15 DECEMBER 1999
M. de Lourdes Cobo, J. Santacruz
Microalgae are used in aquaculture as live feed for molluscs, for larval stages of crustaceans and some fish species, and for zooplankton used in the food chain of cultured species.
The concentration and cryopreservation of microalgae for later use is presented as an alternative for the partial or total dependency on fresh-cultured algae used to feed marine species.
Three marine microalgae - Chaetoceros gracilis, Isochrysis galbana var. tahiti and Tetraselmis maculata - were concentrated by centrifugation and stored at different time periods (15, 30, 60 and 120 days) at -20 C. Dimethylsulfoxide (10% v/v), Methanol (10% v/v), Glycerol (10% v/v), and Glycerol + Glucose (2% v/v) were evaluated as cryoprotectants.
Microalgae viability was determined by algal growth in liquid medium. The cryopreserved microalgae were fed to Penaeus vannamei larvae, juveniles of the mollusc Argopecten circularis and the rotifer Brachionus plicatilis to evaluate the survival and performance of these organisms compared with organisms fed with fresh algae. No artificial or other feed was used.
Chaetoceros gracilis was the only algae which presented viability after 15 and 30 days of preservation, with all the cryoprotectants used.
Penaeus vannamei larvae fed with cryopreserved C. gracilis with dimethylsulfoxide (10% v/v) and methanol (10% v/v) showed comparable survival to those larvae fed with fresh algae. From 30 days of preservation onwards, the larval survival was significantly lower (p < 0,05) than for those fed with fresh algae.
No significant differences (p < 0,0 5) were observed between the survival of A. circularis and B. plicatilis fed with fresh and cryopreserved microalgae, independently of the time of preservation or the cryoprotectant used.
(Fundacion CENAIM - ESPOL, Guayaquil, Ecuador)