IMMEDIATE SCIENTIFIC REPORT
K136: UV IN THE ANTARCTIC AND EFFECTS ON SEA ICE ALGAE
New Zealand Antarctic Research Programme 1990/91
Antarctica New Zealand October 22-November 17 1990
The programme had two parts. The first part characterised the sun and sky light in Antarctic, in particular determining the spectrum and the intensity and polarisation distributions around the sky, and the trends in the UV radiation during the period of the programme. The sky light distribution was found to be that of a strongly multiple-scattering atmosphere, while a clear inverse correlation in the UV with ozone abundance was observed. The second part studied the effects of UV radiation on sea ice algae collected from two sites, under Arrival Heights and at Tent Island. Preliminary results suggest sensitivity at low levels of radiation, but not an accumulating effect with increased dosage.
There has been considerable speculation on the effects of the enhanced UV resulting from the ozone hole during the Antarctic spring. It has been suggested that the sea ice algae which grow rapidly during the spring would be particularly vulnerable to this radiation. The algae grow on the bottom surface of the sea ice. The transmission of ultraviolet and visible light through the sea ice using an artificial light source has been the study of K132-Buckley / Trodahl during the last three years, who have shown that not more than a few percent of incident radiation passes through the ice in the ultraviolet, being scattered by brine inclusions in the ice, and absorbed by the sea ice algae at the bottom.
Our programme has two parts. The first is to characterise the amount of UV and visible radiation falling onto the sea ice - the spectrum, the intensity, where it comes from in the sky, and the polarisation of the radiation. The second is to study the effects of enhanced UV radiation on sea ice algae under radiation levels both visible and ultraviolet which are typical of those encountered insitu.
Scientific endeavours and achievements:
About 10 days were spent at Scott Base, checking our instrumentation and then making measurements. This was followed by a week at Tent Island. The first four days there were snowing. However the next 2 days were perfect and we were able to obtain full measurements in that time.
We used two instruments. The first was a monitor which recorded the total radiation falling onto a flat surface in three bands UV,Violet and Blue. A shadow plate allowed the separation of the direct sun and the sky light, and an auxiliary filter separated UVA from UVB. This monitor was used to determine the variation of the radiation during the complete 24 hour day at Scott Base and at Tent Island, and to monitor the maximum intensity at about noon over page break the period of the project. The radiation in comparison with Wellington is dominated by the indirect skylight. The UV shows an inverse correlation with the ozone abundances determined at Arrival Heights.
The second instrument was a polarisation spectrometer, which was used to determine the sun's spectrum directly with a resolution of 1nm, and was fitted with a 5° field of view telescope, and used to determine the intensity and polarisation of skylight around the sky. These measurements were made at both Scott Base and Tent Island. The maximum polarisation which occurs at 90° to the sun, was about 0.5, which is considerably smaller than the value in New Zealand, and indicates a strongly multiple-scattering atmosphere. This instrument was also used to measure the absorption spectrum of a chlorophyl extract from the sea ice algae, and a transmission spectrum of the algae.
Sea ice algae:
Samples of sea ice algae were collected from 2 sites, under Arrival Heights and near Tent Island. Samples were obtained using an 8 inch Finn auger to cut a 1.5m deep hole in the ice, followed by a Cipre auger to obtain a core of ice from the last 0.5m. The core was shaded from direct light during removal and a sample of algae taken for return to Scott Base. Sub samples of algae were cultured in the presence of 14C at −1.5°C under an artificial light source containing both UV and visible light at irradiances typical of under ice conditions. The visible light was maintained at approximately 5μmol/m2s, while the UV irradiance was varied from experiment to experiment over a wide range. Growth rates of the algae were estimated by measuring the uptake of 14C over time using a beta spectrometer.
We are currently analysing the data and preparing reports for publication.
Negligible. The only possible source of environmental hazard is through the use of 14C. All material which came into contact with this low activity isotope was collected and returned to New Zealand, including all glassware, algal samples, sea water and rinse water.
|UV: 1)||The strongly multiple scattering environment around Scott Base and Tent Island is probably mainly the result of the highly reflecting snow and ice surface cover (high albedo). It would therefore be of some interest to measure the intensity distributions at other sites were the albedo may be different We have already proposed measurements at the South Pole, and again at Lake Vanda in a dry valley.|
|2)||The transmission of the sea ice is very strongly affected by the snow cover, and it page break would be of considerable interest to measure the transmission and scattering properties of snow cover of varying thicknesses.|
|3)||Measuring the colours of sea ice algae requires not a transmission measurement but a diffuse scattering measurement, using probably an integrating sphere. It will be of interest to see if any changes to the colour spectrum can be correlated with the enhanced radiation.|
|Sea-ice algae: 1)||Recent studies have demonstrated that UVA radiation may also be injurious to plant growth, both in concert with UVB and in its own right Future research could examine the relationship of these two bands of radiation to growth rates of sea ice algae.|
|2)||The algae at Tent Island was thicker than at Arrival Heights, and therefore there is the potential for algae closer to the surface to shade those lower down. The response to UV radiation of algae at different layers in the ice could also be studied.|
Management of Science:
We found the support from DSIR/Antarctic to be excellent. The facilities for physical science research were excellent, but the "Biolab" was poorly equipped particularly in space allocated, and in the facilities provided. A much larger area remote from the accomodation area is sorely needed, properly established for biological research.
We are indeed grateful to all those in their different areas of responsibilty who made our work enjoyable, and who kept their cool under our deluge of pressure: Barry Were, John Alexander, Malcolm Macfarlane, Pat Nolan, Ross McDonald, Jack Jenniskens, Helen Phillips and Paul Woodgate.