Ultraviolet Radiation Induced Changes in the Patterns of Production and Composition of Biochemical Compounds in Antarctic Phytoplankton

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Goes0126150There is sufficient evidence to show that present levels of incident ultraviolet radiation (UVR, 280-400nm) are impairing phytoplankton productivity in the Southern Ocean. Yet, efforts at extrapolating these findings to allow accurate and unambiguous predictions of the consequences of UVR on the Antarctic marine food web and biogeochemical cycles in the sea have been confounded with uncertainty. Estimated impacts to the Antarctic marine ecosystem range from insignificant to catastrophic. This disparity has been attributed to lack of information in key areas of UVR photobiology and photochemistry. Generally, studies have been based on broadband UVR, and do not take into account competing responses of phytoplankton at different wavelengths across the UVR waveband. Such information is critical if we are to understand the consequences of UVR enhancement on carbon assimilation by marine phytoplankton and its consequences for the food web and biogeochemical cycles. This is especially true in regions like the Antarctic where stratospheric ozone concentrations can decrease by about 50% each spring altering the proportion of UVB (280-320nm) and UVA (320-400nm) radiation that phytoplankton receive during their growth season. This project will systematically investigate changes in the production rates and composition of biochemical compounds within Antarctic phytoplankton cells under spectrally defined conditions. Investigations of both laboratory cultures and natural populations of Antarctic phytoplankton will be undertaken to understand 1) how phytoplankton cellular biochemical processes are impacted by the interplay between the different UVR wavelengths and visible light, 2) how UVR sensitivity varies across taxonomic groups of phytoplankton and 3) whether this difference in sensitivity is responsible for the dominance of one species over the other. The effect of UVR exposure on nutrient uptake by phytoplankton cells will also be studied. This information will help ascertain the role of UVR in the phytoplankton dynamics of the Southern Ocean.