VGP Technical Report 13 - Regional baseline stygofauna survey, Onshore Otway Basin, Victoria
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Product description:About the Victorian Gas Program: The Victorian Gas Program (VGP) is a comprehensive science-led program, incorporating geoscientific and environmental research to assess the risks, benefits and impacts of potential onshore conventional gas exploration and production. The program is also investigating the potential for further discoveries of onshore conventional and offshore gas in the Otway and Gippsland geological basins and assessing the feasibility of additional onshore underground gas storage in depleted reservoirs around the Port Campbell area. The VGP includes an extensive, proactive and phased community and stakeholder engagement program, through which the results of the scientific studies are being communicated. Executive summary: A regional baseline stygofauna survey across the Otway Basin was conducted as part of the Victorian Gas Program (VGP). No basin-wide survey of stygofauna in the Otway Basin had been undertaken prior to this study. This survey sampled 80 groundwater bores that are part of the Victorian Government State Observation Bore Network (SOBN) to determine if any stygofauna taxa exist within the groundwater of the onshore Otway Basin. Distribution ranges, including any short-range endemism (SRE), for potential conservation value were determined where possible. As part of the VGP environmental studies program, the Geological Survey of Victoria (GSV) is conducting a baseline assessment of the groundwater and atmosphere in the Victorian Otway Basin to determine current environmental conditions. This stygofauna survey provides a baseline dataset to assist in identifying subsurface groundwater dependent ecosystems (GDEs). Stygofauna are aquatic animals that inhabit groundwater for their entire life cycle. In Australia, stygofauna exist within alluvial, karstic, calcrete and certain fractured rock aquifers. Stygofauna can be highly sensitive to water quality changes and therefore may be useful indicators of groundwater health. Studying stygofauna and their subsurface ecosystems will improve the understanding of current groundwater conditions. This regional survey was undertaken with guidance from Dr Peter Serov of Stygoecologia. Samples were collected using specialised net and bailer equipment, preserved in ethanol and analysed by Dr Peter Serov for stygofauna family identification. A total of 149 individual animals, representative of five stygofauna taxa were identified from six groundwater bores across the Otway Basin. All stygofauna were collected from upper unconfined aquifers. Five repeat samples were collected six months after the first sampling campaign. Stygofauna were collected from three out of the five bores included in the repeat sample round, suggesting the sampling technique is replicable and the stygofauna population within a bore can recover following sample collection. The abundance of stygofauna taxa was low compared to other state surveys, but this does not suggest the groundwater environment is of poorer ecological health. Rather, the fine-grained nature of sediments is suggested to be the likely limiting factor for the presence of diverse stygofauna populations in the aquifers tested. Variability in porosity and water quality within the unconfined aquifers also suggests the possibility of genetic isolation. Bibliographic reference: Bold, T.A., Serov, P., Iverach, C.P. & Hocking, M. 2020. Regional baseline stygofauna survey, Onshore Otway Basin, Victoria. Victorian Gas Program Technical Report 13. Geological Survey of Victoria. Department of Jobs, Precincts and Regions. Melbourne, Victoria. Download: The downloadable version of this report is supplied in PDF format (22.3 MB) and accessible version (DOCX 3.6 MB). Related products:
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