不同种类浮游植物对CO2浓度升高的响应

The Response of Different Types of Phytoplankton to the Elevated CO2 Concentration

中文关键词: 海水酸化  浮游植物  生长速率  叶绿素荧光参数

英文关键词: Ocean acidification  Phytoplankton  Growth rate  Chlorophyll fluorescence parameters

中文摘要:

      本研究采用实验生态学的方法，以金藻、硅藻、绿藻3个门中的4种常见饵料藻叉鞭金藻(Dicrateria sp.)、三角褐指藻(Phaeodactylum tricornutum)、小球藻(Chlorella vulgaris)和亚心形扁藻(Platymonas subcordiformis)为研究对象，分析比较不同浮游植物的细胞数量和质量对CO2浓度升高引起的海水酸化的响应情况。结果显示，与对照组相比，(1) CO2浓度升高显著提高了这4种藻的生长速率(P<0.05)；其中，亚心形扁藻平均比生长速率最高，比对照组高出13.5%；小球藻次之，为5.9%；叉鞭金藻和三角褐指藻均为2.2%。(2) CO2浓度升高使浮游植物细胞内的碳(C)含量增加、氮(N)含量降低，C/N提高；种间差异较大，其中，亚心形扁藻的C/N、C/P值、小球藻的C/P值和三角褐指藻的C/N值显著提高，叉鞭金藻不显著。(3) CO2浓度升高使小球藻单位细胞叶绿素a含量显著提高，小球藻通过提高光合作用能力促进生长，而另外3种藻叶绿素a含量与对照组无显著差异；三角褐指藻最大光化学量子产量(Fv/Fm)在实验初期显著升高；叉鞭金藻非光化学淬灭(NPQ)显著降低，快速光曲线初始斜率(α)显著增加；三角褐指藻和亚心形扁藻潜在的最大光合作用能力(rETRmax)显著升高(P<0.05)，但CO2浓度升高对4种藻的光化学淬灭(qP)均没有显著影响(P>0.05)。可见，亚心形扁藻、小球藻和三角褐指藻在高CO2浓度下虽然生长速率加快，但营养质量降低。不同种类的浮游植物对CO2浓度升高的响应不同，这种差异可能会使未来海洋浮游植物群落结构发生变化；浮游植物C/N、C/P值的改变可能通过食物链对次级生产者，诸如浮游动物、滤食性贝类等产生影响。

英文摘要:

      Ocean acidification caused by the rising atmospheric CO2 concentration has been paid attention worldwide, the response process and mechanism of marine phytoplankton to ocean acidification are still not very clear. In this paper, we studied four kinds of microalgae Chrysophyta: Dicrateria sp., Bacillariophyta: Phaeodactylum tricornutum, Chlorophyta: Chlorella vulgaris and Platymonas subcordiformis to assess the response of microalgae to CO2-driven ocean acidification (the future level of the year 2300), and by the variation of quality and quantity of phytoplankton, to predict the potential influence of future global climate change on secondary consumers. The results indicated that compared with the control group, the average growth rates (μ) of the four kinds of microalgae were promoted by elevated CO2 concentration (P<0.05); for the value of μ, P. subcordiformis was the highest, 13.5% higher than the control group, followed by C. vulgaris (μ=5.9%), and then Dicrateria sp. and P. tricornutum (μ=2.2%). High CO2 concentration could increase carbon content and/or decrease nitrogen or phosphorus content, and then increase C/N or C/P ratio of phytoplankton. However, there were species different, both of the C/N, C/P ratio for P. subcordiformis were significantly increased (P<0.05), and C/P ratio of C. vulgaris and C/N ratio of P. tricornutum were significantly increased (P<0.05). The cellular chlorophyll a contents of C. vulgaris was increased significantly by elevated CO2 concentration. However, there were decreasing trends of the others. The maximal efficiency of PSⅡ in a dark-adapted state (Fv/Fm) of P. tricornutum elevated remarkably in the beginning of the experiment, the initial slope of rapid light curves (α) of Dicrateria sp. improved, non-photochemical quenching (NPQ) decreased significantly, and the maximum relative electron transport rate (rETRmax) of P. tricornutum and P. subcordiformis increased significantly (P<0.05). But high CO2 concentration has no remarkable effect on photochemical quenching (qP) of the four phytoplankton (P>0.05). Therefore, the growth rate of P. subcordiformis, C. vulgaris and P. tricornutum accelerated under the high CO2 concentration, whereas nutrition quality declined. Different kinds of phytoplankton have different responses to ocean acidification, which may change oceanic phytoplankton community structure in the future. In addition, the change of C/N and C/P ratio of phytoplankton could influence the primary consumer, such as zooplankton and filtering shellfish, through the food chain.