Population dynamics of Gymnodinium spp. and environmental factors in aquaculture areas of Daya Bay were investigated from January to December 2008. The dominant Gymnodinium species was Gymnodinium sp., and Karenia mikimotoi, Gymnodnium catenatum and Akashiwo sanguinea were found in low density. Obvious seasonal and spatial distribution characteristics were displayed in density of Gymnodnium group. The highest density of 903 cells·mL-1 was observed in May, while the lowest in autumn and winter. And the population density of Gymnodnium group was higher in aquaculture areas and coastal areas than the open sea. Correlation analysis showed that temperature, COD (chemical oxygen demand), DON (dissolved organic nitrogen) and urea played key roles in regulating the density of Gymnodinium group. The optimal temperature range for Gymnodnium group were 25～30 ℃, while DON and urea were 156.38～187 μgN·L-1 and 17.4～38.9 μgN·L-1, respectively. When the temperature was suitable, the rise in organic nitrogen such as urea can play a trigger in the formation of Gymnodinium blooms.%2008年1-12月对大亚湾养殖海域裸甲藻种群动态和主要环境因子进行了周年调查.结果表明,大亚湾海域裸甲藻类群以直径约为16～22μm的小型裸甲藻(Gymnodinium sp.)为主,另外米氏凯伦藻(Karenia mikimotoi)、链状裸甲藻(Gymnodniumcatenatum)和血红哈卡藻(Akashiwo sanguinea)也有少量出现.裸甲藻种群密度呈现出明显的季节性变化特征:5月出现裸甲藻密度高峰,全年最大密度达到903 cells.mL-1,秋冬季节密度最小.不同站位裸甲藻密度也具有明显的空间分布差异,养殖及近岸海域密度普遍高于外海对照区.相关性分析结果表明,裸甲藻密度的关键调控因子包括温度、化学需氧量(COD)、可溶性有机氮(DON)和尿素浓度.裸甲藻高密度、高频率出现的温度范围在24～26℃,DON和尿素的质量浓度范围分别为N 156.38～187μg.L-1和N 17.4～38.9 μg.L-i.在温度适宜的条件下,尿素等有机氮含量的增加可能成为裸甲藻赤潮的触发因子.
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