Abstract: In order to study the effects of solar UV radiation (280-400 nm) on microalgae, the effective quantum yield of Chaetoceros debilis and Pavlova viridis,were examined under full spectrum solar radiation and that screened off UVR. It was found that solar UVR suppressed the effective quantum yield in both species, and the inhibited effective quantum yield recovered under UVR-free dim light. The UVR-induced damage and the following repair rate were similar for both of microalga. However, the recovery of effective quantum yield for C. debilis was faster than that for P. viridis, indicating a significant difference between the species in photochemical responses to solar UVR.

Key words: Chaetoceros debilis, Pavlova viridis, UVR, effective quantum yield