The actual piece of equipment used was an International Light IL 1700Radiometer equipped with broad band detectors to measure PAR, UV-A and erythemal UV-B. The effects of UV-B radiation on the fatty acid, total lipid and sterol composition and content of three Antarctic marine phytoplankton were examined in a preliminary culture experiment. Exponential growth phase cultures of the diatoms Odontella weissflogii and Chaetoceros simplex and the Haptophyte Phaeocystis antarctica were grown at 2 (plus or minus 1)degrees C and exposed to 16.3 (plus or minus 0.7) W.m-2 photosynthetically active radiation (PAR). UV-irradiated treatments were exposed to constant UV-A (4.39 (plus or minus 0.20) W.m-2) and low (0.37 W.m-2) or high UV-B (1.59 W.m-2). UV-B treatments induced species specific changes in lipid content and composition. The sterol, fatty acid and total lipid content and profiles for O. weissflogii changed little under low UV-B when compared with control conditions (PAR alone), but showed a decrease in the lipid content per cell under high UV-B treatment. In contrast, when P. antarctica was exposed to low UV-B irradiance, storage lipids were reduced and structural lipids increased indicating that low UV-B enhanced cell growth and metabolism. P. antarctica also contained a higher proportion of polyunsaturated fatty acids under low UV-B in comparison with PAR irradiated control cultures. The flagellate life stage of P. antarctica died under high UV-B irradiation. However, exposure of P. antarctica to high UV-B irradiance increased total lipid, triglyceride and free fat. The effect of UV-B irradiances on the lipid content of Antarctic marine phytoplankton is species specific. Changes in ambient UV-B may alter the nutritional quality of food available to higher trophic levels. EXPERIMENTAL All measurements of irradiance were made with an International Light IL 1700 Radiometer equipped with broad band detectors to measure PAR, UV-A and erythemal UV-B [14]. A National Institute of Standards and Technology intercomparison package (NIST Test #534/240436-88) was used to calibrate each light sensor. Unialgal cultures of the diatoms Odontella weissflogii and Chaetoceros simplex were isolated from sea ice collected in Prydz Bay, Antarctica during the 1990/91 austral summer. Phaeocystis antarctica was isolated from Prydz Bay in 1982/83 summer. Cultures of diatoms and Phaeocystis antarctica were maintained in 2 l glass flasks using f/2 growth medium [32] and GP5 medium [33] respectively at a temperature of 2 plus or minus 1 degrees C. Cool white fluorescent lights provided photosynthetically active radiation (PAR) intensity of 17.08 J.m-2.s-1 (84.7 micro E.m-2.s-1), with no UV-B enhancement, on a 12 h light : 12 h dark cycle. Immediately before experimental irradiation, three replicate subsamples of approximately 15 ml were obtained from each parental culture and fixed with Lugols iodine, a known sample volume sedimented, and cells counted over 15 replicate fields using a Labovert inverted microscope. Mean cell concentration and standard deviation were then computed. Each exponential growth phase parental culture was thoroughly mixed and 3 replicate 300 ml Costar polystyrene culture flasks (which completely absorbed wavelengths below 295 nm) established for each light treatment (control, low and high UV exposures). Cultures were irradiated for 24 hours in a 48 hour experimental period (6 h light : 12 h dark : 12 h light : 12 h dark : 6 h light) [14, 23]. Exposures were conducted in a Thermoline controlled environment cabinet at 2 plus or minus 1 degrees C with cool white fluorescent tubes to provide PAR and UV-A (320-400 nm), with UV-B provided by FS20T 12 UV-B Westinghouse sunlamps. PAR and UV-A irradiances were 16.3 plus or minus 0.7 W.m-2 (81.3 plus or minus 3.4 micro E.m-2.s-1) and 4.39 plus or minus 0.20 W.m-2 respectively. The spectral distribution and UV-B irradiance were varied by attenuation with glass filters [5] to provide low (0.37 W.m-2) or high UV-B (1.59 W.m-2). Sensors were each covered by an attenuating glass screen and a single layer of Costar culture flask to measure the experimental irradiances to which the algae were exposed. UV-B irradiances were chosen to reflect less than (74%) and greater than (318%) peak UV-B exposure as measured at an Antarctic coastal site (Casey station, 66 degrees S, [34]). Following irradiation each culture was well mixed and approximately 15 ml was fixed with Lugols Iodine for subsequent estimation of cell concentration (as above). Chlorotic and greatly vesicularised cells were considered to be dead [23]. The remainder of each experimental culture was filtered through Whatman GF/F filters. On completion of filtration, the filters were stored at -20C overnight before extraction of lipids the following day.

This metadata record covers ASAC projects 113, 191 and 625. (ASAC_113, ASAC_191, ASAC_625). The total lipid, fatty acid, sterol and pigment composition of water column particulates collected near the Australian Antarctic Base, Davis Station, were analysed over five summer seasons (1988-93) using capillary GC, GC-MS, TLC-FID and HPLC. Polar lipids were the dominant lipid class. Maximum lipid concentrations usually occurred in samples collected in December and January and corresponded with increased algal biomass. Both lipid profiles and microscopic observations showed significant variation in algal biomass and community structure in the water column during each season and on an interannual basis. During the period of diatom blooms (predominantly Nitzschia species) the dominant sterol and fatty acid were trans-22-dehydrocholesterol and 20:5w3, accompanied by a high 16:1w7 to 16:0 ratio. Very high polyunsaturated fatty acid and total lipid concentrations were associated with diatom blooms in the area. Bacterial markers increased late in all seasons after the summer algal blooms. Long chain C30 sterols also increased during the latter half of all seasons. Fjord samples collected in the area reflected greater biomass and diversity in algal and bacterial makers than coastal sites. Signature lipids for the alga Phaeocystis pouchetii, thought to be a major alga in Antarctic waters, were identified in field samples over the five summer seasons studied. Methods Study site Davis Base is situated on the Vestfold Hills, Antarctica and incorporates numerous lakes and fjords (Fig. 1). Samples of water column particulate matter were collected during five summer seasons (1988-93), 500 meters off-shore from Magnetic Island, situated 5 km NW of Davis. Three other sampling areas were situated in the fjords of the Vestfold hills and include two sites in Ellis Fjord, one midway along Ellis Fjord and one near Ellis Fjord mouth and one sample midway along Long Fjord (Fig. 1). These fjords are protected from the marine environment, but are both marine fjords. Davis Station and Magnetic Island were used for the weekly sample sites. The mouth of Long Fjord, the mouth of Ellis Fjord, midway down Long Fjord, the deep basin in Ellis Fjord, O'Gorman Rocks and Hawker island (ocean side) were used for monthly samples. Field collection There was an initial pilot season in 1988-89, which was followed by two more detailed studies in the summers of 1989-90 and 1990-91. Four samples was also analysed from the 1991-92 and five from the 1992-93 summer seasons. During the initial pilot study at Magnetic Island in the 1988-89 summer, three water column particle samples were taken for lipid analyses. The 1989-90 and 1990-91 summer field seasons incorporated weekly sampling of the water column particulates at Magnetic Island. The phytoplankton in the fjords were studied during the summers of 1989-90 and 1990-91. The three sites that were chosen were all sampled three times in each season. Samples were also collected during the 1989-90 and 1990-91 seasons from the Magnetic Island and Fjord site s for pigment analyses. Three and five samples were collected respectively in the 1991-92 and 1992-93 seasons. Samples were also taken for microscopic analyses. For lipid analyses 30-40 liter water column particulate samples were collected at a depth of 10 m. A Seastar or INFILTREX water sampler was used in situ to filter the water through a 14.2 cm Schleicher and Schuell glass fibre filter over a three to four hour period. All filters used during sampling were preheated in a muffle furnace at 500 degrees C overnight to minimise contamination. For pigment analyses 2 to 4 litres were filtered through glass fibre filters (4.7 cm GF/F, nominal pore size 0.7 micro meters). The samples were frozen at -20 degrees C until extraction.