Collaborative Research: Numerical Study of the Unsteady Feeding Currents in Calanoid Copepods

非稳定摄食电流的数值研究本研究项目将解决这样一个问题：“为什么在食草性的摄食桡足动物中存在两种不同类型的摄食电流？”也就是说，为什么动物在每次开始运动时都要克服周围水域的惯性，表现出开关模式，创造出一种不稳定的流动？我们首先会在现场直接观察喂食动物。然后，我们将在实验室中对它们进行3D观察，以确定(1)摄食电流的结构，以及(2)不同食物制度下的时间模式。该数据库包括观察到的动物的形状和大小，将用于使用计算流体动力学(CFD)进行模拟。研究小组由一名应用数学家/环境流体动力学专家(酱，WHOI)、一名生物海洋学家(Paffenhofer，SKIO)和两名实验海洋生物学家(Strickler和Janssen，UWM)组成。实验将在箭牌海洋科学中心进行为期两周的实验，在那里我们将在现场和实验室观察太平洋哲水蚤和鼻蝠。结果将是关于开关馈电电流的频率，以及动物周围水流的结构和时间变化的数据。我们还将研究在不同食物密度下，佐治亚州萨凡纳附近海域的甲鱼类桡足动物的活动模式。所有生成的数据集将不断用于在WHOI的CFD中设计模拟。我们希望找到证据表明生活在营养稀薄环境中的甲鱼类桡足类动物存在不同的生存策略。交替产生喂食电流的策略可能基于低超重、大体型和低食物浓度之间的折衷。这将与高超重、恒定馈电电流、大传感范围和适度食物密度的策略形成对比。智力优势浮游桡足类生活在不同的环境中，往往严重限制了食物的丰度。到目前为止，很少有研究涉及桡足类行为对这种减少的食物供应的适应。我们的研究旨在通过研究自由游泳的鱿鱼来提高我们对桡足类摄食行为的理解，这些鱿鱼会产生不同种类的不稳定的开关摄食电流，然后将新获得的结果与我们迄今关于稳定摄食电流的知识进行比较。更广泛的影响该项目将支持一名年轻的、以身体为导向的科学家与三名有成就的高级生物海洋科学家进行良好整合的跨学科研究。我们关于浮游动物生态、海洋和淡水的网站访问量很高，将有助于鼓励年轻人学习自然科学。数据文件和模拟结果也将上载到我们的网站(http://www.uwm.edu/~jrs))，供公众查阅。我们将在科学文献中传播我们的成果。两名本科生将在斯基德韦与G.-A一起工作。Paffenhofer，并将在项目过程中与PI团队进行互动。

Numerical Study of the Unsteady Feeding Current in Calanoid Copepods This research project will address the question, "Why are there two temporal types of generating feeding currents among herbivorous calanoid copepods"? That is, why do animals show an on/off pattern, creating an unsteady flow, when they have to overcome the inertia of the surrounding water every time they start moving? We will first directly observe feeding animals in situ. Then, we will observe them in 3D in the laboratory to define (1) the structures of the feeding currents, and (2), the temporal patterns under different food regimes. The database, which includes the shapes and sizes of the animals observed, will be used for simulations using computational fluid dynamics (CFD). The research team consists of an applied mathematician/environmental fluid dynamicist (Jiang, WHOI), a biological oceanographer (Paffenhofer, SKIO), and two experimental marine biologists (Strickler and Janssen, UWM). Experiments will be conducted during a two-week stay at the Wrigley Marine Science Center where we will observe Calanus pacificus and Rhincalanus nasutus in situ and in the laboratory. The results will be data on the frequencies of switching the feeding current on/off, and on the structures and temporal changes of the water flow around the animals. We will also study the activity patterns of calanoid copepods from the ocean off Savannah, GA, under different food densities. All the data sets generated will be constantly used to design the simulations in CFD at WHOI. We expect to find evidence that there exist different survival strategies among calanoid copepods living in nutritionally dilute environments. The strategy to alternate the generation of a feeding current may be based on a compromise between low excess weight, large body size, and low food concentrations. This would contrast to the strategy of high excess weight, constant feeding current, large sensing range, and moderate food density. Intellectual Merits Planktonic copepods live in environments of varying and often severely limiting food abundances. So far few if any studies have addressed the adaptations of copepod behavioral repertoires to this diminished food availability. Our study is designed to improve our understanding of copepod feeding behavior by studying empirically free-swimming calanoids, which produce unsteady on/off feeding currents of different kinds, and then compare the newly gained results with our knowledge to date about the steady feeding currents. Broader Impact The project will support the research efforts of a young, physically oriented scientist in a well-integrated interdisciplinary study with three accomplished senior biological ocean scientists. Our well-visited web sites on zooplankton ecology, marine and fresh-water, will serve to stimulate young persons to pursue the natural sciences. Data files and simulation results will also be uploaded onto our website of (http://www.uwm.edu/~jrs) for public access. We will disseminate our results in the scientific literature. Two undergraduate students will be working at Skidaway with G. -A. Paffenhofer and will interact with the team of PIs during the course of the project.