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  • The Leeuwin Current has significant ecological impact on the coastal and marine ecosystem of south-western Australia. This study investigated the spatial and temporal dynamics of the Leeuwin Current using monthly MODIS SST dataset between July 2002 and December 2012. Topographic Position Index layers were derived from the SST data for the mapping of the spatial structure of the Leeuwin Current. The semi-automatic classification process involves segmentation, 'seeds' growing and manual editing. The mapping results enabled us to quantitatively examine the current's spatial and temporal dynamics in structure, strength, cross-shelf movement and chlorophyll a characteristic. It was found that the Leeuwin Current exhibits complex spatial structure, with a number of meanders, offshoots and eddies developed from the current core along its flowing path. The Leeuwin Current has a clear seasonal cycle. During austral winter, the current locates closer to the coast (near shelf break), becomes stronger in strength and has higher chlorophyll a concentrations. While, during austral summer, the current moves offshore, reduces its strength and chlorophyll a concentrations. The Leeuwin Current also has notable inter-annual variation due to ENSO events. In El Niño years the current is likely to reduce strength, move further inshore and increase its chlorophyll a concentrations. The opposite occurs during the La Niña years. In addition, this study also demonstrated that the Leeuwin Current has a significantly positive influence over the regional nutrient characteristics during the winter and autumn seasons. Apart from surface cooling and advection, the Leeuwin Current's sizable cross-shelf movement may be another contributing factor to the seasonal and inter-annual variations of its chlorophyll a concentrations.

  • The East Australian Current (EAC) onshore encroachment drives coastal upwelling and shelf circulations, changes slope-shelf bio-physical dynamics, and consequently exerts significant influence on coastal marine ecosystem along the south-eastern Australian margin. The EAC is a highly dynamic eddy-current system which exhibits high-frequency intrinsic fluctuations and eddy shedding. As a result, low-frequency variability in the EAC is usually overshadowed and rarely detectable. For decades, despite many efforts into the ocean current observations, the seasonality of EAC’s shoreward intrusion remains highly disputable. In this study, for the first time we use a long-term (26 years) remotely sensed AVHRR Sea Surface Temperature (SST) dataset spanning 1992-2018 to map the EAC off the coast of northern New South Wales (NSW), between 28°S - 32.5°S. A Topographic Position Index (TPI) image processing technique was applied to conduct the quantitative mapping. The mapping products have enabled direct measurement (area and distance) of the EAC’s shoreward intrusion. Subsequent spatial and temporal analyses have shown that the EAC move closer to the coast in austral summer and autumn than in austral winter, with the mean distance-to-coast ~6 km shorter and occupying the shelf area ~12% larger. This provides quantitative and direct evidence of the seasonality of the EAC’s shoreward intrusion. Such seasonal migration pattern of the EAC thus provides new insights into the seasonal upwelling and shelf circulations previously observed in this region. As a result, we were able to confirm that the EAC is a driving force of the seasonal ocean dynamics for the northern NSW coast.

  • The concentration of chlorophyll-a in ocean surface waters is a good indicator of primary productivity. As part of a national-scale analysis of ecosystem processes influencing marine biodiversity, daily MODIS images were processed using NASA's SeaDAS software to generate chlorophyll-a monthly data for the period 2009-2011. Results show that Australian oceans have relatively low surface chlorophyll-a concentrations (average 0.2 mg/m3), with concentrations greater than 0.7 mg/m3 considered to indicate 'high' productivity. On this basis, productivity hotspots are mapped for locations that have 'high' productivity greater than 75% of the time (i.e. 9 out of 12 months). As expected, most productivity hotspots are confined to inner shelf and coastal areas, especially embayments. Key areas include the Great Barrier Reef, Gulf of Carpentaria, Van Diemen Gulf, Joseph Bonaparte Gulf, Kimberley coast, Exmouth Gulf and Shark Bay. Seasonally, the period February to June has larger areas of 'high' productivity. Annually, areas of hotspots decrease from 2009 to 2011. Among the 59 existing and proposed Commonwealth Marine Reserves (CMR), nine have hotspots occupying more than 1% of their area; a result consistent with their largely offshore location. In contrast, 47 out of 128 state/territory Marine Protected Areas (MPAs) which lie in inshore waters have more than 1% of area identified as hotspots. In total, chlorophyll-a hotspots occur in more than 20% (by area) of the state/territory MPAs, compared to less than 0.4% of CMRs. Ongoing analysis will relate these patterns to oceanographic models and biodiversity patterns at regional scales, with a focus on northern Australia.

  • Submarine canyons have been recognised as areas of significant ecological and conservation value. In Australia, 713 canyons were mapped and classified in terms of their geomorphic properties. Many of them are identified as Key Ecological Features (KEFs) and protected by Commonwealth Marine Reserves (CMRs) using expert opinion based on limit physical and ecological information. The effectiveness of these KEFs and CMRs to include ecologically significant submarine canyons as prioritised conservation areas needs to be objectively examined. This study used two local-based spatial statistical techniques, Local Moran's I (LMI) and the Gi* statistic, to identify hotspots of Australian canyons (or unique canyons) for conservation priority. The hotspot analysis identified 29 unique canyons according to their physical attributes that have ecological relevance. Most of these unique physical canyons are distributed on the southern margins. Twenty-four of the 29 canyons are enclosed by the existing KEFs and protected by CMRs to varied extents. In addition, the hotspot analysis identified 79 unique canyons according to their chlorophyll a concentrations, all of which are located in the South-east marine planning region. The findings can be used to update or revise the profile descriptions for some existing KEFs. In future, if the boundaries of these KEFs are deemed necessary to be reviewed, the new information and knowledge could also be used to enhance the conservation priorities of these KEFs.

  • Geoscience Australia undertook a marine survey of the Leveque Shelf (survey number SOL5754/GA0340), a sub-basin of the Browse Basin, in May 2013. This survey provides seabed and shallow geological information to support an assessment of the CO2 storage potential of the Browse sedimentary basin. The basin, located on the Northwest Shelf, Western Australia, was previously identified by the Carbon Storage Taskforce (2009) as potentially suitable for CO2 storage. The survey was undertaken under the Australian Government's National CO2 Infrastructure Plan (NCIP) to help identify sites suitable for the long term storage of CO2 within reasonable distances of major sources of CO2 emissions. The principal aim of the Leveque Shelf marine survey was to look for evidence of any past or current gas or fluid seepage at the seabed, and to determine whether these features are related to structures (e.g. faults) in the Leveque Shelf area that may extend to the seabed. The survey also mapped seabed habitats and biota to provide information on communities and biophysical features that may be associated with seepage. This research, combined with deeper geological studies undertaken concurrently, addresses key questions on the potential for containment of CO2 in the basin's proposed CO2 storage unit, i.e. the basal sedimentary section (Late Jurassic and Early Cretaceous), and the regional integrity of the Jamieson Formation (the seal unit overlying the main reservoir). This dataset comprises total chlorin concentrations and chlorin indices from the upper 2cm of seabed sediments.

  • Seafloor bathymetric data and its derivatives fulfil a range of applications that are relevant to supporting the management of marine ecosystems and can provide a potentially powerful physical surrogate for benthic biodiversity. Similarly, morphological and seafloor terrain variables such as slope, curvature and rugosity derived from bathymetry data through GIS analysis not only describe seabed morphology but can also act as proxies for oceanographic processes The distributions of benthic marine fauna and flora most commonly respond to local changes in the topography of the seafloor. When seafloor topography is coupled with biological surveys it can help managers understand which environments contribute most to the growth, reproduction and survival of marine species. These models of habitat suitability provide natural resource managers with a tool with which to visualise the potential habitats of particular species. The accuracy of the habitat suitability models however, is critically reliant on the accuracy of underlying bathymetric data. The uncertainty in the bathymetric data is often ignored and often there is little recognition that the input bathymetric data and the derived spatial data products of the bathymetric data are merely modelled representations of one reality. These models can contain significant levels of uncertainty that are dependent upon the original depth measurements. This research paper explores a method to represent the uncertainty in bathymetric data. We discover that multibeam bathymetry data uncertainties are stochastic at individual soundings but exhibit a distinct spatial distribution with increasing magnitude from nadir to outer beams. We find that the restricted spatial randomness method is able to realistically simulate both the stochastic and spatial characteristics of the data uncertainty. This research concludes that the Monte Carlo method is appropriate for the uncertainty analysis of GIS operations and although the multibeam bathymetry data have notable overall uncertainty level, its impact on subsequent derivative analysis is likely to be minor in this dataset at the 2 m scale. Monitoring and change detection of the seafloor requires detailed baseline data with uncertainty estimates to ensure that features that display change are reliably detected. The accuracy of marine habitat maps and their associated levels of uncertainty are extremely hard to convey visually or to quantify with existing methodologies. The new techniques developed in this research integrate existing statistical techniques in a novel way to improve insights into classification and related uncertainty for seabed habitat maps which will progress and improve resource management for regional and national ocean policy.

  • Population connectivity science involves investigating how populations are related to one another through biological dispersal. Here, we review tools, techniques and analyses used by connectivity researchers, and place them in the context of how they can be used by marine managers and policy-makers to enhance their decision-making capabilities. Specific examples of developing technologies include: advances in mark and recapture techniques, underwater imaging systems, population genetic analyses, as well as four-dimensional dispersal simulations (3D space x time). These data can then be analysed using a wide array of analyses, including matrix analysis, graph theory, and various GIS-based routines. The results can be used to identify key source and sink areas, critical linkages (keystones), natural clusters and groups, levels of accuracy, precision and variability, as well as areas of asymmetric exchange. In turn, this information can be used to help identify natural management units, to target critical conservation areas, to develop efficient sampling strategies through power analysis, and to negotiate equitable allocation of resources to upstream management in cases where downstream benefits are significant. Through a better understanding of how connectivity science can assist decision-making, we hope to encourage increased uptake of these kinds of information into institutional planning processes.

  • Geoscience Australia marine reconnaissance survey TAN0713 to the Lord Howe Rise offshore eastern Australia was completed as part of the Federal Government¿s Offshore Energy Security Program between 7 October and 22 November 2007 using the New Zealand Government¿s research vessel Tangaroa. The survey was designed to sample key, deep-sea environments on the east Australian margin (a relatively poorly-studied shelf region in terms of sedimentology and benthic habitats) to better define the Capel and Faust basins, which are two major sedimentary basins beneath the Lord Howe Rise. Samples recovered on the survey contribute to a better understanding of the geology of the basins and assist with an appraisal of their petroleum potential. They also add to the inventory of baseline data on deep-sea sediments in Australia. The principal scientific objectives of the survey were to: (1) characterise the physical properties of the seabed associated with the Capel and Faust basins and Gifford Guyot; (2) investigate the geological history of the Capel and Faust basins from a geophysical and geological perspective; and (3) characterise the abiotic and biotic relationships on an offshore submerged plateau, a seamount, and locations where fluid escape features were evident. This dataset comprises total oxygen uptake and total carbon fluxes from core incubation experiments. Some relevant publications which pertain to these datasets include: 1. Heap, A.D., Hughes, M., Anderson, T., Nichol, S., Hashimoto, T., Daniell, J., Przeslawski, R., Payne, D., Radke, L., and Shipboard Party, (2009). Seabed Environments and Subsurface Geology of the Capel and Faust basins and Gifford Guyot, Eastern Australia ¿ post survey report. Geoscience Australia, Record 2009/22, 166pp. 2. Radke, L.C. Heap, A.D., Douglas, G., Nichol, S., Trafford, J., Li, J., and Przeslawski, R. 2011. A geochemical characterization of deep-sea floor sediments of the northern Lord Howe Rise. Deep Sea Research II 58: 909-921

  • A short film describing the processes of bathymetric mapping and side scan sonar, used to gather data within the search area for missing Malaysia Airlines flight MH370. Synopsis: The film begins with a brief description of Geoscience Australia's role working with the lead agencies in the search process. It explains that existing satellite data is not detailed enough to assist in the search for MH370 and that more detailed bathymetric surveying is required before an underwater search can commence. The film describes how a bathymetric survey is carried out using sonar systems mounted on a ship's hull. It then shows imagery derived from the bathymetric mapping of the search area. The film then shows how a detailed underwater search is carried out, using the bathymetry as a guide. Animation shows how a towed, submersible vehicle gathers more detailed data while travelling slowly at a height of approximately 100 metres above the sea floor. The animation shows how side scan sonar reveals more detailed information about sea floor features. The film ends with a brief summary of the role of the Australian Government agencies involved in the search. Brief credits follow with a copyright statement and publication information. About the data visualisation: This video contains data visualisation and animation sequences. Bathymetry visualisations are derived from data gathered within the MH370 search area. Side scan sonar visualisations are derived from demonstration data only, not gathered within the MH370 search area. Animation sequences showing ship-mounted bathymetry and towed side-scan sonar are representations only and not to scale. Film production credits: Geoscience Australia Script, Direction: Bobby Cerini, Melinda Holland Edit, Cinematography, Sound: Michael O'Rourke Production Management: Bobby Cerini, Neil Caldwell 3D Data Visualisation, Animation: Neil Caldwell, Michael de Hoog Graphics: Kath Hagan Scientific Advice: Stuart Minchin, Anna Potter, Maggie Tran, Tanya Whiteway, Kim Picard Additional credits: Voiceover: Media Sound Studios Music: 'Namaste' by Jason Shaw, 2013 Animation of Globe: 'Earth in Cycles' by Adriano, 2012 3D Data Visualisation and Animation (ship, bathymetry, side scan, ocean features): Eye Candy Animation Producer: Damian Stocks Creative Director: Rachael Johnson Studio Manager: Jess Burrows Lead Artist: Artur Piwko 3D Artist: Kynan Stevenson

  • This resource contains geochemistry data for the Oceanic Shoals Commonwealth Marine Reserve (CMR) in the Timor Sea collected by Geoscience Australia during September and October 2012 on RV Solander (survey GA0339/SOL5650). This dataset comprises inorganic element data from the fine fraction (Mud: <63um) of the upper ~2cm of seabed sediment. The Oceanic Shoals Commonwealth Marine Reserve survey was undertaken as an activity within the Australian Government's National Environmental Research Program Marine Biodiversity Hub and was the key component of Research Theme 4 - Regional Biodiversity Discovery to Support Marine Bioregional Plans. Hub partners involved in the survey included the Australian Institute of Marine Science, Geoscience Australia, the University of Western Australia, Museum Victoria and the Museum and Art Gallery of the Northern Territory. Data acquired during the survey included: multibeam sonar bathymetry and acoustic backscatter; sub-bottom acoustic profiles; physical samples of seabed sediments, infauna and epibenthic biota; towed underwater video and still camera observations of seabed habitats; baited video observations of demersal and pelagic fish, and; oceanographic measurements of the water column from CTD (conductivity, temperature, depth) casts and from deployment of sea surface drifters. Further information on the survey is available in the post-survey report published as Geoscience Australia Record 2013/38 (Nichol et al. 2013).