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.

This data set was collected from a ocean acidification minicosm experiment performed at Davis Station, Antarctica during the 2014/15 summer season. It includes: - description of methods for all data collection and analyses. - marine microbial community data; Chlorophyll a concentration, particulate organic matter concentration (carbon and nitrogen), bacterial cell abundance. - phytoplankton primary productivity data; 14C-sodium bicarbonate incorporation raw data (decays per minute: DPM) and modelled productivity from photosynthesis versus irradiance (PE) curves, O2-evolution derived net community productivity, respiration, and gross primary productivity. - phytoplankton photophysiology data; community photosynthetic efficiency from PAM measurements (maximum quantum yield of PSII: Fv/Fm), PAM steady state light curve data and derived non-photochemical quenching of Chl a fluorescence (NPQ), relative electron transport rates (rETR), and effective quantum yield of PSII (delta F/Fm'). - phytoplankton carbon concentrating mechanism (CCM) data; maximum quantum yield of PSII (Fv/Fm) and effective quantum yield of PSII (∆F/Fm') from PAM measurements on size-fractionated phytoplankton samples (less than 10 microns and greater than 10 microns cells) exposed to; ethoxzolamide (EZA) which inhibits both intracellular carbonic anhydrase (iCA) and extracellular carbonic anhydrase (eCA), acetazolamide (AZA), which blocks eCA only, and a control (no inhibitor) sample. - bacterial productivity data; 14C-Leucine incorporation raw data (decays per minute: DPM) and calculated productivity.

A times series of data was collected from coastal (land-fast) sea ice at Davis Station, Eastern Antarctica (68 degrees 34' 36" S, 77 degrees 58' 03" E; Figure 1) from November 16 to December 2, 2015. Sea ice temperature and salinity, as well as macro-nutrients (nitrate NO3-, nitrite NO2-, ammonium NH4+, phosphate PO43- and DSi), particulate organic carbon (POC) and chlorophyll a (Chla) in the sea ice were measured six times in 16 days of austral spring and early summer (Nov. 16, Nov. 20, Nov. 23, Nov. 26, Nov. 29, and Dec. 2; in days of the year, 320, 325, 327, 330, 333, and 336). Depths were measured from the top of the ice cores. Seawater below the ice was also sampled for comparison. Samples of snow, sea ice, brine and under-ice seawater were collected under trace metal clean conditions near Davis station during the transition of sea ice from winter to spring conditions (October 2015), on a regular basis (every 4 days) for 3 weeks. 6 sampling events were successfully achieved. The list of parameters collected during the fast ice study include in situ temperature, ice texture, pH, oxygen, iron and Chla, Br/I, carbonate, nutrients and POC, incubations with stable N and C isotopes. Samples are currently returning on V3 and will be analysed in the US, Belgium and Australia in the coming months. The biogeochemical observations will allow us to determine the roles of light versus iron in the initiation of the spring bloom in this region, and the role of the melting fast ice in fertilising the spring time primary production.