Effects of Nitrogen Concentration and Light Intensity on the Growth of Carbophilic Dunaliella salina HTBS
To investigate the effects of different nitrogen concentrations and light intensities on the growth of high bicarbonate toler-ance strain Dunaliella salina HTBS,the cell density,biomass,pigment content,and fluorescence parameters during HTBS cultivation by varying nitrate concentrations(0 mg·L-1,7.5 mg·L-1,75 mg·L-1,750 mg·L-1,500 mg·L-1)and light intensities(20 μmol·m-2·s-1,80 μmol·m-2·s-1,140 μmol·m-2·s-1)were examined.The results showed that 750 mg·L-1 sodium nitrate could effectively promote the growth of HTBS with the most pronounced effect on the HTBS photosynthetic system.The most significant increases were observed in cell density and biomass growth,with increases of 62.6%and 33.4%respectively.The chlorophyll content increased by 44.5%,while the β-carotene content decreased by 19%.Qp increased,while NPQ decreased.Furthermore,Fv/Fm increased by 44.59%,and ΦPSII increased by 125.00%.In comparison to 20 μmol·m-2·s-1,80 μmol·m-2·s-1 increased cell density and biomass by 21.5%and 19.6%respectively,while the chlorophyll content and β-carotene content decreased by 28.3%and 19%respectively.The rETR value exhibited a 165.12%increase,while the Fv/Fm value,ΦPSII,NPQ and Qp demonstrated a downward trend,accompanied by a decline in chemical efficiency.In conclusion,it could be concluded that a light intensity of 80 μmol·m-2·s-1 and a nitrogen concentration of 750 mg·L-1 of sodium nitrate were optimal for the growth of the high bicarbonate tolerance microalga strain Dunaliella salina HTBS.