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

9316035极地海洋浮游植物的生长季节很短，但强度很大。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，这一时期在以前的调查中没有得到强调。该项目是一个跨学科项目的一部分，该项目重点研究南极高产的罗斯海的春季浮游植物水华的动态。整个计划将测试与浮游植物在冰川融化后不久开始繁殖的假设，控制春季浮游植物生长和生产力的机制，春季高生产力的含义和短期命运，以及从春季到仲夏条件的过渡。这项提议的重点是微型浮游动物在控制两种类型水华期间碳的产生和去向方面的作用。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)测量异养细菌和浮游植物的总放牧群落，4)研究哪些食草动物是主要的草食和食菌动物，5)测量微型浮游动物和中浮游动物卵壳的贡献，藻类细胞和群体的下沉，以及与碎屑有关的原生动物组合在250米深度的真光带总碳通量中的下沉。将采集用于丰度和生物量测定的水样，并用荧光显微镜检查样品。放牧率将使用稀释放牧技术和双同位素放射性标记单细胞方法进行测量。使用显微镜分析，将在真光区底部和两个更深的深度用粒子拦截器陷阱收集的下沉材料上测定碳通量。了解合作研究人员研究的这些过程和其他基本过程将有助于理解南大洋在现在、过去和预测的未来碳封存以及其他全球元素循环中的作用。

9316035 Gowing 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 analysis . 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.