Physical-Biological Interactions in the Fertilization Ecology of Broadcast Spawners: The Role of Gamete Traits and Turbulence Structure

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。本研究的目标是确定关键生物和物理因素对广播产卵受精率的作用，这是许多底栖无脊椎动物使用的生殖策略。我们的目标是量化的配子性状，瞬时湍流结构和不稳定的流动现象对随后的配子聚结过程和受精率的影响。受精通常被模拟为双分子反应，受精率与配子的浓度成正比。传统的观点认为，由于湍流会有效稀释配子浓度，因此会阻碍受精成功。然而，这一结论是基于对平均湍流弥散的考虑。最近的工作提供的证据表明，瞬时湍流结构促进局部聚结在较短的时间尺度，稀释发生之前，从而提高施肥率。这项工作将扩大理想化的数值和实验室研究，包括特定的广播产卵过程的生态相关因素。它集成了数值模拟和实验室实验，以研究单个生物和物理因素的过程级影响。数值模拟将考虑配子粘度，流变学和的士的影响，为2D伪湍流，不稳定的障碍物尾流，和3D混沌混合的情况。实验室实验将使用3D边界层湍流、障碍物尾迹和表面波模拟配子粘度、流变学、形态学和浮力的影响。一种新的双色平面激光诱导荧光系统将被用来量化浓度的配子替代品，包括那些地区，他们重叠。使用甘油和生物聚合物的染色溶液制成的替代品将模拟海胆配子的粘度和流变学，荧光颗粒将用于研究大小和惯性效应。漂浮粒子将用于研究自由表面湍流中的会聚区对具有浮力配子的物种的受精率的影响。教育和推广目标是将研究方法融入PI的教学课程中，作为学习流体力学的有效工具，并使用广播产卵的主题让K-16学生对工程和科学感兴趣。一个数值模拟平台将被集成到一门课程;学生将使用模拟环境和他们的Navier-Stokes方程的知识来模拟非定常圆柱尾迹。同样，将开发简化版的障碍物尾流实验作为教学工具。PI还将开发一个交互式实验室演示，供访问团体使用。演示将包括一个可移动的底栖海景床的教学水槽，完成海胆模拟产卵粘性配子代理人。参观者将能够尝试动手道具，如流动障碍和可移动的床粗糙部分。几张永久性的海报和一段关于自然界广播产卵的短片将加强演示。最后，PLIF系统将用于制作教育电影，通过美国物理学会的数字图书馆进行传播。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The goal of this research is to determine the role of key biological and physical factors on fertilization rates in broadcast spawning, the reproductive strategy used by many benthic invertebrates. The objectives are to quantify the effect of gamete traits, instantaneous turbulence structure, and unsteady flow phenomena on subsequent gamete coalescence processes and fertilization rates. Fertilization is typically modeled as a bimolecular reaction, with the fertilization rate proportional to concentrations of gametes. Conventional thought has been that since turbulence produces efficient dilution of gamete concentrations, it hinders fertilization success. However, this conclusion is based on consideration of average turbulent dispersion. Recent work has provided evidence that instantaneous turbulence structure promotes local coalescence at shorter timescales, before dilution takes place, thus enhancing fertilization rates. This work will extend idealized numerical and laboratory studies to include ecologically relevant factors specific to the broadcast spawning process. It integrates numerical simulations and laboratory experiments to investigate process-level effects of individual biological and physical factors. The numerical simulations will consider the effects of gamete viscosity, rheology, and taxis, for 2D pseudo-turbulent flow, unsteady obstacle wakes, and 3D chaotic mixing scenarios. The laboratory experiments will model the effects of gamete viscosity, rheology, morphology, and buoyancy, using 3D boundary layer turbulence, obstacle wakes, and surface waves. A novel two-color planar laser-induced fluorescence system will be used to quantify concentrations of gamete surrogates, including those regions where they overlap. Surrogates made using dyed solutions of glycerol and a biopolymer will model the viscosity and rheology of sea urchin gametes, and fluorescent particles will be used to investigate size and inertial effects. Floating particles will be used to study the effect of convergence zones in free-surface turbulence on fertilization rates for species with buoyant gametes.The educational and outreach goals are to integrate research methods into the PI's teaching curriculum as an effective tool for learning fluid mechanics, and to use the topic of broadcast spawning to get K-16 students interested in engineering and science. A numerical simulation platform will be integrated into a course; students will use the simulation environment and their knowledge of the Navier-Stokes equation to model an unsteady cylinder wake. Likewise, a simplified version of the obstacle wake experiment will be developed as a teaching tool. The PI will also develop an interactive laboratory demonstration to use with visiting groups. The demonstration will include a removable benthic seascape for the bed of the teaching flume, complete with sea urchin mimics that spawn viscous gamete surrogates. Visitors will be able to experiment with hands-on props such as flow obstacles and a removable bed-roughness section. Several permanent posters and a short video about broadcast spawning in nature will enhance the demonstration. Finally, the PLIF system will be used to make educational movies for dissemination via a digital library of the American Physical Society.