The early summer bloom of dinoflagellates in the North Sea,with special reference to 1971

The south-western quarter of the North Sea (between the Wash and the River Tyne) has been investigated for the presence of dinoflagellates. Extensive net surveys were carried out in March, May and June 1971 and a number of other collections were made in the area. North of Flamborough Head, the spring bloom of diatoms was succeeded by a considerable growth of dinoflagellates, of which Dinophysis norvegica was the most abundant organism. Maximum counts of over 28 million dinoflagellates per m³ were recorded. Distribution charts are given for the most common species. A total of 61 species was found during the course of the survey.