CERF
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Autonomous Underwater Vehicles (AUVs) have only recently become available as a tool to investigate the biological and physical composition of the seabed utilizing a suite of image capture and high-resolution geophysical tools. In this study we trialled the application of an AUV, integrating AUV image capture with ship-based high resolution multibeam bathymetry, to map benthic habitats and biodiversity in coastal and offshore waters of SE Tasmania. The AUV successfully surveyed a plethora of marine habitats and organisms, including high-relief kelp-dominated rocky reefs to deep mid-shelf reef and sediments that are otherwise difficult to access. To determine the spatial extent of these habitats within a broader-scale context, the AUV surveys were integrated with larger scale multibeam mapping surveys. The data collected using the AUV significantly improved our understanding of the distribution of benthic habitats and marine organisms in this region, with direct application to the management and conservation of these environments. Integrating the AUV data with the largescale mapping data provided the opportunity to quantify the relationships between the biological and physical variables, and to use thise data to develop predictive models of biodiversity across the region.
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The Carnarvon Shelf Survey (SOL4769, GA survey #0308) was conducted on the R.V. Solander in collaboration with the Australian Institute of Marine Science between 12 August and 15 September 2008. The survey was operated as part of the Surrogates Program of the CERF Marine Biodiversity Hub. The survey was completed under a Memorandum of Understanding between GA and the AIMS and represents the first of three surveys planned under this agreement. The objective was to collect high-quality, accurately co-located data to enable the robust testing of a range of physical parameters as surrogates of patterns of benthic biodiversity. Underwater video footage and still images were collected from 122 stations from water depths of 13-125 m, although video quality varies among transects and some still images were not of suitable quality for analysis. Images from the still camera can be found in 'Image Library', and images from towed video screen captures can be found in 'Tow Video Stills'. Image files from screen captures are named according to area (1 = Mandu, 2 = Point Cloates, 3 = Gnarloo) followed by the station number and video identifier (TVA1). For example, 2_032TVA1 would represent a towed video transect from Station 32 at Point Cloates. See GA Record 2009/02 (Geocat #68525) for further details. Video footage was recorded to mini DV tapes, and copied to digital format. The original mini DV tapes are archived at AIMS-WA.
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Geoscience Australia carried out a marine survey on Lord Howe Island shelf (NSW) in 2008 (SS06-2008) to map seabed bathymetry and characterise benthic environments through co-located sampling of surface sediments and infauna, rock coring, observation of benthic habitats using underwater towed video, and measurement of ocean tides and wave-generated currents. Sub-bottom profile data was also collected to map sediment thickness and shelf stratigraphy. Data and samples were acquired using the National Facility Research Vessel Southern Surveyor. Bathymetric data from this survey was merged with other pre-existing bathymetric data (including LADS) to generate a grid covering 1034 sq km. As part of a separate Geoscience Australia survey in 2007 (TAN0713), an oceanographic mooring was deployed on the northern edge of Lord Howe Island shelf. The mooring was recovered during the 2008 survey following a 6 month deployment. This folder contains the images derived from benthic samples taken on cruise SS06_2008 aboard Southern Surveyor. The main folder houses all images taken while processing samples at the microscope. These images formed the first point of reference in identifying subsequent specimens to save wear and tear on the specimens put aside as reference material. Three additonal folders exist within the main folder. Amphipoda contains repeats of the amphipod taxa, SS062008Biota contains images of live organisms taken as soon as the sample was recovered to the ship and Tanaidacea contains repeats of the tanaid taxa.
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The legacy of multiple marine transgressions is preserved in a complex morphology of ridges, mounds and reefs on the Carnarvon continental shelf, Western Australia. High-resolution multibeam sonar mapping, underwater photography and sampling across a 280 km2 area seaward of the Ningaloo Coast World Heritage Area shows that these raised features provide hardground habitat for modern coral and sponge communities. Prominent among these features is a 20 m high and 15 km long shore-parallel ridge at 60 m water depth. This ridge preserves the largely unaltered form of a fringing reef and is interpreted as the predecessor to modern Ningaloo Reef. Landward of the drowned reef, the inner shelf is covered by hundreds of mounds (bommies) up to 5 m high and linear ridges up to 1.5 km long and 16 m high. The ridges are uniformly oriented to the north-northeast and several converge at their landward limit. On the basis of their shape and alignment, these ridges are interpreted as relict long-walled parabolic dunes. Their preservation is attributed to cementation of calcareous sands to form aeolianite, prior to the post-glacial marine transgression. Some dune ridges abut areas of reef that rise to sea level and are highly irregular in outline but maintain a broad shore-parallel trend. These are tentatively interpreted as Last Interglacial in age. The mid-shelf and outer shelf are mostly sediment covered with relatively low densities of epibenthic biota and have patches of low-profile ridges that may also be relict reef shorelines. An evolutionary model for the Carnarvon shelf is proposed that relates the formation of drowned fringing reefs and aeolian dunes to Late Quaternary eustatic sea level.
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Marine physical and geochemical data can be valuable in predicting the potential distributions and assemblages of marine species, acting as surrogate measures of biodiversity. The results of surrogacy analysis can also be useful for identifying ecological processes that link physical environmental attributes to the distribution of seabed biota. This paper reports the results of a surrogacy study in Jervis Bay, a shallow-water, sandy marine embayment in south-eastern Australia. A wide range of high-resolution co-located physical and biological data were employed, including multibeam bathymetry and backscatter data and their derivatives, parameters that describe seabed sediment and water column physical characteristics, seabed exposure, and infauna species. The study applied three decision tree models and a robust model selection process. The results show that the model performance for three diversity indices and seven out of eight infauna species range from acceptable to good. Important surrogates for infauna diversity and species distributions within the mapped area are broad-scale habitat type, seabed exposure, sediment nutrient status, and seabed rugosity and heterogeneity. The results demonstrate that abiotic environmental parameters of a sandy embayment can be used to effectively predict infauna species distributions and biodiversity patterns. International Journal of Geographical Information Science
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Mapping of benthic habitats seldom considers biogeochemical variables or changes across time. We aimed to: (i) develop winter and summer benthic habitat maps for a sandy embayment; and (ii) compare the effectiveness of various maps for differentiating infauna. Patch-types (internally homogeneous areas of seafloor) were constructed using combinations of abiotic parameters, and are presented in sediment-based, biogeochemistry-based and combined sediment/biogeochemistry-based habitat maps. August and February surveys were undertaken in Jervis Bay, Australia, to collect samples for physical (%mud, sorting, %carbonate), biogeochemical (chlorophyll a, sulfur, sediment metabolism, bio-available elements) and infaunal analyses. Boosted Decision Tree and cokriging models generated spatially continuous data-layers. Habitat maps were made from classified layers using GIS overlays, and were interpreted from a biophysical-process perspective. Biogeochemistry and %mud varied spatially and temporally, even in visually homogeneous sediments. Species turnover across patch-types was important for diversity, and the utility of habitat maps for differentiating biological communities varied across months. Diversity patterns were broadly related to reactive carbon and redox which varied temporally. Inclusion of biogeochemical factors and time in habitat maps provides a better framework for differentiating species and interpreting biodiversity patterns than once-off studies based solely on sedimentology or video-analysis.
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Physical sedimentological processes such as the mobilisation and transport of shelf sediments during extreme storm events give rise to disturbances that characterise many shelf ecosystems. The intermediate disturbance hypothesis predicts that biodiversity is controlled by the frequency of disturbance events, their spatial extent and the amount of time required for ecological succession. A review of available literature suggests that periods of ecological succession in shelf environments range from 1 to over 10 years. Physical sedimentological processes operating on continental shelves having this same return frequency include synoptic storms, eddies shed from intruding ocean currents and extreme storm events (cyclones, typhoons and hurricanes). Modelling studies that characterise the Australian continental shelf in terms of bed stress due to tides, waves and ocean currents were used here to create a map of ecological disturbance, defined as occurring when the Shield's parameter exceeds a threshold of 0.25. We also define a dimensionless ecological disturbance ratio (ED) as the rate of ecological succession divided by the recurrence interval of disturbance events. The results illustrate that on the outer part of Australia's southern, wave-dominated shelf the mean number of days between threshold events that the Shield's parameter exceeds 0.25 is several hundred days.
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Understanding marine biodiversity has received much attention from an ecological and conservation management perspectives. The Australian Government's Department of the Environment, Water, Heritage and the Arts has initiated the Commonwealth Environment Research Facilities (CERF) initiative to enhance the understanding of Australia's natural environment for policy making. One part of the CERF initiative through the marine biodiversity hub was to predict biodivesity from expansive physical variables. This talk presents some of the work arising from this area.
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A growing need to manage marine biodiversity at local, regional and global scales cannot be met by applying the limited existing biological data sets. Abiotic surrogacy is increasingly valuable in filling the gaps in our knowledge of biodiversity hotspots, habitats needed by endangered or commercially valuable species and systems or processes important to the sustained provision of ecosystem services. This review examines the utility of abiotic surrogates across spatial scales with particular regard to how abiotic variables are tied to processes which affect biodiversity and how easily those variables can be measured at scales relevant to resource management decisions.
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Geoscience Australia carried out a marine survey on Carnarvon shelf (WA) in 2008 (SOL4769) to map seabed bathymetry and characterise benthic environments through co-located sampling of surface sediments and infauna, observation of benthic habitats using underwater towed video and stills photography, and measurement of ocean tides and wave-generated currents. Data and samples were acquired using the Australian Institute of Marine Science (AIMS) Research Vessel Solander. Bathymetric mapping, sampling and video transects were completed in three survey areas that extended seaward from Ningaloo Reef to the shelf edge, including: Mandu Creek (80 sq km); Point Cloates (281 sq km), and; Gnaraloo (321 sq km). Additional bathymetric mapping (but no sampling or video) was completed between Mandu creek and Point Cloates, covering 277 sq km and north of Mandu Creek, covering 79 sq km. Two oceanographic moorings were deployed in the Point Cloates survey area. The survey also mapped and sampled an area to the northeast of the Muiron Islands covering 52 sq km.. 0308_carnarvon_shelf contains processed multibeam backscatter data of the Carnarvorn Shelf. The SIMRAD EM3002 multibeam backscatter data were processed using the CMST-GA MB Process, a multibeam processing toolbox co-developed by Geoscience Australia and Curtin University of Technology.