Department of Chemistry, University of Tennessee, Knoxville, TN, USA.
Appl Spectrosc. 2018 Mar;72(3):366-377. doi: 10.1177/0003702817728070. Epub 2017 Oct 6.
With increasing amounts of anthropogenic pollutants being released into ecosystems, it becomes ever more important to understand their fate and interactions with living organisms. Microalgae play an important ecological role as they are ubiquitous in marine environments and sequester inorganic pollutants which they transform into organic biomass. Of particular interest in this study is their role as a sink for atmospheric CO, a greenhouse gas, and nitrate, one cause of harmful algal blooms. Novel chemometric hard-modeling methodologies have been developed for interpreting phytoplankton's chemical and physiological adaptations to changes in their growing environment. These methodologies will facilitate investigations of environmental impacts of anthropogenic pollutants on chemical and physiological properties of marine microalgae (here: Nannochloropsis oculata). It has been demonstrated that attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy can gain insights into both and this study only focuses on the latter. From time-series of spectra, the rate of microalgal biomass settling on top of a horizontal ATR element is derived which reflects several of phytoplankton's physiological parameters such as growth rate, cell concentrations, cell size, and buoyancy. In order to assess environmental impacts on such parameters, microalgae cultures were grown under 25 different chemical scenarios covering 200-600 ppm atmospheric CO and 0.35-0.75 mM dissolved NO. After recording time-series of ATR FT-IR spectra, a multivariate curve resolution-alternating least squares (MCR-ALS) algorithm extracted spectroscopic and time profiles from each data set. From the time profiles, it was found that in the considered concentration ranges only NO has an impact on the cells' physiological properties. In particular, the cultures' growth rate has been influenced by the ambient chemical conditions. Thus, the presented spectroscopic + chemometric methodology enables investigating the link between chemical conditions in a marine ecosystem and their consequences for phytoplankton living in it.
随着越来越多的人为污染物被排放到生态系统中，了解它们的命运和与生物体的相互作用变得越来越重要。微藻作为海洋环境中无处不在的生物，它们吸收无机污染物并将其转化为有机生物量，因此具有重要的生态作用。在本研究中，特别感兴趣的是它们作为大气 CO（一种温室气体）和硝酸盐（有害藻类大量繁殖的一个原因）的汇的作用。已经开发了新颖的化学计量硬模型化方法来解释浮游植物对其生长环境变化的化学和生理适应。这些方法将有助于研究人为污染物对海洋微藻（此处：眼斑拟微绿球藻）的化学和生理特性的环境影响。已经证明衰减全反射傅里叶变换红外（ATR FT-IR）光谱可以深入了解这两者，而本研究仅关注后者。从光谱时间序列中，可以得出微藻生物质在水平 ATR 元件顶部沉降的速率，该速率反映了浮游植物的几个生理参数，例如增长率、细胞浓度、细胞大小和浮力。为了评估环境对这些参数的影响，在 25 种不同的化学条件下培养微藻，涵盖 200-600 ppm 大气 CO 和 0.35-0.75 mM 溶解的 NO。在记录 ATR FT-IR 光谱的时间序列之后，使用多变量曲线分辨交替最小二乘法（MCR-ALS）算法从每个数据集提取光谱和时间分布。从时间分布中发现，在所考虑的浓度范围内，只有 NO 对细胞的生理特性有影响。特别是，培养物的生长速率受到环境化学条件的影响。因此，所提出的光谱+化学计量学方法能够研究海洋生态系统中的化学条件与其对其中浮游植物的影响之间的联系。
