Collaborative Research: Bloom Dynamics and Food Web Structure in the Ross Sea: Role of Microzooplankton in Controlling Production

9315027 Lessard极地海洋中浮游植物的生长季节很短，但很激烈。 越来越多的证据表明，在许多南极栖息地，最活跃的时期可能是季节的早期，这是以前的调查中没有强调的时期。 该项目是一个跨学科计划的一部分，该计划的重点是南极罗斯海一个高产子系统中春季浮游植物水华的动态。 整个计划将测试有关的假设开始后不久，冰融化的浮游植物水华，控制浮游植物生长和生产力的机制，在春季，高生产力的影响和短期的命运，从春季到盛夏的过渡条件。 这项建议的重点是微型浮游动物在控制生产和碳的命运在两种类型的水华的作用。 目标是：1）确定初级生产者组合的生物量、丰度、大小和选定的物种组成，2）确定纳米和微型浮游异养组合的相似特征，3）测量对异养细菌和浮游植物的总群落放牧，4）检查哪些食草动物是主要的食草动物和食菌动物，（5）测量微型浮游动物和中型浮游动物排泄物、藻类细胞和群落的下沉以及原生动物组合与碎屑的下沉对透光层250 m深度总碳通量的贡献。 将采集用于丰度和生物量测定的水样，并用落射荧光显微镜检查样品。 将使用稀释放牧技术和双同位素放射性标记单细胞法测量放牧率。 碳通量将确定下沉的物质收集颗粒拦截器陷阱在底部的透光层和两个更深的深度，使用显微镜分析。 对这些过程和合作调查人员研究的其他基本过程的了解将有助于了解南大洋在目前、过去和预测的未来碳固存以及在其他全球元素循环中的作用。

9315027 Lessard The growing season for phytoplankton in polar oceans is short, but intense. There is an increasing body of evidence that in many Antarctic habitats, the most active period may be very early in the season, a period that has not been emphasized in previous investigations. This project is part of an interdisciplinary program that focuses on the dynamics of the spring phytoplankton bloom in a highly productive subsystem of the Antarctic, the Ross Sea. The overall program will test hypotheses related to the initiation of the phytoplankton bloom shortly after the onset of ice melt, the mechanisms controlling phytoplankton growth and productivity in spring, the implications and short-term fate of high productivity in spring, and the transition from spring to midsummer conditions. The focus of this proposal is the role of microzooplankton in controlling the production and fate of carbon during the two types of blooms. Objectives are: 1) to determine biomass, abundance, size and selected species composition of primary producer assemblages, 2) to determine similar features of nano- and microplanktonic heterotrophic assemblages, 3) to measure total community grazing on heterotrophic bacteria and phytoplankton, 4) to examine which grazers are the major herbivores and bacterivores, and 5) to measure the contribution of microzooplankton and mesozooplankton egesta, sinking of algal cells and colonies, and sinking of protozoan assemblages associated with detritus to the total carbon flux from the euphotic zone through 250 m depth. Water samples for abundance and biomass determinations will be taken and samples will be examined with epifluorescence microscopy. Grazing rates will be measured using the dilution grazing technique and the dual- isotope radiolabeling single cell method. Carbon fluxes will be determined on sinking material collected with particle interceptor traps at the base of the euphotic zone and two deeper depths, using microscopical analys is. An understanding of these processes and other fundamental processes studied by collaborating investigators will contribute to the understanding of the role of the Southern Ocean in present, past and predicted future sequestration of carbon, as well as in other global elemental cycles.