This study provides information on the effect of three light intensities (37.5, 62.5 and lOO!lmol photons.m- 2 s-1) and photoperiods (light:dark) cycle 8:16, 12:12 and  16:8h  on growth rate, duplication time and biomass production  in microalga  Chiarella vulgaris. Stock of C. vulgaris was separated from water samples taken at Anzali Wetland,  purified  and cultured  in  lOOOml  Erlenmeyer  at constant temperature  25±0.5°C,  using Zehnder medium.

Cell count was conducted daily and biomass was measured at the exponential growth phase in different treatments. Analysis of variance indicated  significant  difference  (P<0.05)  among light regimes. The maximum growth rate 1.13d-1 was observed at 10011mol photons.m- 2 s-1 and 16:8h light duration and also  the minimum duplication time 0.61d- 1 occurred at this treatment. The maximum biomass 2.05gr 1 was  recorded  at  62.5!lmol  photons.m -2  s-1  and 8:16h light period.