SGER: Reassessing the Role of Planktonic Amoeboid Protists in Estuarine Microbial Food Webs

最近的方法学进展表明，裸变形虫原生生物（变形虫）是更丰富的浮游生物比以前认为的。利用一组新建立的生物体积关系，估算了哈德逊河口（HRE）浮游变形虫的碳含量，占浮游异养原生生物总碳的3-36%，与受到更多研究关注的纤毛虫相当。因此，变形虫可能发挥重要作用，通过浮游生物在河口的食物网的碳转移，挑战目前的观点微生物C通量通过河口浮游生物。然而，通过阿米巴池的C-通量还没有得到充分的量化，在任何海洋系统和采样阿米巴在HRE迄今已被限制在一个单一的，基于海岸的位置在河口的中盐部分。本计画将量化裸露的异养变形虫对HRE微生物食物网中异养原生生物总碳及碳通量的重要性。附着和自由生活的细菌和异养原生生物的主要群体的生物量将使用显微镜为基础的技术进行量化。将首次在自然条件下测定嗜热阿米巴的生长速率。将在3个月内从HRE盐度梯度沿着的5个地点收集数据，提供来自各种环境设置的观测结果。其结果将是第一次全面的，定量的了解浮游异养原生生物的常设股票和C通量在这个重要的河口，第一次变形虫和其他主要的原生生物群体的浮游生物已充分量化在一起，在任何海洋系统。该项目符合SGER指南，作为一个新兴领域的企业，使用最近开发的专业知识，有可能改变我们对河口浮游微生物群落的既定看法。SGER的资金也将通过华莱士基金会资助的一个配套项目以及联合PI，O.浮游原生生物是从细菌到大型生物（包括无脊椎动物和鱼类）的食物网中的重要环节。然而，由于方法上的障碍，以前的努力，以评估的重要性，浮游原生生物忽视了的作用，浮游变形虫。该项目将使用成熟的和新获得的技术相结合，量化阿米巴对HRE中微生物现存量和碳通量的贡献。这一努力有可能改变目前的理解河口浮游微生物碳通量。这将是第一个研究的浮游原生生物在较低的HRE，和第一个研究比较微生物食物网在不同地区的河口。通过提供信息，通过较低的营养水平的元素通量，本研究的结果将是相关的环境管理的人口最多的河口在美国。HRE为其他河口，特别是具有高颗粒负荷的系统提供了模型。确定环境相关的阿米巴常备股票，增长率，和C通量将促进本研究的结果转移到其他systems.This项目是密切相关的，并高度利用，在HRE的水质高调的研究。水质研究将有一个大的，专门的网络存在，并定于在未来几周内广泛的新闻报道。该项目还提供了一个机会，从一名资深科学家（安德森）到一名初级同事（朱尔）的重要和独特的知识转让有关的鉴定和计数的嗜热阿米巴。此外，本科生将参与研究，并使用她的高级研究论文收集的数据的一部分。

Recent methodological advances have revealed that naked amoeboid protists (amebas) are much more abundant in the plankton than previously thought. Using a newly-established set of biovolume relationships, the carbon content of planktonic amebas in the Hudson River estuary (HRE) was estimated to comprise 3-36% of total planktonic heterotrophic protist carbon, comparable to the ciliates, a group that has received much more research attention. Amebas are therefore likely to play an important role in carbon transfer through planktonic food webs in estuaries, challenging current views of microbial C fluxes through estuarine plankton. Nevertheless, C-flux through the ameba pool has not been adequately quantified in any marine system and sampling for amebas in the HRE has heretofore been restricted to a single, shore-based location in the mesohaline portion of the estuary. This project will quantify the significance of naked planktonic amebas to total heterotrophic protist carbon and C flux through the microbial food web of the HRE. Biomasses of attached and free-living bacteria and the major groups of heterotrophic protists will be quantified using microscopy-based techniques. Growth rates of planktonic amebas will be measured under natural conditions for the first time. Data will be gathered from 5 locations along the HRE salinity gradient over 3 months, providing observations from a wide range of environmental settings. The outcome will be the first comprehensive, quantitative understanding of planktonic heterotrophic protist standing stocks and C fluxes within this important estuary, and the first time amebas and other major protist groups in the plankton have been adequately quantified together in any marine system. This project meets SGER guidelines as a venture into an emerging area using recently-developed expertise to potentially transform our established view of estuarine planktonic microbial communities. SGER funding would also be highly leveraged through a companion project funded by the Wallace Foundation and by the in-kind contribution of time and expertise to the project by Co-PI, O. Roger Anderson.Planktonic protists are important links in the food web from bacteria to larger organisms, including invertebrates and fish. However, because of methodological impediments, previous efforts to assess the importance of planktonic protists have overlooked the role of planktonic amebas. Using a combination of well established and newly-available techniques, this project will quantify the contribution of amebas to microbial standing stocks and carbon fluxes in the HRE. This effort has the potential to transform current understanding of planktonic microbial C fluxes in estuaries. This will be the first study of planktonic protists in the lower HRE, and the first study to compare microbial food webs in different regions of the estuary. By providing information on elemental fluxes through lower trophic levels, the results of this study will be relevant to environmental management of one of the most populated estuaries in the US. The HRE provides a model for other estuaries, especially systems with high particle load. Determining the environmental correlates of ameba standing stocks, growth rates, and C flux will facilitate transferring the results of this study to other systems.This project is closely related to, and highly leveraged by, a high-profile study of water-quality in the HRE. The water-quality study will have a large, dedicated web presence and is slated for extensive press coverage in the coming weeks. The project also presents an opportunity for significant and unique knowledge transfer related to the identification and enumeration of planktonic amebas from a senior scientist (Anderson) to a junior colleague (Juhl). In addition, an undergraduate will participate in the research and use a portion of the data collected for her Senior research thesis.