Abstract

This study examined the recovery capacity of early life stages of the South Pacific kelps Lessonia nigrescens and Lessonia trabeculata after exposure to artificial ultraviolet radiation (UV-B 280-315 nm, UV-A, 315-400 nm) Spores (3 h postrelease) were exposed to different UV doses applied as daily pulses (0.5, 1, 2, 3, 4 h) during 6 days. Afterwards cultures were kept under PAR condition and fertility of gametophytes and formation of sporophytes measured up to day 45 (for L. nigrescens) and 65 (for L. trabeculata). The irradiation with UV-B radiation for 6 days strongly impaired spore germination: at biologically effective UV doses (BED Caldwell > 2 kJ m -2; pulses > 2 h per day), complete mortality of the spores was observed. In contrast, spores irradiated with UV-A retained a germination capacity close to 80 and 70% under high doses (75 kJ m -2; 4 h per day). The surviving spores from both treatments exhibited a recovery during their further development as the fertility of gametophytes and formation of sporophytes increased with age of culture. In the intertidal L. nigrescens, fertility of gametophytes from spores irradiated with UV-B during 0.5 and 1 h per day was between 70 and 100% after 45 days. Treatments with UV-A did not affect markedly the fertility and production of sporophytes, as values were always between 80 and 100% after 45 days. In the subtidal L. trabeculata, recovery of cultures irradiated with UV-B and UV-A were lower, in particular the formation of sporophytes as compared to L. nigrescens. Two major findings are outlined: (1) exposure of spores to UV-B radiation affects the further development of the life cycle, and (2) the surviving spores retained their viability and were able to complete the life history.