Widespread seagrass dieback in central Torres Strait, Australia has been anecdotally linked to the delivery of vast quantities of terrigenous sediments from New Guinea. The composition and distribution, and sedimentological and geochemical properties, of seabed and suspended sediments in north and central Torres Strait have been determined to investigate this issue. In northern Torres Strait, next to Saibai Island, seabed sediments comprise poorly sorted, muddy, mixed calcareous-siliciclastic sand. Seabed sediments in this region are dominated by aluminosilicate (terrigenous) phases. In central Torres Strait, next to Turnagain Island, seabed and suspended sediments comprise moderately sorted coarse to medium carbonate sand. Seabed sediments in this region are dominated by carbonate and magnesium (marine) phases. Mean Cu/Al ratios for seabed sediments next to Saibai Island are 0.01, and are similar to those found in New Guinea south coastal sediments by previous workers. Mean Cu/Al ratios for seabed sediments next to Turnagain Island are 0.02, indicating an enrichment of Cu in central Torres Strait. This enrichment comes from an exogenous biogenic source, principally from foraminifers and molluscs. We could not uniquely trace terrigenous sediments from New Guinea to Turnagain Island in central Torres Strait. If sediments are a factor in the widespread seagrass dieback in central Torres Strait, then our data suggest these are marine-derived sediments sourced from resuspension and advection from the immediate shelf areas and not terrigenous sediments dispersed from New Guinea rivers. This finding is consistent with outputs from recently developed regional hydrodynamic and sediment transport models.

Lord Howe Island in the southwest Pacific Ocean is the subaerial remnant of a Late Miocene hot-spot volcano. Erosion of the island has formed a shallow (20 - 120 m) sub-tropical carbonate shelf 24 km wide and 36 km long. On the mid shelf an extensive relict coral reef (165 km2) surrounds the island in water depths of 30-40 m. The relict reef comprises sand sheet, macroalgae and hardground habitats. Inboard of the relict reef a sandy basin (mean water depth 45 m) has thick sand deposits. Outboard of the relict reef is a relatively flat outer shelf (mean depth 60 m) with bedrock exposures and sandy habitat. Infauna species abundance and richness were similar for sediment samples collected on the outer shelf and relict reef features, while samples from the sandy basin had significantly lower infauna abundance and richness. The irregular shelf morphology appears to determine the distribution and character of sandy substrates and local oceanographic conditions, which in turn influence the distribution of different types of infauna communities.

The sediments deposited beneath the floating ice shelves around the Antarctic margin provide important clues regarding the nature of sub-ice shelf circulation and the imprint of ice sheet dynamics and marine incursions on the sedimentary record. Understanding the nature of sedimentary deposits beneath ice shelves is important for reconstructing the icesheet history from shelf sediments. In addition, down core records from beneath ice shelves can be used to understand the past dynamics of the ice sheet. Six sediment cores have been collected from beneath the Amery Ice Shelf in East Antarctica, at distances from the ice edge of between 100 and 300 km. The sediment cores collected beneath this ice shelf provide a record of deglaciation on the Prydz Bay shelf following the last glaciation. Diatoms and other microfossils preserved in the cores reveal the occurrence and strength of marine incursions beneath the ice shelf, and indicate the varying marine influence between regions of the sub-ice shelf environment. Variations in diatom species also reveal changes in sea ice conditions in Prydz Bay during the deglaciation. Grain size analysis indicates the varying proximity to the grounding line through the deglaciation, and the timing of ice sheet retreat across the shelf based on 14C dating of the cores. Two of the cores contain evidence of cross-bedding towards the base of the core. These cross-beds most likely reflect tidal pumping at the base of the ice shelf at a time when these sites were close to the grounding line of the Lambert Glacier.

The sediments deposited beneath the floating ice shelves around the Antarctic margin provide important clues regarding the nature of sub-ice shelf circulation and the imprint of ice sheet dynamics and marine incursions on the sedimentary record. Understanding the nature of sedimentary deposits beneath ice shelves is important for reconstructing the icesheet history from shelf sediments. In addition, down core records from beneath ice shelves can be used to understand the past dynamics of the ice sheet. Six sediment cores have been collected from beneath the Amery Ice Shelf in East Antarctica, at distances from the ice edge of between 100 and 300 km. The sediment cores collected beneath this ice shelf provide a record of deglaciation on the Prydz Bay shelf following the last glaciation. Diatoms and other microfossils preserved in the cores reveal the occurrence and strength of marine incursions beneath the ice shelf, and indicate the varying marine influence between regions of the sub-ice shelf environment. Variations in diatom species also reveal changes in sea ice conditions in Prydz Bay during the deglaciation. Grain size analysis indicates the varying proximity to the grounding line through the deglaciation, and the timing of ice sheet retreat across the shelf based on 14C dating of the cores. Two of the cores contain evidence of cross-bedding towards the base of the core. These cross-beds most likely reflect tidal pumping at the base of the ice shelf at a time when these sites were close to the grounding line of the Lambert Glacier.

Increased loads of land-based pollutants associated with land use change are a major threat to coastal-marine ecosystems globally. Identifying the affected areas and the scale of influence on marine ecosystems is critical to assess the ecological impacts of degraded water quality and to inform planning for catchment management and marine conservation. Studies using remotely-sensed data have contributed to our understanding of the occurrence and extent of influence of river plumes, as well as to assess exposure of ecosystems to river-borne pollutants. However, refinement of plume modelling techniques is required to improve risk assessments. We developed a novel approach to model exposure of coastal-marine ecosystems to river-borne pollutants. The model is based on supervised classification of true-colour satellite imagery to map the extent of plumes and to qualitatively assess the dispersal of pollutants in plumes. We use the Great Barrier Reef (GBR) to test our approach. We combined frequency of plume occurrence with spatially-distributed loads (based on a cost-distance function) to create maps of exposure to suspended sediment and dissolved inorganic nitrogen. We then compared annual exposure maps (2007-2011) to assess inter-annual variability in the exposure of coral reefs and seagrass beds. Our findings indicate that classification of true colour satellite images is useful to map plumes and to qualitatively assess exposure to river-borne pollutants. This approach should be considered complementary to remote sensing methods based on ocean colour products used to characterise surface water in plumes. The proposed exposure model is useful to study the spatial and temporal variation in exposure of coastal-marine ecosystems to riverine plumes. Observed inter-annual variation in exposure of habitats to pollutants stresses the need to incorporate the temporal component in exposure and risk models.

The Fitzroy catchment is the largest Queensland catchment discharging to the Great Barrier Reef (GBR) lagoon. Sediments and nutrients together with anthropogenic pollutants originating upstream in the catchment are discharged from the Fitzroy River via the Fitzroy Estuary (FE) and ultimately into Keppel Bay (KB). The estuary and the bay act as natural chemical reactors where the materials delivered undergo chemical and physical transformations before some are deposited and stored in the growing deltaic and beach areas, with the remainder transported eastward to the southern zone of the GBR lagoon.

In this study of the beach-ridge plain at Keppel Bay, on the central coast of Queensland, we examine ridge morphology, sediment texture and geochemistry. We build a detailed chronology for the ridge succession using the optically stimulated luminescence (OSL) dating method. Although our interpretations are preliminary, our results suggest that significant changes have occurred in the rate of shoreline accumulation of sediment, catchment sediment source areas, and that there have been minor falls in relative sea level.

In 2003, Geoscience Australia discovered three large patch reefs in the southern Gulf of Carpentaria (GA Survey 238; SS-03/2004; Harris et al., 2004). The submerged platform reefs (R1, R2 and R3) are located east of Mornington Island and appear to have been formed when sea level was ~30 m below its present position, however as the ship did not come prepared with a drill-core sampler, the sub-surface composition of the reefs was not determined. The submerged platforms support live hard corals in many locations and their discovery raised the question of the possibility of widespread reef occurrence in that region. Survey 276 was designed to deliver some answers to these questions. The current survey used rotary drilling of reefs R1, R2 and R3 which recovered coral material from 8 sites and confirmed the coral reef composition of these features. Multibeam sonar bathymetry and rotary drill cores were collected over two sections (R4 and R5) of a large (>100 km long) submerged platform that extends westwards from Mornington Island. The platform exhibits a Karst erosion surface, exhibiting drainage and depressions with raised rims, overprinting relict reef-growth geomorphic features. Reef growth features include raised rims, spur and groove reef front and elevated back-reef mounds. Other platform reefs were mapped in the south-western Gulf (R6 and R7) and in the Arafura Sea (R8). Rotary drilling has confirmed the coral reef composition of these features. Preliminary assessments of the recovered drill cores indicate that reef growth has persisted in the region for several glacial cycles, extending over at least the past 120,000 years. Dating of Holocene corals by the U/Th method demonstrates that a phase of rapid (1-2 m per kyr) reef growth occurred at most sites between 9 and 7 kyr before present, with zero or much reduced growth rates occurring after 7 kyr ago. Although coral growth occurs in many areas, the production of carbonate has not been sufficient to build the reef-tops upwards to the present sea level. The observations of live corals, but low carbonate production rates, are consistent with a 'catch-up' reef growth pattern, in which the upper surfaces of the reefs are submerged 20 to 30 m below present sea level, with isolated local reef-tops having reached to within 18 m of the sea surface. An analysis of the hypsometry of the reef surfaces indicates that platform surfaces at all sites (R1 to R8) are confined to two narrow depth intervals, centred at 26.8 ± 1 m and 30.7 ± 0.3 m. The good correspondence of hypsometric peaks indicates regionally significant phases of carbonate deposition during a prolonged, Pleistocene sea level still stand. This voyage has proved that the southern Gulf of Carpentaria contains a previously unknown major coral reef province in Australia. The reefs support locally diverse and luxuriant coral growth. From a management perspective, the slow rates of coral growth point to the need for protection of these reef systems because of their limited capacity to recover from natural or human-induced disturbances.

Geoscience Australia undertook a marine survey of the Vlaming Sub-basin in March and April 2012 to provide seabed and shallow geological information to support an assessment of the CO2 storage potential of this sedimentary basin. 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 Vlaming Sub-basin is located offshore from Perth, Western Australia, and was previously identified by the Carbon Storage Taskforce (2009) as potentially suitable for CO2 storage. The principal aim of the Vlaming Sub-basin marine survey (GA survey number GA0334) was to look for evidence of fault reactivation and of any past or current gas or fluid seepage at the seabed. The survey also mapped seabed habitats and biota in the areas of interest to provide information on communities and biophysical features that may be associated with seepage. This data package brings together the following datasets which describe biophysical aspects of seafloor sediments: GEOCAT#74276. Underwater video footage from the Vlaming Sub-basin (GA0334). GEOCAT#76463. GA0334 Vlaming sub-basin Species identification of worms from grab. GEOCAT#78540. Vlaming Sub-Basin Marine Environmental Survey (GA-0334/S. Supporter GP 1373) (NCIP Program) - High Resolution Bathymetry grids. GEOCAT# 78550. Seabed environments and shallow geology of the Vlaming sub-basin, Western Australia: Chlorin analyses of seabed sediments. GEOCAT#78551. Seabed environments and shallow geology of the Vlaming sub-basin, Western Australia: Inorganic elements of seabed sediments. GEOCAT#78552. Seabed environments and shallow geology of the Vlaming sub-basin, Western Australia: Bulk organic carbon and nitrogen isotopes and concentrations in seabed sediments. GEOCAT#78553. Seabed environments and shallow geology of the Vlaming sub-basin, Western Australia: Sediment oxygen demand of seabed sediments. GEOCAT#78564. Seabed environments and shallow geology of the Vlaming sub-basin, Western Australia: Chlorophyll a, b and c of seabed sediments. GEOCAT#78565. Seabed environments and shallow geology of the Vlaming sub-basin, Western Australia: %carbonate and specific surface area of seabed sediments. GEOCAT#79176. Seabed environments and shallow geology of the Vlaming sub-basin, Western Australia: Grain size and carbonate concentrations of seabed sediments. GEOCAT#79345. Ecology / Infaunal morphospecies identifications from the Vlaming Sub-basin (GA0334). An account of the field operations is published in: GEOCAT 74626. Nicholas, W. A., Borissova, I., Radke, L., Tran, M., Bernardel, G., Jorgensen, D M., Siwabessy, J., Carroll, A. and Whiteway, T., 2012. Seabed Environments and Shallow Geology of the Vlaming Sub-Basin, Western Australia - Marine data for the Investigation of the Geological Storage of CO2. GA0334 Post-Survey Report. Geoscience Australia, Record 2013/09. A preliminary interpretation of seabed data is provided in: GEOCAT 78846. Nicholas, W. A., Howard, F., Carroll, A., Siwabessy, J., Tran, M., Picard, K., Przeslawski, R. and Radke, L. 2014. Seabed Environments and shallow sub-surface geology of the Vlaming Sub-basin, offshore Perth Basin: summary report on observed and potential seepage, and habitats. Geoscience Australia, Record 2014/XXX. Information on the broader study, evaluating the Vlaming Sub-basin CO2 storage potential and providing details of the suitable storage sites, is available in: GEOCAT 79332. Borissova, I, Lech, M.E., Jorgensen, D.C, Southby, C., Wang, L., Bernardel, G., Nicholas, T., Lescinsky, D.L. and Johnston, S. An integrated study of the CO2 storage potential in the offshore Vlaming Sub-basin. Geoscience Australia, Record 2014/XXX.

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. Seabed sediment samples were collected by a Smith McIntyre grab at a total of 275 locations, divided between Mandu Creek (n=81), Point Cloates (n=92), Gnaraloo (n=92) and Muiron Islands (n=10). The full sample set represents 102 sampling stations at which two sediment grabs were collected in close proximity. The exception to this was at Mandu Creek where three grabs were collected at 19 stations and at Gnaraloo where single grabs were taken at three stations. At Muiron Islands, single grabs were collected at five stations and two grabs at three stations (see Brooke et al. 2009).