Effects of temperature, light intensity, salinity on growth and photosynthetic physiology of Sargassum ilicifolium

Sargassum ilicifolium is the dominant species in the coastal seaweed field of Hainan Island. To provide technical support for the protection and restoration of seaweed field, we studied the physiological and ecological adaptability of S. ilicifolium by using chlorophyll fluorescence technology in addition with analysis of changes in photosynthetic pigment content and growth rate under different growth conditions. At different temperatures (10, 14, 18, 22, 26 and 30 ℃), light intensities (10, 20, 40, 80, 120 and 200 µmol·m⁻²·s ⁻¹) and salinities (20‰, 24‰, 28‰, 32‰, 36‰ and 40‰), we measured the specific growth rate, chlorophyll content and maximum fluorescence yield (F_v/F_m) of S. ilicifolium. The results show that the optimal temperature for the growth of S. ilicifolium was 18–26 ℃; the optimal light intensity was 20–120 µmol·m⁻²·s⁻¹; the optimal salinity was 16‰–36‰. These results indicate that S. ilicifolium is a temperature-loving macroalgae and is more sensitive to low temperature stress. Too low or too high light intensity will lead to algal damage. Therefore, the effects of temperature and light intensity on the growth and spatial distribution should be fully considered in the process of conservation and restoration of the seaweed fields dominated by S. ilicifolium. These results indicate that S. ilicifolium is a temperature-loving macroalgae and is more sensitive to low temperature stress. Too low or too high light intensity will lead to algal damage. Therefore, the effects of temperature and light intensity on the growth and spatial distribution should be fully considered in the process of conservation and restoration of the seaweed fields dominated by S. ilicifolium.