Collaborative Research: The Role of Phytoplankton Ballast Material in Deterring Copepod Grazing

合作研究：浮游植物压载材料在阻止桡足类吃草中的作用

• 批准号: 0648346
• 负责人: David Fields
• 金额: $ 46.28万
• 依托单位: Bigelow Laboratory for Ocean Sciences
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-03-15 至 2011-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0648346&HistoricalAwards=false
• 关键词: Collaborative; Research; Role; Phytoplankton; Ballast

Many groups of marine protists (algae and protozoa) are "armored" with thickened cell walls, coatings of scales, hard "cases" (tests, loricas), or latticework "skeletons". The inferred evolutionary function of these mineral deposits is to deter grazing. However, to date there are no direct measurements of grazing rates on protists as a function of their mineral content. The recent development of silica specific stains and state of the art flow cytometry techniques enable these measurements. This study directly tests the relationship between the cellular mineral quota and the ingestion rates of copepods. Phytoplankton cells that differ in the relative degree of mineral armor will be created using well controlled algal rearing techniques. Mineral load will be determined chemically (chemical digestion), visually (SEM), and photometrically (mineral and cell surface specific dyes and flow cytometry). The grazing protection conferred by biogenic minerals will be examined against copepod predation with detailed examination (microcinematography) of the behavioral mechanisms that underlie the selective process.Preliminary grazing experiments show that copepods have a strong preference for cells with low biogenic mineral content. This suggests that heavily fortified cells are less likely to be packaged into fecal pellets, thus uncoupling the mineral content of plankton from what is exported to the deep ocean. This implies that global biogeochemical cycles are structured, in part, by the ecological and evolutionary constraints of predator-prey interactions. This study includes measurement of the mineral content of the ingested particles and of the fecal pellets of copepods. The hypothesis is that a higher mineral content in the fecal pellet will increase the density of the pellet and therefore, lead to a higher settling velocity. The role of the biological pump in sequestering atmospheric CO2 is driven, in part, by the rapid sinking rates of fecal pellets. Experiments outlined in this proposal will link the mineral content of the copepod diet with the mineral content of the fecal pellet. Subsequently, direct video observations will enable measurement of the sinking rates of fecal pellets as a function of their mineral load.Intellectual Merit: Measuring and understanding the factors that control the flux of organic material to the sediments has been the focus of numerous large oceanographic programs (e.g. JGOFS and ANTARES). Proxies of surface production or mineral ballast content have been proposed to predict deep ocean fluxes. However without a mechanistic understanding of the underlying processes driving the quality and quantity of material reaching the sediments, these proxies are robust only when the mechanisms remain constant. Information on the direct interactions between copepods and primary producers is needed to predict how changes in the phytoplankton/copepod link will manifest in the biological pump of organic matter to the deep ocean.Broader Impacts: The proposal contributes to undergraduate education by incorporating three students during the three year project. The proposal has numerous self-contained sub-projects that will provide exceptional opportunities for motivated undergraduate students to receive hands on research experience. Students will learn sophisticated culturing techniques for different phytoplankton, participate in grazing experiments and learn the fundamentals of optics and microcinematography. In addition, at little financial cost to this proposal two students will gain valuable field experience in sampling and identifying plankton and conducting grazing experiment. Students in our lab will be required to meet weekly to discuss problems, recent success, and pertinent literature to their specific topic. Student participation at meetings and activities of professional societies will be encouraged. Results of the project will also contribute to the development of Bigelow Laboratory educational and outreach programs, most notably the Phytopia project and its allied utilities for learners and teachers at secondary and tertiary levels (http://www.bigelow.org/phytopia/).

许多海洋原生生物（藻类和原生动物）都有厚厚的细胞壁、鳞片、坚硬的外壳或网格状的骨架。推断这些矿藏的进化功能是阻止放牧。然而，到目前为止，没有直接测量原生生物的放牧率作为其矿物质含量的函数。二氧化硅特异性染色剂的最新发展和最先进的流式细胞术技术使这些测量成为可能。本研究直接检验了桡足类细胞矿物质定额与摄食率之间的关系。不同的浮游植物细胞的相对程度的矿物装甲将创建使用良好的控制藻类饲养技术。将通过化学（化学消化）、目视（SEM）和光度（矿物质和细胞表面特异性染料和流式细胞术）测定矿物质负荷。生物矿物质所赋予的放牧保护将被检查对桡足类捕食与详细的检查（显微电影）的行为机制，选择process.Preliminary放牧实验表明，桡足类有一个强烈的偏好低生物矿物质含量的细胞。这表明，经过高度强化的细胞不太可能被包装成粪便颗粒，从而将浮游生物的矿物质含量与出口到深海的物质分开。这意味着，全球生物地球化学循环的结构，在某种程度上，由生态和进化的限制捕食者-猎物的相互作用。本研究包括测量摄入颗粒和桡足类粪便颗粒的矿物质含量。假设是粪便颗粒中较高的矿物质含量将增加颗粒的密度，因此导致更高的沉降速度。生物泵在封存大气二氧化碳中的作用部分是由粪便颗粒的快速沉降率驱动的。本提案中概述的实验将把桡足类食物中的矿物质含量与粪便颗粒中的矿物质含量联系起来。随后，直接视频观测将能够测量作为其矿物质负载函数的粪粒的沉降速率。智力优势：测量和了解控制有机物质向沉积物的通量的因素一直是许多大型海洋学计划（例如JGOFS和ANTARES）的重点。有人提议用表层生产量或矿物压载物含量的代用指标来预测深海通量。然而，如果没有对驱动到达沉积物的物质的质量和数量的基本过程的机械理解，这些代理只有在机制保持不变时才是可靠的。桡足类和初级生产者之间的直接相互作用的信息是必要的，以预测浮游植物/桡足类链接的变化将如何体现在有机物质的生物泵到深海。更广泛的影响：该提案有助于本科教育纳入三年的项目期间的三名学生。该提案有许多独立的子项目，将为有动力的本科生提供获得研究经验的绝佳机会。学生将学习不同浮游植物的复杂养殖技术，参加放牧实验，并学习光学和显微摄影的基础知识。此外，本研究的两名学生将以很少的经济成本获得浮游生物取样和鉴定以及进行放牧实验的宝贵现场经验。我们实验室的学生将被要求每周开会讨论问题，最近的成功，以及与他们的特定主题相关的文献。鼓励学生参加专业协会的会议和活动。该项目的成果还将有助于毕格罗实验室教育和推广方案的发展，最值得注意的是植物学项目及其对中学和大学学习者和教师的相关实用程序（http：//www.bigelow.org/phytopia/）。