Pressures affecting estuarine ecosystems

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Key finding

Sediment, nutrients and chemicals are the major catchment pressures that broadly impact Queensland estuaries but vary in their relative importance between regions.

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Healthy Waterways South East Queensland report card
Great Barrier Reef report card
Fitzroy Basin report card
Gladstone Harbour report card
Mackay-Whitsunday report card
Condamine Catchment report card
QCatchment Bulloo
QCatchment Paroo
QCatchment Warrego
QCatchment Nebine
QCatchment Wet Tropics
QCatchment Lake Eyre

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Queensland

Pressures on Queensland's waterways vary between different regions and are often linked to the types of land uses that occur in the catchment. Overall, sediment, nutrients and chemicals are the major catchment pressures that broadly impact Queensland estuaries, but these vary in their relative importance in different areas.

Healthy Waterways South East Queensland report card

The Healthy Waterways Report Card helps us to understand what pressures are affecting ecosystem health in freshwater, estuarine and marine areas. Historic and current poor land management practices have caused substantial erosion in South East Queensland's catchments. Erosion leads to sediment or mud entering waterways which can smother seagrass and reduce water clarity, affecting estuarine habitats.

Sediment from diffuse rural and urban sources is the current primary threat affecting estuarine health. The amount of sediment entering waterways annually is dependent on the level of rainfall.

These systems are also impacted by nutrients such as from agricultural run-off or in sewage treatment effluent, but a major program of sewage treatment plant upgrades has significantly reduced this pressure over the past 15 years.

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Great Barrier Reef report card

The Great Barrier Reef Report Card helps us understand the pressures affecting the Great Barrier Reef from the adjacent catchments. The decline in marine water quality associated with run-off from the adjacent catchments is a major cause of the current poor state of many of the key marine ecosystems.

The report card assesses changes to catchment indicators including estuarine wetlands as they have a water quality protection function and a value in their own right. The loss of estuarine wetlands is mainly due to draining and bunding associated with the conversion of estuarine plains to freshwater wetlands.

For example, the Shoalwater and Styx catchments within the Fitzroy region have more than 94% of their vegetated freshwater swamps comprised of former estuarine wetlands modified by bunding to convert them into freshwater systems.

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Fitzroy Basin report card

Rainfall is a major influence on the annual fluctuation of report card scores for Fitzroy Basin.

The 2013–2014 year saw drought conditions across much of the Fitzroy catchment following three years of significant wet seasons. Significant rainfall and large floods lead to erosion in the catchment, washing sediment into estuaries.

As 2013–2014 was a dry year, sediment plumes were not a factor resulting in an improved score for the estuary, rating its condition B (good).

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Gladstone Harbour report card

All estuarine zones reported in the 2015 Gladstone Harbour Report Card received good or very good scores for overall water quality.

Excess levels of nutrients, such as nitrogen and phosphorus, are pressures on estuaries in the Gladstone Harbour. Scores for nutrients recorded in the 2015 Gladstone Harbour report card were generally low across all estuarine zones, with the Boyne River Estuary and Boat Creek receiving very low scores. Generally nutrient scores in most estuarine zones improved from those recorded in the 2014 Pilot report card. The cause of the poor grade for nutrients requires further investigation. Sediment quality was very good across all sites.

Dissolved metals such as aluminium, lead, manganese, nickel, zinc and copper measured in the 2015 Gladstone Harbour report card are also pressures on estuaries. Levels of these dissolved metals, with the exception of copper, were found to be consistently very low across most estuarine zones. Lower scores for copper were recorded in all estuarine zones but were still satisfactory.

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Mackay-Whitsunday report card

Current pressures in the Mackay–Whitsunday region range from those occurring on an international level such as climate change to reef-wide pressures and localised regional pressures among them coastal, port and agricultural development, tourism and litter.

Activities in the catchment strongly influence waterway health scores. Mackay–Whitsunday region is a major agricultural area with a significant area of the catchment under cane production: catchment run-off of pollutants, particularly nutrients and pesticides, presents a major pressure.

Loss of wetlands and riparian vegetation also impacts the region’s basins and estuaries.

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