Diatom and biogenic particle fluxes were investigated over a two-year and six-year periods at the Subantarctic and Polar Frontal Zones, respectively, in the Australian Sector of the Southern Ocean. Both sites were located along ~ 140 degrees E: station 47 degrees S was set on the abyssal plain of the central SAZ whereas station 54 degrees S was placed on a bathymetric high of the Southeast Indian Ridge in the PFZ. The data sets contain diatom species and biogeochemical flux data measured at 1000 m at the 47 degrees S site between 1999-2001 and at 800 m at the 54 degrees S site during six selected years between 1997-2007. All traps were MacLane Parflux sediment traps: conical in shape with a 0.5 m2 opening area and equipped with a carousel of 13 or 21 sampling cups. Shortest intervals corresponded with the austral summer and autumn ranging typically between 4.25 and 10 days, whereas the longest intervals were 60 days and corresponded with winter. Total fluxes of particulates at both traps were highly seasonal, with maxima registered during the austral spring and summer and very low fluxes during winter. Seasonality was more pronounced in the 54 degrees S site. Biogenic silica (SiO2) was the dominant bulk component in the PFZ while carbonate (CaCO3) dominated the particle fluxes at the SAZ. POC export was relatively similar between sites despite significant differences in the total diatom flux. Diatom frustules from 94 taxa were identified over the entire experiment. The dominant species of the diatom assemblage was Fragilariopsis kerguelensis at both sites, representing 43% and 59% of the integrated diatom assemblage at the 47 degrees S and 54 degrees S sites, respectively. Secondary contributors to the diatom assemblage at the 47 degrees S were Azpeitia tabularis, Thalassiosira sp. 1, Nitzschia bicapitata, resting spores of Chaetoceros spp., Thalassiosira oestrupii var. oestrupii, Hemidiscus cuneiformis and Roperia tesselata. Subordinate contributions to the diatom assemblage correspond to Pseudo-nitzschia lineola cf. lineola, Pseudo-nitzschia heimii, Thalassiosira gracilis group and Fragilariopsis pseudonana, Fragilariopsis rhombica and Thalassiosira lentiginosa. Data available: two excel files containing sampling dates and depths, raw counts, relative abundance and fluxes (valves m-2 d-1) of the diatom species, and biogenic particle fluxes measured at 1000 m and 800 m depth at the 47 degrees S and 54 degrees S sites, respectively. Each file contains four spreadsheets: raw diatom valve counts, relative abundance of diatom species and valve flux of diatom species and biogenic particle composition and fluxes. Detailed information of the column headings is provided below. Cup - Cup (=sample) number Depth - vertical location of the sediment trap in meters below the surface Mid-point date - Mid date of the sampling interval Length (days) - number of days the cup was open Girdle bands instead of valves were counted for Dactyliosolen antarcticus Castracane. Therefore, D. antarcticus girdles counts were not included in relative abundance calculations. Dates of data collection: 47 degrees S site: July 1999 - October 2001 (two-year record) 54 degrees S site: September 1997 - February 1998, July 1999 - August 2000, November 2002 - October 2004 and December 2005 - October 2007 (six-year record).

Diatom and biogenic particle fluxes were investigated over a one-year period (2001-02) at the southern Antarctic Zone in the Australian Sector of the Southern Ocean. Two vertically moored sediment traps were deployed at 60 degrees 44.43'S 139 degrees 53.97' E at 2000 and 3800 m below sea-level. In these data sets we present the results on the temporal and vertical variability of total diatom flux, species composition and biogenic particle fluxes during a year. A detailed description of the field experiment, sample processing and counting methods can be found in Rigual-Hernandez et al. (2015). Total fluxes of particulates at both traps were highly seasonal, with maxima registered during the austral summer (up to 1151 mg m-2 d-1 at 2000 m and 1157 mg m-2 d-1 at 3700 m) and almost negligible fluxes during winter (up to 42 mg m-2 d-1 at 2000 m and below detection limits at 3700 m). Particulate fluxes were slightly higher at 2000 m than at 3700 m (deployment average = 261 and 216 mg m-2 d-1, respectively). Biogenic silica (SiO2) was the dominant bulk component, regardless of the sampling period or depth (deployment average = 76% at 2000 and 78% at 3700 m). Highest relative contribution of opal was registered from the end of summer through early-autumn at both depths. Secondary contributors were carbonate (CaCO3) (7% at 2000 m and 9% at 3700 m) and particulate organic carbon (POC) (1.4% at 2000 m and 1.2% at 3700 m). The relative concentration of carbonate and POC was at its highest in austral spring and summer. Diatom frustules from 61 taxa were identified over the entire experiment. The dominant species of the diatom assemblage was Fragilariopsis kerguelensis with a mean flux between 53 x 106 and 60 x 106 valves m-2 day-1 at 2000 m (annualized mean and deployment average, respectively). Secondary contributors to the diatom assemblage at 2000 and 3700 m were Thalassiosira lentiginosa, Thalassiosira gracilis var. gracilis, Fragilariopsis separanda, Fragilariopsis pseudonana, Fragilariopsis rhombica, Fragilariopsis curta and Azpeitia tabularis. Data available: two excel files containing sampling dates and depths, raw counts, relative abundance and fluxes (valves m-2 d-1) of the diatom species, and biogenic particle fluxes found at 2000 m and 3700 m depth. Each file contains four spreadsheets: raw diatom valve counts, relative abundance of diatom species and valve flux of diatom species and biogenic particle composition and fluxes. Detailed information of the column headings is provided below. Cup - Cup (=sample) number Depth - vertical location of the sediment trap in meters below the surface Mid-point date - Mid date of the sampling interval Length (days) - number of days the cup was open Girdle bands instead of valves were counted for Dactyliosolen antarcticus Castracane. Therefore, D. antarcticus girdles counts were not included in relative abundance calculations

Sediment cores were collected from the East Antarctic margin, aboard the Australian Marine National Facility R/V Investigator from January 14th to March 5th 2017 (IN2017_V01; (Armand et al., 2018). This marine geoscience expedition, named the “Sabrina Sea Floor Survey”, focused notably on studying the interactions of the Totten Glacier with the Southern Ocean through multiple glacial cycles. The cores were collected using a multi-corer (MC), were sliced every centimetre, wrapped up in plastic bags, and stored in the fridge. Sediment samples were dried in an oven at 40°C and ground using a pestle and a mortar. Biogenic silica (or ‘opal’) analysis was carried out following modification of the protocol of Mortlock and Froelich (1989). About 30 mg of sediment was leached with 30 mL of 1M sodium carbonate (Na2CO3) for 5 hours at 80°C. Every hour, 1 mL of sample was removed and centrifuged at 10,000 rpm for 30 sec. A 200 µL aliquot was removed from the supernatant and diluted 50x with Milli-Q water for SiO2 determination by molybdate-blue spectrophotometry. A standard calibration was prepared by dilution of a SiO2 standard solution (sodium hexafluorosilicate, from 0 to 200 µM). The opal concentrations were calculated using the slope of the last three points of the dissolution curve (Demaster, 1981), or the changing slope part of the curve. References - Armand, L. K., O’Brien, P. E., Armbrecht, L., Baker, H., Caburlotto, A., Connell, T., … Young, A. (2018). Interactions of the Totten Glacier with the Southern Ocean through multiple glacial cycles (IN2017-V01): Post-survey report. ANU Research Publications. - Demaster, D. J. (1981). The supply and accumulation of silica in the marine environment. Geochimica et Cosmochimica Acta, 45, 1715–1732. - Mortlock, R. A., and Froelich, P. N. (1989). A simple method for the rapid determination of biogenic opal in pelagic marine sediments. Deep-Sea Research Part I, 36(9), 1415–1426.

The collection aims to showcase the range of Southern Ocean diatom species found in the major hydrological provinces of the Australian Sector of the Southern Ocean along the 140 degrees E. The collection includes specimens collected in the Sub-Antarctic Zone (SAZ), Polar Frontal Zone (PFZ) and Antarctic Zone (AZ). Samples were collected with McLane Parflux time series sediment traps placed at several depths in the SAZ (47 degrees S site), PFZ (54 degrees S site) and AZ and (61 degrees S site) during the decade 1997-2007. The shortest sampling intervals were eight days and corresponded with the austral summer and autumn, whereas the longest interval was 60 days and corresponded with austral winter. Split aliquots were obtained for taxonomic analysis via scanning electron microscopy (SEM). For improved taxonomic imaging, samples were treated with hydrochloric acid and hydrogen peroxide to remove carbonates and organic matter, respectively. A micropipette was used to transfer the suspension of selected samples to a round-glass cover slip following standard decantation method outlined by Barcena and Abrantes (1998). Samples were air-dried and coated with gold for SEM analysis. SEM analysis was carried out using a JEOL 6480LV scanning electron microscope. Taxonomy Diatoms include all algae from the Class Bacillariophyceae and follow the standardised taxonomy of World Register of Marine Species (WoRMS). Order Asterolamprales Family Asterolampraceae Asteromphalus hookeri Ehrenberg Asteromphalus hyalinus Karsten Order Achnanthales Family Cocconeidaceae Cocconeis sp. Order Bacillariales Family Bacillariaceae Fragilariopsis curta (Van Heurck) Hustedt Fragilariopsis cylindrus (Grunow) Krieger Fragilariopsis kerguelensis (O'Meara) Hustedt Fragilariopsis pseudonana (Hasle) Hasle Fragilariopsis rhombica (O'Meara) Hustedt Fragilariopsis separanda Hustedt Nitzschia bicapitata Cleve Nitzschia kolaczeckii Grunow Nitzschia sicula (Castracane) Husted var. bicuneata (Grunow) Hasle Nitzschia sicula (Castracane) Husted var. rostrata Hustedt Pseudo-nitzschia heimii Manguin Pseudo-nitzschia lineola (Cleve) Hasle Pseudo-nitzschia turgiduloides Hasle Order Chaetocerotanae incertae sedis Family Chaetoceraceae Chaetoceros aequatorialis var. antarcticus Cleve Chaetoceros atlanticus Cleve Chaetoceros dichaeta Ehrenberg Chaetoceros peruvianus Brightwell Chaetoceros sp. Order Corethrales Family Corethraceae Corethron spp. Order Coscinodiscales Family Coscinodiscaceae Stellarima stellaris (Roper) Hasle et Sims Family Hemidiscaceae Actinocyclus sp. Azpeitia tabularis (Grunow) Fryxell et Sims Hemidiscus cuneiformis Wallich Roperia tesselata (Roper) Grunow Order Hemiaulales Family Hemiaulaceae Eucampia antarctica (Castracane) Mangin Order Naviculales Family Plagiotropidaceae Tropidoneis group Family Naviculaceae Navicula directa (Smith) Ralfs Family Pleurosigmataceae Pleurosigma sp. Order Rhizosoleniales Family Rhizosoleniaceae Dactyliosolen antarcticus Castracane Rhizosolenia antennata f. semispina Sundstrom Rhizosolenia antennata (Ehrenberg) Brown f. antennata Rhizosolenia cf. costata Gersonde Rhizosolenia polydactyla Castracane f. polydactyla Rhizosolenia simplex Karsten Proboscia alata (Brightwell) Sundstrom Proboscia inermis (Castracane) Jordan Ligowski Order Thalassiosirales Family Thalassiosiraceae Porosira pseudodenticulata (Hustedt) Jouse Thalassiosira ferelineata Hasle et Fryxell Thalassiosira gracilis (Karsten) Hustedt Thalassiosira lentiginosa (Janisch) Fryxell Thalassiosira oestrupii (Ostenfeld) Hasle var. oestrupii Fryxell et Hasle Thalassiosira oliveriana (O'Meara) Makarova et Nikolaev Thalassiosira tumida (Janisch) Hasle Order Thalassionematales Family Thalassionemataceae Thalassionema nitzschioides var. lanceolatum Grunow Thalassiothrix antarctica Schimper ex Karsten Data available: 73 SEM images of the most abundant diatom species found at the three sampling sites. Samples were collected by several sediment traps placed at different depths in the Subantarctic Zone (47 degrees S site), Polar Frontal Zone (54 degrees S site) and Antarctic Zone (61 degrees S site) during the decade 1997-2007. The collection site and date for each species image can be found in Table 1 (see the word document in the download file).

Antarctic sediments and sea-ice are important regulators in global biogeochemical and atmospheric cycles. These ecosystems contain a diverse range of bacteria whose biogeochemical roles remains largely unknown and which inhabit what are continually low temperature habitats. An integrated molecular and chemical approach will be used to investigate the coupling of microbial biogeochemical processes with community structure and cold adaptation within coastal Antarctic marine sediments and within sea-ice. Overall the project expects to make an important contribution to our understanding of biological processes within low temperature habitats. DATA SET ORGANISATION: The dataset is organised on the basis of publication and is organised on the basis of the following sections: 1. SEDIMENT SAMPLES and ISOLATES Samples collected are described in terms of location, type and where data were obtained chemical features. The designation, source, media used for cultivation and isolation and availability of sediment and other related isolates are provided. Samples included are from the following locations: Clear Lake, Pendant Lake, Scale Lake, Ace Lake, Burton Lake, Ekho Lake, Organic Lake, Deep lake and Taynaya Bay (Burke Basin), Vestfold Hills region; and the Mertz Glacier Polynya region. 2. BIOMASS and ENZYME ACTIVITY DATA Biomass, numbers and extracellular enzyme activity data are provided for Bacteria and Archaea populations from Mertz Glacier Polynya shelf sediments. 3. FATTY ACID and TETRAETHER LIPID DATA Phospholipid and tetraether lipid data are provided for Mertz Glacier Polynya shelf sediments. Whole cell fatty acid data are provided for various bacterial isolates described officially as new genera or species. 4. RNA HYBRIDISATION DATA RNA hybridisation data for Mertz Glacier Polynya sediment samples is provided, including data for oligonucleotide probes specifc for total Bacteria, Archaea, the Desulfosarcina group (class Deltaproteobacteria, sulfate reducing bacterial clade), phylum Planctomycetes, phylum Bacteroidetes (Cytophaga-Flavobacterium-Bacteroides), class Gammaproteobacteria, sulfur-oxidizing and related bacteria (a subset of class Gammaproteobacteria) and Eukaryota. 5. PHYLOGENETIC DATA 16S rRNA gene sequence data are indicated including aligned datasets for three clone libraries derived from the Mertz Glacier Polynya including GenBank accession numbers. Sequence accession numbers are provided for Vestfold Hills lake sediment samples. In addition GenBank numbers are provided for denaturing gradient gel electrophoresis band sequence data from Mertz Glacier Polynya shelf sediment. Other forms of this DGGE data (banding profile analysis) are available in reference Bowman et al. 2003 (AAD ref 10971).