温度与氮浓度对两种微囊藻生长和产毒的影响

Effects of temperature and nitrogen concentration on the growth and microcystins production of two Microcystis strains

采用半连续培养的方法,研究了磷限制条件下温度与氮质量浓度的交互作用对铜绿微囊藻和水华微囊藻的生长及产毒的影响。结果表明,不同温度下,氮质量浓度对两种微囊藻比生长速率的影响不同。随氮质量浓度的增加,15℃和20℃时比生长速率增加较快,25℃时增加缓慢;温度的降低对水华微囊藻的生长抑制作用较铜绿微囊藻小。两种微囊藻的单个细胞叶绿素a含量受温度及氮质量浓度的影响极显著,而交互作用的影响较主效应小。单个细胞藻毒素含量受温度影响最大,显著负相关;氮质量浓度的影响次之,显著正相关。但两种微囊藻的生长状况越好时相应的总毒素质量浓度也越高。因此,磷限制条件下,温度和氮质量浓度对两种微囊藻的生长及产毒有明显的交互作用,氮质量浓度的降低会进一步抑制微囊藻的生长并降低总藻毒素质量浓度。

This paper is aimed to introduce our study on the effects of temperature and nitrogen concentrations on the growth and microeystins production of Microcystis aeruginosa and microcystis flos-aquae under phosphrus limitation in semi-sustaining cultures. It is known that Microcystis aeruginosa and Microcystis flus-aquae are the two dominant strains in Taihu Lake in case when cyanbacteria bloom occurs. In our experiment, we have investigated and measured a nitrogen concentration gradient from 1 mg/L to 11.67 mg/L in combination with a temperature between 15 ℃, 20 ℃ and 25 ℃. At the same lime, we have set the phosphorus concentration to be used in our experiments as 0.01 mg/L fnr all the cultures. In the process of cultivation, the specific growth rate and the cell numbers were observed and detected with the cell numbers calculated. Intracellular chlorophyll a and microcystins concentrations as well as the intracellular microcystins content were detected when the cultures reached a steady state. The results show that the enhancements of temperature and nitrogen concentrations contribute to the growth of Microcystis strains. The effects of nitrogen concentrations to the specific growth rate were fimnd different under different temperatures, that is to say, under 15 ℃ and 20 ℃, the specific growth rate was found growing faster as compared with the condition under the temperature of 25 ℃ whereas negative effects of low temperature to Microcystis flos-aquae proves weaker than Microcystis aeruginosa. In addition, we also observed positive impact of temperature and nitrogen concentrations on the intracellular chlorophyll a of both strains, though the interactive impacts were not as significant as the main effects. Besides, while temperature proves to be a major negative influential factor on the cel lular microcystin concentrations of the two strains, nitrogen concentration proves to have just a mild positive effect. Therefore, the total microcystins concentrations of the cultures should be higher in case it is necessary to enhance the temperature and nitrogen concentration. Thus, it is obvious to see the effects of the two factors on the two strains, and the nitrogen concentration helps to restrain the growth and formation of chlorophyll a and decrease the total microcystins concentrations of Microcystis.