Low Temperature Preservation on Dense Biomass of Nannochloropsis oculata

The consistency supply of microalgae is crucial for hatchery as it plays important role as feed for larvae in the early stages. Thus, ensuring the availability of microalgae needs efficient management of feed, including the technique of biomass preservation. The purpose of this research was to observe the application of various low temperature to preserve Nannochloropsis oculata as feed. The source of N.oculata was filtered through a double set of 0.45 micron of cartridge which then preserved based on treatments A (5°C); B (-20° C); and C (15°C) for 30 days. After 30 days of preservation, each treatment as inoculum were cultured in the volume of 2 liter. Initial density of N.oculata was 23-24x106 cells.ml-1 placed into medium consisted of sterile sea water salinity 30 ppm, KW21™ fertilizer dose 1 ml.l-1. Culture environment was set with illumination 3.000-4.000 lux, homogenized with constant aeration, with 15 days of culture period. The result showed that on the days 9, cell density on treatment A, B and C were significantly different each other (sig 0.001), where treatment A had the highest cell density at 57.42±6.95x106 cell.ml-1, then followed with treatment C with 38.33±2.08x106 cell.ml-1 and B with 20.33±5.35x106 cell.ml-1. The use of low temperature as preservation for N.oculata could help low-middle hatchery with remoted area to maintain the sustainability of N.oculata stocks.