Diatom species of the Australian sector of the Southern Ocean
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).
Diatom species and biogenic particle fluxes in the Australian sector of the southern Antarctic Zone
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