微小亚历山大藻(Alexandrium minutum)的氮磷吸收、生长、产毒动态变化

DYNAMICS OF ABSORPTION OF NITROGEN AND PHOSPHORUS,GROWTH AND TOXIN PRODUCTIVITY IN ALEXANDRIUM MINUTUM

采用浮游植物计数法、高效液相色谱串联质谱法、分光光度法等分析方法,探索了微小亚历山大藻(Alexandrium minutum)在批次培养过程中氮磷吸收、产毒、生物量、p H等参数的动态变化关系。结果表明,微小亚历山大藻对磷的吸收迅速,可以将磷储存于体内,待生长使用。该藻对氮的吸收相对缓慢,环境中氮缺乏时,产毒量不再增加,说明氮对产毒有着重要的调控作用。在第二对数期中出现了碳限制环境,导致叶绿素a在碳限制条件下无法表征藻的生物量,相反,叶绿素a和生物量呈负线性关系,可能是叶绿素转化成其它含碳物质,用于生长。毒素不仅存在于细胞体内,培养液中(胞外)也含有毒素,并且胞外毒素从稳定期开始逐渐升高。胞内毒素的组成中GTX1/4占据绝对优势,GTX2/3含量相对较少。生长延缓期和第一对数期,各种毒素组成比例相对稳定,而在随后的生长期内,GTX1/4在总毒素中的占比逐渐上升,GTX2/3占比逐渐下降,表明微小亚历山大藻毒素组成会随着生长周期的变化而发生变化。

Analysis methods such as phytoplankton counting method, high performance liquid chromatography tandem mass spectrometry, spectrophotometry were used to explore the dynamics of absorption of nitrogen and phosphorus, toxin productivity, biomass and pH in batch culture of Alexandrium minutum. The results showed that the phosphorus in the medium was uptaken rapidly by the A. minutum ,stored in the body for growing. However, nitrogen intake was relatively slow. That toxin production would no longer increase when there was lack of nitrogen, which indicated that nitrogen played an important role in the production of toxin. As the appearance of carbon deficient conditions in the second exponential phase, the content of chlorophyll a could not be used as an index ofphytoplankton cell concentration in this phase. On the contrary, there was a negative linear relationship between the content of chlorophyll a and biomass, which indicated that the transformation of chlorophyll into other carbon component happened for growing. Toxins did not only exist in the body of cell, but also in a rounding medium （out of cell）, and extracellular toxin content increased guadually since the beginning of the stationary phase. The most of intracellaur toxins were GTX1/4, and GTX2/3 content were relatively small. In the lag and first exponential phase, toxin constitution was relatively stable, however, in the growth period, the ratio of GTX1/4 to total toxins raised guadually, and that of GTX2/3 declined all the time, which indicated that toxin constitution of A. minutum would change with the change of growth phase.