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。本研究的目的是确定关键的生物和物理因素对广播产卵受精率的作用，广播产卵是许多底栖无脊椎动物使用的繁殖策略。目的是量化配子性状、瞬时湍流结构和不稳定流动现象对随后配子合并过程和受精率的影响。受精通常被建模为双分子反应，受精率与配子浓度成正比。传统的观点认为，由于湍流有效地稀释了配子浓度，因此阻碍了受精的成功。然而，这个结论是建立在考虑平均湍流色散的基础上的。最近的工作提供了证据，瞬时湍流结构促进局部合并在较短的时间尺度，稀释发生之前，从而提高受精率。这项工作将扩展理想化的数值和实验室研究，以包括具体到广播产卵过程的生态相关因素。它将数值模拟和实验室实验相结合，研究个体生物和物理因素对过程水平的影响。数值模拟将考虑配子粘度、流变性和趋向性对二维伪湍流、非定常障碍尾迹和三维混沌混合场景的影响。实验室实验将模拟配子粘度、流变性、形态和浮力的影响，使用三维边界层湍流、障碍尾迹和表面波。一种新的双色平面激光诱导荧光系统将用于量化配子替代物的浓度，包括它们重叠的那些区域。用甘油和生物聚合物染色溶液制成的替代品将模拟海胆配子的粘度和流变性，荧光颗粒将用于研究尺寸和惯性效应。漂浮粒子将用于研究自由表面湍流中收敛区对浮力配子物种受精率的影响。教育和推广目标是将研究方法整合到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来引起K-16学生对工程和科学的兴趣。将数值模拟平台整合到课程中；学生将使用模拟环境和他们的知识的纳维-斯托克斯方程来模拟一个不稳定的圆柱体尾迹。同样，一个简化版本的障碍尾流实验将开发作为教学工具。项目亦会发展一个互动的实验室示范，供参观团体使用。演示将包括教学水槽床的可移动底栖海洋景观，完成海胆模拟，产生粘性配子替代品。游客们将可以亲自体验一些道具，如流动障碍和可移动的床粗糙度部分。几张永久性海报和一个关于在自然界中产卵的短视频将加强演示。最后，PLIF系统将被用来制作教育电影，通过美国物理学会的数字图书馆传播。

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.