The effect of salinity shock on the growth and rapid light curve of dunaliella salina

Abstract

To confirm the effect of hypersaline shock on the growth of Dunaliella salina, the rapid light curves and chlorophyll fluorescence in D. salina with a NaCl upshift from 80 to 160, 240 and 320 g·L−1, respectively, were measured. Results showed that the photosynthetical saturated light of Dunaliella salina was downregulated to deal effectively with the severe NaCl increase from 80 to 160, 240 and 320 g·L−1. Dunaliella salina can deal effectively with the cells’ rapid increase in NaCl from 80 to 160 g·L−1 by heat dissipation to dissipate the excess energy. Salinity with 240–320 g·L−1 NaCl led to overproduction of QA− and the destruction of the PSII acceptor side, causing inhibition of photosynthetic electron transport. Dunaliella salina can also manage the abrupt rise in NaCl concentration from 80 to 240 g·L−1 by accumulating the amount of β-carotene and glycerol per cell. However, Dunaliella salina cannot effectively manage the rapid increase in NaCl from 80 to 320 g·L−1 due to the stronger inhibition and impaired of the PSII acceptor side. It is suitable to shade D. salina cells to 500 and 800 μmol·m−2·s−1 when cells are exposed to a severe NaCl shift from 80 to 160 g·L−1 and 80 to 240 g·L−1. NaCl ranged from 80 to 240 g·L−1 favoured the growth and carotenoid content of D. salina; however, the survival rate and photosynthetic activity were lowered by the sudden increase in NaCl.