Abstract

VALENZUELA-ESPINOZA, Enrique; LAFARGA-DE LA CRUZ, Fabiola; MILLAN-NUNEZ, Roberto  and  NUNEZ-CEBRERO, Filiberto. Growth, nutrient uptake and proximate composition of Rhodomonas sp. cultured using f/2 medium and agricultural fertilizers. Cienc. mar [online]. 2005, vol.31, n.1a, pp.79-89. ISSN 0185-3880.

We determined the growth, nutrient (PO₄^3-, NO₃^-, NH₄+) uptake and proximate composition of Rhodomonas sp. cultured during seven days in batch culture using f/2 medium and agricultural fertilizers. The growth rate was similar with both media (µ= 0.37 and 0.38 day^-1). Protein content in Rhodomonas sp. cultured with f/2 medium was higher than with agricultural fertilizers (10.7 and 8.96 pg cell^-1, respectively). Carbohydrate and lipid contents decreased during the exponential growth phase and there were no significant differences (P = 0.027 and 0.08, respectively) between both experiments. Carbohydrate content was higher during the slow growth phase in cultures using f/2 medium, whereas lipid content showed little variation during the slow growth phase, but was higher in cells cultured using agricultural fertilizers. During the first five days, total phosphate uptake by Rhodomonas sp. was 39.9 µM (94.3%) in the f/2 medium and 40 µM (99%) in the agricultural fertilizer medium. A total of 667.3 µM of nitrate (72.2%) was consumed during the first four days in the f/2 medium, whereas in the agricultural fertilizer medium formulated with ammonium nitrate, ammonium uptake (418.1 µM, 78.7%) in the first three days was higher than nitrate uptake (37.7 µM, 7.3%); however, when ammonium concentration decreased to 1.83 µM, the nitrate uptake increased. In conclusion, the cellular quantity and quality of Rhodomonas sp. was similar when both media were used and agricultural fertilizers can be used in marine aquaculture programs.

Keywords : agricultural fertilizers; proximate composition; nutrient uptake; Rhodomonas sp.