Elemental Analyses of Marine Phytoplankton Purified by Cell Sorting

通过生物化学和稳定同位素测量，可以了解特定生物的营养状况、相对生长速度、生理和食物网位置。然而，在自然野外样品中，由于存在污染碎屑和其他生物，这些测量几乎总是复杂的。由于对大型浮游植物的直接生物化学测量(通过过滤器收集)通常是模棱两可的，研究人员采用统计方法和培养实验来确定浮游植物的生物量和同化模式。这些间接解决方案的一个强有力的替代方案是流式细胞仪细胞分选。流式细胞术使我们能够根据它们的自发荧光和光散射特性识别几类浮游植物，并在物理上将这些颗粒与所有其他颗粒分开，它将被用于从不同的海洋环境中获取样品，用于测量C和N(其次，测量C和N稳定同位素的自然丰度)。具体来说，奥尔森博士将回答以下有关海洋中氮限制的性质和程度的问题：*浮游植物细胞(和海洋中特定群体的C：N比率)之间的C：N比率是否存在差异浮游植物的碳氮比有季节差异吗？*浮游植物的C：N随深度有变化吗？*浮游植物的C：N比有无变化？*在这些条件下，“非浮游植物”的特征是什么？这一结果将有助于阐明海洋中氮的限制程度和不同浮游植物类群的生态作用，并有助于解释水柱颗粒样品中观测到的同位素丰度模式。它还应该作为浮游生物特定成分的各种其他生化测量的跳板。

Much can be learned of the nutritional status, relative growth rates, physiology and food web position of particular organisms from biochemical and stable isotope measurements. However, these measurements are almost always complicated in natural field samples by the presence of contaminating detritus and other organisms. Since direct biochemical measurements of the bulk phytoplankton (collected on filters) are often equivocal, researchers have employed statistical methods and incubation experiments for determining phytoplankton biomass and assimilation patterns. A powerful alternative to these indirect solutions to the problem is flow cytometric cell sorting. Flow cytometry, which allows us to recognize several classes of phytoplankton based on their autofluorescence and light scatter properties and to physically separate these particles form all others, will be used to obtain samples from a variety of oceanic regimes for measurements of C and N (and secondarily, of the natural abundances of C and N stable isotopes). Specifically,Dr. Olson will answer the following questions about the nature and extent of N limitation in the oceans: * Is there a difference between the C:N ratios of phytoplankton cells (and of specific groups within the phytoplankton) in coastal waters and those in the oligotrophic ocean? * Are there seasonal differences in C:N ratio of phytoplankton? * Are there changes in C:N of the phytoplankton with depth? * Are there diel changes in C:N ratios in the phytoplankton? * What are the characteristics of the "non-phytoplankton" under these sets of conditions? The results will shed light on the extent of N-limitation int he oceans and on the ecological roles of different groups of phytoplankton, and will help interpret observed patterns of isotope abundance in water column particle samples. It should also act as a springboard for a variety of other biochemical measurements of specific components of the plankton.