School of Science and Technology, The Open University of Hong Kong, Hong Kong, China.
Mar Environ Res. 2012 Oct;81:62-9. doi: 10.1016/j.marenvres.2012.08.009. Epub 2012 Sep 4.
Nitrate (N) and phosphate (P) are believed to be two of the most important nutrients for the growth and toxin production for Alexandrium species. The study of the growth and toxicity characteristics of the Alexandrium spp. under the change of N and P can help us to understand the dynamics of algal bloom and toxification events in natural environments. A strain of Alexandrium tamarense (designated as Kci) was successfully isolated from the Drake Passage in 2001 and the clonal culture has been kept in our laboratory (Ho et al., 2003, 2012). In order to extend our understanding on the growth physiology and toxicity of this A. tamarense strain, growth and cellular toxin content were examined in unialgal batch cultures under different concentrations of N and P. The effects of variable N, P concentrations on growth, cellular toxicity (fg STXeq. cell(-1)), and toxin composition (% molar) were determined in both exponential and stationary growth phases. The toxin profile, determined by high-performance liquid chromatography with fluorescence detection (HPLC-FD), was found to be remained relatively stable and was consistently dominated by the N-sulfocarbamoyl C-toxins (>90%) under different conditions and growth phases. There were also trace amounts of other carbamate gonyautoxins consistently expressed. The cellular toxicity varied under different N and P concentrations, as well as different growth stages. A positive correlation was observed between cellular toxicity and N concentrations, but the toxicity was enhanced when P was depleted. Both cell densities and growth rate of the cells were severely suppressed under N- or P-depletion. However, the biovolume of the cells tended to be larger at N- or P-depleted cultures. Results from the present study provide valuable insight for the ecophysiology of Alexandrium species in the coastal ecosystem of Drake Passage.
硝酸盐（N）和磷酸盐（P）被认为是对亚历山大藻属物种生长和毒素产生最重要的两种营养素。研究 N 和 P 变化下亚历山大藻属的生长和毒性特征，有助于我们了解自然环境中藻华和毒素事件的动态。2001 年，从德雷克海峡成功分离到亚历山大藻属的一个株系（命名为 Kci），并在我们的实验室中进行了克隆培养（Ho 等人，2003 年，2012 年）。为了扩展我们对该亚历山大藻属株系生长生理学和毒性的认识，在不同 N 和 P 浓度的单藻分批培养中，检查了生长和细胞毒素含量。在指数和静止生长阶段，确定了可变 N、P 浓度对生长、细胞毒性（fg STXeq. cell(-1))和毒素组成（%摩尔）的影响。通过高效液相色谱法与荧光检测（HPLC-FD）确定的毒素谱，在不同条件和生长阶段下，均发现保持相对稳定，且始终由 N-磺基氨基甲酰 C-毒素（>90%）主导。也始终有痕量的其他氨基甲酸酯冈田酸毒素表达。在不同的 N 和 P 浓度以及不同的生长阶段，细胞毒性也有所不同。在细胞毒性与 N 浓度之间观察到正相关，但当 P 耗尽时，毒性增强。在 N 或 P 耗尽的情况下，细胞密度和细胞生长率都受到严重抑制。然而，在 N 或 P 耗尽的培养物中，细胞的生物量往往更大。本研究的结果为德雷克海峡沿海生态系统中亚历山大藻属物种的生态生理学提供了有价值的见解。
