Algal pigment patterns in different watermasses of the Atlantic sector of the Southern Ocean during fall 1987

During the autumn of 1987 a survey was carriedout in the Atlantic sector of the Southern Ocean in orderto study phytoplankton community structure in relationto hydrological features. The positions of the boundaryzones, determined by means of hydrological and chemicalproperties (especially silicic acid) match with previousstudies. The phytoplankton community structure wasstudied by means of algal pigment fingerprints. A clusteranalysis of the main phytoplankton pigments revealed thepresence of four distinctive phytoplankton communities inthe area. In three cluster groups phytoflagellate pigmentsof different taxonomical groups were found which showeddifferent relative abundance between the cluster groups. Inbetween the Polar Front Zone and the Weddell ScotiaConfluence a fourth group was found which was rich indiatoms as compared to the other cluster groups. Highconcentrations of the fucoxanthin related 19'-hexanoyloxyfucoxanthinindicated the relative importance ofPrymnesiophyceae during fall in this area. The relativecontribution of each taxonomical group to total phytoplanktonbiomass was estimated by using specific pigmentratios. This calculation showed that in this time of the yearphytoflagellate biomass (especially Prymnesiophytes) surpassesdiatom biomass