Effect of salinity and pH on the growth and biomass production in the four species of estuarine cyanobacteria

Four species of cyanobacteria isolated from estuarine habitats were studied in relation to salinity and pH on their growth rate and biomass production. The biochemicals like protein, carbohydrate and lipids were analyzed. The study has shown that although they could survive and grow at varying salinity, the range between 15 and 25 ppt was optimum for growth and biomass production in all the species. Oscillatoria tenuis and Plectonema boryanum showed maximum biomass of 2.2 mg l and 2.4 mg l at 25 ppt respectively, whereas Oscillatoria splendida showed good growth at 15 ppt (2.1mg l). Lyngbya aestuarii grew well at 30 ppt to produce a biomass of 2.4 mg l. The specific growth rate (μ) of each species ranged between 0.52 and 1.07 per day with varying salinity. All the species showed maximum biomass production between pH 6.5 and 7.5. The growth rates ranged between 0.37 and 1.02 per day for all the species with varying pH. Protein was the major component observed in all the four species and it was maximum in Oscillatoria tenuis (33.7% of dry weight). Lyngbya aestuarii showed higher concentration of total carbohydrate (18.4% of dry weight) and total lipid was highest in Plectonema boryanum (17.2% of dry weight). The species could be employed in aquaculture/ mariculture practices.