U.S. JGOFS: Microbial Communities in the Arabian Sea: Composition, Size, Spectra, and Growth Rates from Individual Cell Properties

小行星9311113 JGOFS项目在阿拉伯海的一个中心使命是确定碳泵在该区域的运行效率以及它如何对物理强迫的变化作出反应。 为了解决这些问题，我们需要分析食物网的结构，并确定它是如何随着地理和时间梯度的营养物质供应和水柱混合。 在阿拉伯海的生产和贫营养海洋系统的并列，并在相对恒定的太阳光照条件下，非常高和低的营养供应率之间的定期振荡，为我们提供了机会，以深入了解食物网的调节过程。 在这个项目中，Olson博士将（1）利用双光束流式细胞术和DNA特异性染色来区分异养生物和自养生物，在四个密集站和选定的中间站描述微型浮游生物和微型浮游生物的分布、丰度和光散射特性;（2）根据细胞数目的昼夜模式、光散射特性和深度剖面图中单个细胞的DNA含量，估计特定浮游植物群体的原地生长率和这些群体所受的放牧压力;（3）通过测量浮游植物（特别是颗石藻和微微型浮游植物）的C：N比值，验证了浮游植物在非季风期生理上受N限制的假设。 不同群体的浮游植物氮富集的相对反应将确定从14 C碳酸氢盐孵育实验，然后通过细胞分选，以获得细胞特定的生长速率。

9311113 Olson A central mission of the JGOFS project in the Arabian Sea is to determine how efficiently the carbon pump operates in this region and how it responds to changes in physical forcing. To approach these problems we need to analyze the structure of the food web and determine how it varies with geographical and temporal gradients in nutrients supply and water column mixing. The juxtaposition of productive and oligotrophic oceanic systems in the Arabian Sea, and the regular oscillation between very high and low rates of nutrient supply under relatively constant conditions of solar illumination, offers opportunities for us to gain insights into food web regulation processes. In this project, Dr. Olson will (1) Characterize the distribution, abundance, and light scatter properties of the picoplankton and nanoplankton at the four intensive stations and at selected intermediate stations, using dual beam flow cytometry and DNA specific staining to distinguish heterotrophic as well as autotrophic organisms; (2) Estimate in situ growth rates of specific groups of phytoplankton, and grazing pressure on these groups, from diel patterns in cell number, light scatter properties and DNA content of individual cells from depth profiles; and (3) Test the hypothesis that the phytoplankton are physiologically N-limited during non-monsoon periods by measuring the C:N ratios of phytoplankton ( in particular, coccolithophores and picoplankton) purified by cell sorting. Relative responses of different groups of phytoplankton to N enrichment will be determined from 14C bicarbonate incubation experiments followed by cell sorting to obtain cell-specific growth rates.