Nutrient uptake kinetics, physiology and toxicity of the harmful dinoflagellata Alexandrium tamarense in response to nitrogen supply mode

以氮(N)形式的人为富集是鞭毛藻华的刺激因素之一。沿海生态系统的氮源供给并非总是连续的，而是脉冲的。当浮游植物暴露于不同的氮源（包括混合氮源）或不同的供氮方式时，可以预测其叫声会发生一些生理变化，包括吸收动力学。研究了氮源、浓度和供给方式对柽柳亚历山大菌养分吸收动力学参数和生理特性的影响。细胞碳(C)吸收在不同的氮源和两种供应模式之间表现出不同的模式。这表明，有机产物（如脂类）的合成所需的碳可能取决于所利用的氮。两种供给方式对细胞氮的吸收呈现相反的趋势。这可能是由于不同的代谢途径和氮素在不同植物间的同化。塔玛兰Alexandrium tamarense能够很容易地吸收三种主要形式的氮源，无论供应的类型如何。一般来说，铵诱导的细胞氮吸收率最高，其次是硝酸盐，然后是尿素。本研究表明，亚历山大菌细胞在突然暴露时具有切换不同氮源的能力。在混合N条件下，call可以同时吸收两种N。当铵盐+硝酸盐（或铵盐+尿素）以等浓度供给时，铵盐大部分被吸收和同化。与硝态氮和铵态氮生长的细胞相比，尿素诱导的C: N吸收比更高。碳氮吸收比的变异性表明碳氮代谢之间的主要相互作用。这种相互作用可能使tamarense在不同的氮环境下保持高生长。因此，沿海环境的N供应形式可能在控制有毒鞭毛藻的营养吸收方面发挥重要作用，从而影响鞭毛藻的繁殖潜力。快速同时吸收不同种类氮的能力可能是一个重要的机制，它可能允许A. tamarense在具有复杂氮源的海洋环境中增殖并形成水华。少

Anthropogenic enrichment in the form of nitrogen (N) is one of the stimuli for the dinoflagellate blooms. N sources are not always supplied to the coastal ecosystem continuously, but also in pulses. When phytoplankton is exposed to different N species including mixed N sources or different N supply mode, some physiological changes including uptake kinetics can be predicted to occur in the calls. In this study, the dints of N sources, concentrations and supply modes on the nutrient uptake kinetic parameters and physiological properties of Alexandrium tamarense were examined. The cellular carbon (C) uptake exhibited different patterns among N sources and also between the two supply modes. This suggests that the C requirement for the syntheses of organic products such as lipid might be dependent on the N utilized. The cellular N uptake was observed to display opposite trend among the two supply modes. This could be due to the difference in metabolic pathways and assimilation of N among N … More spumes. Alexandrium tamarense was able to take up readily the three major forms of N sources supplied, regardless of the type of supply. In general, ammonium induced highest cellular N uptake rates, followed by nitrate and then urea. The present study showed that Alexandrium cells have the capability to switch to different N source upon sudden exposure. In mixed N condition, calls could take up two N species simultaneously. When ammonium plus nitrate (or ammonium plus urea) were supplied in equal concentrations, ammonium was mostly taken up and assimilated. Urea induced higher C: N uptake ratio when compared to those of nitrate and ammonium grown cells. Variability in the C: N uptake ratio indicates major interactions between C and N metabolisms. This interaction may allow A tamarense to maintain high growth under different N environments. Therefore, the form of N supply in coastal environments could play an important role in controlling the nutrient uptake of toxic dinoflagellate and thus contribute to the bloom potential of dinoflagellates. The ability to take up different species of N rapidly and also simultaneously would be an important mechanism that may allow A. tamarense to proliferate and form blooms in marine environments with complex N sources. Less