Influence of the food ration and individual density on production efficiency of semicontinuous cultures of Brachionus-fed microalgae dry powder

Abstract

In the present study we examined the effect of food ration and individual density at the time of starting the harvesting stage, in determining the demographic parameters in a semicontinuous culture of the rotifers Brachionus plicatilis and B. rotundiformis fed freeze dried Nannochloropsis oculata. Three daily food rations (25, 50 and 100 mg 1-1) and three rotifer densities (250, 500 and 1000 rotifers ml-1) have been tested, in trying to maintain a constant availability of microalgal cells of 100 ng per individual. Results showed that with 10% daily dilution, the mean rotifer density during the steady state remained at values similar to those pre-fixed at the beginning of the harvesting. The production (rotifers 1-1 d-1) increased with the food ration, but the system efficiency (mg-rotifers produced per mg-microalgae) was the same irrespective of the ration.