The Growth and Biochemical Composition of Nannochloropsis oculata Under Influence of Different Phosphorus Sources for Aquaculture Live food

Abstract

Phosphorus is one of the most important nutritional factors which regulate cell growth and plays a significant role in most cellular processes. The effect of different phosphorus sources on the growth and biochemical composition of Nannochloropsis oculata (N. oculata) was investigated in this study. Four treatments: Mono potassium phosphate )KH₂PO4), potassium di phosphate (K2HPO4), calcium super phosphate (CaH6O9P2), and media without any phosphorus sources were all compared to F/2 media, which has sodium di hydrogen phosphate (NaH2PO4) as control at a concentration of 36 µmol -1. The experiment lasted for 15 days under the conditions of 100 μmol photons per m2s of light intensity, with a light-to-dark (L/D) ratio of24:0, a salinity 25 g/L, temperature maintained at 23± 1 °C, and a pH value of pH 7.5 ±0.3. The growth of N. oculata based on cell density was inhibited in the medium without any phosphorus sources (5.3×106 cell/ mL) and increased significantly in the medium with NaH2PO4 (16.4×106 cell/ mL). All phosphorus sources showed that there were significant differences (P ≤ 0.05) between all treatment media in chlorophyll content; KH₂PO4 achieved the highest significant chlorophyll a content (Chl a) with 4.25 mg/l, followed by K2HPO4 4.12 mg/l. Cells treated with NaH2PO4 produced the highest total protein and lipid content (31.14% and 46.63% by dry weight, respectively). Media without phosphorus had the highest total carbohydrate (22.48%), while the lowest total lipids and total carbohydrate achieved by KH₂PO4 and CaH6O9P2 had the lowest total protein (25.90%).