Alexandrium pacificum Litaker sp. nov (Group IV): Resting cyst distribution and toxin profile of vegetative cells in Bizerte Lagoon (Tunisia, Southern Mediterranean Sea)

Abstract A high spatial resolution sampling of Alexandriumpacificum cysts, along with sediment characteristics (% H 2 O, % organic matter (OM), granulometry), vegetative cell abundance and environmental factors were investigated at 123 study stations in Bizerte Lagoon (Tunisia). Morphological examination and ribotypingof cells obtained from a culture called ABZ1 obtained from a cyst isolated in lagoon sediment confirmed that the species was A. pacificum . The toxinprofile from the ABZ1 culture harvested during exponential growth phase was simple and composed of the N -sulfocarbamoyl toxinsC1 (9.82 pg toxincell −1 ), the GTX6 (3.26 pg toxincell −1 ) and the carbamoyl toxinNeo-STX (0.38 pg toxincell −1 ). The latter represented only 2.8% of the total toxinsin this strain. High abundance of A. pacificum cysts correlated with enhanced percentages of water and organic matter in the sediment. In addition, sediment fractions of less than 63 μm were examined as a favorable potential seedbedfor initiation of future blooms and outbreaks of A. pacificum in the lagoon. A significant difference in the cyst distribution pattern was recorded among the lagoon's different zones, with the higher cyst abundance occurring in the inner waters. Also, no correlation due to the specific hydrodynamics of the lagoon was observed in the spatial distribution of A. pacificum cysts and vegetative cells.