Decreased concentrations of ozone in the stratosphere over Antarctica have resulted in increased levels of ultraviolet radiation in the UV-B portion of the spectrum incident at the earth's surface beneath the 'ozone hole'. There is now world-wide concern that this enhanced flux of UV radiation may cause serious harm to the marine ecosystem in the Southern Ocean. This project, which includes field and laboratory studies, will help to determine the effects of enhanced levels of UV-B radiation on phytoplankton, and to relate such effects to overlying ozone concentrations. UV levels determined from the NSF-Operated UV- Spectroradiometer at Palmer Station will be directly applicable to the interpretation of observed biological effects. Primary attention will be given to the effects of UV-B radiation on photosynthetic rates, on damage to DNA with resulting loss of cell viability, and on the rates and extent to which phytoplankton can minimize cellular UV damage by production of specialized protective pigments. Differential sensitivity to UV-B of dominant phytoplankton species or groups will also be determined, as such differences might have important consequences on the structure of the food web in antarctic waters. As the project's activity will cover the period from September through December, the resulting data set should encompass the period of maximal development of the ozone hole, as well as the time of the summer solstice. This project is important because it will elaborate previous findings and address in detail the extent and the nature of ultraviolet damage to phytoplankton, as well as evaluate the kinds of defenses cells can muster against it.
