Vertical distribution of phytoplankton during investigations of a natural surface film

An interdisciplinary research program (Kombiniertes Oberflächenfilmprojekt KOFF), in the North Sea area about 75 km west of the Island of Sylt, is directed towards gaining further knowledge on the biological importance of the natural surface film. The investigations include the water body below the film as well as dynamic processes at the surface. Persistence of calm weather conditions (cloudless sky) before and during the investigations permitted observations of the diurnal species-specific vertical migration of Dinophyceae. Two groups could be distinguished: (1) Prorocentrum micans and Ceratium furca; (2) C. horridum, C. macroceros and C. fusus. The active accumulation of P. micans in the slick was verified by a significant correlation coefficient—linearly correlated with the time of day. The results presented reveal continuity between surface film and underlying water column.This work was supported by the Sonderforschungsbereich (SFB) 94, Hamburg, of the Deutsche For-schungsgemeinschaft.