Abstract：In the process of ecological restoration using submerged vegetation, green filamentous algae Cladophora will be blooming with decreased nutrients and increased water transparency. To determine the effects of light intensity and phosphorus concentration on growth of C.oligoclona, the growth and photosynthetic activity of C. oligoclona cultured in BBM medium at different concentrations of phosphorus (0.005, 0.02, 0.1,0.6mg/L) and light intensities [10, 30, 50μmol/(m2·s)] for 16 days was examined. The results showed that at the light intensity of 10μmol/(m2·s), the fresh weight of C. oligoclona increased by about 0.05g at the phosphorus concentrations of 0.1mg/L or above. However, the fresh weight of C. oligoclona decreased under other conditions. The greatest fresh weight loss was observed (about 0.49g) at the highest light intensity of 50μmol/(m2·s) and the lowest phosphorus concentration of 0.005mg/L. Chlorophyll fluorescence parameters Fv/Fm values inversely related to light intensity, the value of Fv/Fm decreased as the light intensity increased. Fv/Fm value was 0.75 at 10μmol/(m2·s) whereas Fv/Fm value was only 0.3 at 50μmol/(m2·s). Under the same light intensity, the different concentrations of phosphorus had no significant effects on the Fv/Fm values. These data showed that light intensity exerted more effects on the growth of C. oligoclona than phosphorus concentration. However, higher light intensity was detrimental to the growth of C. oligoclona.
