Metadata record for data expected ASAC Project 2382 See the link below for public details on this project. This entry contains: Locations for sampling sites for ASAC project 2382 on voyage 3 of the Aurora Australis in the 2004/5 season, collected between December and February of 2004/5; CTD bottle-derived seawater viscosity data and CTD bottle-derived in vivo fluorescence data. There are four spreadsheet files in this download file. Each spreadsheet file contains several worksheets. 1) I9_Stations.xls: Transect 1 (CLIVAR I9 = 'I9') station and sampling details: CTD stations, CTD profiles, Surface samples. 2) PET_Stations.xls: Transect 2 (Kerguelen Plateau and Princess Elizabeth Trough = 'PET') station and sampling details: CTD stations, CTD profiles. 3) Viscosity.xls: Viscosity data. 4) Fluorescence.xls: In vivo fluorescence data. For all files -999 = missing data A word document details the sampling protocols for viscosity and in vivo fluorescence. Note: ASAC project 2382 operates in direct collaboration with ASAC project 2596 (Three-dimensional microscale distribution and production of plankton populations).

From the abstract of some of the papers: It has been suggested that increased springtime UVB radiation caused by stratospheric ozone depletion is likely to reduce primary production and induce changes in the species composition of Antarctic marine phytoplankton. Experiments conducted at Arthur Harbour in the Antarctic Peninsula revealed a reduction in primary productivity at both ambient and increased levels of UVB. Laboratory studies have shown that most species in culture are sensitive to high UVB levels, although the level at which either growth or photosynthesis is inhibited is variable. Stratospheric ozone depletion, with resultant increased springtime UVB irradiance, has been occurring with increasing severity since the late 1970's. Thus the phytoplankton community has already experienced about 20 years' exposure to increasing levels of UVB radiation. Here we present analyses of diatom assemblages from high-resolution stratigraphic sequences from anoxic basins in fjords of the Vestfold HIlls, Antarctica. We find that compositional changes in the diatom component of the phytoplankton community over the past 20 years cannot be distinguished from long-term natural variability, although there is some indication of a decline in the production of some sea-ice diatoms. We anticipate that our results are applicable to other Antarctic coastal regions, where thick ice cover and the timing of the phytoplankton bloom protect the phytoplankton from the effects of increased UVB radiation. Growth rate, survival, and stimulation of the production of UV-B (280 to 320 nm) absorbing compounds were investigated in cultures of five commonly occurring Antarctic marine diatoms exposed to a range of UV-B irradiances. Experimental UV-B exposures ranged from 20 to 650% of the measured peak surface irradiance at an Antarctic coastal site (0.533 J per square metre per second). The five diatom species (Nitzschia lecointei, Proboscia alata, P. inermis, Thalassiosira tumida and Stellarima microtrias) appear capable of surviving two to four times this irradiance. In contrast to Phaeocystis cf. pouchetti, another major component of the Antarctic phytoplankton, the concentrations of pigments with discrete UV absorption peaks in diatoms were low and did not change significantly under increasing UV-B irradiance. Absorbance of UV-B by cells from which pigments had been extracted commonly exceeded that of the pigments themselves. Most of this absorbance was due to oxidisable cell contents, with the frustule providing the remainder. Survival of diatoms did not correlate with absorption by either pigments, frustules or oxidisable cell contents, indicating that their survival under elevated UV-B irradiances results from processes other than screening mechanisms. Springtime UV-B levels have been increasing in Antarctic marine ecosystems since the 1970's. Effects on natural phytoplankton and sea-ice algal communities, however, remain unresolved. At the Marginal Ice Edge Zone, enhanced springtime UV-B levels coincide with a shallow, stratified water column and a major phytoplankton bloom. In these areas it is possible that phytoplankton growth and survival is adversely impacted by enhanced UV-B. In coastal areas, however, the sea ice, which attenuates most of the UV-B before it reaches the water column, remains until December/January, by which time UV-B levels have returned to long-term seasonal averages. Phytoplankton from these areas are unlikely to show long-term changes resulting from the hole in the ozone layer. Fjords of the Vestfold Hills, eastern Antarctica, have anoxic basins which contain high-resolution, unbioturbated sedimentary sequences. Diatom assemblages from these sequences reflect the diatom component of the phytoplankton and sea-ice algal assemblages at the time of deposition. Twenty-year records from these sequences show no consistent record of change in species composition, diversity or species richness. Six-hundred-year records from the same area also show changes in species abundance greater than those seen in the last 20 years. From these records it can be seen that recent changes in diatom abundances generally fall within the limits of natural variability and there is little evidence of recent changes that might be associated with UV-B-induced change.

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

Locations of sampling sites for ASAC project 40 on voyage 3 of the Aurora Australis in the 2005/2006 season (the BROKE-West voyage). Samples were collected between January and March of 2008. Three datasets are currently included in this download - an excel spreadsheet and a draft publication providing details on the methodology, etc employed, as well as two copies of corrected fluoro data for BROKE-West (BW_UwayFLuChla - in excel and csv formats). Public Summary from the project: This program aims to determine the role of single celled plants, animals, bacteria and viruses in Antarctic waters. We quantify their vital role as food for other organisms, their potential influence in moderating global climate change through absorption of CO2 and production of DMS, and determine their response to effect of climate change. For more information, see the other metadata records related to ASAC project 40 (ASAC_40). ###### Taken from the abstract of the draft paper: The geographic distribution, stocks and vertical profiles of phytoplankton of the seasonal ice zone off east Antarctica were determined during the 2005-2006 austral summer as part of the Baseline Research on Oceanography, Krill and the Environment-West (BROKE-West) survey. CHEMTAX analysis of HPLC pigment samples, coupled with microscopy, permitted a detailed survey along eight transects covering an extensive area between 30 degrees E and 80 degrees E, from 62 degrees S to the fast ice. Significant differences were found in the composition and stocks of populations separated by the Southern Boundary of the Antarctic Circumpolar Current (SB), as well as a small influence of the Weddell Gyre in the western sector of the zone south of the SB (SACCZ). Within the SACCZ, we identified a primary bloom under the ice, a secondary bloom near the ice edge, and an open ocean deep population. The similarity of distribution patterns across all transects allowed us to generalise a hypothesized sequence for the season. The primary bloom was initiated by release of cells and detritus from melting sea ice, some 35 days before ice melting, with stocks of Chl a ranging from 115-239 mg.m-2, apart one leg (41 mg.m-2), which was sampled late in the season. The bloom was dominated by haptophytes (in particular, colonies and gametes of Phaeocystis antarctica), diatoms and cryptophytes (or Myrionecta rubrum). The detrital material quickly sank from the upper water column, but the bloom of diatoms and, to a lesser extent cryptophytes, continued until 20 days after ice melt. Average Chl a stocks during this bloom ranged from 56-92 mg.m-2 between transects. A bloom of Phaeocystis gametes immediately after ice melt lasted for about 10 days. Grazing activity, as indicated by phaeophytin a, also increased at the same time. The diatom bloom became senescent, probably as a result of iron exhaustion, as indicated by chlorophyllides, which reached 45% of total Chl a. The bloom then rapidly declined, apparently due to grazing krill. Well-defined 'holes' in the chlorophyll distribution of most suggested that the krill were moving southward following the retreating sea ice and clearing the ice edge bloom. There was no evidence that blooms had been terminated by sinking or by vertical mixing. It appears that grazing of the bloom and export of cellular material as faecal pellets stripped the upper water column of iron, preventing its normal recycling via the microbial network. Thus, export of iron by grazing, and possibly sedimentation, created a southward migrating iron front, limiting growth in the upper water column. North of the iron front, a recycling nanoflagellate community developed at depth, sustained by residual iron, as indicated by a close correspondence between distributions of Chl a and profiles of Fv/Fm. Its depth was independent of the mixed layer and the pycnoclines. This community consisted of haptophytes (chiefly Phaeocystis gametes), dinoflagellates, prasinophytes, cryptophytes, and some small diatoms. The community may have derived from, and was possibly sustained by, selective grazing by krill. Average stocks of Chl a ranged from 36-49 mg.m-2 between transects. North of the SB, communities were found in the mixed layer, although they still had low Fv/Fm ratios. Populations were dominated by Phaeocystis gametes (with colonies north of the southern ACC front), diatoms such as Pseudonitzschia sp., Fragilariopsis pseudonana, F. kerguelensis, F. curta, and Gymnodinium sp. Average stocks of Chl a ranged from 40-67 mg.m-2 between transects.These appeared to be recycling communities that had been advected into the BROKE-West study region. These interpretations provide a cogent explanation for the composition and structure of microbial populations in the marginal ice zone during the latter half of the summer. ###### The fields in this dataset are: Peak Pigment name Retention times Visible maxima Comments Leg Zone Latitude Longitude CTD Julian Day Date Ice free days Pigment concentrations Protists

This dataset contains locations of sampling sites for ASAC project 40 on voyage 3 of the Aurora Australis in the 2004/2005 season. Samples were collected between December and February of 2004/2005. It also contains information on chlorophyll, carotenoids, coccolithophorids and species identification and counts. Public Summary from the project: This program aims to determine the role of single celled plants, animals, bacteria and viruses in Antarctic waters. We quantify their vital role as food for other organisms, their potential influence in moderating global climate change through absorption of CO2 and production of DMS, and determine their response to effect of climate change. For more information, see the other metadata records related to ASAC project 40 (ASAC_40). There are three spreadsheets in this download file - one for the CLIVAR I9 transect, and another for a survey in the region of the Princess Elizabeth Trough. A third spreadsheet contains pigment data. Each spreadsheet contains several worksheets. PET - CTD Station details, CTD profiles, CTD Surface Samples. I9 - CTD Station details, CTD profiles, CTD Surface Samples, Transect Surface Samples. CLIVAR_CTD_Pigs_CHEMTAX - Pigment data: Concentrations of various pigments (ug/L) analysed by HPLC (see protocol); Interpretation: Interpretation of pigment data using CHEMTAX to estimate the amount (ug/L) of chlorophyll a present in a range of algal types. There is also a word document detailing some of the HPLC procedures used. The fields in this dataset are: Station Latitude Longitude Time (Universal Time) Sounder depth Sounder offset Bottles Depths (dB) Label Fmax Tmin HPLC Fluorescence FCM Visc/TEP Phyto ID Lugols Glut Bacteria Water Temperature Salinity Conductivity Net Sample Depth (m) Species Chlorophyll a Pigments HPLC

From 1991 to 2000 14 voyages have been completed in the Southern Ocean. Measurements of DMS (Dimethylsulfide) and DMSP (Dimethylsulfoniopropionate) have been carried out on surface and subsurface waters together with physical and biological measurements, with a view to understanding the main processes that affect DMS in the Southern Ocean. The first flux measurements have been carried out for DMS (see Curran and Jones 2000) in the last 3 years a concerted study has been carried out in the seasonal ice zone this study aims to identify the major phytoplankton assemblages responsible for DMS and DMSP production in the sea ice zone. It is thought that the sea ice zone also contributes to DMS in the atmosphere. This is being quantified. The fields in this dataset are: Site Date Time (local) Latitude Longitude Snow Cover (metres) Core Length (metres) DMSPt (nano Mols) Chlorophyl a (micrograms per litre) Sea Ice depth (metres) Pigments Fucoxanthin (micrograms per litre) Peridinin (micrograms per litre) 19' hexanoyloxyfucoxanthin (micrograms per litre) Salinity (ppt) Nitrate (micro Mols) Nitrite (micro Mols) Silicate (micro Mols) Phosphate (micro Mols)