The influence of UV-B radiation on the reproductive cells of the intertidal macroalga, Enteromorpha intestinalis

The relative sensitivity of the reproductive cells of the seaweed Enteromor pha intestinalis to UV-B was assessed by measuring in vivo chlorophyll fluo rescence (F-v variable fluorescence), germination success and growth rates. Zoospores (the asexual reproductive cells) exhibit up to a 6 fold higher s ensitivity to UV-B exposure than the mature thalli (measured as chlorophyll fluorescence, F-v), and differences in growth rates were also found. Consi stent patterns emerged throughout these experiments in variable fluorescenc e, germination success and growth rates, indicating a greater sensitivity i n the sexual reproductive phase of the life cycle compared with the asexual phase. Inhibition of germination success (up to 50%) and growth rates (up to 16.4%) of settled gametes and zoospores after 1-h exposures to elevated levels of UV-B (equivalent to 27 and 31% ozone depletion) showed that damag e to the reproductive cells was irreversible. In conclusion, the ecological significance of elevated UV-B exposure in the marine environment may be se riously under-estimated if effects on the early lifestages of algae are not considered. (C) 2001 Elsevier Science B.V. All rights reserved.