Effects of solar UV radiation and temperature on morphology and photosynthetic performance of Chaetoceros curvisetus

This study investigated the effect of solar ultraviolet radiation (UVR) and temperature on a chain length and photosynthetic performance of diatom Chaetorceros curvisetus.The cells were cultured in large quartz tubes and exposed to PAR, PAR + UV-A (PA), or PAR + UV-A + UV-B (PAB) radiation at 20°C and 28°C for six days, respectively.After recovery for 1 h, the cells were exposed again to three different radiations for 1 h.Then, a change in the photochemical efficiency (Φ PSII ) was examined and UVR-induced photoinhibition was calculated.The percentage of long chains (more than five single cells per chain) in C. curvisetus significantly increased from 8.2% (PAR) to 38.9% (PAB) at 20°C; while it was not notably affected at 28°C.Mycosporine-like amino acids (MAAs) concentration obviously increased by irradiance increment from PAR to PAB at 20°C.Chlorophyll (Chl) a concentration significantly declined with increasing irradiance at 20°C.Both MAAs and Chl a concentrations were not obviously changed by irradiance at 28°C.Before and after reexposure, Φ PSII was significantly reduced both at 20°C and 28°C.UVR-induced photoinhibition at 20°C (39%) was higher than that at 28°C (30.9%).Solar UV radiation, especially UV-B, could significantly influence the percentage of long chains of C. curvisetus, especially at low temperature.UVR-induced photoinhibition can be alleviated by higher temperatures.