EFFECTS OF UV-RADIATION OF DIFFERENT WAVEBANDS ON PIGMENTATION, N-15-AMMONIUM UPTAKE, AMINO-ACID POOLS AND ADENYLATE CONTENTS OF MARINE DIATOMS

Three marine diatoms Lauderia annulata Cleve, Odontella sinensis (Grev ille) Grunow and Thalassiosira rotula Meunier were exposed to ultravio let (UV) radiation of different wavebands under controlled laboratory conditions (0.035 vol% CO2, 18 degrees C). Several changes in the patt erns of pigments in these organisms were seen depending on the waveban d of UV radiation and species examined. UV-B and UV-B plus UV-A radiat ion led to a reduction in the overall pigment content of all three dia toms. The uptake of N-15-ammonium was less affected by 5-h UV-A (WG 32 0) but significantly reduced after UV-B and UV-B plus UV-A exposure. T he pattern of free amino acid pools varied depending on the applied UV wavebands and the tested diatom. The main protein-bound amino acids o f T. rotula decreased after 5-h UV irradiance except leucine. Contents of adenosine 5'-mono-, di-, and triphosphate (AMP, ADP and ATP) were affected differently by UV radiation; ATP values increased at the end of UV-B and UV-B plus UV-A exposure. These results have been discussed with reference to the impact of the different UV sources and the infl uence on the nitrogen metabolism in connection to pigments and supply with energy.