Dynamics of Protistan Grazers: Diversity, Abundance and Prey Relations

原生食草动物的动态：多样性、丰度和猎物关系

• 批准号: 1434440
• 负责人: Rebecca Gast
• 金额: $ 99.94万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1434440&HistoricalAwards=false
• 关键词: Dynamics; Protistan; Grazers; Diversity; Abundance

Some of the most important primary producers and consumers in aquatic ecosystems are protists, or single-celled eukaryotes. It is well established that protistan predation can be a significant source of mortality for bacteria and phytoplankton. Grazing protists in turn serve as prey for zooplankton (copepods), and through the excretion of nitrogen and phosphorus compounds, they play a major role in the release of regenerated nutrients. Despite decades of studies on protistan grazing, knowledge gaps still exist with respect to their abundance, distribution, seasonality, prey selectivity, and co-occurrence patterns. The results from this project will advance the understanding of grazing communities in situ and how they respond to environmental conditions and prey communities. This will be one of very few studies of grazers that is unbiased by artificial prey and containment, and will yield both morphologic and genetic information about the organisms present and the distribution patterns of particular grazer populations. A graduate student will be performing her thesis work as part of this project, and selected undergraduates will be involved in the research. In partnership with the Zephyr Education Foundation's marine science literacy and education program, teachers will develop an educational unit based on the microbial food web that is tailored to grade levels 6-8. This project examines whether the persistence of a group of protistan grazers is determined by its feeding strategy (grazers with specialist feeding strategies are more ephemeral than generalists), and whether certain morphotypes exhibiting generalist feeding strategies have underlying genotypic diversity that maps to specialist feeding strategies. It builds upon an ongoing time series (with hourly resolution since 2006) of automated, high-resolution, measurements of the phytoplankton community by the Imaging FlowCytobot at the Martha's Vineyard Coastal Observatory. These measurements have led to the observation that, in addition to shifts from pico- and small nanoplankton during the summer to larger microplankton in the fall and winter, particular species (especially among the diatoms) exhibit distinct and recurring seasonal patterns. The instrument will be modified to also conduct automated measurements of grazer communities in situ. Links between selected grazer taxa (chosen based on the image time series) and phytoplankton prey will be provided through genetic analyses of individual cells (with their ingested prey). These cells will be obtained by use of a recently developed cell sorter that also captures an image of each sorted cell. In addition to providing predator/prey links, the genetic information will allow the investigators to determine whether a grazer morphotype represents multiple species. A third approach, high throughput sequencing and quantitative PCR analysis of whole water samples, will be applied to investigate abundance patterns of species whose morphology does not reliably map to genotype.

水生生态系统中一些最重要的初级生产者和消费者是原生生物，或单细胞真核生物。已经确定的是，原生生物的捕食可能是细菌和浮游植物死亡的重要来源。食草原生动物反过来又作为浮游动物（桡足类）的猎物，通过排泄氮和磷化合物，它们在释放再生营养物质方面发挥着重要作用。尽管对原生动物放牧进行了数十年的研究，但在其丰度、分布、季节性、猎物选择性和共生模式方面仍然存在知识空白。该项目的结果将促进对当地放牧群落的了解，以及它们如何对环境条件和猎物群落作出反应。这将是为数不多的对食草动物的研究之一，该研究不受人工猎物和遏制的影响，并将产生有关存在的生物体以及特定食草动物种群分布模式的形态和遗传信息。作为本项目的一部分，一名研究生将完成她的论文工作，选定的本科生将参与研究。与Zephyr教育基金会的海洋科学素养和教育计划合作，教师将开发一个基于微生物食物网的教育单元，该单元适合6-8年级。本项目探讨是否持久的一组原生动物食草动物是由其喂养策略（食草动物与专家喂养策略是更短暂的比通才），以及是否某些形态型表现出通才喂养策略有潜在的基因型多样性，映射到专家喂养策略。它建立在一个持续的时间序列（自2006年以来每小时的分辨率）的自动化，高分辨率，测量浮游植物群落的成像FlowCytobot在玛莎葡萄园岛海岸天文台。这些测量导致观察到，除了从夏季的皮科和小型微型浮游生物到秋季和冬季的大型微型浮游生物的转变之外，某些物种（特别是硅藻）表现出独特和重复的季节性模式。将对该仪器进行修改，以便也对当地的食草动物群落进行自动测量。选定的食草动物分类群（选择的基础上的图像时间序列）和浮游植物猎物之间的联系将提供通过遗传分析的个别细胞（与他们摄入的猎物）。这些细胞将通过使用最近开发的细胞分选仪获得，该细胞分选仪还捕获每个分选细胞的图像。除了提供捕食者/猎物的联系，遗传信息将使研究人员能够确定一个食草动物形态型是否代表多个物种。第三种方法，高通量测序和定量PCR分析的整个水样，将被应用于调查物种的形态不可靠的基因型映射的丰度模式。