Photosynthetic Response of Filamentous Green Algae (Oedogonium) to Irradiance and Temperature Variations

Abstract

Oedogonium is a fast-growing filamentous green macroalgae. It has been used for the bioremediation of wastewater, for fertilizer and soil conditioners, and as a tool for carbon sequestration in some countries. In Thailand, this alga is widely distributed in shallow freshwater but is very rare in brackish waters. Recently, this alga has been targeted for biomass applications. However, the different strains of the alga and their physiological responses have not yet been examined. Therefore, the aim of this work was to determine the effects of irradiance and temperature on the photosynthesis of Oedogonium strains ABRC001, ABRC002 and ABRC003. Samples were tested at light intensities of 30, 60, 100, 150, 200, 250 and 500 µmol photons·m^-2·s^-1 and at temperatures of 15, 20, 25, 30, 35 and 40 °C in the laboratory. The results showed differences in the photosynthetic responses among the algal strains. The net photosynthetic rates (P_net) of strains ABRC001, ABRC002, and ABRC003 increased as light intensity increased up to 60, 200 and 100 µmol photons·m^-2·s^-1, respectively, and decreased at higher light intensity (up to 500 µmol photons·m^-2·s^-1). Likewise, the P_net increased with temperature from 20–30 °C and decreased when the temperature increased from 35–40 °C. This study indicated good adaptation of the algal strain ABRC001 to low light intensity (E_k = 30 µmol photons·m^-2·s^-1), while strains ABRC002 and ABRC003 tolerated higher light intensity levels at E_k values of 100 and 60 µmol photons·m^-2·s^-1, respectively.