The materials used in the present study were collected monthly at 17 stations in the waters of Xunjiang, Xi Gang and Jiulongjiang River estuary around Xiamen Island from September 1980 to August 1981. As a result of preliminary analysis of these samples, 49 species of planktonic pyrrophyta were identified, belonging to 13 genera in 11 families, 49% of which are eurythcrmic species, and 51% warm water species.In the region studied there are 9 dominant species:Prorcentrum micans, Dino-physis caudata, Ceratium...