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

Document Type : Original Article

Authors

1 Faculty of Aquaculture and Marine Fisheries, Arish University. El-Arish, North Sinai, Egypt

2 Faculty of Fish Resources, Suez University, Egypt

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%).

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