Mechanical consequences of flexibility for benthic marine organisms

科学背景和知识价值：在几乎所有的海洋系统中，机械灵活的底栖植物和动物是沿海群落中无处不在的成员。当水流经过时，这些生物被动地对水流做出反应。然而，这种运动的全部影响，特别是它影响生物体易受流驱动干扰的方式，人们知之甚少。传统观点认为，柔性结构增强了无根植物或动物在结构上应对时变水运动的能力。然而，最近的研究指出，心流中的被动运动也会产生更微妙的后果。例如，一个附着的生物体被海浪来回扫过，获得动量，当生物体的质量最终在达到其运动范围的极限时减速时，这个动量可以施加随后的惯性力。这种复杂性强调需要对潮间带和潮下生物的灵活性的生物力学和生存意义进行更全面和一致的检查。如果没有这些进一步的检查，对流动（长期以来被认为是干扰的主要因素和影响这些社区人口动态的关键因素）死亡率后果进行定量和机制预测的尝试将仍然无效。满足这一需求是拟议研究的目标。研究工作将集中在测量现场应用于柔性生物的实时力，并将这些力与基于流体动力形状因子（先前确定的相同样本个体的阻力系数）和同时记录的流量的准静态估计进行比较。实际和准静态时间序列的力之间的差异将被用来量化内在地伴随着有机体灵活性的被动运动改变施加力的方式。多组记录将在岸上的三个不同的流体动力学“领域”内进行（潮下，淹没潮间带和受到波浪直接撞击的区域，生物在波浪之间出现）。海带，包括生态上重要的巨囊藻（Macrocystis pyrifera）、褐囊藻（Nereocystis luetkeana）、白鹭（Egregia menziesii）和边缘海藻（Alaria marginata）将作为重点物种。结果将以潜在的无维度参数进行汇编和表达，这些参数共同控制着物种和三个海岸线领域的生物动力学。非量纲参数之间的关系将被定量地检查和综合，以开发一个通用的、连贯的框架，该框架定义了灵活性如何影响在全范围流动环境中生活的各种生物的施加力。随后的生物力学框架将用于预测现场海带的实际流动死亡率，作为无量纲参数的函数，这些预测的死亡率将与观察到的率进行比较，这些率跨越不同尺寸的标记个体，在岸上的深度和高度范围内生长。更广泛的影响：这里提出的活动对预测至关重要的群落参与者（Macrocystis为数百种沿海物种提供了必要的栖息地，包括许多具有经济和娱乐价值的物种）对全球气候变化导致的波浪状态持续变化的反应具有重要意义。生物力学的见解也将告知海岸工程问题，其中海带影响近岸水流和沉积物运输，以及仿生学领域。此外，有很强的教育/合作关系的影响，因为本科生和研究生助理，无论是有偿的还是志愿的，将密切参与核心实验和分析。这样的机会将提供严谨的团队研究经验，促进学生在职业生涯早期的科学发展。该项目的结果将通过将结果纳入正式的大学课程、为一般科学领域编写的书籍以及通过与公共部门机构的现有联系进一步传达给更广泛的受众。通过将三个机构的科学家和实验室聚集在一起的密切合作，将加强基本的知识交流和讨论。

Scientific context and intellectual merit: Mechanically flexible, benthic plants and animals are ubiquitous members of coastal communities in nearly all marine systems. Such organisms move passively in response to flow as water moves past them. However, the full effects of this motion, and in particular the way it influences an organism's vulnerability to flow-driven disturbance, is poorly understood. Traditionally, the view has been that a compliant construction enhances the ability of sessile plants or animals to cope structurally with time-varying water motion. However, more recent research has noted that passive movement in flow can also have subtler consequences. For instance, an attached organism that is swept back and forth by ocean waves acquires momentum, and this momentum can impose a subsequent inertial force when the mass of the organism is eventually decelerated upon reaching the limits of its range of motion. Such complexities emphasize the need for a more complete and consistent examination of the biomechanical and survivorship implications of flexibility for intertidal and subtidal organisms. Without these further examinations, attempts to develop quantitative and mechanistic predictions of the mortality consequences of flow (long recognized as a dominant agent of disturbance and as a critical factor influencing population dynamics in these communities) will remain ineffective. Meeting this need is the goal of the proposed study.Research efforts will focus on measuring real-time forces applied to flexible organisms in the field and comparing those forces to quasi-static estimates based on hydrodynamic shape factors (drag coefficients determined previously for the same sample individuals) and simultaneously recorded flows. Differences between actual and quasi-static time series of force will then be used to quantify the way in which the passive motion that intrinsically accompanies organism flexibility alters applied force. Multiple sets of recordings will be conducted within three distinct fluid-dynamical "realms" on the shore (subtidal, submerged intertidal, and regions subjected to direct wave impingement where organisms are emergent between waves). Laminarian kelps, including the ecologically important Macrocystis pyrifera, Nereocystis luetkeana, Egregia menziesii, and Alaria marginata will be employed as focal species.Results will be compiled and expressed in terms of underlying nondimensional parameters that together govern organismal dynamics across species and the three shoreline realms. Relationships among the nondimensional parameters will be examined quantitatively and synthesized overall to develop a general, coherent framework that defines how flexibility influences imposed force across a wide range of organisms living across a full spectrum of flow environments. This ensuing biomechanical framework will then be used to predict actual rates of flow-mediated mortality for kelps in the field as a function of the nondimensional parameters, and these predicted rates will be compared to the observed rates across tagged individuals of a spectrum of sizes, growing in a range of water depths and heights on the shore.Broader impacts: The activities proposed here have important implications for predicting the response of critically important community players (Macrocystis provides necessary habitat for hundreds of coastal species, including many with economic and recreational value) to ongoing shifts in wave regimes due to global climate change. Biomechanical insights will also inform issues of coastal engineering where kelps affect nearshore currents and sediment transport, and the field of biomimetics. In addition, there are strong educational/partnership implications, since undergraduate and graduate assistants, both paid and volunteer, will be involved intimately in core experiments and analyses. Such opportunities will provide for rigorous, team research experiences that foster the scientific development of students early in their careers. Results of the project will be further conveyed to wider audiences via the incorporation of results into formal university courses, books written for the general scientific arena, and through existing ties with public-sector agencies. Basic intellectual exchange and discourse will be enhanced through a close collaboration that brings together scientists and labs from three institutions.