Long-term preservation of Tetraselmis suecica:influence of storage on viability and fatty acid profile

Aquaculture production could be improved by using preserved microalgal biomass as feedstuff for marine animal larvae and juveniles. The present paper reports the effects of preserving Tetraselmis suecica by freezing with and without cryoprotectant, freezing in liquid nitrogen and maintenance of concentrated cultures at 4°C on viability and fatty acid profile. For long-term preservation (as long as 21 months), freezing can keep the fatty acid profile unaltered although leading to complete loss of cell viability. On the other hand, concentrated cultures kept in darkness at +4"C show a strong capacity for survival closely correlated with cell concentration. At 4 g. l- ', residual photosynthetic activity (ca. 6% of the initial) was still present after 150 days of storage. Furthermore, oxygen availability affected cell survival. Cultures stored in hermetically sealed vials lost their viability much more rapidly than those kept in cotton-plugged vials. Dry weight percentages of all fatty acids slightly increased in stored biomass in comparison with fresh biomass, because of reserve material consumption. Nonetheless, the fatty acid profile on a total fatty acid basis remained unchanged over storage time regardless of viability. This is an important fact to bear in mind as fatty acids play an important role in the quality of the cell as food in aquaculture.