UV-ABSORBING PIGMENTS, PHOTOSYNTHESIS AND UV EXPOSURE IN ANTARCTICA -COMPARISON OF TERRESTRIAL AND MARINE-ALGAE

Since Antarctic plants experience a wide range of ultraviolet (UV) exp osure, the pigment content of Antarctic algae (Palmaria decipiens (Rei nsch) Ricker, Enteromorpha bulbosa (Suhr) Montagne, Prasiola crispa (L ightf.) Kutz. sp. antarctica (Kutzing) Knebel) was monitored over a ye ar. In summer the mature form of the marine rhodophyte Palmaria contai ns a range of UV-absorbing pigments in high concentration providing a broad absorbance with a maximum at 337 nm. Juvenile fronds develop thr ough winter with smaller absorbance maxima at 322 nm, 309 nm and 295 n m. The terrestrial chlorophyte Prasiola crispa contains a single UV-ab sorbing pigment with a maximum at 32 5 nm. Compared with other green a lgae, including the marine Enteromorpha, the UV-absorbing pigment in P rasiola is present in high concentrations. Variations in the level of UV-absorbance relative to chlorophyll in Prasiola, appear to correspon d with varying UV exposure. To test this, Prasiola was maintained with an enhanced ratio of UV-B to visible light to simulate the effects of stratospheric ozone depletion. After 4 weeks the chlorophyll content and photosynthetic rates were reduced in the presence of enhanced UV-B light, but the ratio of UV-absorbing pigments to chlorophyll was unch anged. This suggests that even for Antarctic algae, that contain high levels of UV-absorbing pigments, exposure to sunlight with an increase d ratio of UV-B to visible light is stressful.