ВЖИВАННЯ ХЛОРАМФЕНIКОЛУ ПРИ КУЛЬТИВУВАННІ МІКРОВОДОРОСТІ ISOCHRYSIS GALBANA І КОЛОВЕРТОК BRACHIONUS PLICATILIS

The impact of synthetic antibiotic chloramphenicol (5, 10, 50 and 500 mg l-1) on dynamics of Isochrysis galbana culture and associated bacterial flora was studied in 7-day experiments. At all the tested concentrations, the antibiotic was shown to produce a toxic effect on the microalgal cells, that was manifested by a significant (p<0.05) an increase in the percentage of dying cells with low chlorophyll content. A pronounced effect was indicated from the day 2 of the experiment and its extent was proportional to the antibiotic concentration. The high antibiotic concentrations caused cell degradation and death. Reduction in bacterial abundance was observed in the microalgal culture from the day 2 of the treatment. The minimal antibiotic concentration of 5 mg l-1 was enough for elimination of bacterial strains receptive to chloramphenicol, and increase in the dosage did not result in stronger bactericidal effect that was likely due to chloramphenicol-resistant strains. Antibiotic-pretreated (5 mg l-1 24 h) culture of I. galbana did not have a toxic effect on Brachionus plicatilis when it was used for feeding the rotifers. The rate of ingestion of the pretreated microalgae by the rotifers did not differ from those in the control with untreated microalgae as food. However, the bacterial abundance in the rotifer growth medium with the antibiotic-pretreated isochrisis was lower than in the control over the incubation. Yield of the rotifers grown on the chloramphenicol-pretreated live food was insignificantly higher than in the control.