Effects of Ultraviolet Radiation (UVA plus UVB) on Germination of Carpospores of the Red Macroalga Pyropia acanthophora var. brasiliensis (Rhodophyta, Bangiales): Morphological Changes

Carpospores of Pyropia acanthophora var. brasiliensis are dispersion and reproduction units responsible for giving rise to the diploid filamentous structure of this alga's life cycle. The present study assesses the anthropogenic impact of ultraviolet radiation (UVR) on morphology and ultrastructure, spore viability, autofluorescence of chloroplasts and the amount of intensity of ROS during the germination of carpospores. Carpospores were cultivated at 24 +/- 1 degrees C, 40 +/- 10 mu mol photons m(-2) s(-1) with photoperiod of 12 h and exposed to UVAR + UVBR for 3 h a day for 2 days with a daily dose of 5.05 J cm(-2) for UVAR and 0.095 J cm(-2) for UVBR. Samples were cultured for another five days exposed only to PAR in order to confirm their viability after the initial 2-day exposure. Carpospores showed significant sensitivity to UVR exposure after only 48 h, including changes in developmental rate, overall morphology, cell organization and chloroplast autofluorescence. UVR exposure inhibited germ tube formation in carpospores, which were mostly nonviable and/or altered, showing retracted cytoplasm and disorganized cytoplasmic content. Even in the absence of UVR exposure, carpospores remained collapsed, indicating irreversible damage. It can be concluded that UVR is a limiting factor for the development of P. acanthophora.