University of Tennessee, Department of Chemistry, Knoxville, TN 37996, USA.
Analyst. 2017 Oct 23;142(21):4089-4098. doi: 10.1039/c7an01054k.
Marine phytoplankton acts as a considerable sink of atmospheric CO as it sequesters large quantities of this greenhouse gas for biomass production. To assess microalgae's counterbalancing of global warming, the quantities of CO they fix need to be determined. For this task, it is mandatory to understand which environmental and physiological parameters govern this transformation from atmospheric CO to microalgal biomass. However, experimental analyses are challenging as it has been found that the chemical environment has a major impact on the physiological properties of the microalgae cells (diameter typ. 5-20 μm). Moreover, the cells can only chemically interact with their immediate vicinity and thus compound sequestration needs to be studied on a microscopic spatial scale. Due to these reasons, computer simulations are a more promising approach than the experimental studies. Modeling software has been developed that describes the dissolution of atmospheric CO into oceans followed by the formation of HCO which is then transported to individual microalgae cells. The second portion of this model describes the competition of different cell species for this HCO, a nutrient, as well as its uptake and utilization for cell production. Two microalgae species, i.e. Dunaliella salina and Nannochloropsis oculata, were cultured individually and in a competition situation under different atmospheric CO conditions. It is shown that this novel model's predictions of biomass production are in very good agreement with the experimental flow cytometry results. After model validation, it has been applied to long-term prediction of phytoplankton generation. These investigations were motivated by the question whether or not cell production slows down as cultures grow. This is of relevance as a reduced cell production rate means that the increase in a culture's CO-sinking capacity slows down as well. One implication resulting from this is that an increase in anthropogenic CO may not be counterbalanced by an increase in phytoplankton production. Modeling studies have found that for several different atmospheric CO levels provided to single-species cultures as well as to species in competing scenarios the cell production rate does slow down over time.
海洋浮游植物作为大气 CO 的重要汇，因为它将大量的温室气体固定在生物量中。为了评估微藻对全球变暖的平衡作用，需要确定它们固定的 CO 量。为此，必须了解哪些环境和生理参数控制着这种从大气 CO 到微藻生物量的转化。然而，实验分析具有挑战性，因为已经发现化学环境对微藻细胞的生理特性有重大影响（直径典型为 5-20 μm）。此外，细胞只能与其直接附近的化学物质相互作用，因此需要在微观空间尺度上研究化合物的固定。由于这些原因，计算机模拟比实验研究更有前途。已经开发出描述大气 CO 溶解到海洋中，随后形成 HCO，然后运输到单个微藻细胞的模拟软件。该模型的第二部分描述了不同细胞物种对这种 HCO 的竞争，HCO 是一种营养物质，以及其对细胞生产的吸收和利用。将两种微藻物种，即盐生杜氏藻和眼点拟微绿球藻，分别在不同的大气 CO 条件下进行单独培养和竞争培养。结果表明，该新型模型对生物量产生的预测与实验流式细胞术结果非常吻合。在模型验证后，将其应用于浮游植物产生的长期预测。这些研究的动机是细胞生产是否会随着培养物的生长而减慢。这很重要，因为细胞生产速率的降低意味着培养物 CO 固定能力的增加也会减慢。由此产生的一个含义是，人为 CO 的增加可能不会被浮游植物产量的增加所抵消。建模研究发现，对于几种不同的大气 CO 水平，无论是提供给单一物种培养物还是在竞争情景下的物种，细胞生产速率都会随着时间的推移而减慢。
