Larval Response to Turbulence During Dispersal and Settlement

幼虫在扩散和定居过程中对湍流的反应

• 批准号: 0850419
• 负责人: Lauren Mullineaux
• 金额: $ 92.54万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-03-01 至 2015-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0850419&HistoricalAwards=false
• 关键词: Larval; Response; Turbulence; During; Dispersal

The planktonic larval stage of benthic marine invertebrates provides a mechanism for exchange of individuals between remote populations. Dispersal is affected by swimming behaviors, particularly those that alter the larva's vertical position in the water. Larvae of some species change their vertical positions in response to turbulence by ceasing to swim and sinking downward (diving). By doing so, they can alter their horizontal transport in currents and increase their supply to the seafloor. The main objectives of this study are to investigate behavioral responses of oyster (Crassostrea virginica) larvae to turbulence in the water column and at the seafloor, and to determine how these behaviors affect settlement. The investigators hypothesize that diving behavior enhances settlement into suitable habitat, even where mean bed shear stress is high. They expect that once larvae approach the bottom, they can take advantage of temporal and spatial refuges (such as turbulent lulls in the lee of roughness elements) to settle in otherwise harsh conditions. Investigating larval responses to turbulence is a challenge because it requires simultaneous measurement of time-variant flows and larval behaviors. The investigators will modify a conventional particle image velocimetry (PIV) approach so it can be used to track larval motions and fluid velocities simultaneously. PIV provides information on flow kinematics (e.g., rotation and strain rate) in the immediate vicinity of a larva, as well as bulk dissipation rates and measures of Taylor and integral length scales that likely influence larval acceleration. When these measurements are coupled with a larval trajectory, they provide a history of the fluid environment a larva experiences, and can be used to determine what characteristic of turbulence triggers the diving behavior. They also make it possible to calculate the bottom shear stress an individual larva experiences when it encounters the bottom and attempts to settle. The investigators will examine turbulence effects on larval behaviors in the water column using a grid-stirred tank. They will use a racetrack flume to test the hypothesis that larval settlement success depends on the frequency of lulls of sufficient duration for larval attachment. Intellectual merit. Laboratory experiments will provide a mechanistic understanding of larval behavior that can be used in general theoretical models exploring how behavior influences dispersal and population connectivity. The quantified swimming responses of oysters are critical input for coupled bio-physical models of dispersal in the field. An understanding of larval behavior contributes to our ability to predict the effects of natural and anthropogenic perturbations (some of which are linked to global climate change) on benthic communities in coastal ecosystems where turbulence and habitat suitability vary spatially. This information is critical for informed decision making on shellfish management and design of marine reserves. The technique developed for simultaneous PIV and larval tracking will open new questions in larval ecology and be broadlyapplicable to studies of plankton interactions with turbulence.Broader impacts. Various training and outreach activities that incorporate aspects of this research will be conducted. The investigators will develop an active learning module for the MIT/WHOI Biological Oceanography course based on concepts of organismal responses to flow, and will develop a low-tech version to contribute to the SERC at Carlton College (a web resource for Geoscience faculty). They will provide the graduate student and a series of summer undergraduate research fellows with mentoring and an experience with interdisciplinary research. Co-PI Helfrich will use support to help maintain the Geophysical Fluid Dynamics Laboratory at WHOI, which is recognized as one of the finest facilities of its type and has a tradition of assisting students and scientists in a variety of experiments in fluid dynamics in physical oceanography, geology, and bio-physical interactions.

底栖海洋无脊椎动物的浮游幼虫阶段为遥远种群之间的个体交换提供了一种机制。扩散受到游泳行为的影响，尤其是那些改变幼虫在水中垂直位置的行为。有些种类的幼虫会改变它们的垂直位置，以应对湍流，停止游泳并向下下沉（潜水）。通过这样做，它们可以改变它们在洋流中的水平运输，增加它们对海底的供应。本研究的主要目的是研究牡蛎（Crassostrea virginica）幼虫对水柱和海底湍流的行为反应，并确定这些行为如何影响沉降。研究人员假设，即使在平均床面剪应力高的地方，潜水行为也会促进沉降到合适的栖息地。他们预计，一旦幼虫接近海底，它们就可以利用时间和空间的避难所（比如在粗糙元素的背风处的湍流间歇）在其他恶劣的条件下定居下来。研究幼虫对湍流的反应是一项挑战，因为它需要同时测量随时间变化的流动和幼虫的行为。研究人员将改进传统的粒子图像测速（PIV）方法，使其可以同时跟踪幼虫的运动和流体速度。PIV提供了幼虫附近的流动运动学信息（例如，旋转和应变速率），以及可能影响幼虫加速的体积耗散率和泰勒尺度和积分长度尺度的测量。当这些测量与幼虫轨迹相结合时，它们提供了幼虫经历的流体环境历史，并可用于确定湍流的哪些特征触发了潜水行为。它们也使计算单个幼虫在遇到底部并试图定居时所经历的底部剪切应力成为可能。研究人员将使用网格搅拌槽检查湍流对水柱中幼虫行为的影响。他们将使用一个跑道水槽来测试一个假设，即幼虫的定居成功取决于幼虫附着的足够时间的间歇的频率。知识价值。实验室实验将提供对幼虫行为的机制理解，可以用于探索行为如何影响扩散和种群连通性的一般理论模型。牡蛎的定量游动响应是野外扩散耦合生物物理模型的重要输入。对幼虫行为的理解有助于我们预测自然和人为扰动（其中一些与全球气候变化有关）对沿海生态系统中底栖生物群落的影响，其中湍流和栖息地适宜性在空间上存在差异。这些信息对于贝类管理和海洋保护区设计的知情决策至关重要。同时进行PIV和幼虫跟踪的技术将在幼虫生态学中开辟新的问题，并广泛适用于浮游生物与湍流相互作用的研究。更广泛的影响。将开展包括这项研究各方面内容的各种培训和外联活动。研究人员将为麻省理工学院/WHOI生物海洋学课程开发一个基于生物对水流反应概念的主动学习模块，并将开发一个低技术版本，以贡献给卡尔顿学院的SERC（地球科学教师的网络资源）。他们将为研究生和一系列暑期本科生研究员提供指导和跨学科研究经验。赫尔弗里奇副主任将利用支持来帮助维持WHOI的地球物理流体动力学实验室，该实验室被认为是同类机构中最好的设施之一，并有协助学生和科学家在物理海洋学、地质学和生物物理相互作用的流体动力学方面进行各种实验的传统。