Antioxidants, a radical solution? : antioxidant responses of marine microalgae to ultraviolet radiation

Virtually all sunlit waters around the world are inhabited by microalgae. These unicellular photosynthesizers use solar irradiance as their energy source. Yet, when absorbance of of light energy exceeds the energy needed for consumption, highly energetic electrons accumulate within the photosynthetic electron transport chains. Exposure to ultraviolet radiation stimulates the pile-up of electrons. Eventually these electrons can leak onto molecular oxygen to form reactive oxygen species. To counteract these biologically dangerous oxygen radicals, microalgae are equipped with a network of antioxidants. This thesis describes antioxidant responses of microalgae to excess irradiance conditions. Specials attention is paid to the impact of ultraviolet radiation since the concentration of stratospheric ozone has decreased dramatically over the last few decades. Also, global climate change can have serious effects on the light conditions microalgae are exposed to. Specific questions addressed in this these were: how and when do microalgae deploy their antioxidant network? Are antioxidants used in conjunction with with other protection mechanisms? Do antioxidants increase UV resistance? Can antioxidants explain differences in taxonomic structure of algal populations under various light regimes? Are antioxidants related to geographic or taxonomic background, or cell size?