This study employs data from two satellite-borne instruments namely, the Sea-Viewing Wide Field-of-view Sensor (SeaWiFS) and the Total Ozone Mapping Spectrometer (TOMS). This work was completed as part of an honours project under ASAC project 2210 (UV climate over the Southern Ocean south of Australia, and its biological impact). Further information about the project is available in the word document available for download (extract from the honours thesis). The fields in this dataset are: Region Year Day (Julian Day) Pixels (number of cloud free pixels from SeaWiFS sensor that were available for analysis) Mean Chlorophyll (milligrams per cubic metre) (derived from cloud free pixels) Standard Deviation Ozone (dobson units) from the TOMS sensor (average for whole region).

Minicosm design: Three successive experiments to a maximum incubation of 14 days were performed from mid November to early January in the summer of 2002/03 in a temperature controlled shipping container housing six 500 L polythene tanks or minicosms. Domes of UV transmissive PMMA in the roof of the container directly above the minicosms allowed ambient sunlight to be reflected to the tanks through tubes of anodised aluminium. These tubes reflected greater than 96% of the incident radiation irrespective of wavelength. Light perturbation to each minicosm was achieved by screening materials that attenuated UV wavelengths. UV stabilised polycarbonate removed wavelengths shorter than 400 nm, transmitting only photosynthetically active radiation (PAR) and provided the control treatment (PAR). In minicosm 2, a mylar screen removed UVB wavelengths (280 - 320 nm), providing a treatment (UVA) with PAR and UVA. Minicosms 3, 4 and 5 (UVB1, 2 and 3 respectively) were screened by borosilicate glass of 9, 5, and 3 mm thickness, transmitting ambient light (including UVR) at the equivalent water depths (ED, k=0.4) of 7.15, 5.38 and 4.97 meters respectively. Minicosm 6 (UVB4) was screened with PMMA that transmitted ambient light at an ED of 4.43 m. Light measurements: Measurements of downwelling UV and PAR were obtained using biometer and Licor sensors mounted on the roof of the minicosm container. A Macam, double grating spectroradiometer measured the spectral irradiance on the roof of the container. This was then weighted with the erythemal action spectrum and correlated to that obtained by the UV biometer. The Macam was used to measure the spectral irradiance at the cross of the UV biometer. The spectral intensity of light wavelengths were measured laterally and vertically in the minicosm screened only by UV-transmissive PMMA irradiance. These measurements were used to model the light field within the minicosm. In all other light treatments the Macam measured the spectral irradiance immediately below the water surface and in the centre of the minicosm. The model was then used to predict the spectral distribution and intensity of other light treatments. These measurements were repeated at interval throughout the season to determine whether solar elevation influenced transmission of ambient downwelling irradiance to the minicosms. UV and PAR sensors fixed to the outside of the minicosm container, together with the modelled light climates within each minicosm beneath each light treatment, predicted the quantify the light to which each experimental treatment was exposed. This work was conducted as part of ASAC project 2210. The download file contains three excel spreadsheets, plus three accompanying word documents which provide detailed methods used in the collection of these data, plus more information about the experiments. The fields in this dataset are: Day Treatment UVA UVB PAR - photosynthetically active radiation

Minicosm design: Three successive experiments to a maximum incubation of 14 days were performed from mid November to early January in the summer of 2002/03 in a temperature controlled shipping container housing six 500 L polythene tanks or minicosms. Domes of UV transmissive PMMA in the roof of the container directly above the minicosms allowed ambient sunlight to be reflected to the tanks through tubes of anodised aluminium. These tubes reflected greater than 96% of the incident radiation irrespective of wavelength. Light perturbation to each minicosm was achieved by screening materials that attenuated UV wavelengths. UV stabilised polycarbonate removed wavelengths shorter than 400 nm, transmitting only photosynthetically active radiation (PAR) and provided the control treatment (PAR). In minicosm 2, a mylar screen removed UVB wavelengths (280 - 320 nm), providing a treatment (UVA) with PAR and UVA. Minicosms 3, 4 and 5 (UVB1, 2 and 3 respectively) were screened by borosilicate glass of 9, 5, and 3 mm thickness, transmitting ambient light (including UVR) at the equivalent water depths (ED, k=0.4) of 7.15, 5.38 and 4.97 meters respectively. Minicosm 6 (UVB4) was screened with PMMA that transmitted ambient light at an ED of 4.43 m. Light measurements: Measurements of downwelling UV and PAR were obtained using biometer and Licor sensors mounted on the roof of the minicosm container. A Macam, double grating spectroradiometer measured the spectral irradiance on the roof of the container. This was then weighted with the erythemal action spectrum and correlated to that obtained by the UV biometer. The Macam was used to measure the spectral irradiance at the cross of the UV biometer. The spectral intensity of light wavelengths were measured laterally and vertically in the minicosm screened only by UV-transmissive PMMA irradiance. These measurements were used to model the light field within the minicosm. In all other light treatments the Macam measured the spectral irradiance immediately below the water surface and in the centre of the minicosm. The model was then used to predict the spectral distribution and intensity of other light treatments. These measurements were repeated at interval throughout the season to determine whether solar elevation influenced transmission of ambient downwelling irradiance to the minicosms. UV and PAR sensors fixed to the outside of the minicosm container, together with the modelled light climates within each minicosm beneath each light treatment, predicted the quantify the light to which each experimental treatment was exposed. This work was conducted as part of ASAC project 2210. The download file contains three excel spreadsheets, plus three accompanying word documents which provide detailed methods used in the collection of these data, plus more information about the experiments. The fields in this dataset are: Day Treatment Carbon Hydrogen Nitrogen C:N ratio

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.