UV Radiation in Antarctic Waters: Dynamics Response of Phytoplankton and Attenuation by Pigments

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The flux of ultraviolet-B radiation (UV-B, 280-320 nm) at sea level in the Antarctic may be increasing due to decreases in stratospheric ozone levels. Previous studies have shown that marine phytoplankton in the upper portion of the water column are inhibited by natural UV radiation, and hence further progressive increases in the flux of UV may have damaging effects on the food web in Antarctic waters. Holm-Hansen proposes to measure the flux of natural UV in the euphotic zone with a multi-channel spectral radiometer and document its effect(s) on marine phytoplankton. Analysis of absorption by particulate and dissolved components will enable assessment of the role of phytoplankton and detrital pigments in the attenuation of UV radiation. Marine in situ studies will examine both short-term effects of UV based on rates of radiocarbon incorporation and long-term effects based on phytoplankton growth rates. In addition to marine in situ studies, controlled experiments using artificial light sources will be conducted to evaluate the effect of known UV doses on isolated phytoplankton cultures as well as the differential sensitivities of species in natural water samples. Photoadaptational responses involving synthesis of UV absorbing pigments and their role in protection and/or photosynthesis will be analyzed using HPLC, and particulate absorption and fluorescence spectroscopy. These studies of the dynamic response of phytoplankton to increasing dose-levels of UV will be important for understanding the biological consequences of reduced ozone/enhanced UV-B levels in the Antarctic and, through modeling efforts, will be of value in predicting UV effects elsewhere in the world's oceans.