Pleurosigma Planctonicum, a Rare Diatom in the Dutch Coastal area

Abstract

Since 1973 the main groups of diatoms and dinoflagellates have been analysed in a monthly monitoring programme of phytoplankton in Dutch coastal waters. In 1974 a large, conspicuous diatom, Pleurosigma planctonicum Simonsen (Simonsen, 1974) occurred in small numbers with a denser population at two sampling sites where the salinity was greater than 33%. Details of the distribution are shown in Fig. 1.