Effect of iron on growth, biochemical composition and paralytic shellfish poisoning toxins production of Alexandrium tamarense

Effects of iron (Fe) on growth, biochemical composition and paralytic shellfish poisoning (PSP) toxins production of Alexandrium tamarense were studied. Under Fe-limited conditions (1 nmol L−1 Fe), the alga exhibited a low specific growth rate (0.076 ± 0.017 d−1, n = 3) that was nearly a half of that under Fe-replete conditions (1 μmol L−1 Fe, 0.137 ± 0.00752 d−1, n = 4), and the cell density on day 21 (8210 cells mL−1) was also less than a half of that under Fe-replete conditions (2 × 104 cells mL−1). At the same time, total pigment, chlorophyll a (Chla), protein, carbohydrate contents per cell and Chla/carotenoid ratio decreased. In contrast, the PSP toxins content and the PSP toxicity per cell of the alga increased remarkably. Under Fe-limited conditions, total PSP toxins content and relative toxicity of alga were 2.55- and 2.54-fold of those under Fe-replete conditions, respectively. In addition, the profiles of PSP toxins also changed notably. The cellular content of gonyautoxin 1 + 4 (GTX1 + 4) increased for 5.6-fold along with the decrease of saxitoxin (STX) and gonyautoxin 2 + 3 (GTX2 + 3) contents contrasting to that under Fe-replete conditions. It suggested that the availability of Fe might effectively control the growth and toxic production of the alga and thereby influence the toxic effect of these harmful bloom events.