Tetraselmis suecica cultured in different nutrient concentrations varies in nutritional value to Artemia

Artemia were fed the marine microalga Tetraselmis suecica that had been previously cultured with increasing nutrient concentrations of 0.5, 1, 2, 4, 8 and 16 mg atom N l(-1) under cyclostat regime with a daily semi-continuous renewal of 50% of the culture. The different nutritive qualities of the Tetraselmis suecica cultures generated were reflected in dramatic changes in Artemia survival, dry weight, total length, percentage of gravid females, percentage of spawning and number of nauplii per spawning. All these parameters were positively correlated to nutrient concentration up to 8 mg atom N l(-1), decreasing with 16 mg atom N l(-1). After 19 days of culture, the best results were obtained when Artemia were fed Tetraselmis suecica grown at a nutrient concentration of 8 mg atom N l(-1). In these cultures, the Artemia had a survival rate of 85%, an average length of 8.3 mm, a dry weight of 0.61 mg, a percentage of gravidity of 27%, a percentage of spawning 19%, with a production of 86 nauplii per spawning and a food conversion rate (FCR) of 2.37. The lowest results for all culture parameters were obtained with the lowest nutrient concentration tested. The production of nauplii per spawning was the parameter most influenced, being the best index to test the nutritional quality of the microalgae. The wide variability in the growth parameters of Artemia induced by the changes in the initial inorganic nutrient concentration of the trophic chain could be very useful for physiological studies and for the production of Artemia and nauplii of high nutritive value for the culture of finfish or crustacean larvae in their early developmental stages.