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

Abstract

The relative sensitivity of the reproductive cells of the seaweed Enteromorpha intestinalis to UV-B was assessed by measuring in vivo chlorophyll fluorescence ( F v variable fluorescence), germination success and growth rates. Zoospores (the asexual reproductive cells) exhibit up to a 6 fold higher sensitivity to UV-B exposure than the mature thalli (measured as chlorophyll fluorescence, F v), and differences in growth rates were also found. Consistent patterns emerged throughout these experiments in variable fluorescence, germination success and growth rates, indicating a greater sensitivity in 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 damage to the reproductive cells was irreversible. In conclusion, the ecological significance of elevated UV-B exposure in the marine environment may be seriously under-estimated if effects on the early lifestages of algae are not considered.