VICTORIAN GAS PROGRAM Regional baseline stygofauna survey Onshore Gippsland Basin, Victoria

T.A. Bold, P. Serov, C.P. Iverach & M. Hocking Victorian Gas Program Technical Report 14 February 2020 Authorised by the Director, Geological Survey of Victoria Department of Jobs, Precincts and Regions 1 Spring Street Melbourne Victoria 3000 Telephone (03) 9651 9999

© Copyright State of Victoria, 2020.

Department of Jobs, Precincts and Regions 2020

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Bibliographic reference BOLD, T.A., SEROV, P., IVERACH, C.P. & HOCKING, M. 2020. Regional baseline stygofauna survey, Onshore Gippsland Basin, Victoria. Victorian Gas Program Technical Report 14. Geological Survey of Victoria. Department of Jobs, Precincts and Regions. Melbourne, Victoria. 31p.

ISBN 978-1-76090-261-2 (pdf/online/MS word)

Geological Survey of Victoria Catalogue Record 160955

Key Words stygofauna, Gippsland Basin, groundwater-dependent ecosystems

Acknowledgements All fieldwork and sample collections were carried out by Attila Gaal, Charlotte Iverach, Tiffany Bold, Cassady O’Neill and Josh Grover. Graphs and photos were provided by Tiffany Bold, Dr Peter Serov of Stygoecologia provided the stygofauna identifications, images and conducted a report review, Luong Tran compiled the maps and Allyson Crimp designed the final report.

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.

About the Geological Survey of Victoria The Geological Survey of Victoria (GSV) is the Victorian Government’s geoscience agency and sits within the Department of Jobs, Precincts and Regions.

GSV provides evidence-based knowledge and information to Government, industry, academia and the community, on Victoria’s earth resources, using the latest geoscience technologies and methods.

For more details visit earthresources.vic.gov.au/gsv

Disclaimer This publication may be of assistance to you, but the State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication. The Victorian Government, authors and presenters do not accept any liability to any person for the information (or the use of the information) which is provided or referred to in the report. Table of contents

Summary...... v 1 Introduction...... 1 1.1 Victorian Gas Program...... 1 1.2 What are stygofauna?...... 1 1.3 Australian stygofauna knowledge...... 2 2 Study area...... 4 2.1 Climate...... 4 2.2 Land use...... 5 2.3 Geology...... 5 3 Groundwater dependent ecosystems...... 9 3.1 Stygofauna habitat...... 10 3.2 Stygofauna ecological requirements...... 10 3.3 Factors impacting stygofauna...... 11 4 Methods...... 12 4.1 Survey design...... 12 4.2 Environmental attributes...... 12 4.3 Equipment...... 13 4.4 Stygofauna sampling...... 13 4.5 Laboratory analysis...... 14 4.6 Limitations...... 15 5 Results...... 16 5.1 Stygofauna results...... 16 5.2 Groundwater quality...... 17 6 Discussion...... 20 6.1 Environmental significance...... 21 7 Conclusions...... 22 References...... 23 Glossary ...... 28 Appendix A1 Example field sample sheet...... 29 Appendix A2 Stygofauna results...... 30 Appendix A3 Stygofauna sample groundwater quality results...... 31 List of figures

Figure 1.1 Stygofauna specimen (Amphipoda Melitidae) collected in SW Victoria (Stygoecologia, 2019)...... 3 Figure 2.1 Study area for the baseline stygofauna survey, showing the extent of the VGP environmental study area, the VGP onshore conventional gas program study area and the location of the east and west Gippsland CMAs...... 4 Figure 2.2 Victorian Gas Program Gippsland Basin land use map...... 5 Figure 2.3 Surface geology of the Gippsland Basin, Victoria...... 6 Figure 2.4 Outcropping units of the VAF of the Gippsland Basin, Victoria...... 6 Figure 3.1 The known and potential surface aquatic GDEs of the Gippsland Basin, Victoria...... 9 Figure 3.2 The known and potential surface terrestrial GDEs of the Gippsland Basin, Victoria...... 10 Figure 4.1 Specialised sampling haul nets with weighted base (left photo) and other sample collection equipment (right photo)...... 13 Figure 4.2 Stygofauna equipment set up at SOBN groundwater bore...... 14 Figure 4.3 A stygofauna sample sieved and ready for collection...... 14 Figure 5.1 Location map of stygofauna regional baseline survey of the Gippsland Basin...... 16 Figure 5.2 Enchytraeidae from bore 80866 (Stygoecologia, 2019)...... 17 Figure 5.3 Bore 80866 location and surrounds...... 17 Figure 5.4 Recorded EC of each stygofauna sample grouped into their respective . Black outline indicates sample where stygofauna were collected...... 18 Figure 5.5 Recorded pH values of each stygofauna sample grouped into their respective aquifers. Black outline indicates sample where stygofauna were collected...... 19 Figure 6.1 Total depth of versus electrical conductivity (EC). The black outlines indicate the sample where stygofauna were collected...... 21 Figure A2.1 Tubificida Enchytraeidae from bore 80866 (Stygoecologia, 2019)...... 30 Figure A2.2 Bore 80866 location and surrounds...... 30

List of tables

Table 2.1. Significant aquifers of the Gippsland Basin (modified from GHD, 2012)...... 8 Table 4.1 Bore selection criteria for the stygofauna survey (WMIS=Water Management Information System)...... 12 Table 5.1 Stygofauna survey results...... 16 Table 5.2 Summary statistical descriptors of groundwater quality data categorised by aquifer...... 18 Summary

A regional baseline stygofauna survey across the Gippsland Basin was conducted as part of the Victorian Gas Program (VGP). Prior to this study there has been no basin-wide survey of stygofauna in the Gippsland Basin. This survey sampled 20 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 Gippsland 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 Gippsland Basin to determine current environmental conditions. This stygofauna survey provides a baseline dataset to assist in identifying subsurface groundwater dependent ecosystems (GDEs).

Stygofauna have adapted to survive the restricted conditions of aquifers; 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 sampling 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 five individual of one stygofauna taxon were identified from one groundwater bore sampled across the Gippsland Basin. This stygofauna family was collected within the upper unconfined Quaternary Aquifer. A repeat sample was collected after three months, however no stygofauna were collected at this time.

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 to 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.

Regional baseline stygofauna survey | Onshore Gippsland Basin v 1 Introduction

1.1 Victorian Gas Program

The Victorian Gas Program (VGP) is a program of scientific research and related activities to assess the potential for further discoveries of onshore conventional gas and offshore gas in Victoria, and whether the State’s current underground gas storage capacity could be expanded.

As part of the VGP, the Geological Survey of Victoria (GSV) is assessing the petroleum prospectivity and estimating the prospective gas resources of the Otway and Gippsland geological basins. The VGP is also looking at the potential risks, benefits and impacts associated with onshore conventional gas to inform future decisions made by Government.

In the VGP environmental studies program, GSV is conducting a baseline assessment of the groundwater and atmosphere in the Victorian Gippsland Basin to determine current environmental conditions. This stygofauna survey provides a baseline dataset to assist in identifying subsurface groundwater dependent ecosystems (GDEs).

The aim of this survey was to determine whether stygofauna are present in the aquifers of the Gippsland Basin and identify, if possible, any family distribution range. Recognising what type of stygofauna occur, and the extent, will enhance understanding of the ecological significance of the basin.

1.2 What are stygofauna?

Groundwater dependent ecosystems have been studied since the mid-20th century. They are classified according to their degree of groundwater dependence and whether they occur above or below ground (Serov et al., 2012). Subsurface obligate GDEs are below ground ecosystems that rely entirely on groundwater and have only recently been recognised to be as complex and dynamic as surface aquatic ecosystems (Gibert et al., 1994). This report focuses on the species collectively known as stygofauna that permanently inhabit these subsurface ecosystems.

In Australia, the high diversity of stygofauna has only been recognised in the last 20 years (Humphreys, 2006). This diversity largely reflects the history of the continent, as much of the present subsurface fauna species are descendants of once common surface species that migrated to a groundwater habitat to survive ancient climate change. Therefore, these subsurface species reflect key stages of our continent’s evolution (Hose et al., 2015a).

Stygofauna are aquatic animals that inhabit subsurface waters for their entire life cycle (EPA, 2013, 2016). Stygofauna are blind, colourless invertebrates with slow metabolisms and low reproductive rates (Coineau, 2000). They have adapted to survive the stable conditions of relatively constant temperature, no light, low nutrient (carbon) and low oxygen in aquifers (Humphreys, 2008). They are predominately found in shallow aquifers with sufficient pore spaces in areas of high recharge where nutrients and oxygen are most available (Hancock & Boulton, 2008). In Australia, stygofauna exist within alluvial, karstic, calcrete and certain fractured rock aquifers (Hancock et al., 2005; Humphreys, 2008). Several stygofauna species have been recorded in coal seam aquifers in Queensland (Hose et al., 2015b); however, these coal seams were shallow and flushed with fresh water (Serov 2019, pers. comm., 6 Sept).

Due to their restricted environmental tolerances, stygofauna population and diversity generally decrease with both depth and distance along groundwater flow paths (Datry et al., 2005). These subsurface restrictions allow for a high degree of genetic isolation (endemism) to arise and many Short-Range Endemic (SRE) stygofauna species have been recorded in Australia, such as the stygofaunal beetles and amphipods of the Yilgarn (Cooper et al., 2002, 2007).

Most stygofauna are highly sensitive to water quality changes and environmental conditions of the groundwater they inhabit, and therefore are potentially useful indicators of groundwater health (Tomlinson et al., 2007). Stygofaunal activity such as burrowing and feeding assist in maintaining aquifer flow paths; therefore, an increase in microbial activities may help to maintain water quality (Boulton et al., 2008). Greater knowledge of stygofauna and their ecosystems will continue to improve understanding of the aridification of Australia. (EPA, 2012).

Regional baseline stygofauna survey | Onshore Gippsland Basin 1 1.3 Australian stygofauna knowledge

Australian stygofauna are dominated by crustacean taxa, including Amphipoda, Isopoda, Copepoda, Ostracoda and Syncarida (Figure 1.1). Worm taxa (such as Turbellaria, Nematoda, and Polychaeta) and insects such as the diving beetle (Dytiscidae) and the water mite (Acarina) also exist within the groundwater of Australia (Humphreys, 2008; Hose et al., 2015b). In 2008, it was estimated that at least 750 stygofauna species exist across Australia (Humphreys, 2008); however, Guzik et al. (2010) defined 770 species across the western part of Australia.

In Western Australia, stygofauna occur across many regions with high diversity occurring in the Pilbara and Yilgarn regions (Eberhard et al., 2005; Humphreys, 2006, 2008) and at Cape Range and Barrow Island (Humphreys, 2000). The high species richness and significant levels of endemism identified in Western Australia has been recognised as globally significant (EPA, 2016).

The only large regional survey of stygofauna in Australia was conducted across the Pilbara as part of the Pilbara Biological survey between 2002 and 2007 and recorded 350 species (Eberhard et al., 2005, 2009). It was estimated that between 500 and 550 stygofauna species exist within the Pilbara (Eberhard et al., 2009). Since the 1990s, numerous site- specific stygofauna surveys associated with mineral resource development have been conducted. These surveys identified a particularly rich diversity of crustaceans from the orders Ostracoda and Copepoda (Eberhard et al., 2009). Approximately 70% of stygofauna in the Pilbara are SREs (Eberhard et al., 2009).

Within the Yilgarn region approximately 250 species are recorded, predominantly a range of diving beetles from the family Dytiscidae, occur in isolated karstic calcrete aquifers (Humphreys, 2008).

The significance of stygofauna at Cape Range and Barrow Island has been recognised globally for two known species of groundwater-adapted vertebrates. The blind eel and the cave gudgeon fish occur within a karstic environment (Hose et al., 2015b; EPA, 2016).

In 2002 the Western Australian State Government introduced laws requiring subsurface fauna to be assessed when a development proposal undertakes an environmental impact assessment (EPA, 2012, 2016).

Knowledge of the stygofauna diversity throughout eastern Australia developed largely in the last decade and has focused around locations of groundwater resource development in the Murray–Darling Basin and the mining industry within the Bowen Basin (Glanville et al., 2016). Significant regions in northern and western Queensland have not been sampled for stygofauna (Schulz et al., 2013).

There are approximately 24 known stygofauna species in Queensland, with a rich diversity in both Oligochaeta and Syncarida (Glanville et al., 2016). From mid-2000 the Queensland Government required stygofauna sampling to be undertaken as part of an environmental impact assessment for relevant mining, petroleum or gas developments under the Environmental Protection Act 1994 (Qld) (Granville et al., 2016).

Stygofauna surveys of New South Wales (NSW) have been focused in the Sydney, Hunter Valley and Gunnedah basins and 33 species have been confirmed in cave and systems (Thurgate et al., 2001).

Numerous stygofauna surveys within the alluvial aquifers of NSW identified a rich diversity of stygofauna (Hancock & Boulton, 2008; Hose & Lategan, 2012; Asmyhr et al., 2014a, 2014b; Korbel, 2013, amongst others). Several surveys associated with mine developments expanded the known distribution ranges of several taxa (e.g. Eco Logical, 2013a, 2013b; Stygoecologia, 2006, 2014, 2015a, 2015b, 2015c, 2016a, 2016b). New species of crustaceans have also recently been discovered across the Snowy Mountain region of NSW (Chandra & Serov, 2019).

The South Australian alluvial aquifers of the Flinders Ranges and Eyre Peninsula unearthed diverse stygofauna including a Dytiscidae diving beetle (Leys et al., 2010) and Syncarida (Abrams et al., 2013). From a research project initiated in 2007, over 100 species have been identified to date. These stygofauna species are predominantly from the Mount Lofty Ranges and Flinders Ranges (Goonan et al., 2015).

Regional baseline stygofauna survey | Onshore Gippsland Basin 2 A preliminary survey of the calcrete aquifers of the Ngalia Basin in the Northern Territory found similar species to the calcretes of the Yilgarn region, including the Dytiscidae diving beetle (Balke et al., 2004). A baseline pilot study of the Beetaloo sub-Basin is also currently underway (CSIRO, 2019). Crustacean species dominate the extensive stygofauna found in the karst regions of Tasmania, but there is little knowledge of stygofauna from any non- karstic aquifers, besides a new species of Syncarida and Amphipoda found in a spring near Devonport (Eberhard, 2004) and four new species of Syncarida from alluvial and fractured rock aquifers in central and northern Tasmania (Serov, 2014).

In Victoria, the presence of non-karstic stygofauna is virtually unknown. A single Amphipoda species from Thorpdale, Gippsland (Williams & Barnard, 1988) has been identified along with a Syncarida and Isopoda species found in the Lake Condah area, near Heywood (Department of the Environment, 2011). A single species of the Syncarida family Stygocarididae from the hyporheic zone of the Tambo River, north of Orbost in Gippsland, has been identified (Schminke, 1980; Serov, 2014). As part of the VGP environmental studies, a regional stygofauna survey of the Otway Basin in south west Victoria identified five stygofauna taxa (Bold et al., 2020).

Figure 1.1 Stygofauna specimen (Amphipoda Melitidae) collected in SW Victoria (Stygoecologia, 2019).

Regional baseline stygofauna survey | Onshore Gippsland Basin 3 2 Study area

The baseline stygofauna survey was undertaken in the West and East Gippsland Catchment Management Authority (CMA) regions of the Gippsland Basin in south-east Victoria (referred to herein as the survey area).

This stygofauna survey was focused along the southern coastal portion of the environmental study area, which covers an area of approximately 6500 km2. The stygofauna survey is focused largely within the onshore conventional gas study area (Figure 2.1) between Sandy Point and Bairnsdale. The survey was completed in the first half of 2019.

Figure 2.1 Study area for the baseline stygofauna survey, showing the extent of the VGP environmental study area, the VGP onshore conventional gas program study area and the location of the east and west Gippsland CMAs.

2.1 Climate

The climate in the survey area is temperate. Rainfall is generally winter dominant, but considerable variation does occur, influenced by topography and proximity to the coast. The majority of this region has an average annual rainfall between 600 and 1000 mm, with the exception of the Strzelecki Ranges and Great Dividing Range, where the average annual rainfall is more than 1000 mm. Significant rain shadows occur in the river valleys and on the plains of the Gippsland Basin, such as at Sale where the average annual rainfall is less than 600 mm.

Temperature also varies with topography and proximity to coast. The average annual maximum temperatures in the Latrobe valley and Bairnsdale are 20.1 and 20.5°C respectively (BOM, 2019a). Temperatures along the coast are generally milder due to the moderating effects of the sea. In the highlands at Erica, the average annual maximum temperature observed is 16.7°C and in winter average minimum temperatures in the highland areas can be as low as –4 °C, leading to snowfalls between June and October (BOM, 2019a).

Regional baseline stygofauna survey | Onshore Gippsland Basin 4 2.2 Land use

The primary land use in west Gippsland is privately owned for agricultural purposes (primarily dryland pasture and grazing modified pastures) making up 54% of land use, with minor areas of irrigated pasture existing near Maffra (Agriculture Victoria, 2019). In east Gippsland however, land use is primarily public land. Approximately 87% of east Gippsland is made up of conservation reserves (state forests and national parks) and forestry areas (Figure 2.2).

Figure 2.2 Victorian Gas Program Gippsland Basin land use map.

2.3 Geology

The Gippsland Basin is an east-west striking rift basin that developed during the Early Cretaceous and consists of a 10 km thick sequence of sedimentary and volcanic rocks deposited on older Palaeozoic basement.

The Gippsland Basin covers an area of approximately 56 000 km2, extending from Warragul in the west through to Lakes Entrance in the east, with three-quarters of the basin passing offshore beneath Bass Strait (SKM & GHD, 2009). Basin formation occurred by the continental rifting of Australia from Antarctica beginning in the Late Jurassic with 3000 m of sandstones, shales, conglomerates and thin coal seams deposited. Sedimentation ceased onshore during the Middle Cretaceous when uplift of the south Gippsland highlands commenced. Subsidence and major structural zoning developed during the Tertiary with further deposition of non-marine and marine sediments along with periods of thick volcanic rocks (SKM & GHD, 2009). Several studies have previously described the geology and hydrogeology in detail (Holgate, 2003; Leonard, 2003; Schaeffer, 2008; SRW, 2012; Hofmann & Cartwright, 2013).

The surface geology of the study area is shown in Figure 2.3. Outcropping Cretaceous sedimentary bedrock of the Strzelecki Group and Strzelecki Ranges occur in the uplands in the south-west, while Ordovician to Devonian sedimentary, metamorphic and igneous Palaeozoic basement outcrops in the north and north-east of the study area. A sequence of Upper Cretaceous to Quaternary marine and terrestrial siliclastic sediments, volcanics, coal measures and carbonate sediments overlie the basement rock which extend more than 80 km offshore and comprise the major aquifers of the Gippsland Basin (Beverly et al., 2015).

Regional baseline stygofauna survey | Onshore Gippsland Basin 5 Figure 2.3 Surface geology of the Gippsland Basin, Victoria.

2.3.1 Hydrostratigraphy The Victorian Aquifer Framework (VAF) (SKM & GHD, 2009; GHD, 2012) simplifies the significant aquifers and aquitard units for Victoria into 14 major units. The significant units of the Gippsland Basin are presented in Table 2.1 and the surface coverage in Figure 2.4. The VAF nomenclature is used in this report to describe the aquifers of the Gippsland Basin.

The surficial sediments of the Quaternary aquifer (QA) and Upper Tertiary/Quaternary Aquifer (UTQA) are mostly thin and extend across the plains of the Gippsland Basin (Beverly et al., 2015). The sand and gravel beds of the QA are 5 to 15 m thick and form unconfined aquifers. The Haunted Hill Formation of the UTQA is composed of sands, gravels and clays and conformably overlies the older units across most of the Gippsland Basin. The limited lateral extent of many of these units and usually thin vertical extent means that aquifer yields are variable and therefore are less utilised than the deeper aquifers due to their lower yield potential (Beverly et al., 2015).

The Upper Tertiary Aquifer – Fluvial (UTAF) extends across most the west of the basin and consists of a sequence of sand, silts and clays largely semi confined beneath an upper clay unit (Leonard, 2003) and provides water for irrigation and town supply, particularly around Sale (Beverley et al., 2015).

The Upper Mid Tertiary Aquifer (UMTA) is dominated by the sands and gravel of the Balook Formation, Morwell Formation and Alberton Formation and is largely confined. Permeable parts of the Lakes Entrance Formation and Gippsland Limestone of the Seaspray Group also form parts of this aquifer (Beverly et al., 2015). The Lakes Entrance Formation is mostly considered an aquitard in the onshore part of the basin around Lake Wellington and the Seaspray depression, and acts as a seal for the offshore Latrobe Group hydrocarbon reservoirs (Beverly et al., 2015).

The Lower Tertiary Aquifer (LTA) overlies the Strzelecki Group and is the most productive aquifer of the basin. It largely consists of the Latrobe Group, a 500 m thick sedimentary sequence of sandstones, siltstones and coal seams in the centre of the basin and is confined by the overlying mudstone. In the west of the basin the Childers Formation and the Thorpdale Volcanics (Lower Tertiary Basalt, LTB) overly the Strzelecki Group.

Regional baseline stygofauna survey | Onshore Gippsland Basin 6 Figure 2.4 Outcropping units of the VAF of the Gippsland Basin, Victoria.

Regional baseline stygofauna survey | Onshore Gippsland Basin 7 Table 2.1. Significant aquifers of the Gippsland Basin (modified from GHD, 2012)

VAF Hydro-stratigraphic Groundwater Formation Lithologies Code Unit management units Unconsolidated quartz/ Various alluvial deposits – calcareous sand and silt with floodplain, coastal lagoon, minor clay and marl river terrace Orbost, Wa De Lock, QA Quaternary Aquifer Silica rich cross bedded Curlip Gravel Tarwin, Wy Yung, Denison calcarenite Partly lithified quartz sand with Various aeolian deposits lithic clasts Upper Tertiary/ Haunted Hill Formation UTQA Sand, gravel and mottled clay Quaternary Aquifer Eagle Point Sand member Clay, gravel and fine-course sand Upper Tertiary/ Boisdale Formation (Nuntin Sandy, shelly marl, calcareous UTQD Quaternary Aquitard Clay) sandstone Shelly glauconitic marl, limestone and fine sandstone Medium-course quartzrose UTAF Upper Tertiary Aquifer Boisdale Formation (Wurruk sand with minor coal and Sale, Giffard – Fluvial Sand) carbonaceous silt and sand Hazelwood Formation Upper Tertiary UTD Yallourn Formation Aquitard Jemmy’s Point Formation Latrobe Valley Group: Yarragon Formation, Morwell Fine – medium sand with clay Upper Mid-Tertiary aquifers Latrobe Valley and Lake UMTA and silt Aquifer Wellington depressions Balook formation Shelly karstified limestone Alberton Formation Seaspray Group Lakes Entrance Formation Upper Mid- Tertiary UMTD Tambo River Formation Calcareous clay-silt Aquitard Gippsland Limestone Giffard Sandstone member Latrobe Valley Group: M2C Glauconitic calcarenite and Lower Mid- Tertiary LMTA aquifer limestone with minor quartz Aquifer Seaspray Sands sand Latrobe Group

Traralgon Group Yarram Formation Quartz sand with variable silt, LTA Lower Tertiary Aquifer Honeysuckle Gravels clay, gravel and carbonaceous Moe, Stratford, Yarram Childers Formation content

Burong Formation M2/M2C aquifer (when basal aquifer) Thorpdale Volcanics LTB Lower Tertiary Basalt Leongatha Carrajung Volcanics Strzelecki Group Volcanoclastic sandstone, Cretaceous and BSE siltstone, mudstone with shale Palaeozoic Bedrock All Palaeozoic Basement Rocks and coal

Regional baseline stygofauna survey | Onshore Gippsland Basin 8 3 Groundwater dependent ecosystems

Groundwater dependent ecosystems can be defined as ecosystems which have their species composition and natural ecological processes wholly or partially determined by groundwater (ARMCANZ & ANZECC,1996).

Groundwater dependent ecosystems in Australia were first recognised by Hatton and Evans (1998) and include both surface and subsurface ecosystems. The classification scheme by Serov et al. (2012) defines GDEs by their degree of groundwater dependency and whether they occur above or below ground.

This classification scheme is divided into seven ecosystem types. Surface GDEs including groundwater dependant aquatic ecosystems are wetlands, baseflow streams, estuaries and near shore marine ecosystems, and groundwater dependent terrestrial ecosystems. Subsurface GDEs include karst and cave systems, subsurface phreatic aquifer ecosystems, and baseflow stream subsurface water ecosystems (Serov et al., 2012).

The known GDEs of the Gippsland Basin (BOM, 2019b) are all surface GDEs and are outlined in Figures 3.1 and 3.2. Known aquatic surface GDEs have been identified along the Avon River north of Sale and scattered throughout the highland peatlands. All known terrestrial GDEs are associated with the highland peatlands. Potential aquatic and terrestrial surface GDEs identified through various studies such as Dresel et al. (2010) are also displayed. Currently there are no known subsurface GDEs across Victoria.

This report focuses on identifying the presence and distribution of stygofauna within the aquifers of the Gippsland Basin and therefore may assist in classifying potential subsurface phreatic aquifer ecosystems.

Figure 3.1 The known and potential surface aquatic GDEs of the Gippsland Basin, Victoria.

Regional baseline stygofauna survey | Onshore Gippsland Basin 9 Figure 3.2 The known and potential surface terrestrial GDEs of the Gippsland Basin, Victoria.

3.1 Stygofauna habitat

Stygofauna predominantly occur within aquifers that have a pore or void space greater than a millimetre, allowing organisms to move freely within the porous rock (Humphreys, 2006; Serov et al., 2012). Alluvial, karstic and fractured rock aquifers are considered the most inhabitable subsurface phreatic ecosystems for stygofauna.

Subsurface phreatic aquifer ecosystems can range from a few square kilometres to thousands of square kilometres in size and consist of invertebrate communities that have highly specialised morphology and physiology (Serov et al., 2012). Communities within this classification are often highly endemic and from an ancient lineage (Serov, 2002).

Although stygofauna have adapted to low energy and low oxygen groundwater environments, they are most abundant in shallow aquifers in areas of regular recharge where nutrients and oxygen are available (Hancock & Boulton, 2008). Carbon filtering down from the surface and metabolised by bacteria and fungi (biofilm) form the basis of the stygofauna food web (Hose & Lategan, 2012). Stygofauna population and diversity abundance therefore generally decrease with depth (Datry et al., 2005).

Stygofauna can be found in fresh to saline water; however, they are most common in fresh to brackish water where electrical conductivity (EC) is less than 5000 µs/cm (Hancock & Boulton, 2008; Hose et al., 2015b). The presence of stygofauna at more than 100 m below ground level or where dissolved oxygen (O2) is less than 0.3 mg/L is rare (Hose et al., 2015b).

3.2 Stygofauna ecological requirements

Stygofauna are ecologically dependant on aquifer conditions and are adapted to the stability of the groundwater environment. The three requirements that are essential for stygofauna communities to exist are:

Stable water quality – Stygofauna can tolerate the natural fluctuations in water parameters such as seasonal water levels, EC and temperature. However, variations outside of the natural range of aquifer water quality, such as a pollution plume or dropping water levels from rapid drawdown, may have significant impacts on any stygofauna composition and biodiversity (Stygoecologia, 2019).

Regional baseline stygofauna survey | Onshore Gippsland Basin 10 Surface connectivity – Stygofauna communities require a connection to the surface environment to provide oxygen and organic material. If this connection is disrupted, stygofauna communities are likely to decline over time (Stygoecologia, 2019).

Subterranean connectivity – Stygofauna have restricted dispersal mechanisms. Communities can only migrate through the aquifer by burrowing and swimming, and therefore movement is restricted by an aquifer’s natural hydrological barriers. As aquifer porosity is generally not consistent, these barriers naturally promote endemism. Rapid changes in water level and quality can create barriers that may prevent re-colonisation of a habitat that has been disturbed (Stygoecologia, 2019).

Many species of stygofauna are restricted to small geographical areas, particularly in non- alluvial aquifers. Examples include some of the limestone of NSW (Thurgate et al., 2001), and calcrete aquifers in Western Australia, where one or more species are known only from a single aquifer, or part of an aquifer (Humphreys, 2001). Consequently, any process that threatens the aquifer potentially threatens an entire species. There is also a high degree of endemism known in alluvial aquifers, even between adjacent systems (Hancock & Boulton, 2008).

3.3 Factors impacting stygofauna

Stygofauna are sensitive to environmental changes and therefore are threatened by any activity that alters the quality or quantity of groundwater, disrupts connectivity between the surface and the aquifer, or reduces the pore space of an aquifer (EPA, 2007; Hose et al., 2015b).

Industrial and agricultural operations have the potential to cause some degree of change to a GDE. An activity’s potential impact on groundwater will depend on the scale and duration of the operations as well as techniques used (Serov et al., 2012). Activities may include:

• urban water supply development (groundwater pumping, surface water collection) • agricultural works (Irrigation, fertilisation) • below watertable drilling/mining (dewatering) • tailings production and storage • excavation works • dust suppression • seepage • waste rock storage • backfilling and site rehabilitation work • water diversions and surface sealing • water storage • hazardous goods storage. The direct effects on a GDE from these activities include changes in:

• water quantity (water levels and pressures) • water quality (salinity, chemistry, contamination) • groundwater interactions between subsurface systems and between groundwater and surface systems.

Dropping water levels and aquifer depressurisation from works intersecting aquifers may lead to a loss in access to groundwater, reductions in surface water flow or changes in groundwater quality. Declining watertables result in the substrate becoming unsaturated, which in turn reduces stygofauna habitats (Serov et al., 2012). The effects of a change in water pressure have not been studied; however, is likely to alter the suitability of habitats as well (Hose et al., 2015b).

Changes in groundwater quality may occur when groundwater levels and flow systems are altered allowing inflow of poorer quality water. Groundwater quality may also be contaminated by the seepage of acids and heavy metals from overburden or infiltration of produced waters that are often saline (Hose et al., 2015b).

Climate change is an additional factor that should also be considered. Changes in a GDE may be a result of cumulative impacts from multiple stressors, and therefore understanding the effects of industrial development should not be considered in isolation (Hose at el., 2015b).

Regional baseline stygofauna survey | Onshore Gippsland Basin 11 4 Methods

The regional stygofauna survey was conducted across the Gippsland Basin between Sandy point and Bairnsdale. The survey was completed between February 2019 and June 2019. Stygofauna sampling was collected using two techniques and the groundwater quality of each bore was also measured at this time.

4.1 Survey design

The survey was designed using the Western Australian EPA guidelines (EPA, 2003, 2007), Hancock & Boulton (2008) and Serov (2017 pers. comm., 21st July). These guidelines provide the most comprehensive method and guidance for Australian conditions. A total of 20 bores were selected from the Victorian Government SOBN using several criteria (Table 4.1) to cover as broad a geographic distribution as possible across the survey area. Both active and inactive monitoring bores were included.

Numerous bores that were initially selected were unable to be sampled due to availability and condition. Poor conditions encountered included dry bores and blockages above the screen from either silt or structural collapse. Many bores had been decommissioned and removed. In locations where this occurred, other suitable bores were selected.

Table 4.1 Bore selection criteria for the stygofauna survey (WMIS=Water Management Information System). Attribute Favourable criteria Bore depth (m) Less than 100 m where possible VAF Hydrogeological Unit Favourable shallow aquifer units (higher porosity, increased oxygen) Geographic location Regional coverage across the survey area EC Preference less than 5000 µS/cm (available historic WMIS data) pH Preference between pH 6.5 and pH 8.5 (available historic WMIS data)

4.2 Environmental attributes

Prior to sampling at each bore, all equipment was inspected to ensure it was clean and in good condition. Site specific details including the bore ID number, bore diameter (mm), sample date and sample collector’s name were recorded on a separate field record sheet (Appendix A1) and a site photo was taken.

The total bore and standing water level depths (m) were measured using a Solinst Dip Meter and recorded on the same field record sheet. Extra sample observations such as sediment grain size, colour and odour (i.e. hydrogen sulphide) were also collected where necessary.

4.2.1 Groundwater quality Water quality data was sourced by two methods. This was dependent on whether the bore was due to be groundwater sampled (as part of the VGP groundwater baseline characterisation) after stygofauna sampling occurred. If so, parameters from the initial 10 to 30 L of groundwater pumping was recorded. Parameters include temperature (T), electrical conductivity (EC), pH, dissolved oxygen (DO) and oxidation-reduction potential (ORP) using a calibrated water quality TPS 90-FLMV Multi-meter. For all other bores that were not groundwater sampled, EC and pH were recorded in situ with a stainless-steel bailer, using a calibrated water quality TPS Aqua CP/A Multi-meter.

Care was taken to minimise aeration of the water by inserting probes directly into the bailer. Lowering the probes into the bores was not considered an appropriate method, as the depth to water levels varied considerably and stratification was likely. As a result, it was not possible for dissolved oxygen to be measured accurately.

Regional baseline stygofauna survey | Onshore Gippsland Basin 12 4.3 Equipment

The following equipment were used to complete the stygofauna survey (Figures 4.1 and 4.2):

• specialised sampling nets 300 mm long with 150 µm mesh size, in four diameters: 45 mm, 65 mm, 90 mm and 145 mm with the net connected to a galvanised weighted collection base • stainless steel bailer (1 m, 45 mm) with ball valve • 300 m stainless steel 2 mm cable installed onto hand reel, marked every 10 m • 150 µm mesh, 200 mm stainless steel sieve • 1 L spray bottles • 500 ml HPDE sample bottles • 10 L bucket • funnel • 100% lab grade ethanol • tap water • pencils and paper • cable ties • ‘Decon 90’ decontamination solution • field record sheets.

Figure 4.1 Specialised sampling haul nets with weighted base (left photo) and other sample collection equipment (right photo).

4.4 Stygofauna sampling

Two sampling methods were combined to complete the stygofauna survey: the netting and bailer methods. The combination of methods was used to maximise the potential for sample collection for a baseline taxonomic compositional survey (Serov 2017, pers. comm., 21st July). The specialised sampling net was designed in accordance with Western Australian EPA guidelines (EPA, 2007) and Serov (2017, pers. comm., 21st July). The net was used to collect stygofauna residing in the water column and attached to the sides of the bore, while the groundwater bailer was used to collect any stygofauna residing within the sediment at the bottom of the bore.

These methods assume that the water residing within a bore is representative of the faunal communities and chemical properties of water in the surrounding groundwater system. Hahn & Matzke (2005) found this assumption appropriate when discussing water chemistry and stygofauna taxonomic composition; however, it may not be applicable when assessing the relative abundance of different stygofauna taxa, as abundances are higher within the water column of a bore when compared to aquifer water (Korbel et al., 2017).

A stainless-steel bailer was lowered to the base of the bore using a stainless-steel cable on a hand reel (Figure 4.2). The bailer was raised and lowered off the bottom of the bore three times to agitate the sediment, before slowly raising the bailer fully to the top. The content of the bailer was collected in a bucket and the bailer was rinsed into the same bucket using a spray bottle of tap water. This process was completed three times. The specialised sampling net was then

Regional baseline stygofauna survey | Onshore Gippsland Basin 13 lowered to the bottom of the bore, raised up and down to agitate the sediment and retrieved slowly in one smooth motion (where possible). The content of the net and weighted base was collected into the same bucket. Net and base were rinsed again with tap water, and the process was completed three times. The combined collected sample from the bucket was then poured through the sieve, so only sediment remained (Figure 4.3) and the same spray bottle of tap water was used to gather the entire contents to one edge of the sieve.

Using a spray bottle of 100% ethanol and a funnel, the contents of the sieve were then collected into a sample bottle. Extra ethanol was added to the sample bottle to fully preserve the sample. Bore ID, date and sampler name were recorded on paper and inserted in the bottle. The sample bottle was also labelled with the sample details. All equipment including the bailer, net and sieve were rinsed with a decontamination solution (Decon 90) after sampling.

Figure 4.2 Stygofauna equipment set up at SOBN groundwater bore.

Figure 4.3 A stygofauna sample sieved and ready for collection.

4.5 Laboratory analysis

Samples were processed by Dr Peter Serov from Stygoecologia. Each sample was sorted under a stereomicroscope and stored in 100% ethanol. All specimens were identified to family level identification, under a dissecting microscope using a combination of current taxonomic keys and the taxonomic identification series from the Murray Darling Freshwater Research Centre (Serov, 2002).

Regional baseline stygofauna survey | Onshore Gippsland Basin 14 4.6 Limitations

Regional baseline stygofauna surveys, such as this one, have limitations because they consist of a single ‘grab’ sample that is reliant on several physical factors and environmental conditions.

To effectively collect all possible biota in a bore, appropriate sampling equipment and a combination of techniques are required (Serov, 2017 pers. comms. 21st July; EPA, 2007) as has been used in this study (outlined above). However, stygofauna may still not be collected, even if they are present, due to several limitations (EPA, 2012). Low population numbers within the bore at the time of sampling and even the size of individual organisms can be contributing factors to unsuccessful collection.

Seasonal movement of stygofauna should also be considered when designing a survey (EPA, 2012). As this was a regional study, only a single-phase sampling survey was conducted. The sampling was completed over a five-month period as part of a broader environmental study of current groundwater conditions. The time constraint on delivering this project did not allow for a full multi-phase survey to assess potential seasonal variations in stygofauna population abundance.

Physical limitations include the location and condition of the bores sampled. When sampling aquifers, surveys are usually constrained to groundwater bores that have been established for longer than six months. A significant portion the SOBN bores are more than 40-years old, and many that were visited during this study were in poor condition. Some bore sites originally selected for sampling were unable to be used due to blockages. Several other bores included in the survey had rusted casing flakes included in the sample, indicating possible screen obstruction and therefore decreasing the likelihood of clear access to the aquifer for stygofauna. A number of SOBN bores in poor condition are currently undergoing a refurbishment program. The process of refurbishment involves purging and is likely to disrupt any established stygofauna populations and lower the likelihood of detection if sampling was conducted recently after refurbishment.

This study focuses on identifying the presence and diversity of stygofauna within the survey area. This assessment is part of a broader environmental study of current groundwater conditions and therefore sampling also had a focus on geographic regions relating to conventional gas potential.

Regional baseline stygofauna survey | Onshore Gippsland Basin 15 5 Results

5.1 Stygofauna results

The regional survey sampled 20 SOBN bores across the Gippsland Basin and recorded one bore containing a total of one stygofauna invertebrate taxon. The taxon list is presented in Table 5.1. The location of all bores sampled and where stygofauna were identified are displayed in Figure 5.1. The stygofauna in bore 80866 occurs within the QA of the survey area.

A total number of five animals were identified in bore 80866, all belonging to the worm taxa Tubificida Enchytraeidae. The size of worms ranged up to 5.0 mm, however no animals were observed during field sample collection. The depth of the water level at bore 80866 was 4.8 m and the total depth of the bore was recorded as 10 m.

A repeat sample was attempted approximately three-months later, however only two hauls were collected because the bailer became snagged at the bottom of the bore. No stygofauna were identified in the repeat sample.

Figures 5.2 and 5.3 display the stygofauna taxon identified and the respective bore location of bore 80866.

Table 5.1 Stygofauna survey results.

Repeat Size Abundance Bore ID Order Family Date sampled Date (mm) (# of animals) Sampled 80866 Tubificida Enchytraeidae 5.0 5 17/4/2019 1/7/2019

Figure 5.1 Location map of stygofauna regional baseline survey of the Gippsland Basin.

Regional baseline stygofauna survey | Onshore Gippsland Basin 16 Figure 5.2 Tubificida Enchytraeidae from bore 80866 (Stygoecologia, 2019).

Figure 5.3 Bore 80866 location and surrounds.

5.2 Groundwater quality

The full suite of groundwater quality parameters outlined in Section 4.2.1 were measured at seven of the 20 bores where pumping occurred as part of the VGP groundwater sampling program (Iverach et al., 2020). The depth to water level (DWL), EC and pH were measured for the remaining 13 bores. Water quality data for all bores is detailed in Appendix A3.

Summary statistics for these three parameters are presented in Table 5.2. The average pH across the QA, UTQA, UTAF and UMTA was near neutral. The UTAF and UMTA, on average were slightly more saline than the QA, however the UTQA had a much higher salinity to the other aquifers, as the EC of this aquifer ranged significantly across the survey area with an outlier of 35 700 µS/cm recorded.

Regional baseline stygofauna survey | Onshore Gippsland Basin 17 Table 5.2 Summary statistical descriptors of groundwater quality data categorised by aquifer.

No. of bores EC DWL Total depth Aquifer pH sampled (µS/cm) (m) (m) Range Mean Range Mean Range Mean Range Mean 6.76 to QA 2 7.76 769 to 1008 774 2.95 to 4.76 3.87 5.5 to 10.0 7.8 7.53 5.14 to 1159 to UTQA 5 7.58 9450 1.70 to 9.00 3.86 15 to 30.0 21.8 10.24 35700 UTQD 1 8.3 570 2.3 79.8 6.14 to 50.8 to UTAF 9 7.61 251 to 5080 1800 1.35 to 31.50 16.52 78.0 10.10 99.0 UTD 1 6.59 1834 15.67 25 7.30 to 23.0 to UMTA 2 7.63 1115 to 1860 1488 5.54 to 8.37 6.96 38.0 7.95 53.0 5.2.1 Depth to water level All water levels were recorded from the top of casing (TOC) at the beginning of sampling. Two bores had a water level partially within the filter screen interval at the time of sampling. The remaining 18 bores all recorded water levels above the screen interval. It should be noted that three of the 20 bores did not have screen data available.

5.2.2 Electrical conductivity (EC) The EC for all samples collected in the Gippsland Basin were classified into their respective hydrogeological units and presented in Figure 5.4. EC ranged significantly between the units, from 251 µS/cm to 35 700 µS/cm.

Figure 5.4 illustrates that the UTQA recorded the largest range of EC, from 1159 to 35 700 µS/ cm. The UTAF aquifer also recorded a broad range of EC between 251 and 5080 µS/cm. Nine bores across four units recorded an EC between 1000 and 2000 µS/cm.

The stygofauna identified from the one bore occurred where the EC of the groundwater was less than 1000 µS/cm. However, six of the 20 (30%) groundwater samples measured concurrent with the stygofauna sampling recorded an EC of less than 1000 µS/cm, indicating that low EC is one of several factors contributing to the habitat suitability of stygofauna, which is consistent with previous studies that have recorded stygofauna in fresh to brackish groundwater.

Figure 5.4 Recorded EC of each stygofauna sample grouped into their respective aquifers. Black outline indicates sample where stygofauna were collected.

Regional baseline stygofauna survey | Onshore Gippsland Basin 18 5.2.3 pH The pH data collected in the Gippsland Basin and classified into their respective aquifers are presented in Figure 5.5. pH ranged significantly between the units from 5.14 to 10.24.

Figure 5.5 illustrates that most bores sampled (70%), recorded a pH between 6 and 8 within the QA, UTQA, UTAF, UTD and UMTA. Both the UTQA and UTAF recorded the largest pH ranges as a result of some outliers.

Stygofauna taxon were identified where the pH of the groundwater was 6.76, however three other samples recorded a pH within 5% of this value, indicating that pH is another factor contributing to the habitat suitability for stygofauna.

Figure 5.5 Recorded pH values of each stygofauna sample grouped into their respective aquifers. Black outline indicates sample where stygofauna were collected.

Regional baseline stygofauna survey | Onshore Gippsland Basin 19 6 Discussion

The regional stygofauna survey provides a baseline measure of stygofauna across the upper aquifers of the Gippsland Basin. This survey recorded stygofauna in one of the 20 bores sampled with one worm taxon identified in this bore. This suggests a low biodiversity of stygofauna within the unconfined aquifers of the Gippsland Basin. A repeat sample was collected where stygofauna were initially identified. The absence of stygofauna in this repeat sample indicates that populations may vary seasonally.

To achieve a better understanding of the diversity and distribution of stygofauna along with any seasonal fluctuations, a multi-season sampling program could be conducted (EPA, 2007; Hancock & Boulton, 2009). A monitoring survey across seasons would provide a more confident measure of regional distribution, natural seasonal fluctuation in population abundances, and any possible local species endemism of stygofauna.

The stygofauna identified occurred in the unconfined QA of the Gippsland Basin. The same bore was re-sampled approximately three months after the first sample collection in order to demonstrate seasonal repeatability. Stygofauna were not identified in the repeat sample, suggesting that seasonal variation of population abundance may occur. However, the repeat sample was collected by the bailer method only, as equipment became stuck in the bore preventing collection of a net sample. The absence of stygofauna therefore may also be a result of the incomplete sampling method.

The geology of the QA outlined in Section 2.3.1 provides a potentially suitable habitat for stygofauna. The alluvial/aeolian sediments of the QA generally have higher porosity, are unconsolidated and have direct connectivity with the surface. Bore 80866 is located specifically within an alluvial floodplain environment of unconsolidated sand, silt and gravel associated with the Mitchell River, east of Bairnsdale. There is significant interaction between the river water and groundwater within this floodplain with groundwater recharge occurring from surface water discharge of the river (SKM, 2012).

Vegetation located close to bore 80866 may also be creating larger interstitial space, increasing hydraulic conductivity, and may have provided a more reliable source of nutrients for stygofauna (Hancock & Boulton, 2008; Hose et al., 2015b).

The water quality found to support stygofauna (EC <1000 µS/cm and pH 6.76) is consistent with the suitable groundwater conditions outlined in Western Australian EPA guideline 54a (EPA, 2007) for stygofauna. Only one other bore was sampled within this aquifer, which also recorded similar low salinity and neutral pH measurements. However, this bore was within an aeolian coastal dune deposit and would have different recharge conditions to the alluvial environment where stygofauna were collected.

The depth of the aquifer also appears to be a factor in supporting stygofauna, although no correlation could be made from one result. Figure 6.1 demonstrates there is no correlation between depth and EC, as all samples within the UTAF are deeper than most of the other samples, but display a broad range in EC.

The low number of bores (one of 20) from which stygofauna were collected does not suggest the groundwater environment of the Gippsland Basin is of poorer ecological health. Rather, a combination of the fine-grained nature of sediments and the limited selection of suitable groundwater bores available to sample is the most likely limiting factor for the presence of stygofauna. Variability in porosity and water quality within the unconfined aquifers also suggests the possibility of taxa exhibiting a degree of SRE (Stygoecologia, 2019) as genetic isolation has likely been promoted through this variability.

Regional baseline stygofauna survey | Onshore Gippsland Basin 20 Figure 6.1 Total depth of aquifer versus electrical conductivity (EC). The black outlines indicate the sample where stygofauna were collected.

6.1 Environmental significance

The stygofauna composition of the onshore Gippsland Basin included one order of worm. While taxa were only identified to family level, the limited knowledge of stygofauna communities within Victoria suggests there may be some new species with restricted distributions because of the high levels of endemism already observed throughout Australia (EPA, 2016; Humphreys, 2006). The stygofauna identified is described below.

Oligochaeta

In Australia the Oligochaeta class are represented in freshwater by several orders: Haplotaxidae, Aeolosomatidae, Lumbriculidae, Phreodrilidae, Naididae and Tubificidae (Brinkhurst, 1971). Stygofauna Oligochaeta are represented by two families in Australia: Enchytraeidae and Naididae. Enchytraeidae are a small family of aquatic worms that are poorly known although they have been found in freshwater environments in Victoria, NSW and in groundwaters in Queensland (Pinder & Brinkhurst, 1994). It is often difficult to distinguish between stygofauna and surface forms as they do not have the same unique features such as lack of pigment and absence of eyes that assist in distinguishing crustacean stygofauna.

The worm fauna present within the QA indicates that the water quality is characterised by higher amounts of organic carbon, possibly high levels of dissolved iron and relatively low DO (Stygoecologia, 2019) and this is likely the case for bore 80866 as it sits within a narrow alluvium environment that is heavily irrigated and used for mixed horticulture.

Both the moderate size (5 mm) of the stygofauna present and shallow watertable indicate a direct connectivity with a slow base-flow river system with a shallow alluvial watertable (Stygoecologia, 2019).

Such taxa are an important component of Australian groundwater systems as there are a considerable number of SRE worm taxa already known throughout Australia (Stygoecologia, 2019). Oligochaeta help to maintain open pore spaces and therefore play an important role in increasing the efficiency of bacterial growth through their feeding activities (Danielopol et al., 2000).

Regional baseline stygofauna survey | Onshore Gippsland Basin 21 7 Conclusions

The Victorian Gas Program conducted a regional baseline stygofauna survey to determine whether any stygofauna taxa exist within the aquifers of the onshore Gippsland Basin, and if possible, determine distribution ranges for potential conservation value. The information collected within this report will provide a guide to likely stygofauna populations and subsurface groundwater dependant ecosystems throughout the onshore Gippsland Basin.

The survey identified a total of five individual animals from the stygofauna taxon, Tubificida Enchytraeidae at one groundwater bore. This sample was collected from the upper aquifer, the Quaternary Aquifer. The same bore was sampled approximately three months later to assess seasonal repeatability.

The worm identified indicates a suitable habitat exists for stygofauna within the unconfined, unconsolidated Quaternary Aquifer alluvium of the onshore Gippsland Basin.

The low number of bores from which stygofauna was collected 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 to the presence of stygofauna. Variability in porosity and water quality within the unconfined aquifers also suggests the possibility of genetic isolation and therefore this stygofauna taxon may exhibit short range endemism.

This report has established a baseline assessment of stygofauna taxa across the onshore Gippsland Basin.

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Regional baseline stygofauna survey | Onshore Gippsland Basin 27 Glossary

Term Explanation Basin A geological depression filled with sediments. The amount of pore space between the grains in a rock that are available for air, water, other Porosity fluids or gas to be stored. An instrument used to measure the temperature, EC, pH, dissolved oxygen and redox of TPS 90-FLMV groundwater Phreatic Saturated subsurface zone where voids in the rock are filled with water An area of exposed limestone with distinctive features such as caves, caverns and Karstic and often with underground streams Rock deposit formed in arid environments by groundwater evaporation which causes the Calcrete cementation of superficial gravels by calcium carbonate Biogeographic A region of and plant distribution that have similar environmental characteristics Baseflow The component of stream flow that is sourced from groundwater discharging into the stream A group of organisms of known/inferred relationship. May refer to a formal taxonomic unit such Taxon (plural taxa) as a species or higher category. Short range endemism Species that have a biogeographic distribution of less than 10 000 km2 (SRE) Sources: Serov et al., 2012; EPA, 2016; Harvey, 2002.

Abbreviations and units GDE groundwater dependent ecosystem

SRE short range endemism

µS/cm micro siemens per centimetre

EC electrical conductivity

WMIS water management information system

SOBN state observation bore network

HPDE high density polymer

BOM Bureau of Meteorology

EPA Environment Protection Authority

QA Quaternary Aquifer

UTQA Upper Tertiary/Quaternary Aquifer

UTD Upper Tertiary Aquitard

UTAF Upper Tertiary Aquifer (Fluvial)

UMTA Upper Mid Tertiary Aquifer

LMTA Lower Mid Tertiary Aquifer

LTA Lower Tertiary Aquifer

LTB Lower Tertiary Basalt

BSE Cretaceous Paleozoic Bedrock

Regional baseline stygofauna survey | Onshore Gippsland Basin 28 Appendix A1 Example field sample sheet

Regional baseline stygofauna survey | Onshore Gippsland Basin 29 Appendix A2 Stygofauna results

Figure A2.1 Tubificida Enchytraeidae from bore 80866 (Stygoecologia, 2019).

Figure A2.2 Bore 80866 location and surrounds.

Regional baseline stygofauna survey | Onshore Gippsland Basin 30 Appendix A3 Stygofauna sample groundwater quality results s/cm) µ Sample NumberSample Bore ID Grid/Zone Easting Northing Aquifer DWL (m) EC ( pH Screen Interval (m) DepthTotal (m) Water sample method 1 80866 MGA 55 544977.7 5815480.2 QA 4.76 769 6.76 3 -7 10.0 Bailer 2 100976 MGA 55 424943.2 5701489.4 QA 2.95 540 7.53 2.5 - 4.5 5.5 Bailer 3 WRK059123 MGA 55 475022.18 5742521.43 UMTA 5.54 1860 7.30 17 - 20 23.0 Bailer 4 WRK059122 MGA 55 475054.02 5742514.42 UMTA 8.37 1115 7.95 41 - 47 53.0 Bailer 5 140691 MGA 55 533526.69 5797534.43 UTAF 7.50 251 6.14 61- 64 80 Pump 6 140692 MGA 55 541572.78 5797336.37 UTAF 22.10 677 6.38 69- 72 84.0 Pump 7 145094 MGA 55 487014.65 5738849.07 UTAF 31.33 1570 6.70 n/d 61.0 Bailer 8 145093 MGA 55 534938 5770489 UTAF 8.83 5080 6.88 n/d 79.0 Pump 9 105484 MGA 55 513746.32 5758648.82 UTAF 22.65 1820 7.45 52.24 - 55.3 58.3 Pump 10 65762 MGA 55 548107.1 5796374.48 UTAF 19.90 1420 7.90 70.9 - 77.3 99.0 Bailer 11 46968 MGA 55 554361.08 5802504.81 UTAF 31.50 3580 8.30 36 - 54.2 99.0 Bailer 12 90615 MGA 55 541002.37 5784650.22 UTAF 3.54 642 8.62 65.28 - 71.56 91.0 Pump 13 WRK959783 MGA 55 536577 5791264 UTAF 1.35 1160 10.10 n/d 50.8 Bailer 14 WRK059120 MGA 55 499198.92 5743179.21 UTD 15.67 1834 6.59 18 - 24 25.0 Pump 15 89845 MGA 55 482843.4 5776364 UTQA 1.70 3110 5.14 12 - 17 30.0 Bailer 16 127623 MGA 55 512613.4 5778014 UTQA 2.50 5800 7.30 11 - 14 15.0 Bailer 17 WRK986711 MGA 55 482300 5773048 UTQA 9.00 1480 7.60 6 - 13 18.0 Bailer 18 121803 MGA 55 536628.5 5791294.1 UTQA 3.04 35700 7.60 21.5 - 23.5 25.0 Bailer 19 WRK059111 MGA 55 478136.99 5723583.91 UTQA 3.07 1159 10.24 12 - 18 21.0 Pump 20 86670 MGA 55 510057.87 5786102.36 UTQD 2.30 570 8.30 58.6 - 64.69 79.8 Bailer

Regional baseline stygofauna survey | Onshore Gippsland Basin 31