Abstract: Studies on the growth and physiological response of red tide alga Prorocentrum minimum to three Zn ²⁺ levels were showed that the specific growth rate and biomass were limited in low Zn ²⁺-grown cells (1.4 pmol·L^-1, which were 0.40 d^-1 and 51100 cell·ml^-1 respectively. The specific growth rate was not significantly different when the Zn ²⁺ concentration in medium was increased over 24.4 pmol·L^-1,but there was a slight decrease in biomass; however, both specific growth rate and biomass were much higher than those in low Zn ²⁺-grown cells. It was also showed that chlorophyll a synthesis was limited due to Zn ²⁺ deficient,and therefore,the cells became light saturated at higher irradiance under Zn-limited condition. Light-saturated photosynthetic rates (Pm) and photosynthetic efficiency (α) increased significantly with increasing Zn ²⁺ concentrations. It was concluded that Zn ²⁺ concentration might be one of the key factors affecting red tide blooms in eutrophication environment.

Key words: Red tide, Photosynthesis, Growth, Prorocentrum minimum, Zinc limitation