Effects of solar radiation on growth and mycosporine-like amino acids content in Thalassiosira sp, an Antarctic diatom

Abstract.

The main objective of this study was to investigate the role of mycosporine-like amino acids (MAAs) in the short-term (hours) and long-term (several days) photoacclimation to solar ultraviolet radiation (UVR) of a marine Antarctic diatom (Thalassiosira sp.). The cultures were exposed to natural solar radiation and grown over 72 h and 6 days under three experimental irradiance treatments: (1) photosynthetic available radiation (PAR) + UVR (280–700 nm), (2) PAR + UVA (315–700 nm), and (3) PAR (400–700 nm). Two MAAs were identified and quantified in the cells: porphyra-334 and shinorine. The cultures showed an initial period of growth inhibition and the rate of synthesis of MAAs (µ) was very high in all treatments in the short-term experiment and during the first 2 days of the long-term experiment. No differences between treatments were observed in the accumulation of these compounds. After 2 days of exposure, however, the MAA content per cell was several times higher than that initially found in all treatments, and the cells exposed to the PAR + UVR treatment displayed the maximum concentration.