Toxin profile of Alexandrium tamarense (Dinophyceae) from Hokkaido, northern Japan and southern Sakhalin, eastern Russia

To evaluate the variations in the toxin profiles of Alexandrium tamarense (Dinophyceae) from Hokkaido and southern Sakhalin, paralytic shellfish poison of 103 culture strains obtained from six areas (Funka Bay, Toma- komai, Urakawa, Akkeshi, Okhotsk Sea and Aniva Bay) was analyzed using high performance liquid chromatography- fluorescent detection. All of the strains, except for two culture strains, were classified by a hierarchical cluster analysis into clusters in which the strains had almost the same toxin composition as found in previous studies (major toxins: C2, gonyautoxin 4, neosaxitoxin and gonyautoxin 3). On the other hand, cellular toxin contents of the culture strains varied from 1 to 1,128 fmol cell � 1 and the cellular toxin content (y fmol cell � 1 ) was inversely proportional to the cell density (x cells mL � 1 ) (y� 9942.2x � 0.448 , Spearman's rank correlation coefficient: rs� 0.539, p� 0.01). It can be con- cluded that the toxin compositions of A. tamarense are almost the same in Hokkaido and southern Sakhalin, and high- toxicity blooms of A. tamarense as usually found possibly occur in the natural environment at low cell densities (10 � 2 -10 2 cells mL � 1 ).