A comparative study on growth performance and biochemical composition of mixed culture of Isochrysis galbana and Chaetoceros calcitrans with monocultures

The growth performance, biochemical composition and nutritive value of the mixed culture of Isochrysis galbana and Chaetoceros calcitrans, grown in batch cultures under laboratory conditions was compared with those in monoculture conditions. In mixed culture, both species manifested their monoculture characteristics with some variations: I. galbana, as in its monoculture situation, had an initial rapid growth, while the growth rate of C. calcitrans was half that of its monoculture state. However, as the growth rate of C. calcitrans increased gradually during later stages of the experiment that of I. galbana decreased. Although C. calcitrans dominated the mixed culture during later stages, the population of I. galbana was not totally eliminated. Cellular concentrations of chlorophyll a, protein, carbohydrate, Lipid and particulate organic carbon in monocultures and mixed culture peaked during the late exponential phase but were significantly higher (P < 0.05) in the mixed culture. The calculated dietary energy content was also significantly higher (P < 0.05) in the mixed culture compared to the monocultures during all the growth phases. The study highlights the nutritional implications of mixed algal cultures in hatcheries, particularly in shrimp hatcheries where different species and size groups of larvae are to be fed. (C) 2000 Elsevier Science B.V. All rights reserved.