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Pressures affecting estuarine ecosystems

Key finding

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

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 Land and Water South East Queensland report card

The Healthy Land and Water South East Queensland Report Card helps us to understand what pressures are affecting ecosystem health in freshwater, estuarine and marine areas.

Historic and current land management practices have caused substantial erosion in South East Queensland's catchments. Erosion leads to sediment or mud entering estuaries which reduces water clarity and can smother seagrass and riparian and intertidal plants, affecting estuarine habitats.

Sediment from diffuse rural and urban sources, including construction, is the current primary threat affecting estuarine health. The amount of sediment entering waterways depends on the condition of catchments including the extent of riparian vegetation, agricultural and urban development practices and rainfall.

These systems are also impacted by nutrients from agricultural run-off or in sewage treatment effluent. A major program of sewage treatment plant upgrades and stream rehabilitation has significantly reduced this pressure over the past 15 to 20 years.

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    Great Barrier Reef report card

    Estuarine wetlands have suffered a range of cumulative pressures such as increased nutrient and sediment loads, pesticides, loss of connectivity and changes in hydrology, coastal development, climate change and sea level rise. Changes in hydrology and rainfall patterns, and acute pressures (such as climatic events) are compounded by the chronic stress of poor water quality and can drive localised dieback of mangrove forests in the Great Barrier Reef region. While increased sedimentation has led to the expansion of mangroves in some areas of the Great Barrier Reef, it can also smother mangroves. Saltmarshes can be subjected to direct physical disturbances such as grazing and vehicle transit and these can have a large impact in some locations.

    The Great Barrier Reef 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. 2015 and 2016 saw drought conditions across much of the Fitzroy catchment, like the conditions of 2013-2014, which followed 3 years of significant wet seasons. Significant rainfall and large floods lead to erosion in the catchment, washing sediment into estuaries.

      As 2015-2016 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

        Gladstone Harbour is a busy industrialised harbour in a subtropical climate with distinct wet and dry seasons. Gladstone Harbour and associated waterways are used for a wide range of activities—from agricultural, and urban and industrial development to shipping, fishing and dredging. These activities exert pressure on the harbour ecosystems and species.  Examples of pressures that may change the environmental condition of the harbour are the release of toxic material, physical disturbance of habitats such as mangroves or seagrass, and alterations to the coastline.

        Both the Calliope River Estuary and the Boyne River Estuary received an overall A (‘very good’) for water quality in 2015 and 2016, a slight improvement on previous years.

        Nutrient scores in most estuarine zones have improved from those recorded in the 2014 pilot report card. While scores for nutrients recorded in the 2015 Gladstone Harbour report card were generally low across all estuarine zones, Boat Creek received a very poor score in 2016.

        Sediment quality was very good across all sites.

        Levels of dissolved metals aluminium, lead, manganese, nickel and zinc were consistently very low across most estuarine zones. Low scores for copper were recorded in all estuarine zones but there were still satisfactory.

        Gladstone’s predicted population growth will add further pressure on harbour-related infrastructure and ecosystems.

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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.

          The region was heavily impacted by Severe Tropical Cyclone Debbie in 2017. Its effects will be captured in the 2017 report card.

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            Wet Tropics report card

            Significant industries in the Wet Tropics region — which includes 2 World Heritage Areas — include tourism, agriculture, ports, aquaculture, fishing, urban and heavy industry.

            The main agricultural sectors — grazing, sugarcane and banana growing — collectively contribute nutrients, sediment and pesticides to agricultural runoff which impacts rivers, estuaries and the marine areas.

            Pressures in the Wet Tropics region include the historic loss of wetlands and estuary habitats of riparian, mangrove and saltmarsh areas have led to poor freshwater grades and estuary and hydrology grades in the Wet Tropics Report Card.

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              Condamine Catchment report card

              Estuarine ecosystems not analysed in report card publication.

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              QCatchment Bulloo

              Estuarine ecosystems not analysed in report card publication.

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              QCatchment Paroo

              Estuarine ecosystems not analysed in report card publication.

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              QCatchment Warrego

              Estuarine ecosystems not analysed in report card publication.

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              QCatchment Nebine

              Estuarine ecosystems not analysed in report card publication.

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              QCatchment Lake Eyre

              Estuarine ecosystems not analysed in report card publication.

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              QCatchment Archer

              Estuarine ecosystems not analysed in report card publication.

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              QCatchment Coleman

              Estuarine ecosystems not analysed in report card publication.

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              QCatchment Ducie

              Estuarine ecosystems not analysed in report card publication.

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              QCatchment Endeavour

              Estuarine ecosystems not analysed in report card publication.

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              QCatchment Holroyd

              Estuarine ecosystems not analysed in report card publication.

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              QCatchment Jacky Jacky

              Estuarine ecosystems not analysed in report card publication.

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              QCatchment Jardine

              Estuarine ecosystems not analysed in report card publication.

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              QCatchment Jeannie

              Estuarine ecosystems not analysed in report card publication.

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                QCatchment Lockhart

                Estuarine ecosystems not analysed in report card publication.

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                QCatchment Normanby

                Estuarine ecosystems not analysed in report card publication.

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                QCatchment Olive–Pascoe

                Estuarine ecosystems not analysed in report card publication.

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                QCatchment Stewart

                Estuarine ecosystems not analysed in report card publication.

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                QCatchment Wenlock

                Estuarine ecosystems not analysed in report card publication.

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                Indicator: Pressures identified in report card area

                Pressures identified in various water quality report card areas across Queensland.

                Last updated 8 January 2019

                Assessment summary

                See an overview of gradings for estuarine and marine ecosystems in the assessment summary.