Bynoe Harbour Habitat Mapping Survey 2016: Chlorins and porosity data for seabed sediments

Brief description

This resource contains surface sediment data for Bynoe Harbour collected by Geoscience Australia (GA), the Australian Institute of Marine Science (AIMS) and Department of Land Resource Management (Northern Territory Government) during the period from 2-29 May 2016 on the RV Solander (survey SOL6432/GA4452). This project was made possible through offset funds provided by INPEX-led Ichthys LNG Project to Northern Territory Government Department of Land Resource Management, and co-investment from Geoscience Australia and Australian Institute of Marine Science. The intent of this four year (2014-2018) program is to improve knowledge of the marine environments in the Darwin and Bynoe Harbour regions by collating and collecting baseline data that enable the creation of thematic habitat maps that underpin marine resource management decisions. The specific objectives of the survey were to: 1. Obtain high resolution geophysical (bathymetry) data for outer Darwin Harbour, including Shoal Bay; 2. Characterise substrates (acoustic backscatter properties, grainsize, sediment chemistry) for outer Darwin Harbour, including Shoal Bay; and 3. Collect tidal data for the survey area. Data acquired during the survey included: multibeam sonar bathymetry and acoustic backscatter; physical samples of seabed sediments, underwater photography and video of grab sample locations and oceanographic information including tidal data and sound velocity profiles. This dataset comprises total chlorin concentrations, chlorin indices and porosity measured on seabed sediments. A detailed account of the survey is provided in Siwabessy, P.J.W., Smit, N., Atkinson, I., Dando, N., Harries, S., Howard, F.J.F., Li, J., Nicholas W.A., Picard, K., Radke, L.C., Tran, M., Williams, D. and Whiteway, T., 2016. Bynoe Harbour Marine Survey 2017: GA4452/SOL6432 Post-survey report. Record 2017/04. Geoscience Australia, Canberra. Thanks to the crew of the RV Solander for help with sample collection, Matt Carey, Craig Wintle and Andrew Hislop from the Observatories and Science Support at Geoscience Australia for technical support and Jodie Smith for reviewing the data. This dataset is published with the permission of the CEO, Geoscience Australia

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Maintenance and Update Frequency: asNeeded

Statement: Bottom sediments were collected using a Smith McIntyre grab. Bulk sub-samples (6.5 ml) of surface sediment (0-2 cm) were extruded into vials which were wrapped in Al foil and immediately frozen. Porosity was determined by calculation of the wet volume as a percentage of the total volume, after freeze drying and correction for seawater salts. Wet and dry bulk density were calculated from the same dataset with correction for seawater salts. The accuracy of the wet/dry measurements were >1%. The precision of the volume measurements were >2%. The residual sediments were then ground in the dark, and each successive sample was quickly returned to the freezer. Chlorins were then extracted from freeze-dried sediment using the method of Schubert et al. (2005) (reference below). Relative standard deviations of the precisions on duplicate samples averaged 6.0 ± 5.7 for total chlorins and 2.4 ± 2.4 for chlorin indices. Schubert, C.J., Niggemann, J., Klockgether, G., and Ferdelman, G., 2005. Chlorin Index: A new parameter for organic matter freshness in sediment. Geochemistry Geophysics and Geosystems 6(3), 1-12.