Research Objectives:
There is enough evidence to show that present levels of incident ultraviolet (UV) radiation—280 to 400 nanometers (nm)—are impairing phytoplankton productivity in the Southern Ocean. Yet efforts aimed at extrapolating these findings to allow accurate and unambiguous predictions of the consequences of UV radiation on the antarctic marine food web and biogeochemical cycles in the sea have been confounded by uncertainty. Estimates of the effects of UV radiation on the antarctic marine ecosystem range from insignificant to catastrophic. This disparity has been attributed to lack of information in key areas of photobiology and photochemistry.
Generally, studies have been based on broadband UV radiation and do not take into account competing responses of phytoplankton at different wavelengths across the waveband. Such information is critical if we are to understand the consequences of UV radiation 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 percent each spring, thereby altering the proportion of UV–B (280 to 320 nm) and UV–A (320 to 400 nm) radiation that phytoplankton receive during their growth season.
This study is aimed at understanding the impact of UV under the ozone hole on phytoplankton photosynthesis, growth, and community succession. The principal research objectives are to:
+ Examine the extent of changes in the rates of synthesis and composition of biochemical compounds in antarctic marine phytoplankton during UV exposure,
+ Examine how these changes are impacted by the interplay between the different UV radiation wavelengths and visible light,
+ Examine whether UV sensitivity varies across taxonomic groups of phytoplankton and whether this difference in sensitivity is responsible for the dominance of one species over the other,
+ Determine whether changes in the biochemical composition of phytoplankton resulting from exposure to UVBR are responsible for the decrease in the ability of the cells to take up nitrogenous nutrients, and
+ Observe whether UVR induced changes in the biochemical composition of phytoplankton are large enough, to influence the quality of material sinking out of the euphotic zone.
