Growth and mortality of flagellates and non-flagellate cells of Phaeocystis globosa (Prymnesiophyceae)

Two cell types of the same clone of Phaeocystis globosa, solitarynon-flagellate cells and flagellates, were grown in batch culturesunder identical conditions. The non-flagellate cells had a shorterlag phase (1.4 versus 2.8 days) and a higher growth rate (0.72versus 0.65 day^–1) than flagellate cells. The flagellateshad a longer stationary phase (15.6 versus 9.5 days) and a lowerdeath rate (0.07 versus 0.52 day^–1) than non-flagellatecells. All differences were statistically significant. Biomassyield did not differ between the two cell types. The short lagphase and high growth rate of nonflagellate cells correspondsto field observations of rapidly developing non-flagellate Phaeocystisblooms that are typically observed in nutrient-rich environmentssuch as temperate seas in spring. The flagellate cell type,with its longer stationary phase and lower death rate than non-flagellatecells, is better equipped for survival in oligotrophic environments.This explains why the flagellates of Phaeocystis are abundantafter the spring phytoplankton bloom in temperate seas and inother nutrient-poor environments such as the open ocean.