RUI: Collaborative Research: Do nearby surfaces limit the food uptake of microscopic sessile suspension feeders- 3D feeding flow measurements?

RUI：合作研究：附近的表面是否会限制微型固着悬浮喂食器的食物摄取 - 3D 喂食流量测量？

• 批准号: 1755326
• 负责人: Rachel Pepper
• 金额: $ 36.36万
• 依托单位: University of Puget Sound
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-15 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1755326&HistoricalAwards=false
• 关键词: RUI; Collaborative; Research; Do; nearby

Most of earth is covered by water, and it is essential to keep these ocean and freshwater ecosystems healthy. To do so, scientists must understand how they stay clean and in balance. A critical part of healthy bodies of water are microscopic organisms, which process waste and keep water clean by eating bacteria and debris. The feeding rate of these tiny organisms (how much water they clean per time) determines the impact they have on the health of their environments. Therefore, understanding this feeding rate is important both to predicting how bodies of water will react to change (e.g., pollution, sewage leaks, climate change) and determining how to promote the recovery of unhealthy bodies of water. One type of microscopic organism that is important for clean water and is ubiquitous in freshwater and marine environments is the surface-attached protist. These organisms live in dense aggregations attached to under-water surfaces, such as rocks, plants, and sinking debris and create feeding currents that draws their food to them. The investigators will use a novel holographic microscope to make the first three-dimensional measurements of feeding currents of these organisms in realistic conditions. The findings will be used to validate existing mathematical models of the feeding rates of these microscopic organisms and will inform the development of strategies to clean bodies of water and improve wastewater treatment plant performance. This project will also provide interdisciplinary opportunities for undergraduate and graduate students, including those from groups that are traditionally underrepresented in the STEM workforce. Microscopic sessile suspension feeders (MSSFs) are surface-attached protists that are a ubiquitous and critical component in aquatic ecosystems, performing the vital ecological function of removing bacteria and contaminants and serving as a key trophic intermediate between algae/bacteria and higher eukaryotic taxa. Previous studies of the feeding activity of these surface-attached protists have been limited to confined conditions that distort the flow and 2D measurements do not capture the non-axisymmetric nature of the current. Further, theory predicts that feeding is restricted by closed eddies in the flow caused by the surface of attachment, and that the impact of these eddies on feeding rate depends strongly on the angle of the MSSF with respect to the surface. The researchers will use Vorticella, a sessile ciliate, to determine whether food uptake of MSSFs is limited by the hydrodynamics of feeding attached to surfaces. Using a novel 3D holographic microscope, they will determine: (1) how the 3D feeding flow field of a single MSSF changes with body orientation of the organism relative to the surface, (2) how the dynamics of body orientation for Vorticella in culture compares to those in nature, (3) how feeding flows and body orientations affect food uptake, and (4) how the feeding flows are affected by ambient environmental flows. The measurements will be used to validate hydrodynamic models of MSSFs that can predict clearance rates. The resulting mechanistic understanding of microscopic interactions will ultimately build a foundation to scale up to community- and ecosystem-level processes to inform efforts to protect the health of aquatic ecosystems.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.

地球大部分被水覆盖，保持这些海洋和淡水生态系统的健康至关重要。要做到这一点，科学家必须了解它们如何保持清洁和平衡。健康水体的一个关键部分是微生物，它们通过吃细菌和碎片来处理废物并保持水的清洁。这些微小生物的进食速度（它们每次清洁多少水）决定了它们对环境健康的影响。因此，了解这种摄食率对于预测水体对变化的反应（例如，污染、污水泄漏、气候变化），并确定如何促进不健康水体的恢复。表面附着原生生物是一类对清洁水很重要的微生物，在淡水和海洋环境中普遍存在。这些生物生活在密集的聚集体中，附着在水下表面，如岩石，植物和下沉的碎片上，并创造出将食物吸引到它们身上的进食流。研究人员将使用一种新的全息显微镜，在现实条件下对这些生物的摄食电流进行首次三维测量。研究结果将用于验证现有的这些微生物摄食率的数学模型，并将为制定清洁水体和提高污水处理厂性能的战略提供信息。该项目还将为本科生和研究生提供跨学科的机会，包括那些传统上在STEM劳动力中代表性不足的群体。 微型无柄悬浮饲养者（MSSFs）是一种表面附着的原生生物，是水生生态系统中普遍存在的重要组成部分，具有清除细菌和污染物的重要生态功能，是藻类/细菌与高等真核生物之间的关键营养中间体。以前的研究这些表面附着的原生生物的喂养活动已被限制在有限的条件下，扭曲的流动和二维测量不捕捉电流的非轴对称性质。此外，理论预测，喂养是由封闭的涡流在流动中所造成的表面的附件限制，这些涡流对喂养率的影响强烈地依赖于相对于表面的MSSF的角度。研究人员将使用无柄纤毛虫Vorticella来确定MSSF的食物摄取是否受到附着在表面上的进食流体动力学的限制。使用新型3D全息显微镜，他们将确定：（1）单个MSSF的3D摄食流场如何随着生物体相对于表面的身体取向而变化，（2）培养中的涡形藻的身体取向的动力学如何与自然界中的那些相比，（3）摄食流和身体取向如何影响食物摄取，以及（4）周围环境流如何影响补给流。测量结果将用于验证可预测清除率的MSSF流体动力学模型。由此产生的微观相互作用的机械理解将最终建立一个基础，以扩大到社区和生态系统层面的过程，为保护水生生态系统的健康提供信息。该奖项反映了NSF的法定使命，并被认为值得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来支持。

项目成果

Active sinking particles: sessile suspension feeders significantly alter the flow and transport to sinking aggregates

主动下沉颗粒：固着悬浮给料器显着改变了下沉骨料的流动和运输

• DOI: 10.1098/rsif.2022.0537
• 发表时间: 2023
• 期刊: Journal of The Royal Society Interface
• 影响因子: 3.9
• 作者: Krishnamurthy, Deepak;Pepper, Rachel;Prakash, Manu
• 通讯作者: Prakash, Manu

The effect of external flow on the feeding currents of sessile microorganisms

• DOI: 10.1098/rsif.2020.0953
• 发表时间: 2021-02
• 期刊: Journal of the Royal Society Interface
• 影响因子: 3.9
• 作者: Rachel E. Pepper;E. E. Riley-E.;Matthieu Baron;Thomas Hurot;L. Nielsen;M. Koehl;T. Kiørboe;A. Andersen