A first report on a bloom of the marine prymnesiophycean, Phaeocystis globosa from the Arabian Sea

A thick bloom of the marine prymnesiophycean, Phaeocystis globosa was obser ved in the central Arabian Sea during the summer monsoon period (July-Augus t, 1996). The cells were mostly in colonial form, embedded in gelatinous ma trices. The cell diameter was approximately 7 mu m and showed a distinct do uble feature form. The intensity of the bloom was as high as 3750 x 10(6) c ells m(-2) and the carbon content ranged between 33 and 550 mu g L-1. Almos t 90% of the phytoplankton population was composed of P. globosa in the blo om area. Other common forms were chain-forming diatoms like Rhizosolenia sp p., Nitzschia spp. and Chaetoreros spp. The photosynthetic pigment chloroph yll a, however did not show any concomitant rise with the bloom intensity p robably because the bloom was sampled during a senescent phase. The carbon chlorophyll ratio varied between 112 and 810. This is the first report on t he occurrence of Phaeocystis from the Arabian Sea. It seems pertinent to as k whether this is a result of the genus being introduced and adapted to new environments due to human influence and whether it will influence food cha ins in the future. (C) 2000 Ifremer/CNRS/IRD/Editions scientifiques et medi cales Elsevier SAS.