The genus Alexandrium Halim (Dinophyceae) in Korean coastal waters

Abstract

Outbreaks of paralytic shellfish poisoning (PSP) and dense blooms caused by species in Korea coastal waters have been nearly annual events for many years. To identify the species based on detailed morphological characteristics and molecular phylogenetic analysis, vegetative cells collected water samples and established by the incubation of resting cysts isolated from sediment samples were analyzed. Eight Alexandrium species have been were identified based on morphological characteristics and molecular phylogenetic analysis: A. affine, A. catenella, A.concavum, A. fraterculus, A. insuetum, A. leei, A. pacificum and A. pseudogonyaulax. All of the species has the same plate formula: Po, 4’, 6”, 6c, 7-10s, 5”’, 2””. The resting cysts ranged in shape from spharical (A. affine, A. catenella, A. fraterculus, A. insuetum and A. pseudogonyaulax) to ellipsoidal (A. catenella and A. pacificum). Molecular phylogenetic analysis based on partial large subunit rRNA sequence showed that the grouping of Alexandrium species could be supported by the differences in life-history morphologies and the clade of A. pseudogonyaulax could be a basal lineage of this group. Cultured cells of A. catenella, A. fraterculus, A. pacificum and A. pseudogonyaulax were toxic but A. affine, A. concavum and A. leei clones were non-toxic. This study provides evidence on the presence of PSP toxin-producing Alexandrium species in Korean waters.