Department of Oceanography, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4J1.
J R Soc Interface. 2011 May 6;8(58):650-60. doi: 10.1098/rsif.2010.0503. Epub 2010 Nov 17.
The absorption coefficient of a substance distributed as discrete particles in suspension is less than that of the same material dissolved uniformly in a medium-a phenomenon commonly referred to as the flattening effect. The decrease in the absorption coefficient owing to flattening effect depends on the concentration of the absorbing pigment inside the particle, the specific absorption coefficient of the pigment within the particle, and on the diameter of the particle, if the particles are assumed to be spherical. For phytoplankton cells in the ocean, with diameters ranging from less than 1 µm to more than 100 µm, the flattening effect is variable, and sometimes pronounced, as has been well documented in the literature. Here, we demonstrate how the in vivo absorption coefficient of phytoplankton cells per unit concentration of its major pigment, chlorophyll a, can be used to determine the average cell size of the phytoplankton population. Sensitivity analyses are carried out to evaluate the errors in the estimated diameter owing to potential errors in the model assumptions. Cell sizes computed for field samples using the model are compared qualitatively with indirect estimates of size classes derived from high performance liquid chromatography data. Also, the results are compared quantitatively against measurements of cell size in laboratory cultures. The method developed is easy-to-apply as an operational tool for in situ observations, and has the potential for application to remote sensing of ocean colour data.
悬浮液中呈离散颗粒分布的物质的吸收系数小于同一物质均匀溶解在介质中的吸收系数——这一现象通常被称为“展平效应”。由于展平效应，吸收系数的降低取决于颗粒内部吸收颜料的浓度、颗粒内颜料的特定吸收系数以及颗粒的直径（如果假设颗粒为球形）。对于海洋中的浮游植物细胞，其直径范围从小于 1 µm 到大于 100 µm，展平效应是可变的，有时很明显，这在文献中已有很好的记录。在这里，我们展示了如何利用浮游植物细胞单位浓度的主要色素叶绿素 a 的体内吸收系数来确定浮游植物种群的平均细胞大小。我们进行了敏感性分析，以评估由于模型假设中潜在的误差而导致的估计直径的误差。使用模型计算的现场样本的细胞大小与从高效液相色谱数据得出的间接估计的大小类别的定性比较。此外，还将结果与实验室培养物中的细胞大小测量值进行了定量比较。所开发的方法易于应用于现场观测的操作工具，并且有可能应用于海洋颜色数据的遥感。
