Stygofauna in Australian groundwater systems: Extent of knowledge

[摘要] The extraction of coal and gas from coal seams often intersects aquifers with the potential consequence of changing the volume, quality, pressure and movement of groundwater. While such hydrological changes are well understood and can be modelled relatively accurately, the effects of these changes on the ecosystem that exists within aquifers are not well known and, accordingly, are difficult to predict.Once considered devoid of life, aquifers in Australia and worldwide are increasingly being recognised for their biodiversity. The invertebrates inhabiting aquifers, commonly referred to asstygofauna, are diverse and are morphologically and physiologically different from even closely related surface-dwelling species. It is the unique invertebrate fauna that may be at risk from the effects of mining activities.The CSIRO was commissioned by ACARP to provide a review of the status of knowledge regarding stygofauna diversity, ecology and biogeography within Australia and to identify potential hazardsand issues that may arise due to dewatering of aquifers and coal seams as part of mining operations and coal seam gas extraction. The objectives of this study were to- undertake a desktop review of the state of knowledge and information available on the distribution and ecology of stygofauna in Australia and overseas (Sections 2 and 3);- develop a preliminary identification of the potential hazards of dewatering on stygofauna (Section 4); and- examine regional water balances associated with groundwater use in major production regions (Bowen, Surat and Hunter Regions) (Section 5);- provide a survey of knowledge gaps, research priorities and recommendations for future research (Section 6).Stygofauna are found in aquifers across Australia, predominantly in aquifers with large (mm or greater) pore spaces, especially alluvial, karstic and some fractured rock aquifers. The size of the pore spaces is a key determinant of the suitability of an aquifer as stygofauna habitat. Stygofauna have been recorded occasionally in coal seam aquifers, particularly where those aquifers are hydrologically connected to a shallow alluvial aquifer.‘Stygofauna’ as a term encompasses a variety of different types of organisms that are found in groundwater, and includes animals that are obligate, groundwater-adapted organisms (stygobionts), and those that are not specifically groundwater-adapted but are able to survive the harsh conditions in aquifers (stygoxenes). Stygofauna are dominated by crustaceans, but also includes beetles, snails, mites and a variety of worms, and include groups that are only found ingroundwaters.The diversity of stygofauna in Australia is comparable to that of other regions of the world with more than 4000 groundwater-adapted stygobionts estimated to occur in Australia. The stygofauna of Australia reflect those types of organisms found elsewhere in the world, and indeed, the current global distribution of some species of stygofauna reflect past geological epochs, in which Australia was part of the supercontinents Pangaea and Gondwana.Stygofauna are adapted to conditions of constant temperature, no sunlight, and low nutrient (particularly carbon) and oxygen content in the groundwater environment. The aquifer food web is based on inputs of carbon and nutrients that filter from the surface and so stygofauna are most abundant in shallow aquifers where food supply and oxygen are generally more plentiful. Their abundance decreases with depth and distance along groundwater flow paths as nutrient supplies also decline. Stygofauna are rarely found more than 100 m below ground level nor where dissolved oxygen concentrations in the groundwater are less than 0.3 mg O2/L. Stygofauna are found across a range of water quality conditions (from fresh to saline), but most common in fresh and brackish water (electrical conductivity (EC) less than 5000 μS/cm).The coal mining industry and the rapidly growing coal seam gas industry can, t...

[发布机构] CSIRO

[学科分类] 地球科学(综合)