Short-term effects of solar UV radiation and NO3- supply on the accumulation of mycosporine-like amino acids in Pyropia columbina (Bangiales, Rhodophyta) under spring ozone depletion in the sub-Antarctic region, Chile

Short-term variations of mycosporine-like amino acids (MAAs) in Pyropia columbina (Montage) W.A. Nelson exposed to nitrate (NO3-) enrichment under different outdoor light treatments during the spring ozone depletion of 2008 in Punta Arenas (Chile) were investigated. Segments of P. columbina thalli were cultivated under three treatments of solar radiation without or with NO3- supply (0.38 mmol l(-1)): PAR (P), PAR+UVA (PA), and PAR+UVA+UVB (PAB). Samples were taken at 8:00 h (initial value), 9:30, 12:30, 15:30, and 18:00 h on November 8 and at 9:00 h on November 9 (recovery period). A complex dynamic of MAAs affected by light quality and NO3- supply was observed. During the light period, the highest content of MAAs was reached under PAB and NO3- enrichment, whereas MAAs increased during the recovery period in P and PAB with no NO3- supply. Five MAAs were identified: porphyra-334, shinorine, asterina-330, palythine, and mycosporine-glycine. The hourly accumulation of each MAA varied mainly according to the time of exposure and NO3- supply. In general, the percentage of porphrya-334 increased, whereas the other MAAs decreased during the exposure period. These results suggest that MAA content in P. columbina varied in the short-term (hours) and the changes were related to the solar irradiance received and NO3- availability.