Department of Primary Industry and Resources

Visual Presentation E3 The Orphan Well project evolved from the recommendations in the Final Report of the NT Hydraulic Fracturing Inquiry (HFI). The purpose is to assess wells that were drilled under petroleum permits or licences, and which have subsequently been surrendered by the titleholder and are now the responsibility of the NT Government. The project’s objective is to confirm the current status of these wells and to put forward recommendations for remedial works and/or monitoring for wells assessed to have an integrity risk. The assessment primarily focusses on the risk of fugitive methane gas. Two petroleum engineers were employed to undertake the project of assessing 113 orphan wells scattered over 1.4 million km2 of the NT. As it is a requirement to rehabilitate the land after petroleum activities have ceased, access to orphan wells is often not maintained; therefore, logistical consideration is undertaken. The project involved an initial desktop study of well history (construction) followed by a field site inspection. The drilling of these wells can date as far back as the 1960s. These older wells can have less detail in the well records and their survey location, and being pre-GPS, can have location errors of several kilometres. Remote helicopter travel is used to undertake fieldwork and locate these wells. The site inspections commenced in February 2022 and as at 31 December 2022 there have been on ground field inspections at 96 wellsites. This paper provides insight as to how the Orphan Well team developed its processes in both desktop study and site investigations. To access the Visual Presentation click the link on the right. To read the full paper click here

Artificial reefs have many applications but are best known for their deployments to enhance recreational fisheries by creating new habitat in areas where natural reef is otherwise limited. The expectation is that fish assemblages will take up residence on artificial reefs and that these assemblages will become at least similar, if not more diverse and abundant, to those on natural reefs. Although designed, purpose-built artificial reefs are becoming more widely used in support of recreational fisheries and many of the historic issues have been resolved, conservation practitioners and managers still face challenges as to the type, number, and arrangement of structures and where to deploy them to maximize benefits and minimize risks. The ecological literature was reviewed to develop and enhance contemporary principles of artificial reef best practices for utilization. Our review identified optimal shapes, vertical relief, void spaces, and unit arrangements for increasing volumes and diversity of catch to recreational fishers and we provide a tool for identifying the least constrained areas for artificial reef deployment. We suggest; (a) monitoring of noncatch motivators in combination with quantitative indicators of the fishing activity (e.g., catch rate and effort) will provide the best understanding of success or failure of an artificial reef deployment; (b) choosing target species for informing purpose-built artificial reef designs to be reef-associated, demersal, philopatric, territorial, and obligatory reef species that are desired by local recreational fishers; and (c) considering the ecosystem services provided by artificial reefs beyond those associated with recreational fishing.

<p>There is still little known about the occurrence, formation and spatial distribution of long-lived cratonic basins that form during hundreds of millions of years of subsidence. Their histories often span multiple phases of super-continent break-up, dispersal and amalgamation. Each of these phases resulted in the modification of sedimentation rates and drainage within the basins but the broader basin persisted. These changing conditions are recorded in the detrital zircon record, providing a tool for understanding the basin evolution and consequently its palaeogeography.</p><p>The informally termed greater McArthur Basin is a regionally extensive Proterozoic basin that overlies the North Australian Craton. It is a vast sedimentary system that stretches across the northern part of the Northern Territory from north-eastern Western Australia to north-western Queensland. It includes Palaeo- to Mesoproterozoic successions of the McArthur and Birrindudu basins, the Tomkinson Province and likely the Lawn Hill Platform and South Nicholson Basin (to the south-east); all interpreted to be contemporaneous systems. However, the full extent of the greater McArthur Basin sedimentary system is still being unravelled. The basin records nearly one billion years of Earth history, from ca. 1.82 Ga to ca. 0.85 Ma. This sedimentary system temporally overlaps with episodes of Palaeo- to Mesoproterozoic tectonism and igneous activity that affected underlying and adjacent terranes, including the Aileron, Warumpi and Musgrave provinces to the present-day south, Pine Creek Orogen and Arnhem Province to the north, Halls Creek Orogen and Tanami Region to the west, and Mount Isa and Murphy provinces to the east.  </p><p>LA-ICP-MS detrital zircon U–Pb geochronology and Lu–Hf isotope data provide new constraints on the lower sedimentary successions of the McArthur Basin (Tawallah and Katherine River Groups) and demonstrate they are coetaneous with the Tomkinson Province (Tomkinson Creek Group). U–Pb detrital zircon data show major <sup>207</sup>Pb /<sup>206</sup>Pb peaks at ca. 1860 Ma and ca. 2500–2400 Ma in both the McArthur Basin and Tomkinson Province sediments. Combined with Lu–Hf isotope data, the detrital zircon age data from the McArthur Basin show similarities to the Aileron Province (to the south) and magmatic rocks of the Gawler Craton, suggesting that these terranes might be possible source areas. Comparatively, the oldest succession within the Tomkinson Province (Hayward Creek Formation), shows similar spectra to units within the Lawn Hill Platform succession (McNamara Group, Surprise Creek Sandstone and Carrara Range Group) possibly suggesting a correlation between the two areas.</p><p>Here we explore the links between the North Australia Craton and surrounding continents to further elucidate the evolution of this enigmatic basin throughout the Proterozoic. New palaeogeographic reconstructions link the ‘greater’ McArthur basin to the Yanliao Basin and coeval rocks in the North China Craton. The ‘greater’ McArthur basin may also have extended into southern Australia, Laurentia and Siberia as a vast intra-continental gulf (the McArthur-Yanliao Gulf) within the core of the supercontinent Nuna/Colombia.</p>

Seedbanks and the science that underpins our work provide practical and fun options for students to engage with native plant conservation.Seedbanks provide a safe space for students to understand the importance of Australia's native plants and to explore the

The modification of river flow regimes poses a significant threat to the world’s freshwater ecosystems. Northern Australia’s freshwater resources, particularly dry season river flows, are being increasingly modified to support human development, potentially threatening aquatic ecosystems and biodiversity, including fish. More information is urgently needed on the ecology of fishes in this region, including their habitat requirements, to support water policy and management to ensure future sustainable development. This study used electrofishing and habitat survey methods to quantify the dry season habitat use of 20 common freshwater fish taxa in the Daly River in Australia’s wet-dry tropics. Of twenty measured habitat variables, water depth and velocity were the two most important factors discriminating fish habitat use for the majority of taxa. Four distinct fish habitat guilds were identified, largely classified according to depth, velocity and structural complexity. Ontogenetic shifts in habitat use were also observed in three species. This study highlights the need to maintain dry season river flows that support a diversity of riverine mesohabitats for freshwater fishes. In particular, shallow fast-flowing areas provided critical nursery and refuge habitats for some species, but are vulnerable to water level reductions due to water extraction. By highlighting the importance of a diversity of habitats for fishes, this study assists water managers in future decision making on the ecological risks of water extractions from tropical rivers, and especially the need to maintain dry season low flows to protect the habitats of native fish.

Bluetongue virus (BTV), transmitted by midges (Culicoides sp), is distributed worldwide and causes disease in ruminants. In particular, BT can be a debilitating disease in sheep causing serious trade and socio‐economic consequences at both local and global levels. Across Australia, a sentinel cattle herd surveillance program monitors the BTV activity. Prior to 2014, BTV‐1, ‐2, ‐3, ‐7, ‐9, ‐15, ‐16, ‐20, ‐21 and ‐23 had been isolated in Australia, but no bluetongue disease has occurred in a commercial Australian flock. We routinely use a combination of serology, virus isolation, RT‐PCR and next generation and conventional nucleotide sequencing technologies to detect and phylogenetically characterize incursions of novel BTV strains into Australia. Screening of Northern Territory virus isolates in 2015 revealed BTV‐5, a serotype new to Australia. We derived the complete genome of this isolate and determined its phylogenetic relationship with exotic BTV‐5 isolates. Gene segments 2, 6, 7 and 10 exhibited a close relationship with the South African prototype isolate RSArrrr/5. This was the first Australian isolation of a Western topotype of segment 10. Serological surveillance data highlighted the antigenic cross‐reactivity between BTV‐5 and BTV‐9. Phylogenetic investigation of segments 2 and 6 of these serotypes confirmed their unconventional relationships within the BTV serogroup. Our results further highlighted a need for a revision of the current serologically based system for BTV strain differentiation and importantly, implied a potential for genome segments of pathogenic Western BTV strains to rapidly enter Southeast Asia. This emphasized a need for continued high‐level surveillance of vectors and viruses at strategic locations in the north of Australia The expansion of routine characterization and classification of BTV to a whole genome approach is recommended, to better monitor the presence and level of establishment of novel Western topotype segments within the Australian episystem.

To assess the effect on healing and pain-associated behaviours of covering exposed sinuses after horn amputation under extensive production conditions in northern Australia. Horned, weaned Brahman-cross heifers (n = 50) aged approximately 6 months were alternately allocated to have their dehorning wounds either patched with a dry, non-sterile gauze swab or left untreated. Adherence of swabs and growth rates, healing and pain-associated behaviour were monitored for 88 days post-surgery. Half of the patches were lost by 24 h post-surgery, with most of the rest falling off 2-6 weeks later. Patching resulted in healing 5.5 days earlier (P = 0.018). Sealing of exposed frontal sinuses occurred in most heifers within 3 weeks and full healing occurred within 13 weeks. Patching reduced haemorrhage (P < 0.01) regardless of when the patches were dislodged, prevented insect invasion of the wound and reduced the incidence of secondary infection (P < 0.01). Wound patches did not affect behaviour in the weeks following surgery. In the days after surgery, the heifers did not eat and showed a high incidence of behaviours indicating pain. Behaviour was relatively normal by 2 weeks after surgery, although the heifers avoided social interaction with other unbranded calves for 4 weeks. The application of gauze swabs to dehorning wounds advanced healing, reduced the incidence of haemorrhage and secondary infections, and may reduce deaths. Efficacy is expected to improve if high rates of 24-h retention of patches can be achieved. The prolonged time to healing and the pain-associated behaviours highlight the need for better welfare of dehorned calves through improvements in analgesia, surgical procedures and post-surgical care.

Abstract AimThe aim of this study was to test historical and contemporary influences on population structure in the giant clams, Tridacna maxima (Röding, 1798) and T. crocea (Lamarck, 1819). To refine the location of clade boundaries within a newly resurrected species, Tridacna noae (Röding, 1798).LocationIndo‐Australian archipelago, including Indonesia, the Philippines, Australia, Papua New Guinea, the Solomon Islands, Republic of Kiribati, the Line Islands and Taiwan.MethodsWe used isolation‐migration (IMa) coalescent models and distance‐based redundancy analyses (dbRDA) to test the relative influence of barriers and continuous distances on historical divergence, gene flow and population structure of T. maxima and T. crocea. Continuous metrics of distance included present‐day and Last Glacial Maximum overwater distances along with probability of larval dispersal (LD) among sampling sites. We combined new mitochondrial cytochrome oxidase subunit I (mtDNA COI) sequences with existing data to compile the largest data set of these species yet analysed.ResultsThe Pleistocene land barriers of the Sunda Shelf and Torres Strait were associated with old (&gt;0.5 Myr) divergence times. The western and eastern boundaries of the Halmahera Eddy were also locations of significant, but more recent, divergence. No gene flow was detected across any of the four barriers tested. Larval dispersal distances between sampling sites were significant predictors of T. crocea population structure, accounting for differentiation above and beyond the contribution of barriers. We further delineated the species range of T. noae and showed that its two known clades are sympatric in central Indonesia.Main conclusionsThe strong signature of historical barriers on genetic differentiation argues against the assumption that Indo‐Pacific Tridacna are open meta‐populations. Despite similar life histories, T. maxima and T. crocea differ in their mtDNA population structure. The widespread species (T. maxima) exhibits population structure linked solely with historical factors, whereas T. crocea's population structure reflects both historical factors and LD distances.