Seafloor environments of the eastern Timor Sea, Northern Australia: Chlorophyll a,b,c and pheaophytin a concentrations in seabed sediments.

Brief description

The Timor Sea and its tropical marine environment support significant and growing economic activity including oil and gas exploration. To reduce uncertainty in decision making regarding the sustainable use and ongoing protection of these marine resources, environmental managers and resource users require sound scientific information on the composition and stability of seabed environments and their biological assemblages. Surveys SOL4934 and SOL5117 to the eastern Joseph Bonaparte Gulf were undertaken in August and September 2009 and July and August 2010 respectively, in collaboration with the Australian Institute of Marine Science, with research collaborations from the RAN Australian Hydrographic Office, the Geological Survey of Canada and the Museum and Art Gallery of the Northern Territory. The purpose of these surveys were to develop biophysical maps, and deliver data and information products pertaining to complex seabed environment of the Van Diemen Rise and identify potential geohazards and unique, sensitive environments that relate to offshore infrastructure. This dataset comprises chlorophyll a,b, and c, and phaeophytin a concentrations in the upper 2cm of seafloor sediments. Some relevant publications are listed below: 1. Heap, A.D., Przeslawski, R., Radke, L., Trafford, J., Battershill, C. and Shipboard Party. 2010. Seabed environments of the eastern Joseph Bonaparte Gulf, Northern Australia: SOL4934 Post Survey Report. Geoscience Australia Record 2010/09, pp.81. 2. Anderson, T.J., Nichol, S., Radke, L., Heap, A.D., Battershill, C., Hughes, M., Siwabessy, P.J., Barrie, V., Alvarez de Glasby, B., Tran, M., Daniell, J. & Shipboard Party, 2011b. Seabed Environments of the Eastern Joseph Bonaparte Gulf, Northern Australia: GA0325/Sol5117 - Post-Survey Report. Geoscience Australia, Record 2011/08, 58pp. 3. Radke, L.C., Li, J., Douglas, G., Przeslawski, R., Nichol, S, Siwabessy, J., Huang, Z., Trafford, J., Watson, T. and Whiteway, T. Characterising sediments of a tropical sediment-starved continental shelf using cluster analysis of physical and geochemical variables. Environmental Chemistry, in press

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Maintenance and Update Frequency: asNeeded

Statement: Sediments were collected using either a Smith-McIntyre grab or a Shipek grab. For chlorophylls, 0.4 ml samples of surface sediment (0-0.5 cm) were syringed into plastic bags. The samples were wrapped in Al foil and frozen. Chlorophyll concentrations were calculated on sediment extracts (90% acetone + 0.1% MgCO3) at spectrophometric readings at wavelengths of 647, 630, 750 and 664 nm. For chlorophyll-a (Chl-a) and phaeophytin-a, wavelengths of 664 nm and 750 nm (before and after the addition of 200 -L-1 0.1 mol L-1 HCl per 2 mL extractant) and the equation derived by Lorenzen (1967) were used. Chlorphyll b and c concentrations were calculated according to equations provided by Jeffrey and Welschmeyer (2003). The reproducibility of the measurements is expected to be +/-10%. Lorenzen, C. J. (1967). Determination of chlorophyll and pheopigments: Spectrophotometric equations. Limnology and Oceanography 12, 343-346. Jeffrey, S.W., and Welschmeyer, N.A. (2003). Thanks to the crew of the RV Solander for help with sample collection.