Chemical compositon of three microalgae species for possible use in mariculture

The purpose of this study was to determine the chemical composition of Chaetoceros gracilis, Cylindrotheca closterium and Tetraselmis gracilis, species frequently used as food for aquaculture in the northeast of Brazil. The species were grown in f/2 medium, in carboys, aerated from one liter, with constant illumination and analyses were made in late exponential growth phase. Cellular density (8,447 x 10(6) cell.L-1), soluble carbohydrates (0.10+/-0.01 mg.L-1) and magnesium (14.78+/-0.08 mg.L-1) were the highest in C. gracilis. C. closterium had the highest amount of chlorophyll a (13.76+/-1.11 mg.L-1), soluble proteins (0.62+/-0.04 mg.L-1), total amino acids (23.82+/-0.84 mg.L-1), nitrate (0.36+/-0.02 mg.L-1), sodium (0.46+/-0.05 mg.L-1) and phosphorus (2.80+/-0.38 mg.L-1). Both the species had potassium levels of 0.02 mg.L-1 and sulfur levels of 0.03 mg.L-1. T. gracilis had the lowest values in almost all the analyzed variables, except for chlorophyll a. Therefore, among the analyzed species and tested conditions, C. closterium represented the best nutritional option for aquaculture projects.