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

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