In recent years, reduced levels of atmospheric ozone observed in the early austral spring (September - October) over the South Polar region have been accompanied by increased levels of incident ultraviolet radiation (UVR). UVR is potentially very damaging to phytoplankton, the microscopic plants which constitute the base of the food web in aquatic ecosystems. This project is a quantitative assessment of the effects of UVR on Antarctic marine phytoplankton. The impact of chronic exposure to UVR will be evaluated via a month-long incubation experiment to be conducted at Palmer Station, Antarctica using flow-through chambers and natural surface seawater. Phytoplankton will be exposed to five different UVR regimes: incident, two reduced levels and two enhanced levels. Changes in biomass, primary productivity and pigment composition will be monitored at 15-day intervals. Concurrent with the month-long incubation, natural samples will also be exposed to the various UVR treatments over short time intervals (2, 4 and 8 hours) to evaluate the effects of acute UVR exposure on phytoplankton productivity and pigment composition. Such a combination of experiments will address the potential ecological consequences of increasing levels of UVR on Antarctic phytoplankton in particular and on the Antarctic marine ecosystem in general.
