Abstract: In order to know the effects of solar UV radiation (280-400 nm) on coastal phytoplankton in Nanao, Shantou, the relationship between photosynthetic carbon fixation and solar radiation were examined under full spectrum solar radiation or filtering out UVR or UV-B. The biological weighting function (BWF) was checked. It was found that solar UVR suppressed the photosynthetic carbon fixation. However, the less inhibition was detected when solar UVR or UV-B were cutoff. The most serious inhibition was observed under the 100% whole solar radiation. The BWF showed that phytoplankton was more sensitive to UV-B than UV-A.

Key words: BWF, phytoplankton, photosynthesis, UVR