Characterizing and quantifying the impact of phagotrophic protists at hot spots of primary production at Axial Seamount

微生物是我们星球上生命的祖先，在塑造地球环境的过程中发挥了重要作用。在海洋中，微生物原核生物和真核生物通过它们的活动和相互作用形成了海洋食物网的基础。单细胞微生物真核生物（或原生生物）是地球上最重要的物种之一，但我们对它们的活动如何影响和调节海洋生态系统的理解却很少。特别是在深海热液喷口，如果不包括微生物真核生物的作用，我们对微生物食物网动力学的理解是不完整的。该项目提供了在热液喷口高产的扩散喷口混合区栖息的微生物群落的吞噬原生生物的定量研究，与周围的深层海水相比，热液喷口流体-海水界面促进了生物活性的增加。研究结果有助于深入了解喷口流体-海水界面真核微生物群落的多样性和代谢活动，通过量化捕食压力确定真核微生物对深海初级生产的影响程度，并估计从初级生产者转移到更大生物的碳量。调查人员正在培训科德角社区学院的社区大学生，让他们通过暑期实习参与实验室研究。其目标是通过实践研究经验、点对点指导和专业发展机会，促进社区大学生的科学、技术、工程和数学素养，同时鼓励学生转学到四年制大学，获得STEM学科的学位，并继续在STEM领域学习。微生物真核生物的放牧是海洋微生物死亡的一个重要来源，从而影响群落的组成，并作为有机物质向所有生物再矿化的主要途径。本项目旨在量化深海初级生产力热点地区真核生物对原核生物群落的原位放牧率，并表征海底微生物真核生物的多样性、丰度和代谢活动。这项工作的重点是海底火山轴状海山，这是海洋观测倡议（OOI）区域电缆阵列的所在地，具有明显的低温扩散排气流体特征。这项工作的两个目标是：1。量化在低温弥漫性流体混合带海底，吞噬性真核微生物放牧对原核生物群落的速率和影响。表征低温弥漫流体混合带海底微生物真核生物多样性、丰度和代谢基因表达。模块化微生物取样器-潜水孵育装置（MS-SID）正在用于海底示踪剂的原位孵育，并与拟议放牧研究的船上孵育进行比较。这种技术组合提供了对原生生物群落的详细和定量评估，并确定了微生物真核生物对深海初级生产的影响程度。预期结果包括量化海底混合带内原生生物对细菌和古细菌群落的掠食率，比较喷口-海水界面和周围深海水域的捕食压力，以及确定热液混合带内关键的细菌捕食者、真菌和其他原生生物以及相关的主要活性代谢途径。由于目前对深海热液喷口处微生物生态的描述通常不包括微生物真核生物的作用，因此该项目在理解深海微生物循环方面取得了重大进展。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Microorganisms are the ancestral forms of life on our planet and have been instrumental in shaping all of Earth’s environments into what they are today. In the ocean, microbial prokaryotes and eukaryotes form the foundation of marine food webs through their activity and interactions. Single-celled microbial eukaryotes (or protists) are some of the most important species on the planet, yet our understanding of how their activities influence and regulate the ocean ecosystem is poorly constrained. At deep-sea hydrothermal vents in particular, our understanding of microbial food web dynamics is incomplete without including the role of microbial eukaryotes. This project provides quantification of phagotrophic protistan grazing on the microbial communities inhabiting the highly productive diffuse vent mixing zone at hydrothermal vents, where the vent fluid-seawater interface promotes an increase in biological activity compared to the surrounding deep seawater. The results are contributing novel insights into the diversity and metabolic activities of the microbial eukaryotic community at vent fluid-seawater interfaces, establish the extent to which microbial eukaryotes impact primary production in the deep ocean by quantifying predation pressure, and estimate the amount of carbon transferred from primary producers to larger organisms. The investigators are training community college students from Cape Cod Community College by involving them in laboratory research through summer internships. The goal is to promote science, technology, engineering and math literacy among community college students through hands-on research experiences, peer-to-peer mentoring, and professional development opportunities, while also encouraging students to transfer to a four-year university, obtain a degree in a STEM subject, and continue on in a STEM field.Grazing by microbial eukaryotes is a significant source of mortality for microbes in the oceans, thus influencing the composition of communities and serving as a major route for remineralization of organic material to all organisms. This project is quantifying the in situ rates of eukaryotic grazing on prokaryotic communities at hot spots of primary productivity in the deep sea and characterize the diversity of microbial eukaryotes, their abundance, and metabolic activities at the seafloor. The focus of the effort is at the underwater volcano Axial Seamount, home of the Ocean Observatories Initiative (OOI) Regional Cabled Array with well-characterized low-temperature diffusely venting fluids. The two objectives of the work are to:1. Quantify the rates and impact of phagotrophic microbial eukaryote grazing on prokaryotic communities at the seafloor in low-temperature diffuse fluid mixing zones.2. Characterize microbial eukaryotic diversity, abundance, and metabolic gene expression at the seafloor in low-temperature diffuse fluid mixing zones.The modular Microbial Sampler-Submersible Incubation Device (MS-SID) is being used for in situ seafloor tracer incubations and compared to shipboard incubations for the proposed grazing studies. This combination of technology provides detailed and quantitative assessments of protistan communities and establishes the extent to which microbial eukaryotes impact primary production in the deep ocean. Expected outcomes include the quantification of protistan grazing rates on bacterial and archaeal communities within the seafloor mixing zone, comparison of predation pressure at the vent-seawater interface and surrounding deep ocean water, as well as identification of key bacteriovores, fungi, and other protists and associated major active metabolic pathways within the hydrothermal mixing zones. The project is providing a significant advance in the understanding of the microbial loop in the deep ocean as current depictions of microbial ecology at hydrothermal vent sites do not typically include the role of microbial eukaryotes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.