Open Cut » Environment
Central Queensland's Bowen Basin contains Australia's most extensive known coal supplies, beneath the river catchments of one of Australia's largest river basins, the Fitzroy Basin. At more than 142,000km2, the Fitzroy Basin is the third largest river basin in Australia and the largest that flows into the Great Barrier Reef lagoon. The Fitzroy Basin also supports extensive grazing enterprises (77% of land use is beef cattle grazing), as well as coal seam gas extraction, mineral mining, quarries, horticulture, forestry and national parks
An annual aquatic ecosystem health report card for the Fitzroy Basin, produced by the Fitzroy Partnership for River Health, communicates the condition of waterways using indicators that are currently actively monitored in the region, primarily water quality indicators including physicochemical, nutrients and metal concentrations. Due partly to regulatory requirements, most monitoring in the region is restricted to water quality parameters. The use of water quality data as a replacement for aquatic environmental quality assessment has long been recognised as an issue for effective river management, and there is a recognised need for more monitoring and reporting of biological indicators that provide information on ecosystem quality and processes, including fish.
It is important to monitor biological indicators, as they provide a more comprehensive assessment of ecosystem health, capture cumulative impacts and represent key assets that the community can identify with. Fish are the dominant organisms in terms of biomass, feeding ecology and significance to humans, in aquatic ecosystems. In comparison to fish from the Northern Hemisphere, there is limited information on the environmental tolerances of tropical Australian freshwater fish species, and most current information is circumstantial, derived through field observations of water quality and the fish species present at the time of sampling.
Whilst the tolerance of various Australian freshwater fish species to commonly monitored stressors such as electrical conductivity (EC), turbidity, nutrients and low dissolved oxygen concentrations have been documented in this way, there is even less available data on the tolerance of freshwater species to environmental toxicants such as pesticides, metals and hydrocarbons. There is, however a large and increasing body of literature addressing these impacts for freshwater fishes globally.
This research aimed to develop practical indicators of fish health that are demonstrably applicable to monitoring in coal mining regions of the Fitzroy Basin, thereby improving overall aquatic ecosystem health assessments and informing regional water management. Using desktop, field and laboratory study methods, existing fish assemblage indicators were tested and new indicators developed, for assessment of fish habitats and individual fish health. The project objectives were to develop practical indicators suitable for deployment in monitoring programs and for reporting on waterway health, by:
· Investigating and testing existing indicators of fish assemblage health in the Fitzroy Basin;
· Designing new indicators relevant to mine-associated waters of the Fitzroy Basin; and
· Developing a rapid fish health assessment toolbox applicable to the Fitzroy Basin.
The impacts of coal mining on fish and habitat health within receiving environments, while monitored through programs such as the Receiving Environment Monitoring Program, remain a poorly researched area in terms of the application of monitoring data to assessment and reporting. By applying known and new indicators of fish health, and fish habitat health, to the ephemeral aquatic environments of the Fitzroy Basin, this project aimed to develop a monitoring and assessment system that is capable of detecting changes in this vital component of aquatic ecosystem health.
The project involved development and testing of fish indicators over four sampling events including post-wet season (April 2015 and April 2016) and pre-wet season (October 2015 and October 2016), at six test locations in coal mining areas of the Fitzroy Basin. The six locations represented a range of waterway types and land uses upstream and downstream of coal mine sites. Water quality habitat condition and fish communities were sampled at each location using a multi-method approach relevant to waterway type. Data from the test sites were used to develop a series of regionally-relevant fish indicators, which were validated across the Fitzroy Basin in an extensive field sampling regime running from September to December 2016 and covering 20 priority sampling sites. In March 2017 the Fitzroy Basin experienced heavy rainfall and severe flooding associated with ex-tropical cyclone Debbie. An extra sampling period was added to the project to collect post-event data and test the effects of flooding on fish indicators and the Fish Health Index (FHI), at nine sites during May 2017.
By applying known and new indicators of fish health, and fish habitat health, to the ephemeral aquatic environments of the Fitzroy Basin, this project has developed a monitoring and assessment system capable of detecting changes in this vital component of aquatic ecosystem health. The proposed FHI includes nine indicators within four categories:
· Species composition (Percentage of Atheriniformes, Percentage of Clupeiformes and Hypseleotrids, and Number of Atheriniformes species recorded);
· Species diversity (Shannon Diversity, Chao 1 Estimator, and Presence of Introduced Species);
· Trophic composition (Percentage of omnivores); and
· Fish condition (Fulton's Condition Factor of M. splendida splendida, and Presence of individuals with abnormalities).
While the FHI was developed in, and for, a coal mining region in Central Queensland, the index is potentially transferable to other regions with similar land uses of coal mining or extensive agriculture, or to similar bioregions. The primary consideration for aquatic ecosystem health in coal mining regions is regulated and occasional accidental release of coal-mine affected water from mine sites and in Australia the major water quality parameters of concern are salinity (measured as EC), heavy metal ion concentrations and pH. Fish communities can be impacted by these parameters, and in the Fitzroy Basin, fish communities are also subject to the impacts of other land uses, particularly agriculture, which can contribute nutrients, sediments and pesticides to waterways.
Ongoing efforts to monitor and minimise the impacts of various land uses and preserve the biotic integrity of rivers in the Fitzroy Basin is likely to require a versatile approach, addressing both habitat degradation and the need for comprehensive monitoring methods that measure the cumulative impacts of various stressors. Biological monitoring programs can provide a better assessment of the cumulative and long term environmental risks of various land uses to waterways, than can be achieved through water quality spot-checks alone. The Fitzroy Basin FHI reported here includes indicators which were identified as being responsive to local environmental conditions. A regular monitoring program for fish in the Fitzroy Basin, combined with data from this study, would provide sufficient data within about two years to assess the long-term sensitivity of the FHI and its indicators throughout the Fitzroy Basin, and to make any necessary adjustments to the fish indicators. The FHI provides an objective and regionally relevant fish health assessment toolbox that can be widely employed in monitoring programs at relatively low cost in comparison to more extensive fish health monitoring activities. Results will be provided to the Fitzroy Partnership for River Health to consider the incorporation of fish indicators into the Fitzroy Basin Report Card.