Abstract: In order to study the combined effects of the light and temperature on the growth and physiological performance, the chosen Ulva prolifera grew under three temperature levels (20, 25 and 30℃) and two light conditions (70, 250 μmol/m2·s), then the parameters like the growth rate, Chl a content, chlorophyll fluorescence parameters, dark respiration and photosynthetic oxygen evolution rate were determined. The results showed that the growth of U. prolifera was enhanced by higher light; there were no significant difference in the growth rates between 20 and 25℃ treatments, but the growth was significant inhibited at 30℃. The effective quantum yield (Fv′/Fm′) and the maximal relative electron transfer rate (rETRmax) were lowest under the 30℃ and 250 μmol/m2·s treatment. U. prolifera showed higher dark respiration rate (Rd) and net photosynthetic oxygen evolution rate (Pn) at 25℃ under high light level with lowest value in Rd/Pn. In one word, the effects of higher temperature on U. prolifera were mediated by light levels.

Key words: Ulva prolifera, light intensity, photosynthetic oxygen evolution, chlorophyll fluorescence parameters, temperature