Growth of the marine microalga Tetraselmis suecica in batch cultures with different salinities and nutrient concentrations

The marine microalga Tetraselmis suecica is known for its ability to tolerate a wide range of salt concentrations. Cultures were grown under 48 different nutrient concentration-salinity conditions, ranging from 2 to 64 mM NaNO3 and from 0 to 35‰ S. Salinity was more important for the growth rate of the microalgae when it was related to the nutrient concentration in the culture medium. Optimal growth conditions were between 25 and 35‰ salinity and nutrient concentrations of 2, 4 and 8 mM of NaNO3, resulting in 0.55 doublings/day and a maximum cellular density of 1.3 × 106 cells/ml. Variations in salinity and in nutrient concentration had a greater effect on the final biomass than on the growth velocity. The total protein of the culture and protein per cell increased when the salinity increased for a given nutrient concentration. The total protein of the cultures decreased when the nutrient concentration increased for a given salinity. Protein per cell decreased with increasing salinity up to 20‰ but from this point of the process was reversed. The nitrate-protein transformation rate increased with the salinity and decreased with increasing nutrient concentrations. The maximum rate was 64%.