Papers arising from phytoplankton experiments associated with the SAZ (Subantarctic Zone) project. This work was complete as part of ASAC (AAS) project 1156. Taken from the abstracts of the referenced papers: Subantarctic Southern Ocean surface waters in the austral summer and autumn are characterised by high concentrations of nitrate and phosphate but low concentrations of dissolved iron (Fe, ~0.05 nM) and silicic acid (Si, less than 1 micro M). During the Subantarctic Zone AU9706 cruise in March 1998 we investigated the relative importance of Fe and Si in controlling phytoplankton growth and species composition at a station within the subantarctic water mass (46.8 degrees S, 142 degrees E) using shipboard bottle incubation experiments. Treatments included unamended controls; 1.9 nM added iron (+Fe); 9 micro M added silicic acid (+Si); and 1.9 nM added iron plus 9 micro M added silicic acid (+Fe+Si). We followed a detailed set of biological and biogeochemical parameters over 8 days. Fe added alone clearly increased community growth rates and nitrate drawdown and altered algal community composition relative to control treatments. Surprisingly, small, lightly silicified pennate diatoms grew when Fe was added either with or without Si, despite the extremely low ambient silicic acid concentrations. Pigment analyses suggest that lightly silicified chrysophytes (type 4 haptophytes) may have preferentially responded to Si added either with or without Fe. However, for many of the parameters measured the +Fe+Si treatments showed large increases relative to both the +Fe and +Si treatments. Our results suggest that iron is the proximate limiting nutrient for chlorophyll production, photosynthetic efficiency, nitrate drawdown, and diatom growth, but that Si also exerts considerable control over algal growth response, suggesting that both Fe and Si play important roles in structuring the subantarctic phytoplankton community. The influence of irradiance and iron (Fe) supply on phytoplankton processes was investigated, north (47 degrees S, 142 degrees E) and south (54 degrees S, 142 degrees E) of the subantarctic Front in austral autumn (March 1998). At both sites, resident cells exhibited nutrient stress. Shipboard perturbation experiments examined two light (mean in situ and elevated) and two Fe (nominally 0.5 and 3 nM) treatments under silicic acid-replete conditions. Mean in situ light levels (derived from incident irradiances, mixed layer depths (MLDs), wind stress, and a published vertical mixing model) differed at the two sites, 25% of incident irradiance I0 at 47 degrees S and 9% I0 at 54 degrees S because of MLDs of 40 (47S) and 90 m (54S), when these stations were occupied. The greater MLD at 54S is reflected by tenfold higher cellular chlorophyll a levels in the resident phytoplankton. In the 47S experiment, chlorophyll a levels increased to greater than 1 micro gram per litre only in the high-Fe treatments, regardless of irradiance levels, suggesting Fe limitation. This trend was also noted for cell abundances, silica production, and carbon fixation rates. In contrast, in the 54S experiment there were increases in chlorophyll a (to greater than 2 micro grams per litre), cell abundances, silica production, and carbon fixation only in the high-light treatments to which Fe had been added, suggesting that Fe and irradiance limit algal growth rates. Irradiance by altering algal Fe quotas is a key determinant of algal growth rate at 54S (when silicic acid levels are nonlimiting); however, because of the integral nature of Fe/light colimitation and the restricted nature of the current data set, it was not possible to ascertain the relative contributions of Fe and irradiance to the control of phytoplankton growth. On the basis of a climatology of summer mean MLD for subantarctic (SA) waters south of Australia the 47 and 54S sites appear to represent minimum and maximum MLDs, where Fe and Fe/ irradiance, respectively, may limit/colimit algal growth. The implications for changes in the factors limiting algal growth with season in SA waters are discussed.

Five (out of a possible 7) ice stations were sampled for the Main Biology Site, collected from -63.88S 119.9E off East Antarctic in September to November 2012 during the Sea Ice Physics and Ecosystems eXperiment (SIPEX) II. Sampled pack ice floes were several 100 meters to several kilometres apart, and indicated variation in the degrees of physical deformation and biological characteristics. The sampled sites were selected on each floe due to low snow cover disturbances, were level, and free from surface deformations (limited rafting). For the production and carbon allocation dataset, the bottom 2 cm of 3 x 5 - 8 (dependant on level of biomass) cores were collected and combined within a 4 m grid using a 9 cm diameter SIPRE corer. Biology was isolated from the ice by gently mixing with 0.22 micron filtered sea water collected from the site with a Niskin bottle, and pass through a sieve. The liquid was then analysed for bacterial and algae productivity. The corresponding dataset (P:\Data\ Copy of SIPEX C14_Ugalde_Raw Data_St 8) describes data (expressed in disintegrations per minute) directly input into an excel file from the scintillation counter measured on board the Aurora Australis. The additional dataset (P:\Data\ SIPEX C14_Chloro_SIPEXII_Updated to Station 8) describes data directly input into an excel file of volume filtered for chlorophyll analysis (expressed in mls) of both the ice and liquid fraction. For the Main Biology dataset, 6 cores were taken from the same site: Core 1: temperature profile Core 2: nutrients, extracellular polymeric substances Core 3 and 4: chlorophyll, pigments (HPLC), bacteria and cell counts Core 5: particulate organic carbon/nitrogen, dissolved organic carbon Each core was sectioned from the ice-water interface at 0 - 2 cm, 2 - 10 cm, and then the remaining core was quartered. Core 1 was discarded after the temperature profile was taken. Core 3 and 4 were slow-melted in at 6 degrees cold room with 0.22 micron filtered sea water collected from the site as above (200 ml per cm ice). Cores 2 and 5 were slow-melted as above without the addition of filtered sea water. Additional measurements included 5 replicates of snow thickness and freeboard level. After melting, samples were taken/filtered for the parameters above within 12 hours of melting. The corresponding dataset (P:\Data\Data Updated to Station 8\ Main Bio Data Sheet_SIPEX II_Updated to Station 8) describes descriptive and quantitative parameters of the above cores, directly input into a spreadsheet.

This data set contains concentrations of phytoplankton, protozoa, total bacteria and metabolically active bacteria assessed by flow cytometry on transects 12, 1, 3, 5, 7, 9 and 11 of the BROKE-West survey of the Southern Ocean between January and March 2006. Only total bacterial concentrations were assessed for transect 11. Between 4 and 12 depths were sampled for marine microbes and concentrations were assessed using FACScan flowcytometer. Phytoplankton were identified and counted based on the autofluorescense of chlorophyll a when excited by the 488 nm laser of the FACScan. Protozoa were identified and counted after staining with the acid vacuole stain Lysotracker Green. Total bacteria were identified and counted using the cell permeant SYTO 13 nucleic stain. Metabolically active bacteria were identified and counted after staining for intracellular esterases with the esterase stain 6CFDA. The fields in this dataset are: Latitude Longitude Transect Number CTD number, flow file Depth (m) Total bacteria (per millilitre) Active bacteria (per millilitre) Dead bacteria (per millilitre) Protozoa (per millilitre) Phytoplankton (per millilitre) This work was completed as part of ASAC project 40 (ASAC_40).

Taken from the biology report for Davis Station, 1982, prepared by Mark Tucker. A hardcopy of the report and field books are available in the Australian Antarctic Division library, and pdf copies of the report and field books are available for download at the provided URLs. Introduction The year biology programme for the 1982 season was divided amongst three persons into Phytoplankton, Chlorophyll, Invertebrates and Fish. As the zoologist, I will therefore concentrate on the animal, aspect. The aims of this programme as outlined in the ARPAC approved "A survey of the inshore marine area of Davis" are: 1) A systematic investigation to determine the flora and fauna of the marine inshore environment. 2) To explain their distribution and abundance in response to environmental variables. The first aim can be divided into two categories: 1) Wide range collection of the benthic, planktonic, pelagic and epontic faunas from the inshore waters of the Vestfold Hills. 2) Quantitative examination of the seasonal and distributional changes of the more common species. Most of the wide range collecting of the benthos and to a certain extent the plankton was carried out over the 81/81 summer. Collections were made from as far north as the Wyatt Earp islands and in the south near the Sorsdal Glacier. As wide a coverage as possible of the Vestfolds was made plus a visit to the Rauer group on one occasion. The planktonic fauna was collected throughout the year on a monthly basis from three sites from January 82 to December 82 while the pelagic and epontic faunas were collected monthly from the same sites after fast ice formation - April to December. Additions were made to the benthic collections throughout the year if any previously uncollected or interesting specimens were observed. These collections have culminated in over 150 species. I would expect the total number of different species to be around 200 once all are identified. Representatives of all the species collected will be returned to Biology, Kingston, for reference for future workers in the marine invertebrate field. The second aim, the quantitative examination, was carried out over a 12 month period from January 82 to December 82 at three sites - A, B and C (figure 1). These sites were selected on the criteria of depth, proximity to Davis and most importantly sediment types. Site A is 9m deep with a sandy bottom and a few odd rocks. It has a relatively low (5% or less) macrophytic cover. Site B is 20m deep with a mud bottom and zero macrophytes while site C is 15m deep with a rocky bottom and scattered pockets of sand and shell fragments etc. and 5-10% macrophyte cover. Sites A and B are relatively flat while C is situated on quite a steep slope. Sediment samples have been retained from each site to enable particle size analysis for more accurate descriptions of the sediment types. Several zooplankton, sediment inhabiting and macroscopic benthic species were monitored on a monthly basis for the year. Fish were sampled at sites A and C while the epontic community was sampled after ice formation at all three sites. The environmental variables measured were ice and snow thickness, tide, hours of daylight, salinity, nutrients, water temperature plus chlorophyll data and phytoplankton numbers. These variables are to be used in statistical analysis as a means of explaining the abundance and distribution of the species studied.