Observations of flagellates in colonies of Phaeocystis globosa (Prymnesiophyceae); a hypothesis for their position in the life cycle

Flagellates of Phaeocystis globosa were observed inside colonies in North Sea samples in 1992. Field data suggest that low phosphate concentrations (less than or equal to0.5 muM) and, as a consequence of sedimentation, a 20- to >100-fold reduction of daily irradiance (to m), (ii) the haploid mesoflagellate (4.2 +/- 0.1 mum), (iii) the diploid macroflagellate (6-7 mum) which is Kornmann's (Kornmann, 1955) 'Makrozoospore', and (iv) the diploid non-flagellate colonial cell (6.1 +/- 0.2 mum). A life cycle for Phaeocystis is presented, and the life-cycle transitions still to be tested are identified.