We investigated the effects of different nutrients on the concentration of polyamines by mesocosm experiment in an area of frequent red tide occurrence in the East China Sea. As essential components of cellular regulation, polyamines are synthesized by algae and secreted into the surrounding waters, particularly during the decomposition period following a bloom, and may thus drive the succession of future blooms. In 2010, where blooms of the dinoflagellate Prorocentrum donghaiense occurred, it was the dominant species, the nutrient content of the water was low, and there was no evidence of species succession in any of the mesocosms. According to our results, P. donghaiense growth period length and maximal biomass would be enhanced with increased levels of nutritive salt, specifically PO₄. Polyamines were significantly higher in mesocosms to which nutritive salt was added than in the control mesocosm. Spermine levels showed a wavelike, inverse trend decreasing with P. donghaiense growth and increasing with its decline. Putrescine concentrations were higher than spermine, fluctuated significantly, and were positively associated with growth of P. donghaiense in every mesocosm except the control. Spermidine had the lowest concentration of all the polyamines and fluctuated the least in all mesocosms. In 2011, we detected a succession in species from Skeletonema costatum to P. donghaiense in all mesocosms where S. costatum blooms occurred. The nutrient content of the seawater, specifically PO₄, was sufficient to sustain dinoflagellate populations. However, our results suggest that the addition of NO₃ and SiO₃ would prolong the S. costatum growth period, and increase its maximal biomass. When just NO₃ concentrations were increased, the absorption of PO₄ increased significantly, and S. costatum died off more quickly. This suggests that an influx of NO₃ could initiate an earlier turnover to P. donghaiense. When more NO₃ was added, the maximal biomass of P. donghaiense was higher. If nutrients are added before S. costatum die-off, the rate of turnover might be slower, delaying the appearance of P. donghaiense. In every mesocosm in the second year, putrescine concentration was the most abundant polyamine. In the early growth stages of S. costatum, the level of putrescine initially decreased. Levels then increased with S. costatum growth, and fell again with P. donghaiense growth in the later stages of the experiment. We suggest that S. costatum and P. donghaiense absorb exogenous putrescine, causing it to decrease in the mesocosms. In every mesocosm, spermine concentrations were low and fluctuated greatly during the succession. Similarly, the level of spermidine was low in all microcosms; however, it had no obvious fluctuation during succession. Variation in nutrients affected concentrations of polyamines indirectly by influencing phytoplankton growth. From this 2-year mesocosm experiment, we found that as both S. costatum and P. donghaiense decompose, they release polyamines. We refer to this as the dispersion period. We also found that during growth periods both species metabolize and secrete polyamines. In conditions of lower nutrient availability, exogenous polyamines could stimulate P. donghaiense growth. Algal enzymes catalyze the conversion of polyamines, and thus the growth and decomposition of these dinoflagellates during times of bloom results in significant polyamine fluctuations.