The nutritional value of four Australian microalgal strains fed to Pacific oyster Crassostrea gigas spat

Abstract

Four Australian microalgal isolates ( Pavlova pinguis, Rhodomonas salina, Tetraselmis sp. CS-362 and Nannochloropsis-like sp. CS-246) were compared to an overseas isolate ( Isochrysis sp. (T.ISO)) to assess their potential as food for bivalve aquaculture. When fed to Pacific oyster spat, the best growth was observed with a mixed diet comprising the four Australian species plus Isochrysis sp. (T.ISO) (161% increase in organic weight over 21 days). The best growth using the monospecific diets was produced by P. pinguis (111% increase), followed by Isochrysis sp. (T.ISO) and R. salina (85% and 82%); then Tetraselmis sp. CS-362 (51%), and Nannochloropsis-like sp. CS-246 (35%). The growth rates (based on an increase in organic weight) of oysters fed the monospecific diets were correlated to the amounts of protein and carbohydrate they ingested. The gross biochemical composition of the microalgae grown in semicontinuous culture differed significantly. Protein ranged from 48% of the dry weight ( R. salina) to 17% ( Nannochloropsis-like sp. CS-246); carbohydrate ranged from 41% ( P. pinguis) to 22% ( R. salina); and lipid from 16% ( Tetraselmis sp. CS-362) to 26% ( Nannochloropsis-like sp. CS-246). The instantaneous growth rate ( μ) of Isochrysis sp. (T.ISO) ( μ=0.48 day −1) was greater than the Australian strains, the best of which was R. salina ( μ=0.37).