Collaborative Research: Turbulence and Suspension Feeding - a New Approach using the Lobate Ctenophore Mnemiopsis Leidyi

捕食者的猎物选择、摄食以及最终的营养影响是由发生在有机体层面的一系列事件决定的——捕食者、猎物和它们的环境之间的个体相互作用。此外，由于大多数捕食者-猎物相互作用发生在流动的流体中，因此在流体动力学背景下观察和量化捕食者-猎物相互作用至关重要。对自然环境中营养格局的成功预测受到以下能力的限制：1)直接观察湍流对远洋生物摄食的影响；2)了解湍流环境中动物与流体相互作用的机制基础；3)将静水实验室研究的定量观察与自然联系起来。这些限制在更大范围的海洋生态学的营养交换研究中普遍存在。最近的技术进步，以及联合pi的专业知识，使湍流对众所周知的侵入性叶栉水母的摄食影响的有意义的研究成为可能。记忆藻是一种精致的凝胶状捕食者，它利用层流进食电流牵引和捕获猎物。通过一种非常有效的摄食策略，浮游动物种群数量和总体浮游动物生物多样性减少，浮游植物种群数量通过营养级联增加。然而，像许多悬浮取食动物一样，记忆藻产生的取食电流可能容易受到环境水流的流体动力学破坏。事实上，湍流事件可能会改变像记忆水母这样的叶状栉水母的行为、分布和猎物选择。该物种是确定湍流影响生态影响浮游悬浮食性动物营养交换模式机制的理想模式生物。本研究将结合实验室和现场方法，在有机体水平上量化湍流对记忆藻捕食机制和捕食者-猎物相互作用的影响。了解这些湍流效应如何转化为群落水平，将通过现场采样技术来完成，该技术将自然湍流水平与记忆藻的摄食率、猎物选择和捕食影响联系起来。这种方法超越了目前的实验室和模型研究，具有建立明确的因果关系的潜力。智力优势：本研究将：1)直接量化湍流对原位捕食者-猎物相互作用的影响；2)对影响重要海洋入侵物种生态影响的关键变量提供机制认识；3)开发一种在实验室和实地研究小规模物理-生物相互作用的新方法。了解湍流如何影响叶状栉水母的摄食，在生物的尺度上和生态上都是有价值的。这里开发的方法也可以应用于各种其他湍流主导的情况（例如，锋面混合，动物-海洋雪相互作用）或其他生物（其他浮游生物，底水柱交换）。在所有情况下，结果都取决于小规模的物理-生物过程。更广泛的影响：本科生（5名）、研究生和合作项目负责人将在现场和实验室作为一个团队工作，为所有参与者提供研究各个方面的经验。加州理工学院的一个项目（新生暑期学院研究项目）将促进代表性不足的本科生的参与，该项目旨在为来自全国各地校园的少数族裔学生提供研究机会。加州理工学院的合伙人将继续担任该项目的指导老师。作为一种可以显著影响半封闭水体内食物链的入侵物种，雷氏记忆藻是国际上广泛关注的焦点。补救一直是持续讨论（和实验）的主题；因此，本研究结果将及时传达给国际科学界。此外，与参与公众科学教育的媒体（例如，PBS生命形态系列，新英格兰水族馆的神奇水母展览）的联系将被用来传达新的发现。

Prey selection, intake and, ultimately, the trophic impact of predators are determined by a succession of events that occur at the organismal level -- individual interactions among predators prey, and their environments. Furthermore, because the majority of predator-prey interactions occur in moving fluids, it is critical to observe and quantify predator-prey interactions within a hydrodynamic context. Successful predictions of trophic patterns in natural settings are limited by the ability to: 1) observe directly the effects of turbulence on feeding in pelagic organisms; 2) understand the mechanistic bases of animal-fluid interactions in turbulent environments; and 3) relate quantitative observations from still-water laboratory studies to nature. These limitations are pervasive in studies of trophic exchange within the larger scope of marine ecology. Recent technological advances, and the combined expertise of the Co-PIs, enables meaningful studies of the influence of turbulence on feeding by the notoriously invasive lobate ctenophore, Mnemiopsis leidyi. Mnemiopsis is a delicate gelatinous predator which uses a laminar feeding current to entrain and capture prey. Using a remarkably effective feeding strategy, zooplankton standing stocks and overall zooplankton biodiversity are reduced, and standing stocks of phytoplankton are increased via a trophic cascade. Like many suspension feeders, however, the feeding current produced by Mnemiopsis may be vulnerable to hydrodynamic disruption by ambient flows. In fact, turbulent events may change the behavior, distribution and prey selection of lobate ctenophores such as Mnemiopsis. This species is an ideal model organism to determine the mechanisms by which turbulence affects trophic exchange patterns of ecologically influential planktonic suspension feeders. Involving a combination of laboratory and in situ methods to quantify, at the organismal level, this study will determine effects of turbulent flows on the feeding mechanics and predator-prey interactions of Mnemiopsis. Understanding how these turbulent effects translate to the community level will be accomplished via in situ sampling techniques that relate natural turbulence levels to ingestion rates, prey selection and predatory impact of Mnemiopsis in the field. This approach extends beyond current laboratory and modeling studies, with the potential of establishing clear cause-and-effect relationships.Intellectual Merit: This research will: 1) directly quantify turbulent effects on in situ predator-prey interactions; 2) provide mechanistic understanding of key variables influencing the ecological impact of an important invasive marine species; and 3) develop a novel approach for studying small-scale physical-biological interactions both in the laboratory and in the field. Knowing how turbulence affects feeding in lobate ctenophores is valuable at the scale of the organism, as well as ecologically. The approach developed here also may be applied to a variety of other turbulence-dominated situations (e.g., mixing at fronts, animal-marine snow interactions) or to other organisms (other plankton, benthic-water column exchanges). In all cases, the outcomes depend upon small-scale physical-biological processes.Broader Impacts: Undergraduates (5), the graduate student, and the Co-PIs will work as a team in both the field and the laboratory, providing all participants with experience in every aspect of the research. The participation of underrepresented undergraduates will be facilitated through a program at Caltech (Freshmen Summer Institute Research Program) aimed at providing research opportunities to minority students from campuses across the nation. The Caltech Co-PI will continue his role as faculty advisor to this program. An invasive species that can dramatically affect the food chain within semi-enclosed bodies of water, Mnemiopsis leidyi is the focus of broad international interest. Remediation has been the subject of ongoing discussions (and experiments); therefore, results of this research will be communicated to the international scientific community in a timely fashion. In addition, contacts with media (e.g., PBS Shape of Life series, Fantastic Jellies exhibit at the New England Aquarium) involved in scientific education of the general public will be used to convey new findings.