UV-B screening potential is higher in two cosmopolitan moss species than in a co-occurring Antarctic endemic moss – implications of continuing ozone depletion

Concentrations of UV-B absorbing pigments and anthocyanins were measured in three moss species, over a summer growing season in Antarctica. Pigment concentrations were compared with a range of climatic variables to determine if there was evidence that pigments were induced by UV-B radiation, or other environmental parameters, and secondly if there were differences between species in their pigment responses. Significant seasonal differences in the potential UV-B screening pigments were found, with the two cosmopolitan species Bryum pseudotriquetrum and Ceratodon purpureus appearing better protected from the potentially damaging effects of ozone depletion than the Antarctic endemic Schistidium antarctici. 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. The negative associations between water availability measures and UV-B absorbing and anthocyanin pigments also suggest that B. pseudotriquetrum is well protected in the desiccated state. This could offer B. pseudotriquetrum an advantage over the other species when high UV-B radiation coincides with low temperatures and low water availability, thus limiting physiological activity and consequently, active photoprotective and repair mechanisms. Since these pigments could act as either direct UV-B screens or antioxidants, the results suggest that B. pseudotriquetrum is best equipped to deal with the negative effects of increased exposure to UV-B radiation due to ozone depletion. The most exposed species, C. 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. Schistidium antarctici appears poorly protected and showed no evidence of any UV photoprotective response, providing additional evidence that this endemic is more vulnerable to climate change