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This data set was collected during an ocean acidification mesocosm experiment performed at Davis Station, Antarctica during the 2014/15 summer season. It includes: - description of methods for all data collection and analyses. - diatom cell volume - bulk silicification - species specific silicification via fluorescence microscopy - bulk community Fv/Fm on day 12 - single-cell PAM fluorometry data (maximum quantum yield of PSII: Fv/Fm) A natural community of Antarctic marine microbes from Prydz Bay, East Antarctica were exposed to a range of CO2 concentrations in 650 L minicosms to simulate possible future ocean conditions up to the year ~2200. Diatom silica precipitation rates were examined at CO2 concentrations between 343 to 1641 micro atm, measuring both the total diatom community response and that of individual species, to determine whether ocean acidification may influence future diatom ballast and therefore alter carbon and silica fluxes in the Southern Ocean. Described and analysed in: Antarctic diatom silicification diminishes under ocean acidification (submitted for review) Methods described in: Antarctic diatom silicification diminishes under ocean acidification (submitted for review) Location: Prydz bay, Davis Station, Antarctica (68 degrees 35'S, 77 degrees 58' E) Date: Summer 2014/2015 Worksheet descriptions: Bulk silicification - raw data Measured total and incorporated biogenic silica using spectrophotometer for all tanks on day 12 after 24 h incubation with PDMPO - raw data Bulk Fv/Fm - dark-adapted maximum quantum efficiency of PSII (Fv/Fm) on whole community - raw data Measured Fv/Fm of individual cells from 3 mesocosm tanks. Single-cell silicificiation, Fluorescence microscopy - raw data Measured autofluorescence and PDMPO fluorescence of individual diatoms from 6 mesocosm tanks Single-cell PAM, dark-adapted maximum quantum efficiency of PSII (Fv/Fm) - raw data Measured Fv/Fm of individual cells from 3 mesocosm tanks. Cell volume Calculated cell volume (um3) of 7 species from minicosm tanks 1 and 6 - raw data Abbreviations: Fv/Fm Maximum quantum yield of PSII PDMPO 2-(4-pyridyl)-5-((4-(2-dimethylaminoethylaminocarbamoyl)methoxy)phenyl)oxazole Tant Thalassiosira antarctica DiscLg Large Discoid centric diatoms Stella Stellarima microtrias Chaeto Chaetoceros spp. Prob Proboscia truncata Pseu Pseudonitzschia turgiduloides FragLg Fragilariopsis cylindrus / curta Centric Large Discoid centric diatoms LargeThalassiosira Large Discoid centric diatoms
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 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).
We studied the gut contents of four dominant copepod species (Calanoides acutus, Calanus propinquus, Calanus simillimus and Rhincalanus gigas) during the summer (2014-2015) along a latitudinal gradient (sampled every 5° between 40°S and 65°S) in the Indian sector of the SO. Diatoms were the most abundant food item found in the guts, comprising 24 of the 25 species found, and 15 were common to the four species of copepod studied. Diatoms accounted for the lowest proportion of the diet in the warmer, northern waters while all the large diatoms (e.g. Chaetoceros atlanticus, C. criophilus, C. dichaeta, Corethron spp.) were only found at 65oS. The most frequent species in the guts were the centric diatoms Thalassiosira spp. (4 to 57%) and the pennate diatoms Fragilariopsis kerguelensis (27 to 80%) and Trichoctoxon reinboldii (2 to 50%); proportions varied within a species across locations. These species were found at all sites examined, whereas some diatoms were specific to one copepod species: Asteromphalus spp. (in R. gigas), C. criophilus and C. dichaeta (in C. acutus), Nitzschia lecointei and N. sicula (in C. propinquus).
Metadata record for data from ASAC Project 2146 See the link below for public details on this project. From the abstracts of the referenced papers: Early season phytoplankton communities in both Omega and Taynaya Bays are characterised by diatoms sedimenting out of the overlying sea ice. Initial nitrate, phosphate and silicate levels are high and the bay waters are covered with ice and well mixed. In Taynaya Bay the ice cover is retained throughout the season while Omega Bay is free for 6-8 weeks. After ice break out in Omega Bay, the phytoplankton community changes from one dominated by diatoms to one dominated by the phtyoflagellates, Pyramimonas spp., Cryptomonas sp. and Gymnodinium sp. In Taynaya Bay the ice remained and even though phtyoflagellates became more common, diatoms still dominated. These differences in community composition result from differences in light climate, extent of stratification and nutrient levels. Sediment cores from Abel and Platcha Bays, in the Vestfold Hills, east Antarctica, contain evidence for a local late Holocene increase in fast ice extent and a possible ice cap retreat at approximately 1750 yr BP, a similar time to the Chelnock Glaciation. Prior to this time both bays experienced periods of isolation that lead to changes in their diatom flora, C:N ratio, percentage of biogenic silica and total organic carbon. Three new diatom indices are proposed; the fast ice index, based on the proportion of benthic taxa and the snow index, based on the proportion of Berkelaya adeliense and Thalassiosira australis. These indices show strong relationships with the percentage of biogenic silica, total organic carbon and percentage sand. A weak relationship exists between the fast ice index and delta 13 C and no relationship with the C:N ratio. The fields in these datasets are: Date Julian Day Sample Volume filtered (L) Acetone Volume (ml) Abs Chlorophyll Phytoplankton
From the abstract of one of the papers: Phytoplankton biomass and speciation were monitored at an inshore site near Davis Station, East Antarctica during three consecutive summer seasons (December-February, 1992-5). Four distinct phytoplankton assemblages were identified in which the dominant species were: Phaeocystis sp., an undescribed Cryptomonas species, Thalassiosira dichotomica, and a mixed assemblage containing Fragilariopsis spp. and Nitzschia spp. Little interannual consistency was found in either the timing of the appearance or disappearance of the various assemblages. Similarly, the seasonal trends in biomass varied dramatically from year to year. Variations in the phytoplankton community can be ascribed, to some extent, to the random variation in a number of factors, including the date of fast ice break out, water column stratification, temperature and salinity, zooplankton grazing and strong winds. Periods of strong wind result in the introduction of offshore or deeper water masses into the shallow inshore environment, where the physical and chemical conditions allow blooms to develop. A number of the papers listed in the reference section are available as pdf's in the download section.