Nannochloropsis sp. and Tetraselmis sp. cultured at different pH also showed significant changes on the total carbohydrate content of both microalgae (Fig. 10). Increase or decrease in the normal seawater pH of 7.5e8.5 towards acidic and alkaline pH leads to the decrease in the carbohydrate content. Nannochloropsis sp. showed a significantly higher carbohydrate content when cultured at pH 8.5 whereas Tetraselmis sp. showed the highest value at pH 7.5 under control condition. For significantly higher yield of carbohydrate,natural condition at the salinity of 30 ppt and pH 7.5 to 8.5 favors all other treatment conditions for both Nannochloropsis sp. and Tetraselmis sp.