Influence of Microalgae Supernatant, and Bacteria Isolated from Microalgae Cultures, on Microbiology, and Digestive Capacity of Larval Gilthead Seabream, Sparus aurata, and Senegalese Sole, Solea senegalensis

Abstract

This study aimed at investigating addition of microalgae in the rearing of marine fish larvae (green water technique). Addition of microalgae supernatant, or bacteria isolated from microalgae cultures, to the rearing tanks of larval Senegalese sole, Solea senegalensis, and gilthead seabream, Sparus aurata, had no significant (P < 0.05) influence on survival or growth of the larvae. Addition of four bacterial strains isolated from microalgae decreased however the numbers of presumptive Vibrio in gilthead seabream larvae and seawater were compared with the control treatment 7 d after hatching (P < 0.05). No such effects were shown on the numbers of presumptive Vibrio in the rearing of sole larvae. Addition of bacteria improved the digestive capacity of gilthead seabream larvae, as the total activity (U/larva) of trypsin, amylase, and alkaline phosphatase in the treatment with added bacteria were significantly higher (P < 0.05) than in larvae from the control treatment 10 d after hatching. No such effects were shown in the case of sole larvae. The present results indicated that bacteria associated with microalgae may play an important role for the inhibition of proliferation of Vibrio and improvement of digestive capacity during the first days of feeding of gilthead seabream larvae, but does not appear to be beneficial for larvae of Senegalese sole.