This dataset is a climatological summer chlorophyll-a layer for the Southern Ocean south of 40S, following the OC3M algorithm of Johnson et al. (2013). The climatology was calculated from level-3 binned MODISA RRS products spanning the 2002/03 to 2015/16 austral summer seasons (summer taken as day 355 to day 80).

See the referenced paper for additional details. Sampling. Sampling was conducted on board the RSV Aurora Australis during cruise V3 from 20 January to 7 February 2012. This cruise occupied a latitudinal transect from waters north of Cape Poinsett, Antarctica (65_ S) to south of Cape Leeuwin, Australia (37_ S) within a longitudinal range of 113-115_ E. Sampling was performed as described in ref. 29, with sites and depths selected to provide coverage of all major SO water masses. At each surface station, E250-560 l of seawater was pumped from E1.5 to 2.5m depth. At some surface stations, an additional sample was taken from the Deep Chlorophyll Maximum (DCM), as determined by chlorophyll fluorescence measurements taken from a conductivity, temperature and depth probe (CTD) cast at each sampling station. Samples of mesopelagic and deeper waters (E120-240 l) were also collected at some stations using Niskin bottles attached to the CTD. Sampling depths were selected based on temperature, salinity and dissolved oxygen profiles to capture water from the targeted water masses. Profiles were generated on the CTD descent, and samples were collected on the ascent at the selected depths. Deep water masses were identified by the following criteria: CDW 1/4 oxygen minimum (Upper Circumpolar Deep) or salinity maximum (Lower Circumpolar Deep); AABW 1/4 deep potential temperature minimum; AAIW 1/4 salinity minimum 18. The major fronts of the SO, which coincide with strong horizontal gradients in temperature and salinity 19,30, separate regions with similar surface water properties. The AZ lies south of the Polar Front (which was at 51_ S during sampling), whereas the PFZ lies between the Polar Front and the Subantarctic Front. In total, 25 samples from the AZ, PFZ, SAMW, AAIW, CDW and AABW were collected for this study (Fig. 1, Supplementary Data 1). Seawater samples were prefiltered through a 20-mm plankton net, biomass captured on sequential 3.0-, 0.8- and 0.1-mm 293-mm polyethersulphone membrane filters and filters immediately stored at _80 _C31,32. DNA extraction and sequencing. DNA was extracted with a modified version of the phenol-chloroform method 31. Tag pyrosequencing was performed by Research and Testing Laboratory (Lubbock, USA) on a GS FLXb platform (Roche, Branford, USA) using a modification of the standard 926F/1392R primers targeting the V6-V8 hypervariable regions of bacterial and archaeal 16S rRNA genes (926wF: 50-AAA-CTY-AAA-KGA-ATT-GRC-GG-30 , 1,392 R: 50-ACG-GGCGGT-GTG-TRC-30). Denoising, chimera removal and trimming of poor quality read ends were performed by the sequencing facility.

Chloropyll a data were collected along the WOCE transect on voyage 1 of the Aurora Australis, during October of 1991. These data were collected as part of ASAC project 40 (The role of antarctic marine protists in trophodynamics and global change and the impact of UV-B on these organisms).

Chlorophyll data was used to measure growth rates of sea ice algae in CO2 incubations. Sea ice brine microalgae was collected from sackholes. Replicate samples were incubated in ambient air (~0.04% CO2), 0.1% CO2, 1.0% CO2 and 2.0% CO2 concentrations. AT the end of the incubations the 50 ml samples were filtered through a 25 mm GF/F filter using vacuum filtration. The filters were placed in 15 ml plastic falcon tubes containing 10 ml of methanol, covered in aluminium foil and kept in the dark at 4 degrees C for 12 hours. Chl a concentration was measured using a 10AU Turner fluorometer following the acidification method of Strickland and Parsons (1972). Data in spread sheet shows the extracted chl + phaeophytin, phaeophytin and chlorophyll concentrations (micro grams l-1) for each of the three experiments. Data were collected at SIPEX Ice Stations 1-8 and SIPEX CTD stations 2-5

Chloropyll a data were collected on voyage 4 of the Aurora Australis, during the 1991-1992 season. These data were collected as part of ASAC project 40 (ASAC_40) (The role of antarctic marine protists in trophodynamics and global change and the impact of UV-B on these organisms).

Processed CTD instrument data - Corrected fluorescence profiles at the Southern Kerguelen Plateau, Indian Sector of the Southern Ocean. The fluorometer was calibrated through the regression of burst measurements against in situ chlorophyll a measured at the same depths and sites using high performance liquid chromatography (Wright et al. 2010). Zero chlorophyll a reference points were included in the regression and were obtained through averaging fluorometry data over 200-300 m bins. The resulting linear equation used to convert flourometry data was: chlorophyll = 0.262*fluorescence + 0.101. Column measurements (µg L-1) and integrated data (0-150 m, mg m-2) for each CTD station are provided.

This dataset contains chlorophyll a data collected by the Aurora Australis on Voyage 7 1992-93, taken in the Prydz Bay region between January and February 1993. These data were collected as part of ASAC project 40 (The role of antarctic marine protists in trophodynamics and global change and the impact of UV-B on these organisms).

This dataset contains the chlorophyll a data from Voyage 6 (FISHOG) 1991-92 of the Aurora Australis. The observations were taken from the Heard Island area in January and February 1992. These data were collected as part of ASAC project 40 (The role of antarctic marine protists in trophodynamics and global change and the impact of UV-B on these organisms).

The ASPeCt - Bio dataset is a compilation of currently available sea ice chlorophyll a (chl-a) data from pack ice (i.e., excluding fast ice) cores collected during 32 cruises to the Southern Ocean sea ice zone from 1983 to 2008 (Table S1). Data come from peer-reviewed publications, cruise reports, data repositories and direct contributions by field-research teams. During all cruises the chl-a concentration (in micrograms per litre) was measured from melted ice core sections, using standard procedures, e.g., by melting the ice at less than 5 degrees C in the dark; filtering samples onto glassfibre filters; and fluorometric analysis according to standard protocols [Holm-Hansen et al., 1965; Evans et al., 1987]. Ice samples were melted either directly or in filtered sea water, which does not yield significant differences in chl-a concentration [Dieckmann et al., 1998]. The dataset consists of 1300 geo-referenced ice cores, consisting of 8247 individual ice core sections, and including 990 vertical profiles with a minimum of three sections. An updated dataset was provided in 2017-12-15, which included a compilation Net CDF file.

This dataset contains chlorophyll a data collected by the Aurora Australis on Voyage 6, 1997-1998 - the SAZ (Subantarctic Zone) cruise. Samples were collected in March of 1998. These data were collected as part of ASAC project 40 (The role of antarctic marine protists in trophodynamics and global change and the impact of UV-B on these organisms).