation and aesthetics.

    Australia's coastal waters are generally in good condition and support the above environmental values. In the tropical north most coastal waters are in good condition, but where agricultural, urban or industrial development has occurred, coastal waters have been degraded to some extent.

    Pollution of coastal waters is derived from both land and marine sources, with land-based sources generally regarded as either point sources (e.g. waste water treatment plants) or as diffuse sources (e.g. urban and agricultural runoff). Marine sources of pollution are associated with harbour dredging, shipping (including fuel and hazardous cargo spills), the use of hull antifouling paints, and aquaculture. The relative contributions of these sources of pollution are poorly defined, but it is widely considered that land-based sources represent the greatest threat to the environmental values of Australia's coastal waters. Only very limited information is available on marine sources of pollution.

    Point-source pollution has been well characterised and is regulated through pollution control legislation. Diffuse source pollution from agricultural and urban runoff, however, remains largely unchecked because of:

    • the inability or unwillingness of authorities to enforce regulations (where they exist),
    • a failure to plan and control the impact of agricultural and urban development on water quality,
    • community perceptions that individual actions do not contribute to cumulative impacts, and
    • a lack of an integrated management system that recognises environmental values.

    There is no comprehensive national coastal water quality monitoring program, and national trends in water quality cannot be reported. However, all States and some other organisations undertake coastal water quality monitoring programs, particularly adjoining large population centres or where there is extensive catchment development and concerns about degraded coastal water quality.

    Key pollutants of marine and estuarine waters

  • Nutrients
  • Sediment
  • Pathogens
  • Toxicants
  • Acid sulfate soils
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    Coastal waters can be degraded by a range of pollutants, including nutrients, sediment, pathogens and toxicants (including heavy metals, hydrocarbons and organochlorines). Some coastal waters are also degraded by acidic leachates from coastal acid sulfate soils.

    Nutrients [CO Indicators 6.4 and 7.5]

    Nitrogen and phosphorus support the growth of plants and phytoplankton in coastal waters. Nitrogen availability generally limits plant growth, and in estuarine systems where nitrogen fixing algae proliferate, phosphorus is often the limiting nutrient (e.g. in Peel Inlet and Harvey Estuary in Western Australia, and the Gippsland Lakes in Victoria).

    The National Pollutant Inventory (NPI) provides information on the relative contributions of nitrogen and phosphorus from both point and diffuse source discharges to coastal waters. However, it should be noted that the data for diffuse source pollution is likely to be largely an estimate at this early stage of implementation of the NPI.

    Table 5: Total nutrient emissions for selected coastal regions (1000 kg).
    Coastal region Land use Phosphorus Nitrogen
    Point A Diffuse B Point A Diffuse B
    Peel-Harvey (WA) Agriculture na 260 na 1 800
    Esk/Tamar (Tas) Agriculture 150 360 390 1 600
    Dawson River (Qld) Agriculture 20 1 700 28 6 400
    Latrobe-Thomson (Vic) Agriculture 18 410 44 3 800
    Richmond River (NSW) Agriculture 5.8 250 na 1 700
    Darwin Harbour (NT) Mix 68 47 270 590
    South-east Queensland (Qld) Mix 1 300 1 500 3 300 7 000
    Water Catchment Adelaide (SA) Urban/Industrial 210 64 920 550
    Port Phillip Bay (Vic) Urban/Industrial 2 500 190 8 500 2 300
    Botany Bay (NSW) Urban/Industrial 1 300 48 7 600 280
    Lake Illawarra (NSW) Urban/Industrial 190 25 970 170

    A Emissions of Total Phosphorus and Nitrogen from Reporting Facilities 1999-2000.
    B Emissions of Total Phosphorus and Nitrogen to Water from Aggregate Sources 1999-2000. Diffuse source pollution represents aggregated data for which there may be significant error of estimation, ranging up to +/- 50% for data for WA and 3 to 13 times for diffuse source estimates in Tasmania. There are significant qualifications to the National Pollutant Inventory estimates and information on the website should be consulted before quoting and/or interpreting these figures.
    na none reported.

    Source:  (October 2001).

    This early data suggests coastal and marine waters adjacent to:

    • heavily urbanised or industrialised areas (e.g. Port Philip Bay, Botany Bay, Adelaide) are likely to receive the majority of their nutrients from point sources, and
    • less populated rural and agricultural lands (e.g. Dawson River, Latrobe-Thomson, Richmond River) are likely to receive the majority of their nutrient loads from diffuse sources.

    One area that has been well studied is the Great Barrier Reef region, which is particularly susceptible to nutrient enrichment because it is relatively enclosed and shallow (EPA 1999a). A June 1999 workshop discussed the sources, fates and consequences of pollutants within the Great Barrier Reef (Hutchings and Haynes 2000). The reduction of pollution loads from agricultural catchments continues to be the key to the ecological health of the Reef system.

    Point sources of nutrient pollution to coastal waters are derived from a number of activities, including wastewater treatment plants, landfills, and industries such as wood product manufacturing and paper production.

    Discharges from wastewater treatment plants represent the great majority of phosphorus and nitrogen point source discharges. Table 6 indicates the relative contribution of nutrients from wastewater treatment plants to the total nutrient load from point sources in some coastal regions.

    Table 6: Proportion of total point source emissions of nutrients to coastal regions attributable to wastewater treatment plants.
    Coastal catchment Major wastewater treatment plants %P %N
    Water Catchment Adelaide Glenelg, Port Adelaide 100 100
    Darwin Harbour Ludmilla, Leanyer Sanderson, Larrakeyah 98 90
    Derwent Macquarie Point, Prince of Wales, Rosny 92 87
    Esk/Tamar Ti-tree Bend, Hoblers Bridge, Newnham, Norwood 87 97
    Dawson River Calliope River 100 100
    SE Queensland Luggage Point, Elanora, Rocklea 92 94
    Port Phillip Bay Werribee, Bangholme 100 99
    Botany Bay Cronulla, Malabar 100 99
    Lake Illawarra Bellambi, Port Kembla, Shellharbour, Wollongong 100 100
    Richmond River Casino 100 na

    Source:  (October 2001).

    Where urban expansion is planned, there is the potential to increase nutrient loads to already nutrient-rich marine waters. The Western Australian Environment Protection Authority, for example, is concerned that proposed urban expansion along Perth's south-east and north-east corridors could increase nutrient loads to the already highly eutrophic Swan-Canning estuary system. Phosphate inputs from new residential areas in the Southern River catchment could start affecting the Southern River in less than 10 years (Gerritse 1999).

    Sediment [CO Indicator 6.3]

    Sediment levels in coastal environments are highly variable, depending on climatic and catchment factors. Extreme rainfall events combined with an extensively cleared catchment will result in relatively high sediment losses. Essentially all sediment transported to coastal areas is from diffuse sources, suspended in agricultural and urban runoff. However, building and construction sites can contribute significantly at the local level.

    Most sediment exported during infrequent, intense storms, includes adsorbed phosphorus, organic material and pesticides that may be on suspended clay particles. For example, during Cyclone Sadie in 1994 the Herbert River in Queensland discharged over 100 000 tonnes of suspended sediment, sourced principally from grazing land. This would be sufficient to cover the whole of Sydney in 2 centimetres of soil (Mitchell and Bramley 1997). (For more information refer to the Land Theme Report).

    Queensland's State of the Environment Report (EPA 1999a) notes that the increase in catchment sediment yield is considered to be attributable to higher sediment yield from cleared land. In view of continuing vegetation clearing, the natural sediment supply regime can be expected to be affected further in some regions and be particularly evident in more remote regions. Given the already significant impacts of sediment discharges, this should raise major concerns over permitting additional agricultural clearing and coastal development in Queensland and elsewhere, specifically in terms of the potential for further sediment pollution of estuaries and coastal waters.


    Public health may be at risk from high concentrations of faecal coliform and enterococcal bacteria in estuarine and coastal waters, either through contact recreation (especially swimming) or consumption of contaminated seafood. Along some beaches (e.g. in the Sydney Harbour) and under certain conditions (following heavy rains or sewage system overflows), beach users risk a range of illnesses such as carditis, conjunctivitis, hepatitis, and skin and wound infections.


    Toxicants are chemical contaminants such as metals, aromatic hydrocarbons, pesticides and herbicides that can potentially have toxic effects at concentrations that might be encountered in the environment. The use of pesticides and herbicides, especially in agricultural production, can result in these compounds being transported by stormwater into estuarine and marine environments where they accumulate in sediments and can affect the communities of invertebrates living in soft sediment habitats.

    There is no national overview of the extent and levels of toxicants found in coastal waters and sediments, neither is there nationally available information for the emission of toxicants from diffuse source pollution.

    Although concentrations of heavy metals and organochlorine compounds along the Great Barrier Reef coast are generally low, there are hot spots of pollution adjacent to ports and harbours, urban centres and areas adjacent to intensive agricultural activity (Haynes and Johnson 2000).

    Although there have been only two reporting periods since the National Pollutant Inventory reporting commenced, there are signs of possible reductions in emissions from some facilities. Most notable in Table 7 are the reductions in emission of:

    • various hydrocarbons from th e BP refinery at Bulwer Island, Brisbane,
    • ammonia and copper from the Bangholme wastewater treatment plant, Melbourne, and
    • arsenic and chromium from the Caltex refinery, Brisbane.

    Along with reductions to some emissions there are also increased emissions, for example in:

    • cadmium emissions from the Caltex refinery, Brisbane, and
    • chromium emissions from the BP refinery, Brisbane.
    Table 7: Selected emissions from selected reporting facilities for 1998-2000 (kg).
    Reporting periods 1 July 1998-30 June 1999 and 1 January 1999-31 December 1999.
    Reporting Facility Substance 1998-1999 1999-2000
    Werribee wastewater treatment plant, Melbourne Arsenic and compounds
    Chromium VI and compounds
    Lead and compounds
    1 300
    BHP Steel, Port Kembla Cadmium and compounds
    Lead and compounds
    3 800
    Caltex refinery, Kurnell Benzene
    5 000
    3 200
    3 300
    BP refinery, Brisbane Benzene
    Cadmium and compounds
    Chromium VI and compounds
    Lead and compounds
    Polycyclic aromatic hydrocarbons (PAHs)
    Toluene (methylbenzene)
    Xylene and isomers
    Caltex refinery, Brisbane Arsenic and compounds
    Cadmium and compounds
    Chromium VI and compounds
    Cyanide (inorganic) compounds
    Bangholme wastewater treatment plant, Melbourne Ammonia (total)
    Chromium and compounds
    Copper and compounds
    Lead and compounds
    3 200 000
    2 500
    3 000 000
    2 100

    Source:  (October 2001).

    While information in Table 7 represents known discharges of toxicants from point source pollution, unauthorised and unreported spills may be significant, such as the alleged discharge of 1032 kilograms of arsenic to Cockburn Sound by Wesfarmers CSBP between July and September 1999 (DEPWA 2000).

    Tributyl tin (TBT) is used as an antifouling treatment for boats and ships, and has been shown to cause imposex in marine snails at extremely low concentrations. Imposex is the development of male reproductive organs in female snails, making the snails sterile. This phenomenon raises concerns about the ecological impacts of continued TBT use (DEPWA 2000).

    In general, toxicant contamination is associated with industry and past effluent management practices. Point-source discharges have, since the 1970s, had to meet increasingly stringent emission limits. However diffuse-source discharges of toxicants, from both agricultural and urban sources, continue effectively unchecked.

    Acid sulfate soils

    Coastal acid sulfate soils (CASS) have been recognised as contributing to one of the most important water quality issues in coastal lowlands and estuaries (see Coastal Settlement). Acid runoff causes adverse impacts to the environment, in terms of:

    • poor water quality with loss of amenity;
    • loss of fisheries, wetland biodiversity and aquacultural production;
    • additional maintenance of community infrastructure, particularly from acid erosion; and
    • the need for rehabilitation of disturbed areas.

    Increased acidity in waterways causes fish kills, outbreaks of fungal diseases in fish and leads to the presence of aluminium and iron flocs in the water. The full extent of ecological impacts of acidic waters in estuaries is not yet known.

    Nutrients affecting the Cockburn Sound environment

    Cockburn Sound, located south of Fremantle, is the most intensively used marine embayment in Western Australia. Increasing urban and industrial development of the adjacent coast since 1954, and increased inputs of industrial discharges and sewage during the 1960s, led to substantial loss of seagrass.

    Management plans put in place in the 1970s had some success in reducing point source discharges. However, water quality has remained at levels found in the 1970s because high winter river flow from the Peel-Harvey and Swan-Canning estuaries carries land-sourced nutrients into the marine environment. The export of nutrients from these catchments to the ocean is estimated to have increased fourfold over the past 50 years (DEPWA 1996).

    Seagrass meadows have continued to decline in area, and the species which grows in Cockburn Sound (Posidonia), may only recolonise very slowly (if at all), so the losses may be permanent.

    The trend in nutrient-related water quality of Cockburn Sound since the 1970s has been initial improvement and subsequent deterioration (Environment Western Australia 1998).

    To deal with the issues of coordination and integration in Cockburn Sound, the Cockburn Sound Management Authority was established in 2000 to manage the various uses of the Sound.