Nitrogen and carbon isotopes of particulate organic matter during the K-Axis voyage of the Aurora Australis, 2016

Published: 2018-01-12

Water samples were collected from the seawater line on the Aurora Australis during the K-Axis voyage of the Aurora Australis, in 2016. The voyage was so named because data were collected along the "Kerguelen Axis" of the undersea Kerguelen Plateau. 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. Samples of phytoplankton and sea ice algae will be analysed for elemental and stable isotope composition, and used as baseline values for determining the diet and predominant carbon sources of zooplankton. The data files will contain elemental (carbon, hydrogen, nitrogen) and stable isotope (del15N and del13C) compositions for each of the analysed samples.