During the summer months of 1983 Prorocentrum minimum (Pavillard) Schiller, not earlier recorded from the Adriatic, constituted a considerable proportion of the regular summer bloom in the Sibenik Bay (eastern Adriatic coast). During the subsequent years (1984,1985,1986) the proportions of P. minimum in summer blooms in the Ŝibenik Bay was constantly increasing (Marasović, 1986; Marasović, in press). At the same time its presence was reported from the other parts of the Adriatic coast, attributed to the intensified eutrophication of the Adriatic waters (Pucher-Petković & Marasović, 1987; Marasović et al., 1988; Pucher-Petković et al., 1988; Marasović, 1989).