Spencer Gulf Research Articles

Measuring, interpreting and monitoring economic efficiency in South Australia’s Spencer Gulf and West Coast Prawn Fisheries

Fishers and fishing vessels are not homogeneous, with their level of catch affected by the choice of physical inputs such as engine size, boat size and the type of fishing technology employed, as well as less tangible factors such as skipper skill and experience. Economic output also vitally depends upon the value of the product in the market and the cost of inputs. These differences in the ability of individual fishers to catch fish, and create economic returns, can be assessed through the application of efficiency analysis. This paper provides an empirical examination of efficiency indicators in the South Australian Spencer Gulf and West Coast Prawn Fisheries. Applying data envelopment analysis (DEA) to a unique vessel-level dataset that includes both quantity and value information, we estimate measures of efficiency in these input-controlled fisheries where effort decisions are made in real-time using a participative management approach. We find that quantity and value-based efficiency measures are relatively high but that the variability of value-based measures is increasing. This increasing heterogeneity in value, despite the homogeneity in quantities, has potential implications for pressures on cooperative management going forwards as fishers pursue different business strategies. Comparing the measures of efficiency to direct measures of individual profit, we find a divergence: technical and cost measures of efficiency are more strongly positively related to short-run economic performance while revenue-efficiency is more strongly positively correlated with long-run economic performance, suggesting that different efficiency metrics may be required for short- and long-run monitoring.

Whyalla and the transition to a decarbonised future

ABSTRACT Whyalla, an old steel town in the Upper Spencer Gulf in South Australia, has had a chequered history. Steel production has been precarious for a decade and more. Now, the promise of ‘Green Steel’ and a local major Hydrogen Hub holds out the hope of regional security. In this article, I trace the history of Whyalla, the region, and its steel works and outline the promise of a new future based on renewable industries. I start by outlining the importance of stressing both time and place in analysing the process and pattern of regional development. Insodoing, I question the validity of much ‘place-based’ analysis and point to Deep Place analysis as a possible alternative. I examine the limits and possibilities of the current transition and suggest that the future may not yet be entirely secure.

Integrating management of marine activities in Australia

Integrated management (IM) has been widely proposed, but difficult to achieve in practice, and there remains the need for evaluation of examples that illustrate the practical issues that contribute to IM success or failure. This paper synthesises experiences of academics and practitioners involved in seven Australian case studies in which there have been attempts to integrate or take a broader, holistic perspective of management. The evaluative framework of Stephenson et al. (2019a) was used as a lens to explore, through workshops and a questionnaire survey, the nine key features and five anticipated stages of IM in the Gladstone Harbour Project, the Great Barrier Reef, the Northern Prawn fishery and regional development, the South-East Queensland Healthy Waterways Partnership, the Australian Oceans Policy, the New South Wales Marine Estate reforms, and progress toward Integrated Management in the Spencer Gulf. Workshops involving experts with direct experience of the case studies revealed that most of the key features (recognition of the need; a shared vision for IM; appropriate legal and policy frameworks; effective process for appropriate stakeholder participation; comprehensive suite of objectives (ecological, social, cultural, economic and institutional); consideration of trade-offs and cumulative effects of multiple activities; flexibility to adapt to changing conditions; process for ongoing review, evaluation and refinement; and effective resourcing) were seen as important in all case studies. However, there are only a few examples where key features of IM were implemented ‘fully’. A subsequent questionnaire of participants using ‘best-worst’ scaling indicated that an appropriate legal and institutional framework is considered to have most influence on IM outcomes, and therefore is the most important of the key features. This is followed in salience by effective stakeholder participation, effective resourcing, capacity and tools, and recognition of the need for IM. Key features may change in relative importance at different stages in the trajectory of IM.

Concurrent 12. Presentation for: Recycling of Australian oil and gas assets, an Australian Basel-compliant solution

Presented on Wednesday 18 May: Session 12 Australian offshore petroleum infrastructure decommissioning strategies are dictated by legal requirements set out in the Offshore Petroleum and Greenhouse Gas Storage Act, requiring prima facie that assets are removed from the title area. Legally, once assets are decommissioned, they require disposal at a Basel-compliant facility. This lack of Australian capability has forced titleholders to contemplate leaving infrastructure in situ (rigs-to-reef), which may well breach Australia’s international law obligations under the United Nations Convention on the Law of the Sea, and the London Convention on Dumping at Sea (and associated Protocols). Australia’s closest Basel-compliant facility is located in Turkey. The experience of the Iron Chieftain in 2019 demonstrated the difficulty in using this facility. In 2019 the bulk carrier Iron Chieftain caught fire in Port Kembla, and was declared a Constructive Total Loss (CTL). Disposal required decontamination, seeking Basel export approval, and towing to Turkey via South Africa. Following 9 months to complete the application, the vessel commenced its tow. The vessel was not permitted to stop or enter the port waters of any port other than Turkey after leaving. If it did stop, the application ceased and a new application was required to be commenced. If the vessel arrived in a condition not acceptable to authorities, the vessel would be turned away, requiring it to return to its home port of Port Kembla where the application commenced from. In response to such difficulties, a new Basel-compliant recycling facility has been established, co-located to a green steel recycling works, delivering a near carbon-neutral asset recycling and disposal solution for Australia’s offshore energy infrastructure. Strategically located in the mouth of the Spencer Gulf, South Australia, this facility will provide a green whole-of-asset recycling and disposal solution in-country, removing towage expenses and CO2 emissions. This extended abstract articulates the Iron Chieftain experience, highlighting the issues facing petroleum infrastructure decommissioning and disposal in accordance with Basel requirements. It also provides an overview of the Whyalla recycling and disposal facility, presenting the case for circular economy, ethical asset decommissioning and Australian capability. To access the presentation click the link on the right. To read the full paper click here

Recycling of Australian oil and gas assets, an Australian Basel-compliant solution

Australian offshore petroleum infrastructure decommissioning strategies are dictated by legal requirements set out in the Offshore Petroleum and Greenhouse Gas Storage Act, requiring prima facie that assets are removed from the title area. Legally, once assets are decommissioned, they require disposal at a Basel-compliant facility. This lack of Australian capability has forced titleholders to contemplate leaving infrastructure in situ (rigs-to-reef), which may well breach Australia’s international law obligations under the United Nations Convention on the Law of the Sea, and the London Convention on Dumping at Sea (and associated Protocols). Australia’s closest Basel-compliant facility is located in Turkey. The experience of the Iron Chieftain in 2019 demonstrated the difficulty in using this facility. In 2019 the bulk carrier Iron Chieftain caught fire in Port Kembla, and was declared a Constructive Total Loss (CTL). Disposal required decontamination, seeking Basel export approval, and towing to Turkey via South Africa. Following 9 months to complete the application, the vessel commenced its tow. The vessel was not permitted to stop or enter the port waters of any port other than Turkey after leaving. If it did stop, the application ceased and a new application was required to be commenced. If the vessel arrived in a condition not acceptable to authorities, the vessel would be turned away, requiring it to return to its home port of Port Kembla where the application commenced from. In response to such difficulties, a new Basel-compliant recycling facility has been established, co-located to a green steel recycling works, delivering a near carbon-neutral asset recycling and disposal solution for Australia’s offshore energy infrastructure. Strategically located in the mouth of the Spencer Gulf, South Australia, this facility will provide a green whole-of-asset recycling and disposal solution in-country, removing towage expenses and CO2 emissions. This extended abstract articulates the Iron Chieftain experience, highlighting the issues facing petroleum infrastructure decommissioning and disposal in accordance with Basel requirements. It also provides an overview of the Whyalla recycling and disposal facility, presenting the case for circular economy, ethical asset decommissioning and Australian capability.

Developing indicators for adaptive capacity for multiple use coastal regions: Insights from the Spencer Gulf, South Australia

Spatially large and multiple use coastal regions face unprecedented pressures. Decision makers need to build policy that links social, economic and ecological dimensions in ways that build the adaptive capacity of these systems while not compromising individual values. This paper reports on an inter-disciplinary project that used a Capitals approach to build socio-economic indicators robust enough to use in integrated community assessments of adaptive capacity. Using the Spencer Gulf, South Australia as a case study, we demonstrate the utility of these indicators to derive quantitative assessments of socio-economic adaptive capacity. We argue that such assessments used at regular periods, in conjunction with scientific indicators, have the potential to be powerful management tools and provide ongoing ability to measure community adaptive capacity over time.

Peesey Swamp—a Last Interglacial (MIS 5e) marine corridor across southern Yorke Peninsula, southern Australia

Peesey Swamp on southern Yorke Peninsula, southern Australia, is a north-northwesterly—south-southeasterly trending lowland depression, approximately 24 km long and 4 to 10 km wide. The richly fossiliferous mollusc and foraminiferal faunal assemblages of the last interglacial Glanville Formation in Peesey Swamp indicate that the paleoenvironment was a low- to medium-energy, sheltered sandflat to shallow-water seaway during the Last Interglacial Maximum (Marine Isotope Substage [MIS] 5e; 128–116 ka). The presence of the fossil bivalve molluscs Katelysia rhytiphora, Chlamys (Equichlamys) bifrons and Fulvia tenuicostata, in life position, indicate that the paleowater depth was ≤4 m in Peesey Swamp. The seaway cut across southern Yorke Peninsula, establishing a marine connection between southern Spencer Gulf and Investigator Strait during deposition of these taxa. Amino acid racemisation dating of the fossil marine molluscs Katelysia sp. and Fulvia tenuicostata confirms that the shelly assemblages at Peesey Swamp are correlative with the last interglacial Glanville Formation, a succession of richly fossiliferous, mixed quartz–skeletal carbonate sands documented from many sites along the southern Australian coastline. This study illustrates the significant changes in the geographical configuration of coastlines that may accompany relatively modest (<5 m) sea-level changes on low-gradient coastal landscapes. KEY POINTS Peesey Swamp on southern Yorke Peninsula was flooded by seawater forming a 4 to 10 km-wide seaway during the Last Interglacial Maximum (MIS 5e). Fossil mollusc and foraminiferal assemblages reveal deposition within shallow subtidal to intertidal sandflat environments indicating that the paleowater depth and height of sea-level in Peesey Swamp was ≤4 m. Amino acid racemisation dating of fossil marine molluscs confirms that the shelly assemblages at Peesey Swamp are of last interglacial (MIS 5e) age. The distribution of the foraminifer Marginopora vertebralis indicates that the eastward flow of the warm-water Leeuwin Current, during the Last Interglacial Maximum, was retarded by the biogeographical barriers of Kangaroo Island and Fleurieu Peninsula.

Evaluation of a popular spatial cumulative impact assessment method for marine systems: A seagrass case study.

Human activities put stress on our oceans and with a growing global population, the impact is increasing. Stressors rarely act in isolation, with the majority of marine areas being impacted by multiple, concurrent stressors. Marine spatial cumulative impact assessments attempt to estimate the collective impact of multiple stressors on marine environments. However, this is difficult given how stressors interact with one another, and the variable response of ecosystems. As a result, assumptions and generalisations are required when attempting to model cumulative impacts. One fundamental assumption of the most commonly applied, semi-quantitative cumulative impact assessment method is that a change in modelled cumulative impact is correlated with a change in ecosystem condition. However, this assumption has rarely been validated with empirical data. We tested this assumption using a case study of seagrass in a large, inverse estuary in South Australia (Spencer Gulf). We compared three different seagrass condition indices, based on survey data collected in the field, to scores from a spatial cumulative impact model for the study area. One condition index showed no relationship with cumulative impact, whilst the other two indices had very small, negative relationships with cumulative impact. These results suggest that one of the most commonly used methods for assessing cumulative impacts on marine systems is not robust enough to accurately reflect the effect of multiple stressors on seagrasses; possibly due to the number and generality of assumptions involved in the approach. Future methods should acknowledge the complex relationships between stressors, and the impact these relationships can have on ecosystems. This outcome highlights the need for greater evaluation of cumulative impact assessment outputs and the need for data-driven approaches. Our results are a caution for marine scientists and resource managers who may rely on spatial cumulative impact assessment outputs for informing policy and decision-making.

Temperate southern Australian coastal waters are characterised by surprisingly high rates of nitrogen fixation and diversity of diazotrophs.

Biological dinitrogen (N2) fixation is one mechanism by which specific microorganisms (diazotrophs) can ameliorate nitrogen (N) limitation. Historically, rates of N2 fixation were believed to be limited outside of the low nutrient tropical and subtropical open ocean; however, emerging evidence suggests that N2 fixation is also a significant process within temperate coastal waters. Using a combination of amplicon sequencing, targeting the nitrogenase reductase gene (nifH), quantitative nifH PCR, and 15N2 stable isotope tracer experiments, we investigated spatial patterns of diazotroph assemblage structure and N2 fixation rates within the temperate coastal waters of southern Australia during Austral autumn and summer. Relative to previous studies in open ocean environments, including tropical northern Australia, and tropical and temperate estuaries, our results indicate that high rates of N2 fixation (10–64 nmol L−1 d−1) can occur within the large inverse estuary Spencer Gulf, while comparatively low rates of N2 fixation (2 nmol L−1 d−1) were observed in the adjacent continental shelf waters. Across the dataset, low concentrations of NO3/NO2 were significantly correlated with the highest N2 fixation rates, suggesting that N2 fixation could be an important source of new N in the region as dissolved inorganic N concentrations are typically limiting. Overall, the underlying diazotrophic community was dominated by nifH sequences from Cluster 1 unicellular cyanobacteria of the UCYN-A clade, as well as non-cyanobacterial diazotrophs related to Pseudomonas stutzeri, and Cluster 3 sulfate-reducing deltaproteobacteria. Diazotroph community composition was significantly influenced by salinity and SiO4 concentrations, reflecting the transition from UCYN-A-dominated assemblages in the continental shelf waters, to Cluster 3-dominated assemblages in the hypersaline waters of the inverse estuary. Diverse, transitional diazotrophic communities, comprised of a mixture of UCYN-A and putative heterotrophic bacteria, were observed at the mouth and southern edge of Spencer Gulf, where the highest N2 fixation rates were observed. In contrast to observations in other environments, no seasonal patterns in N2 fixation rates and diazotroph community structure were apparent. Collectively, our findings are consistent with the emerging view that N2 fixation within temperate coastal waters is a previously overlooked dynamic and potentially important component of the marine N cycle.

REEVALUATION OF THE INFERRED RELATIONSHIP BETWEEN LIVING RHODOLITH MORPHOLOGIES, THEIR MOVEMENT, AND WATER ENERGY: IMPLICATIONS FOR INTERPRETING PALEOCEANOGRAPHIC CONDITIONS

ABSTRACT Free-living forms of crustose coralline algae (rhodoliths) accumulate on shallow-water marine shelves in many regions worldwide. They form their own benthic habitats termed ‘rhodolith beds' and their deposits are well preserved in the rock record. Characteristics of rhodolith deposits can be used to interpret ancient water depths, light levels, and water energies. Accurate paleoceanographic interpretations rely on large-scale, detailed studies of living rhodolith beds, but these studies are scarce. Spencer Gulf in South Australia has the largest living rhodolith beds in southeastern Australia (∼ 3,000 km2). Documentation of these rhodolith deposits includes facies analysis, coralline algal taxonomy, characterization of growth forms and morphometrics, and integration with oceanographic data. Extensive oceanographic data and hydrodynamic modeling enable comparisons between rhodolith morphologies and bottom water energies with unprecedented accuracy. Rhodolith deposits in the gulf are intermixed with carbonate sands and muds under diverse hydrodynamic conditions, with current speeds up to 1.04 m s−1. At least five coralline algal genera construct rhodoliths in Spencer Gulf. Growth forms include fruticose, lumpy, and warty. Rhodolith morphologies imply that water energy is not the only thing affecting rhodolith movement and growth; rhodoliths can also be shifted by fish and invertebrates. Linear regression models in this study evaluate relationships between rhodolith morphometrics (mean diameter, sphericity, and branch density) and maximum bottom water speeds in Spencer Gulf and their results support the idea that water energy is not a major control on rhodolith morphology under these water energy conditions. Previous studies have revealed that the relationship between rhodolith morphologies and water energy levels is complicated and many authors have cautioned to not rely solely on rhodolith morphologies to interpret paleoceanographic conditions. Results of this study demonstrate that accurate paleoceanographic interpretations cannot be made based on rhodolith morphologies alone, but should also include sedimentology, coralline taxonomy, and associated biota.

Extreme Effects of Extreme Disturbances: A Simulation Approach to Assess Population Specific Responses

In South Australia, discrete populations of bottlenose dolphins inhabit two large gulfs, where key threats and population estimates have been identified. Climate change, habitat disturbance (shipping and noise pollution), fishery interactions and epizootic events have been identified as the key threats facing these populations. The Population Consequences of Disturbance (PCoD) framework has been developed to understand how disturbances can influence population dynamics. I used population estimates combined with population specific bioenergetics models to undertake a PCoD assessment, comparing how the two populations respond to the identified regional threats. Populations were modeled over a five year period looking at the influence of each disturbance separately. As expected, extreme disturbance scenarios, in terms of frequency and intensity, had the biggest influence on population trends. However, the magnitude of the effect differed by population, with Spencer Gulf showing a 43% and Gulf St Vincent a 23% decline under high frequency and high impact epizootic scenarios. Epizootic events were seen to have the largest influence on population trends and reproductive parameters for both populations, followed by climate change. Modeling provides insights into how disturbances may affect different populations, and informs management to mitigate their potential effects while there is still time to act. Keywords: Bioenergetics, marine mammals, disturbances, bottlenose dolphins, Bayesian modelling, fecundity, population trends Article Impact Statement: Human induced disturbances impact coastal bottlenose dolphins with varying severity depending on the population and disturbance.

Deciphering organic matter sources and ecological shifts in blue carbon ecosystems based on molecular fingerprinting

Blue carbon ecosystems (BCE) play an essential role in the global carbon cycle by removing atmospheric carbon dioxide and storing it as organic carbon (OC) in biomass and sediments. However, organic matter (OM) deposition and degradation/preservation processes are poorly understood, especially on the long-term and at molecular scales. We analysed sediment samples from six cores collected in tidal marshes, mangroves and seagrasses (up to 150 cm long cores spanning up to 10,000 yrs of OC accumulation) from Spencer Gulf (South Australia), by pyrolysis (Py-GC–MS and THM-GC–MS), and we compared the results with elemental and stable isotope data, to decipher OM provenance and to assess degradation/preservation dynamics. The results showed that: (1) the major biopolymers preserved were polysaccharides, polyphenolic moieties (lignin and tannin) and polymethylenic moieties (e.g. cutin, suberin, chlorophyll) with smaller apportions of proteins and resins; (2) the OM originates predominantly from vascular plant materials (in particular lignocellulose) that have been well-preserved, even in some of the oldest sediments; (3) mangroves were found to be the most efficient OC sinks, partially explained by syringyl lignin preservation; (4) seagrasses were shown to store polysaccharide-enriched OM; (5) large proportions of polycyclic aromatic hydrocarbons (PAHs) in surficial tidal marsh and mangrove sediments probably reflect pyrogenic OM from industrial combustion, and; (6) “ecosystem shifts”, i.e. mangrove encroachment in tidal marsh and transition from seagrass to mangrove, were detected. Deposition environment and source vegetation control OC sequestration and there is no specific recalcitrant form of OM that is selectively preserved. For the first time, we demonstrate how analytical pyrolysis in combination with stable isotope analysis can be used to reconstruct (palaeo-)ecological shifts between different BCE. This study improves our knowledge on OC accumulation dynamics and the response of BCE to environmental change, which can inform the implementation of strategies for climate change mitigation.

Comparing maximum entropy modelling methods to inform aquaculture site selection for novel seaweed species

Maximum entropy (maxent) modelling is a widely used method for developing species distribution models (SDMs), but default maxent modelling methods can result in overly complex models with poor transferability. Methods suggested to reduce overfitting include increasing regularisation, using only linear and quadratic features, or applying forward selection of predictors using maximum likelihood (ML) methods. We built models using these options to determine environmental suitability within existing aquaculture zones for eight seaweed species, four red (Rhodophyta: Florideophyceae) and four brown (Ochrophyta: Phaeophyceae), that are being investigated for aquaculture in southern Australia. Forward selection models were the most parsimonious, but we encountered failure of ML methods for Pterocladia lucida (Rhodophyta) due to separation. Separation is a known issue for logistic regression and has recently been recognised in maxent models. Separation occurs where a variable, or combination of variables, is a perfect predictor for a binary response, here, species occurrence, and results in ML parameter estimates tending to infinity. One method for obtaining finite parameter estimates under separation is to apply a Cauchy prior distribution for coefficients. We therefore also built models for each species using a Cauchy-prior version of the forward selection method, and found that these models performed similarly to those built with ML methods. Default models achieved marginally higher predictive performance than other options based on training data metrics, but simpler models performed equivalently to, or better than, default models at predicting independent presence-absence test data. Predictive performance using test data varied considerably between species, but the difference in performance between models within each species was generally small. Our results confirm the concern that default maxent models may suffer from over-fitting and poor transferability. Model transferability and interpretability were important for our purpose, hence, based on the principle of parsimony, forward selection models were preferred. We also found that forward selection models retained similar predictive performance to the best model as assessed by each metric, further supporting use of these models. Where ML methods failed due to separation, the use of the Cauchy-prior method was a viable alternative. Predictions for the region of interest (Spencer Gulf, South Australia) were generated using the most parsimonious models, and Solieria robusta (Rhodophyta) showed the highest predicted suitability of the eight candidate species within existing aquaculture zones, especially in northern Spencer Gulf. Predicted suitability was low for the other Rhodophyta considered, while each of the Phaeophyceae showed moderate to high suitability in at least some southern Spencer Gulf aquaculture zones. These model results help to inform selection of the best candidate species and suitable farming areas for future research.

Oil spill from the Era: Mangroves taking eons to recover

Mangroves are highly susceptible to oil exposure. Depending on the severity, oil exposure can result in initial defoliation and eventual recovery through to mass mortality and complete loss of habitat. Some aspects of the impact of oil on mangroves and their recovery are well studied, but the focus has been on short-term responses, and the understanding of the longer-term trajectory of mangrove recovery from oiling is very limited. Here, we combine field results from sampling in the two years following a significant oiling event, with analysis of canopy cover in aerial images from before the event to 26 years afterwards. Approximately 100 ha of a monospecific stand of Avicenna marina mangroves were oiled as a result of a spill from the Era tanker in Spencer Gulf in southern Australia in September 1992. While lightly oiled trees made a full recovery, trees in heavily oiled areas experienced mass defoliation and ultimately mortality within several months of the oiling event. An analysis of aerial images indicated that there was no recovery in heavily oiled areas for 10 years following the oiling event. Between 10 and 25 years, seedling establishment and growth saw canopy cover increase to 35% of pre-oiling cover within heavily oiled areas. Predictive modelling estimates that complete recovery of mangroves to pre-oiling cover will take 55 years (median prediction in 2047). Our findings indicate that although mangroves can recover following a heavy oiling event, the rate of recovery can be slow, with full recovery in the order of half a century, much longer than has previously been anticipated.

Discriminating Natal Source Populations of a Temperate Marine Fish Using Larval Otolith Chemistry

The life cycles of many marine species depend on a dispersive larval stage that connects spatially segregated populations. However, quantifying larval movement among populations remains one of the greatest challenges in marine ecology. Such movement determines whether a population is essentially a self-recruiting stock, or if it forms part of a larger meta-population where recruits originate from multiple sources. Previous research has struggled to differentiate between such stock structure models for King George whiting (Sillaginodes punctatus; Perciformes) in southern Australia, largely due to difficulties in identifying the source populations of dispersing larvae. In this study, pelagic larvae were collected throughout the only recognized spawning area in South Australia in 2017 and 2018. First, we identified that the distribution of larvae was broadly divisible into two groups – those in southern Spencer Gulf and those in Investigator Strait. Then, the incremental structure and elemental composition of otoliths of larvae from the two regions were compared to determine if they had originated from a common source population. There were no spatial differences in the sizes (3.0-5.0 mm SL), ages (5-21 d), hatch dates (7-24 April) or average growth rates (0.09-0.21 mm d-1) of larvae. However, multi-elemental (Li, Mg, Mn, Sr and Ba) otolith signatures differed significantly between the two regions, primarily driven by differences in concentrations of Li and Ba. Although otolith signatures were year-specific, larvae were assigned to their region of capture with 70-82% accuracy. Larvae in each region hatched at the same time yet had significantly different otolith chemistry, providing strong evidence that those in southern Spencer Gulf and Investigator Strait originated from spatially segregated water masses. This study has demonstrated the ability of otolith chemistry to discriminate source populations of pelagic larvae in a fully marine environment, which provides a basis to quantify larval movement between fish populations.

Marine Transgression, Aboriginal Narratives and the Creation of Yorke Peninsula/Guuranda, South Australia

This paper provides new palaeogeographical reconstructions of the Spencer Gulf and Yorke Peninsula/Guuranda region of South Australia for the period ca. 20,000–6000 cal. BP. The rich complexity of traditional Aboriginal (Narungga) sea-level narratives is also explored. These narratives, which form a highly significant system of knowledge, are considered together by the Narungga and non-Narungga authors of the paper to generate a new dialogue about Aboriginal traditions and scientific data. The dialogue between the Narungga knowledge systems and palaeogeographic mapping reveals a strong concordance for events/time slices inclusive of the onset of marine transgression, the creation of northern Spencer Gulf and the formation of some islands—while also establishing that there are deeper complexities inherent within Narungga narratives that demonstrate layers of meaning at multiple scales. The palaeogeographic reconstructions are also considered in relation to the known archaeology and geomorphology of the region as well as new observations arising from this research. Targets for future underwater (and terrestrial) investigation relating to the periods of marine transgression are also outlined.

Suitability of the Southern Australia Integrated Marine Observing System’s (SA-IMOS) HF-Radar for operational forecasting

ABSTRACTThe IMOS HF-Radar array in South Australia provides observations of the ocean waters south of Spencer Gulf. In addition to ocean surface currents, the data from this array can be processed to provide near real-time observations of wave statistics and wind direction. The Australian Bureau of Meteorology requires access to these observations for forecast modelling but currently only have a single Waverider buoy operating in South Australian waters at Cape du Couedic, south of Kangaroo Island, which provides no directional information. The HF-Radar array could potentially be used to augment the current operational observation systems used by the Bureau. In this paper, we evaluate the performance of the HF-Radar system against observations from the Waverider buoy and an automatic weather station at Neptune Island and also compare the HF-Radar observations to a wave model based on the eSA-Marine forecast grid. The results suggest that upgrading the HF-Radar to provide near real-time wave and wind data would provide a new, independent source of environmental observations for the Bureau.

Refining a Nordmøre-grid bycatch reduction device for the Spencer Gulf penaeid-trawl fishery.

Incremental refinements were made to a generic Nordmøre-grid to minimise bycatches of blue swimmer crabs Portunus armatus and giant cuttlefish Sepia apama, while maintaining catches of western king prawns Melicertus latisulcatus in the Spencer Gulf penaeid-trawl fishery. These refinements involved varying bar spaces, escape-exit areas and guiding-panel lengths, and were compared against a conventional trawl. Catches of teleosts and M. latisulcatus largely remained unaffected by the changes. Maximum reductions in P. armatus and S. apama bycatches (both ~90%) were achieved with a Nordmøre-grid comprising 38-mm bar spaces, 0.81- or 1.05-m2 escape exits and a 2.7-m guiding panel. Catching fewer P. armatus should reduce abrasion and crushing of M. latisulcatus in the codend and so increase the value of this targeted species. While noting some unresolved operational concerns, these results demonstrate the potential improvements in selectivity in this fishery using a Nordmøre-grid, primarily by mechanical separation.

Pathology of the skeleton of Indo-Pacific bottlenose dolphins Tursiops aduncus: a comparison of adjacent gulfs in South Australia

Studies of skeletal pathology of marine mammals can contribute to conservation measures, yet few have focused on causative factors. Museums hold vast collections of skeletons relevant to this knowledge gap. Indo-Pacific bottlenose dolphin Tursiops aduncus carcasses (n = 162) were collected from Gulf St Vincent (GSV) and Spencer Gulf (SG), South Australia (SA), between 1988 and 2013, and post-mortem examinations were carried out. After preparing skeletons, their gross pathology was classified into 4 categories: lytic lesions, degenerative lesions, fractures and malformations. Comparisons were made between gulfs based on pathology type, relative age, period of collection and cause of death (anthropogenic vs. non-anthropogenic). Pathology prevalence (76%) was higher than reported in other studies but observed pathologies were similar. More than one pathology was observed in 88% of dolphins that had pathology. Vertebrae were often the site of pathology. Prevalence of lesions were: fractures (82%), lytic lesions (75%) including spondylo-osteomyelitis and osteomyelitis, degenerative lesions (57%) including spondylosis deformans, and malformations (17%). Prevalence of pathology increased with dolphin relative age, and GSV dolphins had more pathology than those in SG. In SG, anthropogenic cases had more pathology than non-anthropogenic cases, and dolphins collected after 2000 had more degenerative lesions than those collected before 2000. There were more malformations in SG dolphins than those from GSV, although this was not statistically significant. In one anomalous case, an individual was found with 5 detached transverse processes on 4 lumbar vertebrae. Heavy metal toxicity reported for T. aduncus from SG may be related to the malformations reported in this study.

Seagrass soil archives reveal centennial-scale metal smelter contamination while acting as natural filters

The upper Spencer Gulf in South Australia hosts the world's largest single stream Pb-Zn smelter, which has caused environmental and health issues related to elevated metal concentrations in the surrounding environment. The area also has extensive seagrass meadows, occupying >4000 km2. We reconstructed the fluxes of heavy metals over the last ~3000 years through a multi-parameter study of the soil archives formed by the seagrass Posidonia australis. Pb, Zn and Cd concentrations increased up to 9-fold following the onset of smelter operations in the 1880s, and the stable Pb isotopic signatures confirmed the smelter has been the main source of lead pollution in the seagrass soils until present. Preliminary estimates suggest that over the past 15 years seagrass meadows within 70 km2 of the smelter accumulated ~7–15% of the smelter emissions in their soils. Here we demonstrate that seagrass meadows act as pollution filters and sinks while their soils provide a record of environmental conditions, allowing baseline conditions to be identified and revealing the time-course of environmental change.