Effect of UVB radiation on utilization of inorganic nitrogen by Antarctic microalgae

The impact of UVB (280-315 nm) radiation (WG 305) on uptake of N-15-ammonium and N-15-nitrate of marine phytoplankton from station 219 (47 degrees W, 61.5 degrees S) and sea ice-algae from station 265 (22.6,degrees W, 73.29 degrees S) was studied during the Polarstern Cruise (EPOS III, Leg 3) to the Weddell Sea, Antarctica 1989. Uptake rates (NH4+)-N-15 were higher and more affected by UVB radiation than those of (NO3-)-N-15. Pool sizes of the main amino acids changed in response to the used inorganic nitrogen source and UV exposure, Pools of glutamine, serine and glycine decreased, whereas those of alanine, asparagine and glutamate increased after UVB irradiation, The N-15-incorporation into the amino acids was reduced as a result of UVB exposure of phytoplankton and ice algae, Results are discussed with reference to an inhibitory effect on the enzymes of both carbon and nitrogen metabolism as well as to adaptation strategies.