Effect of UV radiation on the maximal quantum yield of fluorescence (F_v ⁄ F_m) of four Antarctic algae collected to different depths.

<p>Algae were exposed for 6 h to PAR+UV-A+UV-B (PAR + UV) and PAR conditions (20 μmol m^-2 s^-1 for PAR, 3 W m^-2 for UV-A and 0.25 W m^-2), and returned to control culture conditions under dim PAR for 12 h (recovery). Initial is the time cero before the 6 h exposure to UV radiation. Values are means ± S.D., n = 9. The significant decrease in photosynthesis in the UV treatment relative to PAR (ANOVA and Tukey HSD post hoc test) is indicated.