Effect of Salinity on the Growth Parameters of Halotolerant Microalgae, Dunaliella spp.

Abstract

Dunaliella strains (T35, T36 and T37) were isolated from saline river of Namibia. The effects of salinity stress on their growth and pigment content was investigated. The specific growth rate (μ) of Dunaliella was established in a controlled environment. NaCl concentration has a strong effect on the growth rate and generation time of these halotolerant microalgae. Dunaliella strains were shown to withstand large variations of salinity of the growth medium, 0.5 - 4.0 M NaCl. The optimum conditions for their growth were 1.0 M NaCl at 25 oC, pH 7.5 and 45 μmol m-2 s-1. Increasing salinity from 1.0 to 4.0 M NaCl decreased cell density by 40 %. Increased cellular chlorophyll content was observed form 2 to 14 days of inoculation for all the three strains investigated. However, after day 10 of inoculation there was no significant difference in the pigment content per cell in all strains (p ≤ 0.05). This study shows that there is a good relationship between growth rate and efficient photosynthetic apparatus during the cultivation.Keywords: Dunaliella, salinity stress, chlorophyll, specific growth rate