[Effects of temperature and light intensity on the growth and biochemical composition of Sargassum thunbergii].

A two-factorial experiment was designed to study the effects of temperature (10, 15, 20, and 25 degrees C) and light intensity (20, 60, 100, 140, and 180 microE x m(-2) x s(-1)) on the growth and biochemical composition of Sargassum thunbergii. The results showed that temperature, light intensity, and their interactions had significant effects on the growth of S. thunbergii. A higher growth rate of S. thunbergii was observed at 15 degrees C - 20 degrees C, and, with the increase of temperature, the light intensity for the maximum growth rate of S. thunbergii had an increasing trend. At 10 degrees C and 15 degrees C, higher light intensity had definite inhibition effect on the growth of S. thunbergii; while at 20 degrees C and 25 degrees C, the growth rate was generally increased with increasing light intensity. Both temperature and light intensity had significant effects on the chlorophyll a and fucoxanthin contents of S. thunbergii, and the effects of light intensity was greater than those of temperature. In general, the chlorophyll a and fucoxanthin contents of S. thunbergii decreased significantly with increasing light intensity but increased with increasing temperature. The carbohydrate content of S. thunbergii increased with increasing light intensity, while no significant difference was observed at different temperature. The protein content of S. thunbergii decreased with increasing light intensity, and was higher at 10 degrees C and 15 degrees C but tented to decrease with increasing temperature. The variation of light intensity and temperature induced the changes in the biochemical composition of S. thunbergii, and these changes could be an active physiological adjustment for the adaptation to the variation of environmental factors, which was of ecological significance to the growth and survival of S. thunbergii.