Comparative studies on mycosporine-like amino acids, paralytic shellfish toxins and pigment profiles of the toxic dinoflagellates Alexandrium tamarense, A. catenella and A. minutum

Surface bloom-forming species, predominantly of the Dinophyceae, have the capacity to accumulate high amounts of mycosporine-like amino acids (MAAs). The 3 dinoflagellate species (Gonyaulacales, Dinophyceae), Alexandrium tamarense, A. catenella and A. minutum are bloom-forming toxic isolates. They are usually found forming blooms near the surface, hence, they are exposed to high light conditions. Using an improved HPLC methodology, 9 MAAs were separated and identified. Several forms of atypical MAAs, not previously reported in the literature, were also revealed. The chromatographic behaviour of these new compounds, UV spectra, chemical properties and mass spectra indicate that they contain 2 or more common MAAs linked among themselves. These atypical MAAs were present in the 3 Alexandrium species. At the same time, the chromatographic profile of A. minutum, A. tamarense and A. catenella, showed great differences. The biochemical composition of the cells is highly variable with growth conditions. Hence, we also reported, for the sake of a comparative discussion, the toxin and pigment composition of these Alexandrium isolates. The 3 species showed the same pigment pattern characteristic of peridinin-containing dinoflagellates. On the contrary, as reported previously, great variation of the toxin profiles was observed among the Alexandrium species. We conclude that, although MAAs are common among phytoplankton, the occurrence of different types of novel MAAs in the 3 Alexandrium species studied here would indicate some degree of biogeographic or ecotypic diversification.