Pavlova lutheri: Production, preservation and use as food for Crassostrea gigas larvae

The haptophyte Pavlova lutheri was cultivated in a 4-l flat alveolar photobioreactor (FAP) in semi-continuous mode during 35 days, achieving a mean volumetric productivity of 0.4 g l-1 day-1. The microalgal culture was harvested from the photobioreactor at an average concentration of 3.5 g l-1 and subjected to different storage conditions in which the effects of temperature (1 °C, 4 °C and 25 °C), air supply and preservative (ascorbic or propionic acid) addition on the viability of the stored suspensions were investigated. Low temperatures (1 and 4 °C) and air-bubbling extended the shelf-life of the stored suspension, while no beneficial effects of ascorbic or propionic acid were found. The influence of temperature and air-bubbling on fatty acid content and profile was also evaluated over a 23-day period of storage. Air-bubbled suspensions exhibited, on the average, a 70% decrease of total fatty acid content (TFA) during storage. Non-bubbled suspensions showed a much lower decrease. The decrease mainly involved the saturated 14:0 and 16:0 and the monounsaturated 16:1n-7 and 18:1n-9. The polyunsaturated eicosapentaenoic acid (20:5n-3; EPA) and docosahexaenoic acid (22:6n-3; DHA) decreased significantly only at the end of the storage period. A feeding trial on Pacific oyster (Crassostrea gigas) larvae was carried out with fresh and preserved P. lutheri biomass kept under the best storage conditions previously defined (1 °C; darkness; air-bubbling). After 14 days of rearing no significant differences in growth or survival were detected when fresh or preserved P. lutheri was used in a monospecific diet or in association with the diatom Chaetoceros calcitrans forma pumilum.