Marine ecosystems require good quality water to remain healthy. The Great Barrier Reef Marine Park Authority has Water Quality Guidelines for the Great Barrier Reef Marine Park (2010) with set levels for specific pollutants which when exceeded prompt managers to take action.
The guidelines focus on levels of sediments, nutrients and pesticides — the main catchment run-off pollutants that affect water quality on the Great Barrier Reef. Regional catchment-level objectives are being implemented under Queensland’s Environmental Protection (Water and Wetland Biodiversity) Policy 2019 for the Reef catchment.
In some locations current water quality condition is as good as or better than the guideline levels — however the objective of the guidelines remains the same. In areas where water quality is not as high, further improvement to current conditions is the target objective. These objectives are derived to support high ecological value ecosystems.
Information for specific basins and their adjacent marine waters can be found at the Environmental Protection Policy (Water and Wetland Biodiversity) webpage. There are basin level water quality objectives in:
- Wet Tropics region including all waters of the Daintree, Mossman, Barron, Mulgrave-Russell and Trinity Inlet, Johnstone, Tully, Murray, Hinchinbrook Island and Herbert River basins.
- Townsville region including all waters of the Black and Ross River basins, Cleveland Bay, Magnetic Island.
- Mackay-Whitsundays region including all waters of the O'Connell, Pioneer and Proserpine River basins, Plane Creek and Whitsunday Island basins, Repulse Bay, the Whitsundays.
- Capricorn and Curtis Coast region including all waters of the Styx, Shoalwater and Water Park Creek Basins, Keppel Bay, the Boyne, Calliope and Curtis Island Basins, including Gladstone Harbour, the Narrows, lower Fitzroy estuary.
- Other basins include Cape York, Wet Tropics (coastal waters), Burdekin-Don-Haughton, Mackay-Whitsunday (coastal waters) and the Fitzroy region.
For waters of the Great Barrier Reef that are outside state coastal waters, the objectives from adjacent waters of the same type apply. For instance, mid-shelf water quality objectives for Michaelmas Cay would apply to the mid-shelf waters of Opal Reef.
Each of the regional schedule documents has a description of the data that have been analysed and outlines the decision process supporting the guidelines. The general approach is to use locally applicable data as a basis for deriving guidelines. The data for open coastal waters and further seaward waters are generally sourced from Australian Institute of Marine Science monitoring programs.
Guidelines values are derived from site data that falls within particular water bodies. These values were compared against the current water quality guidelines. Where local water quality data meet or exceed the guideline values, values were set to maintain this condition. Where data did not meet these guideline values, the 2010 guideline value was adopted (i.e. annual and seasonal means).
Benthic light guidelines that support seagrass growth have been implemented through these schedules. These are sourced from James Cook University and predecessor agencies. Light levels are specified as photosynthetic active radiation moving averages depending on seagrass species.
Updated guideline levels for a number of pesticides have been determined in the intervening years since initial publication, and more are proposed. These levels are undergoing a national guidelines review process. When that process is complete the intention is that they would supersede those published in the current guidelines. Updates can be found at the Australian and New Zealand Guidelines for Fresh and Marine Water Quality 2018 webpage.
In recognition of the outstanding universal value of this World Heritage Area pollutant concentrations derived to be protective of 99 per cent of species are applied routinely as trigger values for catchment run-off toxicants.
Actions and progress to improve marine water quality is tracked and reported primarily through the Marine Monitoring Program’s annual technical reports for inshore water quality and the review process for pesticides is underway.