Summary
Concentrations of UV-B absorbing pigments and anthocyanins were measured in three moss species, over a summer growing season in Antarctica. Significant seasonal differences were found in the potential UV-B screening pigments. The most exposed species, Ceratodon purpureus, has intermediate and stable concentrations of UV-B absorbing pigments, suggesting it may rely on constitutive UV-B screens. Anthocyanin pigments were more responsive in this species and could offer increased antioxidant protection during periods of high UV-B radiation. Bryum pseudotriquetrum accumulated the highest concentration of UV-B screening pigments and showed positive associations between UV-B radiation and both UV-B absorbing and anthocyanin pigments. Since these pigments could act as either direct UV-B screens or antioxidants, the results suggest that B. pseudotriquetrum ought to be best equipped to deal with the negative effects of increased exposure to UV-B radiation due to ozone depletion. However, studies of UV-B induced DNA damage show that C. purpureus is less susceptible to damage than B. pseudotriquetrum. We have therefore explored the location of these pigments within the plant to determine if this explains the higher tolerance of C. purpureus. Overall, the two cosmopolitan species B. pseudotriquetrum and C. purpureus appear better protected from the damaging effects of ozone depletion than the Antarctic endemic Grimmia antarctici. Since the endemic showed no evidence of any UV photoprotective response and accumulated the most DNA damage we conclude that it is the most vulnerable to climate change.