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The succession of macro- and microalgal communities in the Antarctic will be investigated in field experiments under various UV radiation (UVR) conditions and in the absence or presence of grazers. The observed differences in the succession process will be correlated to physiological traits of single species, especially in spores and germlings, which are the most vulnerable stages in their life histories. Photosynthetic activity of the different developmental stages will be measured routinely. Additionally we plan the determination of pigment composition, C:N ratios, content of UV protective pigments and of possible DNA damage. The experiments will start in spring, concomitant to the time of highest UVBR, due to the seasonal depletion of the ozone layer in the Antarctic region. Supplemental laboratory experiments will be conducted to determine the effects of UVR on spores and germlings of individual species. In addition to the above analyses, we plan to examine of UVR induced damage of cell fine structure and of the cytoskeleton. The results of both the field and laboratory experiments will allow us to predict the consequences of enhanced UVR for the diversity and stability of the algal community.
Due to its high energy, UV radiation can induce severe damage at the molecular and cellular level. On the molecular level proteins and lipids, as well as nucleic acids are particularly affected. Conformation changes of certain proteins involved in photosynthesis, such as the reaction center protein (D1) of photosystem II or the CO2 fixing enzyme in the Calvin cycle (RuBisCo) lead to an inhibition of photosynthesis, and consequently to a decrease in biomass production. This might shift certain algal species into deeper waters, not reached by UV radiation. The aim of the studies is to demonstrate how strong an increase of UV radiation due to stratospheric ozone depletion will influence the depth distribution and biomass production of macroalgae, and which molecules and processes are most severely affected. Moreover, it will be studied, which stage in the life cycle of the individual species is most sensitive to UV radiation as it will be this particular stage, which in the end determines the upper distribution limit of a certain species on the shore.