The Role of Protozoan Zooplankton in Plankton Community Structure, Composition and Fate in the Equatorial Pacific

该项目是美国赤道太平洋中部全球海洋通量联合研究的一部分。在这一地区的一些观测结果与我们关于营养状况和浮游生物群落结构与垂直通量之间关系的一些传统概念相矛盾。通常与富营养化条件有关的高氮浓度和供应率与相对较低的叶绿素、初级生产力和“新产量”共存，这些都是低营养水域的特征。较小的微浮游生物和纳米浮游生物细胞主宰着浮游植物（查韦斯等）。在出版社)，但显著的生物沉积速率发生，并与初级生产相关。高通量通常被认为与大细胞有关，如硅藻，从地表水中下沉或被更大的细胞消耗，产生粪便颗粒的后浮游动物。这些明显的矛盾表明，浮游植物的大小结构、原生动物与后生动物的放牧以及它们与表层物质垂直通量的关系尚未完全了解。本项目将通过测量地表水中嗜光微小浮游生物、光养和异养纳米浮游生物以及吞噬性原生动物的丰度和生物量，以及原生浮游动物的放牧影响和生长速率来检验这些矛盾。我们的研究将采用成熟的，最先进的彩色图像分析结合荧光显微镜来描述浮游生物的大小，营养和分类结构。研究结果将用于确定原生浮游动物在赤道太平洋中部表层水体中颗粒有机物质的生产、消耗和输出耦合中的作用。

This project constitutes a portion of U.S. joint global ocean flux study (JGOFS) of the central equatorial Pacific. Several observations have been made in this region which contradict some of our conventional concepts of trophic status and the relationship between plankton community structure and vertical flux. High nitrogen concentrations and supply rates, usually associated with eutrophic conditions, co-exist with relatively low chlorophyll, primary productivity, and "new production" - which are characteristics of oligotrophic waters. Smaller pico- and nanoplankton cells dominate the phytoplankton (Chavez, et.al. in press), yet significant rates of biogenic sedimentation occur and is correlated with primary production. High flux rates are usually thought to be associated with large cells, such as diatoms, sinking out of surface waters or being consumed by larger cells, fecal pellet-producing metazooplankton. These apparent contradictions indicate that the consequences of phytoplankton size structure, protozoan versus metazoan grazing, and their relationship to vertical flux of material out of the surface layer are not fully understood. This project will examine these contradictions by measuring the abundances and biomass of the phototropic picoplankton, phototrophic and heterotrophic nanoplankton, and phagotrophic protozoans in the surface water, and the grazing impact and growth rates of protozooplankton. We study will employ proven, state-of-the-art color image analysis combined with epifluorescence microscopy to describe the size, trophic and taxonomic structure of the plankton. Results will be used to determine the role of protozoan zooplankton in the coupling of production, consumption and export of particulate of particulate organic matter in the surface waters of the central equatorial Pacific.