Physiological response of Nannochloropsis sp. to saline stress in laboratory batch cultures

In the present paper, we investigated the physiological response of the marine microalga Nannochloropsis sp. to salt stress (13, 27, 54, and 81 g L−1 NaCl). Increasing the sodium chloride concentration caused up to a 70 % decrease in the chlorophyll a concentration, cell growth, and net photosynthesis rate. The chlorophyll a fluorescence measurements indicated a strong reduction in the effective quantum yield of photosystem II (−60 %) and an increase in nonphotochemical quenching when the cells were exposed to NaCl concentrations greater than 27 g L−1 (control). In contrast, the specific lipid content increased up to 80 % when the sodium chloride concentration was increased from 27 to 54–81 g L−1. These results are relevant for the outdoor cultivation of this microalga using open photobioreactors, in which microalgae are subjected to strong changes in salinity concentration caused by water evaporation.