EFFECTS OF ENVIRONMENTAL FACTORS ON THE GROWTH AND INGESTION CHARACTERISTICS OF CHRYSOPHYCEAN POTERIOOCHROMONAS SP.

A chrysophycean Poterioochromonas sp.with two different flagella,isolated from Microcystis cultures in 2002,can not only photosynthesize with chloroplast,but also efficiently ingest and digest preys,such as Microcystis.In order to investigate the potential role of Poterioochromonas sp.in cyanobacteria bloom control,experiments were carried out to study its growth and ingestion characteristics under different environmental factors in both autotrophic and mixotrophic conditions.The results showed that the growth rate of autotrophic Poterioochromonas sp.was significantly affected by light intensity and temperature except pH.When providing preys,the growth of Poterioochromonas sp.was accelerated significantly.The growth and ingestion rate of Poterioochromonas sp.increased hyperbolically with prey concentration,and their relationships could be estimated respectively by the Michaelis-Menten equation and Monod equation.The correlation between the growth of mixotrophic Poterioochromonas sp.and light intensity was significant,while there were no relationships between the growth rate and temperature and pH.PH had negative effects on the ingestion rate,while the correlations between the ingestion rate and temperature and light intensity were not significant.In a word,this Poterioochromonas has the ability to grow and graze Microcystis in many culture conditions.The present study had also shed light on the possibility of utilizing this organism,together with other agents,for the control of Microcystis bloom.