| Summary: | Progress Code: completed Statement: In some cases, the amount of sample was very small - notes about the quality of each measurement are made on the spreadsheet. Purpose The samples were primarily collected to help establish an isotopic baseline for understanding trophic positions of zooplankton and fish. The data (particularly delta 15N) have also been used for interpreting iron dynamics in the water across the Kerguelen Plateau. Water samples were collected from the seawater line on the Aurora Australis during the K-Axis voyage. They were filtered so that two fractions of each sample were collected: a fraction that was between 1.2 and 210 um and a fraction that was between 210 and 1000 um. A 47 mm diameter 1000 um mesh was placed upstream of all samples, and this prevented larger particles (e.g. zooplankton) from entering the samples. The underway water was taken from the pCO2 rig at 1.4 to 1.5 atmospheres. All samples were collected on 25 mm diameter 1.2um Sterlitech silver membrane filters. The greater than 210 samples were collected on mesh and refiltered onto silver filters. The filters were stored frozen until they were processed in Hobart. Subsamples of the filters were analysed at the Central Science Laboratories, University of Tasmania to determine elemental N and C. The remainder of the filters were analysed by ANSTO (NSW) to determine delta15N and delta13C. Volumes are in litres, and the values for the nitrogen isotopes are presented as ratios.
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