铁浓度诱导的三角褐指藻生长和生化组分变化

采用试验生态学方法,以海洋硅藻三角褐指藻(Phaeodactylum tricornutum)为研究材料,设置一系列铁浓度处理(3.15mg·L-1、6.30 mg·L-1、9.45 mg·L-1、18.90 mg·L-1和34.65 mg·L-1),着重测定藻液光密度(OD450)、比生长率、藻细胞密度、藻生物量、叶绿素含量和蛋白质含量等生理生化指标,探讨铁浓度对海洋微藻生长特性和生化组分的影响.结果表明,铁浓度对三角褐指藻的生长状况产生了显著的影响.三角褐指藻经培养48 h后,不同铁浓度下的藻液光密度(OD450)存在显著的差异,6.30 mg·L-1铁浓度下的藻液光密度值(OD450)最高,而随着铁浓度的进一步升高,藻液光密度值(OD450)却明显降低;比生长率和藻细胞密度在3.15 mg·L-1到9.45 mg·L-1铁浓度范围内随着铁浓度升高而增大(最大值分别约为0.609 d-1和1200×104 cell·mL-1),但高于9.45 mg·L-1的铁浓度显著降低了比生长率和藻细胞密度;在试验所设置的铁浓度范围内,藻生物最表现出随铁浓度的升高而增大的趋势,34.65 mg·L-1铁浓度下的藻生物量高达0.460 mg·ML-1.同样地,微藻叶绿素a含量和蛋白质含量也明显地受到铁浓度的影响.在3.15 mg·L-1到18.90 mg·L-1铁浓度范围内,叶绿素a含量逐渐增高(最大值为2.41 mg·L-1);同样地,蛋白质含量在9.45 mg·L-1.铁浓度下达到最大值(0.153 mg·mL-1),而随着铁浓度的逐渐升高,叶绿素和蛋白质含量却明显降低.研究结果表明.铁浓度诱导海洋微藻的生长及代谢发生变化.一定较高浓度的铁显著地促进了藻细胞的生长繁殖和藻细胞化学组分的转化和积累.这些发现将有利于加深认识铁浓度在海洋生态系统中扮演的角色,进一步明确赤潮爆发的生理生态机制,从而有助于人们采取有效的预测、预防和管理措施以降低赤潮的危害.

Iron Concentration-Induced Changes in Growth and Biochemical Compositions of Marine Diatom Phaeodactylum tricornutum(Bacillariophyceae)

As long as microalgal growth is not overprolific in the water, marine microalgae are of great benefit to marine ecosystem because they not only form the basis of marine food web, but also consume the greenhouse gas carbon dioxide in the atmosphere during photosynthesis. Sometimes, however, red tides would occur due to the overproliferation or overassemblage of some marine microalgae within a certain short time under some given conditions. The role of iron in the formation of red tides has been a long-standing puzzle before the earlier studies demonstrating that phytoplankton growth in some major nutrient-rich waters was limited by iron deficiency. In order to further investigate the growth characteristics and some important biochemical compositions of marine microalgae induced by iron concentrations, optical density of algal culture, specific growth rate, cell density, cell biomass, chloro-phyll a and protein of Phaeodactylum tricornutum were characterized in a laboratory simulative experiment by employing a range of varying iron concentrations including 3.15 mg·L-1, 6.30 mg·L-1, 9.45 mg·L-1, 18.90 mg·L-1 and 34.65 mg·L-1. Our results indicated that algal growth differed greatly under different iron concentrations set in the present trial. Optical density at 450 nm(OD450) peaked at 0.877 under the iron concentration of 6.30 mg·L-1 in the termination of the experiment, and decreased with continually higher iron concentrations. Specific growth rate and cell density increased obviously with the increasing iron concentrations within the range of iron concentration from 3.15 mg·L-1 to 9.45 mg·L-1, whereas much higher iron concentrations were associated with a decrease in specific growth rate and cell density. While, the cell biomass appeared to be concentration-dependent, which was increased gradually over the entire range of iron concentrations. In addition, iron concentration also induced significant changes in the chlorophyll a content and protein content of marine mieroalga Phaeodactylum tricornutum. Chlorophyll a content rose under iron concentration ranging from 3.15 mg·L-1 to 18.90 mg·L-1, but declined under continually higher iron concentrations. Protein content was increased up to 0.153 mg·mL-1 by 9.45 mg·L-1 iron concentration and it was decreased by much higher iron concentrations, with the manifestly lowest protein content of 0.104 mg·mL-1 occurring under the iron concentration of 34.65 mg·L-1. The results have provided experimental evidence for the role of iron concentration playing in the marine raicroalgal proliferation and metabolism, and these fndings are particularly important in understanding mechanisms underlying the massive occurrence of red tides around the world, as well as in developing effective strategies for prediction, prevention, and mitigation of red tides.