EFFECT OF SALINITY ON THE CULTURE OF STANDARD MICROALGAE SPECIES USED IN AQUACULTURE.

Three standard microalgae species viz. Nannochloropsis oculata, Tetraselmis chui and Chaetoceros muelleri , commercially used in aquaculture in many countries, were cultured in small scale batch culture for 28 days to determine the effect of salinities (05 ppt to 30 ppt ) on the growth under laboratory conditions at Brackishwater Station of Bangladesh Fisheries Research Institute (BFRI). The BFRI microalgae culture nutrient medium, which is the modification of Guillard’s f/2 medium (Gillard & Ryther, 1962), was used as the culture medium. Nannochloropsis oculata showed maximum cell growth (345 X 104 cells /ml) at 20 ppt salinity. Tetraselmis chui showed better growth at salinities ranging from 25 ppt to 30 ppt but failed to grow at salinities from 5 to 10 ppt. The maximum cell density (458X 10 4 cells / ml) of Tetraselmis chui was observed at 30 ppt on the 24Ul day. Chaetoceros muelleri did not tolerate a salinity of 5 ppt but grew well at the salinity range of 20-30 ppt and the highest cell density (395 X 10 4 cell/ ml) of this alga was found at 25 ppt.