Physiological Effects of Light Intensity on the Opportunistic Algae Ulva rigida C. Agardh (Chlorophyta)

Intertidal seaweeds exposed to strong fluctuation in light quantity and spectral light quality. Light plays an important role controlling seaweed growth and physiology. Therefore, we conducted a culture experiment to determine the physiological effects of light intensity on the opportunistic algae Ulva rigida C. Agardh. For this reason, samples were exposed to two different light intensities (55 µmol photons m -2 s -1 and 100 µmol photons m -2 s -1 ) and their some physiological features including photosynthetic performance, growth rate, pigment content, total protein and nitrate reductase activity were measured. According to our results, the maximum relative electron transport rate  and saturation irradiance point were not significantly different between the treatments. On the other hand, relative growth rate, nitrate reductase activity and chlorophyll- a concentrations of U. rigida were significantly decreased under low light condition. Consequently, our data indicated that photosynthetic perfomance of Ulva rigida was not affected to treated light intensity, while growth and nitrogen metabolism were primarily controlled by light.